A&A 370, 765-867 (2001)
DOI: 10.1051/0004-6361:20010090
M. A. W. Verheijen1,2 - R. Sancisi2,3
1 -
NRAO, PO Box O, Socorro, NM 87801, USA
2 -
Kapteyn Institute, Postbus 800, 9700 AV Groningen, The Netherlands
3 -
Osservatorio Astronomico di Bologna, Via Ranzani 1, 40127 Bologna, Italy
Received 15 November 2000 / Accepted 1 December 2000
Abstract
In this data paper we present the results of an extensive 21 cm-line
synthesis imaging survey of 43 spiral galaxies in the nearby Ursa Major
cluster using the Westerbork Synthesis Radio Telescope. Detailed
kinematic information in the form of position-velocity diagrams and
rotation curves is presented in an atlas together with HI channel maps,
21 cm continuum maps, global HI profiles, radial HI surface density
profiles, integrated HI column density maps, and HI velocity fields. The
relation between the corrected global HI linewidth and the rotational
velocities
and
as derived from the rotation curves is investigated.
Inclination angles obtained from the optical axis ratios are compared to those
derived from the inclined HI disks and the HI velocity fields. The
galaxies were not selected on the basis of their HI content but solely
on the basis of their cluster membership and inclination which should be
suitable for a kinematic analysis. The observed galaxies provide a
well-defined, volume limited and equidistant sample, useful to
investigate in detail the statistical properties of the Tully-Fisher
relation and the dark matter halos around them.
Key words: galaxies: fundamental parameters - galaxies: kinematics and dynamics - galaxies: spiral - galaxies: structure
The statistical properties of the Tully-Fisher relation (TFr), like its scatter and slope, and in more detail the characteristics of dark matter halos around galaxies, like their core densities and radii, are of great interest to those who study galaxy formation scenarios. The relevant observables for the TFr are total luminosities and rotational velocities while actual rotation curves and luminosity profiles are required to obtain constraints on the density profiles of dark matter halos. However, the available data sets from which these observables can be obtained are often suffering from incompleteness, distance uncertainties and inhomogeneous observing and data analysis techniques.
Furthermore, the interpretation of the observables is not always unambiguous. For instance, the rotational velocity of a galaxy is generally inferred from the width of its global HI profile and often this measured width is being related directly to the dark matter potential (e.g. Navarro & Steinmetz 2000). However, the width of the HI profile is a complicated convolution of the 2-dimensional distribution of HI in a galaxy disk and the shape and extent of its rotation curve as sampled by the HI gas. Needless to say one has to exercise caution when relating the observed scatter and slope in the TFr to the outcome of numerical and semi-analytical simulations of galaxy formation. This is especially the case when the observed TFr was constructed to serve as an empirical distance estimator and the selection criteria and applied corrections to the raw observables were optimized to linearize the relation and minimize its scatter.
To overcome some of the observational issues, we initiated a program to obtain detailed multi-band photometric and kinematic information on individual galaxies in a well-defined, complete sample. The nearby Ursa Major cluster of galaxies provides a particularly suitable sample. In the first place, the galaxies in the cluster are all at roughly the same distance. Therefore, there is little doubt about their relative luminosities, sizes and masses. Furthermore, the Ursa Major cluster contains overwhelmingly gas-rich systems and the morphological mix of its galaxy members is close to that of the lower density field. A detailed discussion on the definition of the Ursa Major cluster is given by Tully et al. (1996) (Paper I). The characteristics of this cluster will be discussed in more detail in Sect. 2.
In this paper we present the results of an extensive 21 cm-line synthesis
imaging survey of individual galaxies in the Ursa Major cluster using
the Westerbork Synthesis Radio Telescope (WSRT). The HI data are
presented in the form of an atlas. Multi-band optical and near-infrared
imaging photometry is presented in Paper I together with B-band and
-band images of all identified cluster members. Forthcoming
papers in this series will use these data to investigate the TFr while
the HI rotation curves will be supplemented in the inner regions with
already obtained high resolution optical rotation curves to derive
constraints on the structural properties of the dark matter halos and
the mass-to-light ratios of the stellar populations.
This data paper is organized as follows. Section 2 describes the Ursa
Major cluster in more detail and contains morphological and photometric
information on the galaxies observed with the WSRT. Data acquisition and
reduction procedures are explained in Sect. 3. Section 4 explains how
the corrected linewidth can be matched to and
from the rotation curves through an
appropriate correction for turbulent motion. Inclinations are derived
from the optical images, HI column density maps and HI velocity fields
and Sect. 5 presents a comparison of these inclinations. The layout of
the HI atlas is described in Sect. 6 with details about the various
elements of the atlas pages. The HI properties of the Ursa Major cluster
galaxies as a sample are presented in Sect. 7. Some concluding remarks
are given in Sect. 8.
The nearby Ursa Major cluster as defined in Paper I has 79 identified
members. It is located in the Supergalactic plane at an angular
distance of 38 degrees from the core of the Virgo cluster. It has a
recession velocity of 950 km s-1 and a velocity dispersion of
only 150 km s-1. In Paper I and in Tully & Verheijen
(1997) (Paper II) a distance of 15.5 Mpc was adopted. However,
new HST cepheid distances to local TFr calibrators (e.g. Sakai et al.
2000) and a new correction formalism for internal extinction
(Tully et al. 1998) now place the Ursa Major cluster galaxies
at a mean distance of 18.6 Mpc (Tully & Pierce 2000). At this
distance, 1 arcmin corresponds to 5.4 kpc. The morphological mix of the
cluster members is made up overwhelmingly by late type systems and only
a dozen lenticulars are known members. Morphological and photometric
properties in the optical and near-infrared of individual galaxies are
described in detail in Paper I. The galaxy distribution shows no
concentration toward any core and no X-ray emitting intra-cluster gas
has been detected.
It should be noted that individual galaxies in the nearby Virgo (Warmels 1988a, 1988b; Cayatte et al. 1990), A1367 (Dickey & Gavazzi 1991), Hercules (Dickey 1997) and Coma (Bravo-Alfaro et al. 2000) clusters have also been studied in detail and the effect of the dense environment on the properties of the HI disks in these clusters has been clearly demonstrated. The HI disks in the cores of these rich clusters are in general very small and often offset from the optical galaxy. On the other hand, the volume limited survey of the Hydra cluster (McMahon 1993) does not show such an HI deficiency although some interesting dynamical substructure has been revealed in this system. It should be stressed that the Ursa Major cluster is markedly different from these more massive and denser clusters. In selecting the Ursa Major sample, these environmental effects are carefully avoided as well as fore- and background contamination caused by high velocity dispersions and complex dynamical and spatial substructures.
Since the Ursa Major galaxies are all at the same distance, the effects
of incompleteness and uncertain relative distances are minimized. A
complete sample of 62 galaxies brighter than
,
i.e.
roughly twice the luminosity of the Small Magellanic Cloud, was
constructed and nearly all cluster members were observed with the WSRT.
In this paper, however, only those 49 galaxies which are more inclined
than 45 degrees, as derived from the optical axis ratio, will be
considered for a detailed kinematic study.
Table 1 gives a summary of the positional and morphological properties of these 49 galaxies while photometrics are presented in Table 2, based on a 18.6 Mpc distance. There are 3 additional galaxies in the tables which do not meet the luminosity (f) and inclination (i) criteria but happened to be in the same WSRT fields as galaxies from the complete sample. Of all those 52 galaxies, the HI synthesis data of 30 were fully analyzed. Thirteen systems were observed and detected but the HI data of these galaxies are presented in an abbreviated form comprising only the channel maps, global profiles and position-velocity diagrams. Two of the smaller galaxies were detected in HI but they are confused with the HI emission from their more massive companions. Finally, there are 7 galaxies in the complete sample which have not been observed or detected because of their low HI content known from single dish observations. These are in general S0 or Sa systems.
Table 1 presents the following positional and morphological information:
Column (1) gives the NGC or UGC numbers.
Columns (2) and (3) provide the equatorial coordinates (B1950) derived from the optical
images.
Columns (4) and (5) give the Galactic coordinates.
Column (6) provides the morphological type.
Column (7) gives the observed major axis diameter of the 25th mag arcsec-2 blue
isophote.
Column (8) contains the position angle of the receding side of the galaxy. For galaxies
which are not observed or not detected in HI, this is the smallest position angle of the major axis
measured eastward from the north.
Column (9) contains the observed ellipticity of the optical galaxy image.
Column (10) gives the inclination
as derived from the observed axis ratio
(b/a). See Sect. 5.1 for further details.
Column (11) gives the adopted inclination angle as derived from several methods described
in Sect. 5.
Column (12) indicates whether a galaxy has a low (LSB) or high surface brightness (HSB)
according to Paper II.
Columns (13) and (14) provide the galactic extinction in
the B-band according to
Burstein & Heiles (1984)
(BH) and
Schlegel et al. (1998) (SFD) as reported by the NASA Extragalactic Database.
Table 2 presents the following photometric information:
Column (1) gives the NGC or UGC numbers.
Columns (2)-(5) give the observed total magnitudes in the B, R, I and passbands from Paper I.
Column (6) contains the corrected HI line widths at the 20% level, used to calculate the
internal extinction as explained below.
Columns (7)-(10) present the calculated internal
extinction corrections in thee B, R, I and
passbands toward
face-on
,
calculated according to
Tully et al. (1998):
where WiR,I is the distance independent HI line width
corrected for instrumental resolution as described in Sect. 3.2,
corrected for turbulent motion according to Tully & Fouqué
(1985) (TFq hereafter) with
Wt,20=22 km s-1 as motivated in
Sect. 4 and corrected for inclination using
from Table 1. For dwarf galaxies with
WiR,I<85 km s-1 and for lenticulars with no dust features, the value of
is
set to zero at all passbands.
Columns (11)-(14) give the total absolute B, R, I and
magnitudes corrected for Galactic and internal extinction and
a distance modulus of 31.35 corresponding to a distance to the Ursa
Major cluster of 18.6 Mpc:
The HI data presented in this paper were obtained with the Westerbork
Synthesis Radio Telescope (WSRT) between 1991 and 1996. The integration
times varied between
and
depending on the required
signal-to-noise. The angular resolution at the center of the cluster is
or
kpc at
the adopted distance of 18.6 Mpc. The FWHM of the primary beam is
37.4 arcminutes or 202 kpc. As a result, often more than one galaxy was
mapped in a single field of view. The observed bandwidth was either 2.5
or 5 MHz, depending on the width of the global profiles. The
observations of the NGC 3992-group and the NGC 4111-group required a
broad frequency band of 5 MHz and at the same time also sufficient
velocity resolution for the dwarf systems. To comply with the
correlator restrictions, those two fields were observed only in one
polarization (XX) which allowed for a velocity resolution of
10 km s-1 but resulted in less sensitivity. During the earlier
measurements an on-line Hanning taper was applied but this tapering was
abandoned later to obtain the highest possible velocity resolution. The
various obtained velocity resolutions (dependent on the correlator
restrictions) were 5, 8, 10, 20 or 33 km s-1, corresponding to typical
rms-noise levels of respectively 3.1, 1.9, 2.9, 1.6 and
1.0 mJy beam-1 for a single 12h observation
at the highest angular resolution. The data of NGC 4013 were kindly made
available by R. Bottema who studied this system in great detail
(Bottema 1996 and references therein).
More details on the observational parameters for each field are tabulated in the atlas along with the data. What follows is a brief description of the reduction procedures.
Name | RA | Dec | Galactic | Type | D25(B) | PA | 1-b/a |
![]() |
![]() |
S.B. | [BH] | ||
|
(1950) | Long. | Lat. | (![]() |
(![]() |
(![]() |
(![]() |
mag | mag | ||||
(1) |
(2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) | (11) | (12) | (13) | (14) |
Galaxies with fully analyzed HI data: | |||||||||||||
U6399 |
11 20 35.9 | 51 10 09 | 152.08 | 60.96 | Sm | 2.40 | 140 | 0.72 | 79 | ![]() |
LSB | 0.00 | 0.07 |
U6446 | 11 23 52.9 | 54 01 21 | 147.56 | 59.14 | Sd | 2.27 | 200 | 0.38 | 54 | ![]() |
LSB | 0.00 | 0.07 |
N3726 | 11 30 38.7 | 47 18 20 | 155.38 | 64.88 | SBc | 5.83 | 194 | 0.38 | 54 | ![]() |
HSB | 0.01 | 0.07 |
N3769 | 11 35 02.8 | 48 10 10 | 152.72 | 64.75 | SBb | 2.97 | 150 | 0.69 | 76 | ![]() |
HSB | 0.01 | 0.10 |
U6667 | 11 39 45.3 | 51 52 32 | 146.27 | 62.29 | Scd | 3.43 | 88 | 0.88 | 90 | ![]() |
LSB | 0.00 | 0.07 |
N3877 | 11 43 29.3 | 47 46 21 | 150.72 | 65.96 | Sc | 5.40 | 36 | 0.78 | 84 | ![]() |
HSB | 0.01 | 0.10 |
N3893 | 11 46 00.2 | 48 59 20 | 148.15 | 65.23 | Sc | 3.93 | 352 | 0.33 | 49 | ![]() |
HSB | 0.02 | 0.09 |
N3917 | 11 48 07.7 | 52 06 09 | 143.65 | 62.79 | Scd | 4.67 | 257 | 0.76 | 82 | ![]() |
LSB | 0.01 | 0.09 |
N3949 | 11 51 05.5 | 48 08 14 | 147.63 | 66.40 | Sbc | 2.90 | 297 | 0.38 | 54 | ![]() |
HSB | 0.03 | 0.09 |
N3953 | 11 51 12.4 | 52 36 18 | 142.21 | 62.59 | SBbc | 6.10 | 13 | 0.50 | 62 | ![]() |
HSB | 0.01 | 0.13 |
N3972 | 11 53 09.0 | 55 35 56 | 138.85 | 60.06 | Sbc | 3.43 | 298 | 0.72 | 79 | ![]() |
HSB | 0.00 | 0.06 |
U6917 | 11 53 53.1 | 50 42 27 | 143.46 | 64.45 | SBd | 3.17 | 123 | 0.46 | 59 | ![]() |
LSB | 0.03 | 0.12 |
U6923 | 11 54 14.4 | 53 26 19 | 140.51 | 62.06 | Sdm | 1.97 | 354 | 0.58 | 68 | ![]() |
LSB | 0.00 | 0.12 |
U6930i | 11 54 42.3 | 49 33 41 | 144.54 | 65.51 | SBd | 3.00 | 39 | 0.14 | 32 | ![]() |
LSB | 0.05 | 0.13 |
N3992 | 11 55 00.9 | 53 39 11 | 140.09 | 61.92 | SBbc | 6.93 | 248 | 0.44 | 58 | ![]() |
HSB | 0.01 | 0.13 |
U6940f | 11 55 12.4 | 53 30 46 | 140.17 | 62.06 | Scd | 0.83 | 135 | 0.72 | 79 | ![]() |
LSB | 0.00 | 0.12 |
U6962i | 11 55 59.5 | 43 00 44 | 154.08 | 71.05 | SBcd | 2.33 | 179 | 0.20 | 38 | ![]() |
HSB | 0.00 | 0.09 |
N4010 | 11 56 02.0 | 47 32 16 | 146.68 | 67.36 | SBd | 4.63 | 65 | 0.88 | 90 | ![]() |
LSB | 0.00 | 0.11 |
U6969 | 11 56 12.9 | 53 42 11 | 139.70 | 61.96 | Sm | 1.50 | 330 | 0.69 | 76 | ![]() |
LSB | 0.01 | 0.13 |
U6973 | 11 56 17.8 | 43 00 03 | 153.97 | 71.10 | Sab | 2.67 | 40 | 0.61 | 70 | ![]() |
HSB | 0.00 | 0.09 |
U6983 | 11 56 34.9 | 52 59 08 | 140.27 | 62.62 | SBcd | 3.20 | 270 | 0.34 | 50 | ![]() |
LSB | 0.01 | 0.12 |
N4051 | 12 00 36.4 | 44 48 36 | 148.88 | 70.08 | SBbc | 5.90 | 311 | 0.34 | 50 | ![]() |
HSB | 0.00 | 0.06 |
N4085 | 12 02 50.4 | 50 37 54 | 140.59 | 65.17 | Sc | 2.80 | 255 | 0.76 | 82 | ![]() |
HSB | 0.01 | 0.08 |
N4088 | 12 03 02.0 | 50 49 03 | 140.33 | 65.01 | Sbc | 5.37 | 231 | 0.63 | 71 | ![]() |
HSB | 0.01 | 0.09 |
N4100 | 12 03 36.4 | 49 51 41 | 141.11 | 65.92 | Sbc | 5.23 | 344 | 0.71 | 77 | ![]() |
HSB | 0.03 | 0.10 |
N4102 | 12 03 51.3 | 52 59 22 | 138.08 | 63.07 | SBab | 3.00 | 38 | 0.44 | 58 | ![]() |
HSB | 0.01 | 0.09 |
N4157 | 12 08 34.2 | 50 45 47 | 138.47 | 65.41 | Sb | 6.73 | 63 | 0.83 | 90 | ![]() |
HSB | 0.02 | 0.09 |
N4183 | 12 10 46.5 | 43 58 33 | 145.39 | 71.73 | Scd | 4.77 | 346 | 0.86 | 90 | ![]() |
LSB | 0.00 | 0.06 |
N4217 | 12 13 21.6 | 47 22 11 | 139.90 | 68.85 | Sb | 5.67 | 230 | 0.74 | 80 | ![]() |
HSB | 0.00 | 0.08 |
N4389 | 12 23 08.8 | 45 57 41 | 136.73 | 70.74 | SBbc | 2.50 | 276 | 0.34 | 50 | ![]() |
HSB | 0.00 | 0.06 |
Galaxies with partially analyzed HI data: |
|||||||||||||
N3718 |
11 29 49.9 | 53 20 39 | 147.01 | 60.22 | Sa | 7.53 | 195 | 0.58 | 68 | ![]() |
HSB | 0.00 | 0.06 |
N3729 | 11 31 04.9 | 53 24 08 | 146.64 | 60.28 | SBab | 2.80 | 164 | 0.32 | 48 | ![]() |
HSB | 0.00 | 0.05 |
U6773 | 11 45 22.1 | 50 05 12 | 146.89 | 64.27 | Sm | 1.53 | 341 | 0.47 | 60 | ![]() |
LSB | 0.00 | 0.07 |
U6818 | 11 48 10.1 | 46 05 09 | 151.76 | 67.78 | Sd | 2.20 | 77 | 0.72 | 79 | ![]() |
LSB | 0.00 | 0.09 |
U6894 | 11 52 47.3 | 54 56 08 | 139.52 | 60.63 | Scd | 1.67 | 269 | 0.84 | 90 | ![]() |
LSB | 0.00 | 0.06 |
N3985 | 11 54 06.4 | 48 36 48 | 145.94 | 66.27 | Sm | 1.40 | 70 | 0.37 | 53 | ![]() |
HSB | 0.05 | 0.11 |
N4013 | 11 55 56.8 | 44 13 31 | 151.86 | 70.09 | Sb | 4.87 | 245 | 0.76 | 88 | ![]() |
HSB | 0.00 | 0.07 |
U7089 | 12 03 25.4 | 43 25 18 | 149.90 | 71.52 | Sdm | 3.50 | 215 | 0.81 | 90 | ![]() |
LSB | 0.00 | 0.07 |
U7094 | 12 03 38.5 | 43 14 05 | 150.14 | 71.70 | Sdm | 1.60 | 39 | 0.64 | 72 | ![]() |
LSB | 0.00 | 0.06 |
N4117 | 12 05 14.2 | 43 24 17 | 149.07 | 71.72 | S0 | 1.53 | 21 | 0.56 | 67 | ![]() |
LSB | 0.00 | 0.06 |
N4138 | 12 06 58.6 | 43 57 49 | 147.29 | 71.40 | Sa | 2.43 | 151 | 0.37 | 53 | ![]() |
HSB | 0.00 | 0.06 |
N4218 | 12 13 17.4 | 48 24 36 | 138.88 | 67.88 | Sm | 1.17 | 316 | 0.40 | 55 | ![]() |
HSB | 0.00 | 0.07 |
N4220 | 12 13 42.8 | 48 09 41 | 138.94 | 68.13 | Sa | 3.63 | 140 | 0.69 | 76 | ![]() |
HSB | 0.00 | 0.08 |
Galaxies with confused HI data: |
|||||||||||||
1135+48 |
11 35 09.2 | 48 09 31 | 152.71 | 64.77 | Sm | 1.23 | 114 | 0.69 | 76 | ![]() |
LSB | 0.01 | 0.10 |
N3896 | 11 46 18.6 | 48 57 10 | 148.10 | 65.29 | Sm | 1.60 | 308 | 0.33 | 49 | ![]() |
LSB | 0.02 | 0.09 |
Not observed or too little HI content: |
|||||||||||||
N3870 |
11 43 17.5 | 50 28 40 | 147.02 | 63.75 | S0a | 1.13 | 17 | 0.31 | 47 | ![]() |
HSB | 0.00 | 0.07 |
N3990 | 11 55 00.3 | 55 44 13 | 138.25 | 60.04 | S0 | 1.47 | 40 | 0.50 | 62 | ![]() |
HSB | 0.00 | 0.07 |
N4026 | 11 56 50.7 | 51 14 24 | 141.94 | 64.20 | S0 | 4.37 | 177 | 0.74 | 80 | ![]() |
HSB | 0.04 | 0.10 |
N4111 | 12 04 31.0 | 43 20 40 | 149.53 | 71.69 | S0 | 4.47 | 150 | 0.78 | 84 | ![]() |
HSB | 0.00 | 0.06 |
U7129 | 12 06 23.6 | 42 01 08 | 151.00 | 72.99 | Sa | 1.27 | 72 | 0.31 | 47 | ![]() |
HSB | 0.00 | 0.06 |
N4143 | 12 07 04.6 | 42 48 44 | 149.18 | 72.40 | S0 | 2.60 | 143 | 0.46 | 59 | ![]() |
HSB | 0.00 | 0.06 |
N4346 | 12 21 01.2 | 47 16 15 | 136.57 | 69.39 | S0 | 3.47 | 98 | 0.67 | 75 | ![]() |
HSB | 0.00 | 0.06 |
Name |
![]() |
![]() |
![]() |
![]() |
WR,Ii | AiB | AiR | AiI |
![]() |
Mb,iB | Mb,iR | Mb,iI |
![]() |
Db,i25 |
|
mag | mag | mag | mag |
![]() |
mag | mag | mag | mag | mag | mag | mag | mag | (![]() |
(1) |
(2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) | (11) | (12) | (13) | (14) | (15) |
Galaxies with fully analyzed HI data: | ||||||||||||||
U6399 |
14.33 | 13.31 | 12.88 | 11.09 | 172 | 0.47 | 0.36 | 0.27 | 0.06 | -17.56 | -18.44 | -18.77 | -20.33 | 1.84 |
U6446 | 13.52 | 12.81 | 12.58 | 11.50 | 174 | 0.18 | 0.14 | 0.10 | 0.02 | -18.08 | -18.72 | -18.90 | -19.88 | 2.07 |
N3726 | 11.00 | 9.97 | 9.51 | 7.96 | 331 | 0.34 | 0.25 | 0.20 | 0.05 | -20.76 | -21.67 | -22.07 | -23.45 | 5.32 |
N3769 | 12.80 | 11.56 | 10.99 | 9.10 | 256 | 0.67 | 0.50 | 0.39 | 0.09 | -19.32 | -20.35 | -20.80 | -22.35 | 2.34 |
U6667 | 14.33 | 13.11 | 12.63 | 10.81 | 167 | 0.74 | 0.58 | 0.43 | 0.10 | -17.83 | -18.87 | -19.18 | -20.65 | 2.18 |
N3877 | 11.91 | 10.46 | 9.72 | 7.75 | 335 | 1.06 | 0.78 | 0.62 | 0.15 | -20.60 | -21.73 | -22.29 | -23.76 | 3.95 |
N3893 | 11.20 | 10.19 | 9.71 | 7.84 | 382 | 0.31 | 0.23 | 0.18 | 0.04 | -20.55 | -21.45 | -21.86 | -23.56 | 3.67 |
N3917 | 12.66 | 11.42 | 10.85 | 9.08 | 276 | 0.87 | 0.64 | 0.51 | 0.12 | -19.65 | -20.63 | -21.05 | -22.40 | 3.48 |
N3949 | 11.55 | 10.69 | 10.28 | 8.43 | 321 | 0.33 | 0.24 | 0.20 | 0.05 | -20.22 | -20.96 | -21.31 | -22.98 | 2.66 |
N3953 | 11.03 | 9.66 | 9.02 | 7.03 | 446 | 0.60 | 0.43 | 0.35 | 0.08 | -21.05 | -22.20 | -22.74 | -24.41 | 5.38 |
N3972 | 13.09 | 11.90 | 11.34 | 9.39 | 264 | 0.76 | 0.56 | 0.44 | 0.11 | -19.08 | -20.05 | -20.48 | -22.08 | 2.62 |
U6917 | 13.15 | 12.16 | 11.74 | 10.30 | 224 | 0.31 | 0.23 | 0.18 | 0.04 | -18.63 | -19.49 | -19.84 | -21.10 | 2.84 |
U6923 | 13.91 | 12.97 | 12.36 | 11.04 | 160 | 0.28 | 0.22 | 0.16 | 0.04 | -17.84 | -18.67 | -19.20 | -20.36 | 1.67 |
U6930i | 12.70 | 11.71 | 11.39 | 10.33 | 231 | 0.08 | 0.06 | 0.05 | 0.01 | -18.86 | -19.78 | -20.07 | -21.04 | 2.98 |
N3992 | 10.86 | 9.55 | 8.94 | 7.23 | 547 | 0.56 | 0.40 | 0.33 | 0.08 | -21.18 | -22.28 | -22.80 | -24.21 | 6.27 |
U6940f | 16.45 | 15.65 | 15.44 | 13.99 | 50 | 0.00 | 0.00 | 0.00 | 0.00 | -15.02 | -15.77 | -15.96 | -17.37 | 0.64 |
U6962i | 12.88 | 11.88 | 11.42 | 10.11 | 327 | 0.16 | 0.11 | 0.09 | 0.02 | -18.72 | -19.64 | -20.06 | -21.27 | 2.26 |
N4010 | 13.36 | 12.14 | 11.55 | 9.22 | 254 | 1.20 | 0.89 | 0.70 | 0.17 | -19.30 | -20.17 | -20.55 | -22.31 | 2.97 |
U6969 | 15.12 | 14.32 | 14.04 | 12.58 | 117 | 0.20 | 0.17 | 0.11 | 0.02 | -16.56 | -17.28 | -17.48 | -18.80 | 1.19 |
U6973 | 12.94 | 11.26 | 10.53 | 8.23 | 364 | 0.71 | 0.52 | 0.42 | 0.10 | -19.21 | -20.67 | -21.28 | -23.23 | 2.21 |
U6983 | 13.10 | 12.27 | 11.91 | 10.52 | 221 | 0.21 | 0.16 | 0.12 | 0.03 | -18.58 | -19.31 | -19.61 | -20.87 | 2.99 |
N4051 | 10.98 | 9.88 | 9.37 | 7.86 | 308 | 0.28 | 0.21 | 0.17 | 0.04 | -20.71 | -21.72 | -22.18 | -23.54 | 5.45 |
N4085 | 13.09 | 11.87 | 11.28 | 9.20 | 247 | 0.78 | 0.58 | 0.46 | 0.11 | -19.12 | -20.11 | -20.57 | -22.27 | 2.08 |
N4088 | 11.23 | 10.00 | 9.37 | 7.46 | 362 | 0.74 | 0.54 | 0.43 | 0.10 | -20.95 | -21.94 | -22.45 | -24.00 | 4.40 |
N4100 | 11.91 | 10.62 | 10.00 | 8.02 | 386 | 0.97 | 0.70 | 0.57 | 0.14 | -20.51 | -21.49 | -21.97 | -23.48 | 4.07 |
N4102 | 12.04 | 10.54 | 9.93 | 7.86 | 393 | 0.46 | 0.34 | 0.27 | 0.07 | -19.86 | -21.20 | -21.73 | -23.57 | 2.69 |
N4157 | 12.12 | 10.60 | 9.88 | 7.52 | 399 | 1.40 | 1.02 | 0.82 | 0.20 | -20.72 | -21.83 | -22.33 | -24.04 | 4.64 |
N4183 | 12.96 | 11.99 | 11.51 | 9.76 | 228 | 1.01 | 0.76 | 0.59 | 0.14 | -19.46 | -20.16 | -20.46 | -21.74 | 3.13 |
N4217 | 12.15 | 10.62 | 9.84 | 7.61 | 381 | 1.05 | 0.76 | 0.62 | 0.15 | -20.33 | -21.54 | -22.16 | -23.90 | 4.29 |
N4389 | 12.56 | 11.33 | 10.87 | 9.12 | 212 | 0.20 | 0.15 | 0.12 | 0.03 | -19.05 | -20.21 | -20.63 | -22.27 | 2.31 |
Galaxies with partially analyzed HI data: |
||||||||||||||
N3718 |
11.28 | 9.95 | 9.29 | 7.47 | 476 | 0.77 | 0.55 | 0.45 | 0.11 | -20.90 | -21.99 | -22.54 | -24.00 | 6.30 |
N3729 | 12.31 | 10.94 | 10.30 | 8.60 | 296 | 0.25 | 0.18 | 0.15 | 0.03 | -19.34 | -20.62 | -21.22 | -22.78 | 2.60 |
U6773 | 14.42 | 13.61 | 13.15 | 11.23 | 112 | 0.09 | 0.08 | 0.05 | 0.01 | -17.09 | -17.87 | -18.28 | -20.14 | 1.35 |
U6818 | 14.43 | 13.62 | 13.15 | 11.70 | 151 | 0.39 | 0.31 | 0.22 | 0.05 | -17.40 | -18.10 | -18.46 | -19.71 | 1.69 |
U6894 | 15.27 | 14.31 | 14.00 | 12.40 | 124 | 0.37 | 0.31 | 0.21 | 0.05 | -16.51 | -17.39 | -17.59 | -19.01 | 1.13 |
N3985 | 13.25 | 12.26 | 11.81 | 10.19 | 180 | 0.18 | 0.14 | 0.10 | 0.02 | -18.39 | -19.30 | -19.69 | -21.19 | 1.29 |
N4013 | 12.44 | 10.79 | 9.95 | 7.68 | 377 | 1.10 | 0.80 | 0.64 | 0.15 | -20.08 | -21.40 | -22.07 | -23.83 | 3.61 |
U7089 | 13.73 | 12.77 | 12.36 | 11.11 | 138 | 0.42 | 0.34 | 0.24 | 0.05 | -18.11 | -18.96 | -19.26 | -20.30 | 2.46 |
U7094 | 14.74 | 13.70 | 13.22 | 11.58 | 76 | 0.00 | 0.00 | 0.00 | 0.00 | -16.67 | -17.69 | -18.16 | -19.78 | 1.29 |
N4117 | 14.05 | 12.47 | 11.81 | 9.98 | 285 | 0.00 | 0.00 | 0.00 | 0.00 | -17.36 | -18.92 | -19.57 | -21.38 | 1.29 |
N4138 | 12.27 | 10.72 | 10.09 | 8.19 | 374 | 0.36 | 0.26 | 0.21 | 0.05 | -19.50 | -20.93 | -21.50 | -23.22 | 2.22 |
N4218 | 13.69 | 12.83 | 12.41 | 10.83 | 150 | 0.15 | 0.12 | 0.09 | 0.02 | -17.88 | -18.68 | -19.06 | -20.55 | 1.06 |
N4220 | 12.34 | 10.79 | 10.03 | 8.36 | 399 | 0.94 | 0.68 | 0.55 | 0.13 | -20.03 | -21.29 | -21.91 | -23.13 | 2.85 |
Galaxies with confused HI data: |
||||||||||||||
1135+48 |
14.95 | 14.05 | 13.61 | 11.98 | 111 | 0.17 | 0.15 | 0.09 | 0.02 | -16.67 | -17.51 | -17.88 | -19.40 | 0.97 |
N3896 | 13.75 | 12.96 | 12.47 | 11.35 | 83 | 0.00 | 0.00 | 0.00 | 0.00 | -17.69 | -18.45 | -18.92 | -20.01 | 1.49 |
Not observed or too little HI content: |
||||||||||||||
N3870 |
13.67 | 12.71 | 12.16 | 10.73 | 127 | 0.08 | 0.06 | 0.04 | 0.01 | -17.83 | -18.74 | -19.26 | -20.64 | 1.06 |
N3990 | 13.53 | 12.08 | 11.36 | 9.54 | ... | 0.00 | 0.00 | 0.00 | 0.00 | -17.89 | -19.31 | -20.02 | -21.82 | 1.28 |
N4026 | 11.71 | 10.25 | 9.57 | 7.65 | ... | 0.00 | 0.00 | 0.00 | 0.00 | -19.74 | -21.16 | -21.82 | -23.71 | 3.32 |
N4111 | 11.40 | 9.95 | 9.25 | 7.60 | ... | 0.00 | 0.00 | 0.00 | 0.00 | -20.01 | -21.44 | -22.13 | -23.76 | 3.24 |
U7129 | 14.13 | 12.80 | 12.19 | ... | ... | 0.08 | 0.06 | 0.04 | 0.01 | -17.36 | -18.65 | -19.23 | ... | 1.19 |
N4143 | 12.06 | 10.55 | 9.84 | 7.86 | ... | 0.00 | 0.00 | 0.00 | 0.00 | -19.35 | -20.83 | -21.54 | -23.50 | 2.30 |
N4346 | 12.14 | 10.69 | 9.96 | 8.21 | ... | 0.00 | 0.00 | 0.00 | 0.00 | -19.27 | -20.70 | -21.42 | -23.15 | 2.75 |
|
This study | Literature | ||||||||||
Name | W20 | ![]() |
Res. |
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W20 | ![]() |
Res. |
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Ref. | |
- - - km s-1 - - - | - Jy km s-1 - | - - - km s-1 - - - | - Jy km s-1 - | |||||||||
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) | (11) | (12) | |
U6399 |
188.1 | 1.4 | 8.3 | 10.5 | 0.3 | 178 | 20 | 22 | 10.1 | 1.9 | 1 | |
U6446 | 154.1 | 1.0 | 5.0 | 40.6 | 0.5 | 162 | 10 | 22 | 45.9 | 4.1 | 1 | |
N3718(c) | 492.8 | 1.0 | 33.2 | 140.9 | 0.9 | 480 | 10 | 5.5 | 84.9 | 26.4 | 1 | |
508m | .. | 33 | 120 | ... | 8 |
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||||||
N3726 | 286.5 | 1.6 | 5.0 | 89.8 | 0.8 | 290 | 10 | 5.5 | 83.9 | 10.8 | 1 | |
N3729
![]() |
270.8 | 1.5 | 33.2 | 5.5 | 0.3 | ... | .. | .. | ... | ... | .. | |
279m | .. | 33 | 25? | ... | 8 |
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||||||
N3769i | 265.3 | 6.7 | 8.3 | 62.3 | 0.6 | 276 | 20 | 7.4 | 44.1 | 4.2 | 2 | |
U6667 | 187.5 | 1.4 | 5.0 | 11.0 | 0.4 | 210 | 20 | 22 | 11.6 | 2.2 | 1 | |
N3877 | 373.4 | 5.0 | 33.2 | 19.5 | 0.6 | 352 | 10 | 22 | 24.8 | 5.6 | 1 | |
U6773 | 110.4 | 2.3 | 8.3 | 5.6 | 0.4 | 118 | 8 | 22 | 5.6 | 0.7 | 6 | |
N3893(c) | 310.9 | 1.0 | 5.0 | 69.9 | 0.5 | 313 | 8 | 22 | 85.3 | 5.1 | 1 | |
N3917 | 294.5 | 1.9 | 8.3 | 24.9 | 0.6 | 284 | 10 | 22 | 21.9 | 4.7 | 1 | |
U6818 | 166.9 | 2.3 | 8.3 | 13.9 | 0.2 | 168 | 15 | 22 | 14.8 | 2.1 | 1 | |
N3949 | 286.5 | 1.4 | 8.3 | 44.8 | 0.4 | 289 | 10 | 22 | 42.7 | 5.4 | 1 | |
N3953l | 441.9 | 2.4 | 33.1 | 39.3 | 0.8 | 423 | 10 | 22 | 41.0 | 3.9 | 1 | |
U6894 | 141.8 | 1.1 | 8.3 | 5.8 | 0.2 | 159 | 20 | 7.4 | 5.1 | 1.7 | 2 | |
N3972 | 281.2 | 1.4 | 8.3 | 16.6 | 0.4 | 270 | 15 | 22 | 14.0 | 2.6 | 1 | |
U6917 | 208.9 | 3.2 | 8.3 | 26.2 | 0.3 | 211 | 10 | 22 | 31.5 | 4.1 | 1 | |
N3985 | 160.2 | 3.7 | 8.3 | 15.7 | 0.6 | 168 | .. | 22 | 14.1 | 0.9 | 5 | |
U6923 | 166.8 | 2.4 | 10.0 | 10.7 | 0.6 | 175 | 15 | 22 | 8.2 | 2.9 | 1 | |
189m | 15 | 41.4 | 15.6 | ... | 12 |
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||||||
U6930 | 136.5 | 0.5 | 8.3 | 42.7 | 0.3 | 145 | 8 | 22 | 38.2 | 3.5 | 1 | |
N3992l | 478.5 | 1.4 | 10.0 | 74.6 | 1.5 | 480 | 10 | 22 | 81.2 | 5.3 | 1 | |
507m | 15 | 41.4 | 79.9 | ... | 12 |
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||||||
U6940 | 59.3 | 3.8 | 10.0 | 2.1 | 0.3 | 226 | .. | 22 | 7.0 | 1.0 | 3 | |
121m | 15 | 41.4 | 2.7 | ... | 12 |
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||||||
N4013 | 425.0 | 0.9 | 33.0 | 41.5 | 0.2 | 403 | 10 | 22 | 33.8 | 3.7 | 1 | |
U6962(c) | 220.3 | 6.6 | 8.3 | 10.0 | 0.3 | ... | .. | 22 | 21.6 | 4.4 | 1 | |
235 | .. | 33 | 9.2 | 1.0 | 4 |
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||||||
N4010 | 277.7 | 1.0 | 8.3 | 38.2 | 0.3 | 281 | 10 | 22 | 38.1 | 3.4 | 1 | |
U6969c | 132.1 | 6.4 | 10.0 | 6.1 | 0.5 | 146 | .. | 13.2 | 6.0 | 1.4 | 3 | |
159m | 15 | 41.4 | 6.9 | ... | 12 |
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||||||
U6973
![]() |
367.8 | 1.8 | 8.3 | 22.9 | 0.2 | ... | .. | .. | ... | ... | .. | |
408 | .. | 33 | 18.3 | 1.2 | 4 |
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||||||
U6983 | 188.4 | 1.3 | 5.0 | 38.5 | 0.6 | 205 | 10 | 22 | 36.2 | 4.4 | 1 | |
N4051l | 255.4 | 1.8 | 5.0 | 35.6 | 0.8 | 274 | 15 | 22 | 43.4 | 3.3 | 1 | |
N4085c | 277.4 | 6.6 | 19.8 | 14.6 | 0.9 | 299 | 20 | 7.4 | 23.3 | 2.5 | 2 | |
311m | .. | 33 | 24! | ... | 13 |
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||||||
N4088(c) | 371.4 | 1.7 | 19.8 | 102.9 | 1.1 | 381 | 8 | 22 | 109.2 | 6.4 | 1 | |
378m | .. | 33 | 128! | ... | 13 |
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||||||
U7089(c) | 156.7 | 1.7 | 10.0 | 17.0 | 0.6 | 162 | 10 | 22 | 17.8 | 2.2 | 1 | |
176 | .. | 33.4 | 18.9 | ... | 11 |
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||||||
N4100 | 401.8 | 2.0 | 19.9 | 41.6 | 0.7 | 420 | 20 | 22 | 54.0 | 7.3 | 1 | |
U7094c | 83.7 | 1.7 | 10.0 | 2.9 | 0.2 | 112 | 8 | 22 | 6.0 | 0.6 | 6 | |
153? | .. | 33.4 | 2.5 | ... | 11 |
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||||||
N4102 | 349.8 | 2.0 | 8.3 | 8.0 | 0.2 | 327 | 20 | 7.4 | 10.3 | 2.1 | 2 | |
N4117
![]() |
289.4 | 7.5 | 10.0 | 6.9 | 1.1 | ... | .. | .. | ... | ... | .. | |
314 | .. | 33.4 | 5.3 | ... | 11 |
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||||||
N4138 | 331.6 | 4.5 | 19.9 | 19.2 | 0.7 | 354m | 30 | 6.8 | 16 | ... | 14 | |
340 | 5 | 5.2 | 20.6 | 0.3 | 7 |
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||||||
N4157(c),l | 427.6 | 2.2 | 19.9 | 107.4 | 1.6 | 436 | 10 | 22 | 123.9 | 9.5 | 1 | |
N4183 | 249.6 | 1.2 | 8.3 | 48.9 | 0.7 | 258 | 10 | 22 | 49.6 | 5.3 | 1 | |
N4218 | 138.0 | 5.0 | 8.3 | 7.8 | 0.2 | 160 | 20 | 13 | 5.7 | 0.9 | 9 | |
N4217 | 428.1 | 5.1 | 33.2 | 33.8 | 0.7 | 426 | 20 | 22 | 51.8 | 7.2 | 1 | |
N4220 | 438.1 | 1.3 | 33.1 | 4.4 | 0.3 | 382m | .. | 11 | 3.3 | ... | 10 | |
N4389 | 184.0 | 1.5 | 8.3 | 7.6 | 0.2 | 174 | 20 | 7.4 | 7.6 | 0.8 | 2 |
(c): |
the authors suggest possible confusion with a dwarf companion. | |
c: | flagged by the authors as confused with near companion. | |
l: | large correction factor (>1.20) applied for primary beam flux attenuation. | |
i: | flagged by the authors as possibly interacting. | |
![]() |
no useful single dish profile available due to obvious confusion. | |
m: | line width directly measured from the published HI profile. | |
!: | the integrated flux as quoted by the author is a factor 2 larger than is quoted by | |
any other source. Therefore, half the integrated flux was adopted from this source. | ||
![]() |
synthesis observation with the WSRT. | |
![]() |
synthesis observation with the VLA. | |
References: | 1: Fisher & Tully (1981) | 8: Schwarz (1985) |
2: Appleton & Davies (1982) | 9: Thuan & Martin (1981) | |
3: Richter & Huchtmeier (1991) | 10: Magri (1994) | |
4: Oosterloo & Shostak (1993) | 11: Van der Burg (1987) | |
5: Huchtmeier & Richter (1986) | 12: Gottesman et al. (1984) | |
6: Schneider et al. (1992) | 13: Van Moorsel (1983) | |
7: Jore et al. (1996) | 14: Grewing & Mebold (1975) |
The raw UV-data were calibrated, interactively flagged and Fast
Fourier Transformed (FFT) using the NEWSTAR software developed at the
NFRA in Dwingeloo. The UV points were weighted according
to the local density of points in the UV plane and a Gaussian baseline
taper was applied with a FWHM of 2293 (m) which attenuates the longest
baseline by 50%. To deal with the frequency dependent antenna pattern,
five antenna patterns were calculated for each data cube at a regular
frequency separation thoughout the bandpass. Pixel sizes of 5 arcsec in
RA and
arcsec in declination ensure an
adequate sampling of the synthesized beam,
.
After the FFT, the datacubes and antenna patterns were further processed
using the Groningen Image Processing SYstem (GIPSY). Several channels
at the low and high velocity end of the bandpass were discarded because
of their higher noise. As a result, there are 110 or 53 usable channels
for a bandpass of 2.5 or 5 MHz respectively, except for the N3992 and
N4111 fields which had 110 channels across a 5 MHz bandpass. All
datacubes were smoothed to lower angular resolutions of
and
.
This facilitates the
detection of extended low level HI emission and the identification of
the "continuum'' channels which are free from line emission.
The channels free from HI emission were averaged and the resulting
continuum map was subtracted from all channels in the data cube. The
residuals of the frequency dependent grating rings were only a minor
fraction of the noise in the channels containing the line emission. The
dirty continuum maps were cleaned (Högbom 1974) down to
0.3.
The clean-components were restored with a Gaussian beam of
similar FWHM as the synthesized beam. When radio continuum emission
from a galaxy was detected, its continuum flux was determined from the
cleaned continuum map. In cases of no detection, an upper limit for
extended emission was derived by calculating the rms scatter in the flux
values obtained by integrating the noise in each of fifteen elliptical
areas enclosed by the 25th mag blue isophote and
positioned at various emission-free regions in the map.
At all three spatial resolutions, the regions of HI emission were
defined by the areas enclosed by the 2
contours in the "dirty''
60
resolution maps. Grating rings and noise peaks
above this level were removed manually. The selected regions were
enlarged by moving their boundaries 1 armin outwards to account for
possible emission in the sidelobes. The resulting masks vary from
channel to channel in shape, size and position due to the rotation of
the HI disk. These masks defined the regions that were cleaned down to
0.3
at all three spatial resolutions.
The clean-components were restored with a Gaussian beam of similar FWHMas the synthesized beam. The global HI profiles were derived by determining the primary beam corrected flux in each cleaned region. Since the size and shape of the clean masks vary as a function of velocity, the uncertainty in the flux densities at each velocity in the global HI profile varies as well. The noise on the global HI profile was determined by projecting each clean mask at nine different line-free positions in a channel map and integrating over each of them.
For further analysis, each profile was divided up in three equal
velocity bins in which the peak fluxes
,
and
were determined for the low, middle
and high velocity bin respectively. These three peak fluxes were then
used to classify a global profile shape according to:
Double peaked:
Gaussian:
Distorted:
or
Boxy:
.
In case of a double peaked profile, the peak fluxes on both
sides were considered separately when calculating the 20% and 50%
levels. In all other cases, the overal peak flux was used. The four
velocities
,
,
and
corresponding to these 20% and 50% levels were
determined by linear interpolation between the data points, going from
the center outward. In the few cases of non-monotonically decreasing
edges, this procedure tends to slightly underestimate the widths. The
widths are calculated according to
The most widely used method to correct for broadening of the global HI
profiles due to a finite instrumental velocity resolution was provided
by Bottinelli et al. (1990). For the widths at the 20%
and 50% levels of the peak flux they advocate the following linear
relations:
However, the correction method applied here deviates from Bottinelli
et al.'s method and is based on more analytic considerations. It is easy to
imagine that both edges of an intrinsic global profile, when chopped off
at their peaks and glued together, approximate a Gaussian with
dispersion .
The width at the 20% level of this "true''
Gaussian is then given by
level |
![]() |
||||
- - - - - R (km s-1) - - - - - | |||||
5.0 | 8.3 | 16.5 | 19.9 | 33.1 | |
20% | 2.0 | 2.4 | 1.2 | 0.2 | -7.8 |
50% | 0.2 | -0.3 | -3.1 | -4.7 | -12.8 |
The larger differences occur for the poorest resolutions at which only the broadest profiles were observed. Consequently, the differences are a negligible fraction of the line widths.
Figure 1 shows the comparison of the widths and integrated fluxes
derived from the new WSRT global profiles and those from the literature.
There are no significant systematic differences. The unweighted average
difference in widths is
with a rms scatter
of 14 km s-1. The unweighted average difference in integrated
flux is
percent with a rms scatter of 25 percent. It can
therefore be concluded that on average the WSRT results are in excellent
agreement with the results from single dish observations.
![]() |
Figure 1: A comparison of the present WSRT results with pre-existing single dish and synthesis data from the literature |
Open with DEXTER |
As a next step, the total integrated HI maps were constructed from the
cleaned datacubes. The clean-masks were used to define the
regions with HI emission. Outside these regions, the pixels were set to
zero and all the channels containing a non-zero area were added to build
up the integrated column density map. This was then corrected for
attenuation by the primary beam. Although the advantage of this
procedure is a higher signal-to-noise ratio at a certain pixel in the HI
map, the disadvantage is that the noise is no longer uniform across the
map. As a result, the 3-contour level in an integrated HI map is
not defined. Signal-to-noise maps have been made, however, using the
prescription outlined in Appendix A and the average pixel value of all
pixels with
was determined. This average value
was adopted as the "3
'' level for the column density.
The integrated column density maps were used to derive the radial HI surface density profiles by azimuthally averaging in concentric ellipses. The orientations and widths of the ellipses were the same as those of the projected tilted rings fitted to the HI velocity field (see Sect. 3.6.1). In the case of a warp with overlapping ellipses, the flux in the overlapping regions was proportionally assigned to each ellipse. The azimuthal averaging was done separately for the receding and approaching halves of each tilted ring to reveal possible asymmetries. Pixels in the HI map without any measured signal were set to zero. Finally, the entire radial profile was scaled by the total HI mass as derived from the global HI profile. No attempt was made to correct the profiles for the effect of beam smearing.
This method for extracting the surface density profiles from integrated HI maps breaks down for nearly edge-on systems; the highly inclined annuli with large major axis diameters could still pick up some flux along the minor axis due to beam smearing. In such cases, Lucy's (1974) iterative deprojection scheme as adapted and developed by Warmels (1988b) might be preferable.
Due to the complex noise structure of the integrated HI map, no attempt was made to estimate the errors on the radial HI surface density profiles.
The HI data cubes were smoothed to velocity resolution of
in order to obtain a good spectral
signal-to-noise ratio.
HI velocity fields were then constructed by fitting single Gaussians to
the velocity profiles at each pixel. Initial estimates for the fits were
given by the various moments of the profiles determined over the
velocity range covered by the masks. Only those fits were accepted for
which 1) the central velocity of the fitted Gaussian lies inside the
masked volume, 2) the amplitude is larger than five times the rms noise
in the profile and 3) the uncertainty in the central velocity is smaller
than
the velocity resolution.
Due to projection effects and beam smearing, the velocity profiles in highly inclined systems and in the central regions of galaxies may deviate strongly from a Gaussian shape. The exact shape depends on the spatial and kinematic distribution of the gas within a synthesized beam. Fitting single Gaussians to these usually skewed profiles results in an underestimate of the rotational velocity at that position. As a consequence, the gradients in the velocity field become shallower. There are several methods to correct for the effects of beam smearing. In the present cases, however, the signal-to-noise was in general too low to allow a useful application of these methods, and, since only a small number of systems were recognized as seriously affected, the HI velocity fields were not corrected for the effects of beam smearing.
The rotation curves were derived in two ways; 1) by fitting tilted-rings to the velocity fields (Begeman 1987) and 2) by estimating the rotational velocities by eye from the position-velocity diagrams.
The determination of the rotation curves from the velocity fields was
done in three steps by fitting tilted rings to the velocity field (see
Begeman 1987, 1989). The widths of the rings
were set at
of the width of the synthesized beam (i.e.
,
or
).
First, the systemic velocity and the dynamical center were determined. In this first step the inclination and position angles were the same for each ring and kept fixed at the values derived from the optical images. The systemic velocity, center and rotational velocity were fitted for each ring. All the points along the tilted ring were considered and weighted uniformly. In general, no significant trend as a function of radius could be detected for the systemic velocity and center. The adopted values were calculated as the average of all rings.
Second, the systemic velocity and center of rotation were kept fixed for
each ring while the position angle, inclination and rotational velocity
were fitted. All the points along the tilted ring were considered but
weighted with cos()
where
is the angle in the plane of
the galaxy measured from the receding side. Hence, points along the
minor axis have zero weight. While the position angle can be determined
accurately, the inclination and rotational velocity are rather strongly
correlated for inclinations below 60 degrees and above 80 degrees
(Begeman 1989). As a result, the fitted inclinations can
vary by a large amount from one ring to another. However, a possible
trend in the inclination with radius due to a central bar or a warp can
be detected. A change in inclination angle often goes together with a
change in the more accurately determined position angle.
Third, the rotational velocity was fitted again for each ring while
keeping the systemic velocity, center of rotation, inclination and
position angle fixed. Again, all the points along the tilted ring were
considered but weighted with cos(). The fixed values for the
inclination and position angles were determined in the second step by
averaging the solutions over all the rings or fixing a clear trend. For
nearly edge-on galaxies, the inclinations determined in the second step
were often overruled by higher values based on the clear presence of a
dust lane (e.g. N4010, N4157, N4217) or the very thin distribution of
gas in the column density maps (e.g. U6667). However, uncertainty in the
inclinations of nearly edge-on systems does not significantly influence
the amplitude of the rotational velocity.
The results of this 3-step procedure were used to construct a model velocity field. This model was subtracted from the actual observed velocity field to yield a map of the residual velocities. In some cases (e.g. N3769, N4051, N4088) this residual map shows significant systematic residuals, indicative of non-circular motion or a bad model fit due to a noisy observed velocity field. As a further check, the derived rotation curve is projected onto the position-velocity maps along the major and minor axis.
The errors on the inclination and position angles and the rotational velocity are formal errors. They do not include possible systematic uncertainties due to, for instance, the beam smearing.
It has already been remarked (see Sect. 3.5) that beam smearing affects the determination of the velocity fields, especially in the central regions of galaxies and in highly inclined disks. As a consequence, the rotation curves derived from such velocity fields are underestimated as one can see from their projection on the XV-maps. In order to overcome this problem, the rotation curves were derived directly from the major axis XV-maps in a manner similar to that used for edge-on systems (cf. Sancisi & Allen 1979). This was done by two independent human neural networks trained to estimate the maximum rotational velocity from the asymmetric velocity profiles, taking into account the instrumental band- and beam-widths and the random gas motions. This was done for both the receding and approaching side of a galaxy. The rotation curves were then deprojected (also accounting for possible warps) by using the same position and inclination angles as fixed in the third step described in the previous section. In general, the average rotation curves derived from the XV-diagrams are in reasonable agreement with those obtained by the tilted ring fits. As expected, significant differences can only be noted for galaxies which are highly inclined or have a steeply rising rotation curve.
From the XV-diagrams it is clear that many galaxies have kinematic asymmetries in the sense that the rotation curve often rises more steeply on one side of a galaxy than on the other side (e.g. N3877, N3949). The rotation curves as derived from the velocity fields and XV-diagrams are tabulated in Table 4 for the approaching and receding parts separately. The adopted changes in inclination and position angles of N3718 and N4138 are motivated in the notes on the atlas pages of these galaxies. The uncertainties quoted in Table 4 are not 1-sigma Gaussian errors but rather reflect fiducial velocity ranges, based on the position-velocity diagrams.
Rad. |
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i | PA | ||
(
![]() |
- - - km s-1 - - - | - - - km s-1 - - - | km s-1 | (![]() |
(![]() |
||||
U6399 | |||||||||
10 | 25 | 12 | 7 | 25 | 10 | 7 | 25 | 75 | 141 |
20 | 44 | 10 | 7 | 49 | 7 | 7 | 46 | 75 | 141 |
30 | 61 | 12 | 7 | 61 | 7 | 5 | 61 | 75 | 141 |
40 | 70 | 7 | 5 | 69 | 5 | 5 | 70 | 75 | 141 |
50 | 77 | 7 | 5 | 78 | 3 | 5 | 78 | 75 | 141 |
60 | 82 | 10 | 5 | 84 | 5 | 5 | 83 | 75 | 141 |
70 | 84 | 5 | 5 | - | - | - | 84 | 75 | 141 |
80 | 86 | 5 | 5 | - | - | - | 86 | 75 | 141 |
90 | 88 | 5 | 5 | - | - | - | 88 | 75 | 141 |
U6446 | |||||||||
10 | 39 | 8 | 8 | 23 | 10 | 10 | 31 | 51 | 188 |
20 | 49 | 8 | 8 | 61 | 8 | 10 | 55 | 51 | 188 |
30 | 57 | 5 | 5 | 65 | 5 | 8 | 61 | 51 | 188 |
40 | 63 | 5 | 5 | 65 | 5 | 8 | 64 | 51 | 188 |
50 | 69 | 8 | 5 | 65 | 5 | 5 | 67 | 51 | 188 |
60 | 71 | 5 | 5 | 70 | 5 | 5 | 70 | 51 | 188 |
70 | 75 | 5 | 5 | 72 | 5 | 5 | 74 | 51 | 188 |
80 | 79 | 8 | 5 | 77 | 5 | 5 | 78 | 51 | 188 |
90 | 81 | 8 | 5 | 81 | 5 | 5 | 81 | 51 | 188 |
100 | 81 | 5 | 5 | 80 | 5 | 5 | 81 | 51 | 188 |
110 | 81 | 5 | 5 | 82 | 5 | 5 | 81 | 51 | 189 |
120 | 82 | 8 | 5 | 83 | 5 | 8 | 82 | 51 | 191 |
131 | 82 | 8 | 5 | 84 | 5 | 8 | 83 | 51 | 193 |
142 | 83 | 8 | 8 | 86 | 8 | 8 | 85 | 51 | 195 |
153 | 83 | 8 | 8 | 86 | 8 | 8 | 84 | 51 | 197 |
164 | 82 | 11 | 11 | 85 | 8 | 11 | 83 | 51 | 199 |
176 | 80 | 11 | 11 | - | - | - | 80 | 51 | 201 |
N3726 | |||||||||
40 | 112 | 10 | 7 | 92 | 12 | 10 | 102 | 53 | 195 |
60 | 131 | 7 | 7 | 119 | 10 | 10 | 125 | 53 | 195 |
80 | 144 | 5 | 5 | 146 | 7 | 10 | 145 | 53 | 195 |
100 | 156 | 5 | 5 | 172 | 5 | 7 | 164 | 53 | 195 |
120 | 154 | 7 | 7 | 171 | 5 | 7 | 162 | 53 | 195 |
140 | 155 | 7 | 5 | 166 | 7 | 7 | 160 | 53 | 195 |
160 | 152 | 7 | 7 | 159 | 5 | 7 | 156 | 53 | 195 |
183 | 145 | 10 | 7 | 148 | 5 | 5 | 147 | 57 | 188 |
256 | 157 | 8 | 8 | 159 | 6 | 6 | 158 | 72 | 180 |
316 | 169 | 9 | 12 | - | - | - | 169 | 75 | 179 |
344 | 169 | 9 | 12 | - | - | - | 169 | 75 | 179 |
373 | 167 | 15 | 15 | - | - | - | 167 | 75 | 179 |
N3769 | |||||||||
20 | 89 | 13 | 10 | 86 | 20 | 10 | 88 | 70 | 149 |
40 | 103 | 10 | 8 | 109 | 13 | 10 | 106 | 70 | 149 |
60 | 112 | 8 | 8 | 119 | 8 | 8 | 116 | 70 | 149 |
80 | 120 | 8 | 8 | 130 | 8 | 10 | 125 | 70 | 149 |
100 | 123 | 5 | 8 | 129 | 5 | 8 | 126 | 70 | 149 |
120 | 124 | 5 | 8 | 122 | 5 | 8 | 123 | 70 | 150 |
141 | 120 | 5 | 5 | 115 | 8 | 8 | 118 | 70 | 152 |
166 | 120 | 8 | 10 | 110 | 8 | 10 | 115 | 70 | 155 |
196 | 122 | 14 | 17 | - | - | - | 122 | 70 | 158 |
364 | 121 | 10 | 10 | - | - | - | 121 | 70 | 167 |
396 | 118 | 10 | 10 | - | - | - | 118 | 70 | 167 |
426 | 113 | 11 | 11 | - | - | - | 113 | 70 | 168 |
U6667 | |||||||||
10 | 27 | 5 | 5 | 27 | 7 | 7 | 27 | 89 | 89 |
20 | 43 | 2 | 2 | 47 | 5 | 5 | 45 | 89 | 89 |
30 | 55 | 5 | 5 | 59 | 7 | 5 | 57 | 89 | 89 |
40 | 64 | 2 | 5 | 74 | 5 | 5 | 69 | 89 | 89 |
Rad. |
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i | PA | ||
(
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- - - km s-1 - - - | - - - km s-1 - - - | km s-1 | (![]() |
(![]() |
||||
U6667 (cont.) |
|||||||||
50 | 73 | 5 | 5 | 82 | 5 | 5 | 77 | 89 | 89 |
60 | 78 | 5 | 5 | 84 | 5 | 7 | 81 | 89 | 89 |
70 | 82 | 2 | 5 | 87 | 5 | 5 | 84 | 89 | 89 |
80 | 83 | 2 | 5 | 87 | 5 | 5 | 85 | 89 | 89 |
90 | 83 | 5 | 5 | 89 | 5 | 5 | 86 | 89 | 89 |
N3877 | |||||||||
10 | 35 | 10 | 10 | 40 | 15 | 15 | 38 | 76 | 37 |
20 | 81 | 10 | 10 | 80 | 15 | 15 | 80 | 76 | 37 |
30 | 129 | 10 | 10 | 113 | 15 | 12 | 121 | 76 | 37 |
40 | 150 | 8 | 8 | 134 | 12 | 12 | 142 | 76 | 37 |
50 | 157 | 8 | 8 | 149 | 10 | 10 | 153 | 76 | 37 |
60 | 161 | 8 | 8 | 159 | 8 | 8 | 160 | 76 | 37 |
70 | 163 | 8 | 8 | 163 | 8 | 8 | 162 | 76 | 37 |
80 | 164 | 8 | 8 | 171 | 5 | 5 | 167 | 76 | 37 |
90 | 163 | 8 | 8 | 174 | 8 | 8 | 169 | 76 | 37 |
100 | 164 | 8 | 8 | 177 | 8 | 5 | 171 | 76 | 37 |
110 | 165 | 8 | 8 | 176 | 8 | 5 | 171 | 76 | 37 |
120 | 165 | 8 | 8 | 174 | 10 | 8 | 170 | 76 | 37 |
130 | 166 | 10 | 10 | 171 | 10 | 10 | 169 | 76 | 37 |
N3893 | |||||||||
20 | 140 | 10 | 10 | 150 | 10 | 10 | 145 | 49 | 345 |
40 | 175 | 10 | 10 | 173 | 10 | 10 | 174 | 49 | 345 |
60 | 191 | 10 | 10 | 197 | 10 | 7 | 194 | 49 | 345 |
80 | 192 | 7 | 7 | 189 | 10 | 7 | 191 | 49 | 346 |
101 | 192 | 10 | 8 | 181 | 8 | 8 | 186 | 47 | 351 |
125 | 194 | 8 | 11 | 182 | 8 | 11 | 188 | 45 | 362 |
151 | 190 | 10 | 13 | 184 | 10 | 16 | 187 | 43 | 371 |
176 | 179 | 11 | 15 | - | - | - | 179 | 41 | 377 |
198 | 161 | 15 | 12 | 190 | 19 | 19 | 176 | 39 | 379 |
218 | 153 | 12 | 12 | 181 | 24 | 24 | 167 | 37 | 380 |
233 | 148 | 21 | 17 | - | - | - | 148 | 36 | 381 |
N3917 | |||||||||
10 | 21 | 5 | 5 | 28 | 7 | 5 | 24 | 80 | 257 |
20 | 45 | 5 | 5 | 54 | 7 | 5 | 50 | 80 | 257 |
30 | 69 | 7 | 7 | 78 | 7 | 7 | 74 | 80 | 257 |
40 | 99 | 7 | 5 | 103 | 5 | 7 | 101 | 80 | 257 |
50 | 102 | 5 | 5 | 113 | 5 | 5 | 107 | 80 | 257 |
60 | 108 | 5 | 5 | 122 | 5 | 5 | 115 | 80 | 257 |
70 | 118 | 5 | 5 | 128 | 5 | 7 | 123 | 80 | 257 |
80 | 127 | 5 | 5 | 134 | 5 | 7 | 130 | 80 | 257 |
90 | 133 | 5 | 5 | 134 | 5 | 5 | 134 | 79 | 257 |
100 | 137 | 7 | 5 | 136 | 5 | 5 | 136 | 78 | 257 |
110 | 137 | 7 | 5 | 136 | 5 | 5 | 137 | 77 | 257 |
120 | 137 | 5 | 5 | 136 | 5 | 5 | 136 | 77 | 257 |
130 | 137 | 5 | 5 | 137 | 5 | 5 | 137 | 76 | 257 |
140 | 137 | 5 | 5 | 138 | 5 | 5 | 137 | 75 | 257 |
150 | 137 | 5 | 5 | - | - | - | 137 | 75 | 257 |
160 | 138 | 5 | 5 | - | - | - | 138 | 74 | 257 |
170 | 137 | 8 | 8 | - | - | - | 137 | 73 | 257 |
N3949 | |||||||||
10 | 58 | 10 | 10 | 79 | 14 | 14 | 68 | 55 | 298 |
20 | 106 | 10 | 7 | 141 | 7 | 7 | 123 | 55 | 298 |
30 | 138 | 7 | 10 | 152 | 7 | 7 | 145 | 55 | 298 |
40 | 150 | 5 | 7 | 155 | 10 | 12 | 152 | 55 | 298 |
50 | 156 | 7 | 7 | 159 | 7 | 14 | 157 | 55 | 297 |
60 | 161 | 5 | 5 | 161 | 10 | 24 | 161 | 55 | 295 |
70 | 165 | 7 | 7 | 165 | 7 | 34 | 165 | 55 | 294 |
81 | - | - | - | 169 | 7 | 44 | 169 | 55 | 293 |
Rad. |
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i | PA | ||
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- - - km s-1 - - - | - - - km s-1 - - - | km s-1 | (![]() |
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||||
N3953 | |||||||||
40 | 178 | 7 | 10 | 184 | 15 | 10 | 181 | 62 | 13 |
60 | 200 | 10 | 10 | 207 | 10 | 7 | 203 | 62 | 13 |
80 | 214 | 7 | 10 | 219 | 7 | 7 | 217 | 62 | 13 |
100 | 218 | 7 | 10 | 227 | 10 | 7 | 223 | 62 | 13 |
120 | 219 | 7 | 7 | 229 | 10 | 7 | 224 | 62 | 13 |
140 | 222 | 7 | 7 | 224 | 10 | 10 | 223 | 62 | 13 |
160 | 229 | 10 | 7 | 218 | 7 | 10 | 224 | 62 | 13 |
175 | 234 | 10 | 7 | - | - | - | 234 | 62 | 13 |
180 | - | - | - | 215 | 10 | 10 | 215 | 62 | 13 |
N3972 | |||||||||
10 | 24 | 5 | 5 | 55 | 10 | 7 | 40 | 77 | 297 |
20 | 68 | 7 | 7 | 78 | 7 | 7 | 73 | 77 | 297 |
30 | 86 | 12 | 10 | 93 | 7 | 7 | 89 | 77 | 297 |
40 | 101 | 10 | 7 | 103 | 5 | 7 | 102 | 77 | 297 |
50 | 111 | 7 | 5 | 110 | 5 | 7 | 110 | 77 | 297 |
60 | 117 | 7 | 5 | 116 | 5 | 7 | 116 | 77 | 297 |
70 | 122 | 5 | 5 | 124 | 7 | 7 | 123 | 77 | 297 |
80 | 129 | 5 | 5 | 131 | 5 | 7 | 130 | 77 | 297 |
86 | 131 | 7 | 7 | - | - | - | 131 | 77 | 297 |
90 | - | - | - | 134 | 5 | 7 | 134 | 77 | 297 |
100 | - | - | - | 134 | 5 | 5 | 134 | 77 | 297 |
U6917 | |||||||||
20 | 60 | 5 | 5 | 59 | 5 | 5 | 59 | 56 | 123 |
30 | 71 | 5 | 8 | 72 | 5 | 5 | 71 | 56 | 123 |
40 | 86 | 8 | 5 | 83 | 8 | 5 | 85 | 56 | 123 |
50 | 96 | 8 | 8 | 91 | 5 | 5 | 94 | 56 | 123 |
60 | 98 | 5 | 5 | 97 | 5 | 5 | 98 | 56 | 123 |
70 | 100 | 5 | 5 | 100 | 5 | 5 | 100 | 56 | 123 |
80 | 101 | 8 | 5 | 101 | 5 | 5 | 101 | 56 | 123 |
90 | 105 | 5 | 5 | 102 | 5 | 5 | 103 | 56 | 123 |
100 | 110 | 5 | 5 | 101 | 5 | 8 | 105 | 56 | 123 |
110 | 116 | 7 | 7 | 104 | 5 | 7 | 110 | 57 | 123 |
120 | - | - | - | 111 | 5 | 7 | 111 | 60 | 124 |
U6923 | |||||||||
11 | 41 | 6 | 9 | - | - | - | 41 | 65 | 341 |
23 | 54 | 6 | 6 | - | - | - | 54 | 65 | 341 |
34 | 70 | 6 | 6 | 76 | 9 | 6 | 73 | 65 | 341 |
44 | 80 | 6 | 6 | 77 | 6 | 6 | 78 | 65 | 344 |
53 | - | - | - | 79 | 5 | 5 | 79 | 65 | 347 |
61 | - | - | - | 81 | 5 | 5 | 81 | 65 | 350 |
U6930 | |||||||||
20 | 58 | 12 | 10 | 52 | 12 | 12 | 55 | 32 | 39 |
40 | 88 | 10 | 7 | 83 | 12 | 10 | 85 | 32 | 39 |
60 | 94 | 7 | 7 | 94 | 10 | 10 | 94 | 32 | 39 |
80 | 98 | 7 | 7 | 100 | 7 | 7 | 99 | 32 | 39 |
100 | 102 | 7 | 7 | 105 | 7 | 7 | 103 | 32 | 39 |
120 | 105 | 7 | 7 | 109 | 7 | 7 | 107 | 32 | 39 |
140 | 107 | 7 | 7 | 110 | 7 | 7 | 109 | 32 | 39 |
150 | - | - | - | 110 | 7 | 7 | 110 | 32 | 39 |
160 | 108 | 7 | 7 | - | - | - | 108 | 32 | 39 |
180 | 108 | 7 | 7 | - | - | - | 108 | 32 | 39 |
190 | 108 | 7 | 7 | - | - | - | 108 | 32 | 39 |
N3992 | |||||||||
80 | 253 | 7 | 10 | 244 | 10 | 12 | 249 | 56 | 248 |
120 | 264 | 7 | 10 | 265 | 7 | 12 | 264 | 56 | 248 |
160 | 273 | 7 | 10 | 272 | 7 | 7 | 272 | 56 | 248 |
200 | 274 | 7 | 7 | 268 | 7 | 10 | 271 | 56 | 248 |
240 | 273 | 7 | 7 | 256 | 7 | 7 | 264 | 56 | 248 |
280 | - | - | - | 242 | 7 | 7 | 242 | 56 | 248 |
Rad. |
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i | PA | ||
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- - - km s-1 - - - | - - - km s-1 - - - | km s-1 | (![]() |
(![]() |
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N3992 (cont.) | |||||||||
320 | 247 | 7 | 7 | 242 | 7 | 7 | 244 | 56 | 248 |
360 | 241 | 7 | 7 | 242 | 10 | 10 | 241 | 56 | 248 |
400 | 237 | 7 | 10 | - | - | - | 237 | 56 | 248 |
U6940 | |||||||||
10 | 19 | 5 | 5 | 18 | 5 | 5 | 18 | 79 | 315 |
20 | 41 | 5 | 5 | 34 | 5 | 8 | 37 | 79 | 315 |
U6962 | |||||||||
10 | 50 | 20 | 15 | 75 | 12 | 10 | 62 | 37 | 359 |
20 | 107 | 10 | 7 | 106 | 10 | 7 | 106 | 37 | 359 |
30 | 129 | 7 | 7 | 126 | 7 | 7 | 128 | 37 | 359 |
40 | 142 | 7 | 7 | 145 | 10 | 7 | 144 | 37 | 359 |
50 | 155 | 7 | 7 | 163 | 10 | 10 | 159 | 37 | 359 |
60 | 171 | 7 | 7 | - | - | - | 171 | 37 | 359 |
N4010 | |||||||||
0 | 34 | 15 | 15 | -34 | 15 | 15 | 0 | 90 | 66 |
10 | 59 | 12 | 10 | 20 | 7 | 7 | 39 | 90 | 66 |
20 | 66 | 7 | 10 | 43 | 7 | 7 | 55 | 90 | 66 |
30 | 69 | 5 | 10 | 62 | 12 | 10 | 66 | 90 | 66 |
40 | 80 | 5 | 5 | 88 | 10 | 7 | 84 | 90 | 66 |
50 | 84 | 5 | 5 | 104 | 12 | 10 | 94 | 90 | 66 |
60 | 96 | 5 | 5 | 113 | 10 | 10 | 104 | 90 | 66 |
70 | 108 | 7 | 5 | 122 | 7 | 7 | 115 | 90 | 66 |
80 | 125 | 7 | 5 | 129 | 7 | 7 | 127 | 90 | 66 |
90 | 128 | 7 | 5 | 131 | 7 | 7 | 129 | 90 | 66 |
100 | 123 | 7 | 5 | 131 | 7 | 7 | 127 | 90 | 66 |
110 | 119 | 7 | 5 | 129 | 7 | 7 | 124 | 90 | 66 |
120 | 119 | 5 | 5 | 125 | 5 | 7 | 122 | 90 | 66 |
U6969 | |||||||||
10 | - | - | - | 26 | 5 | 7 | 26 | 76 | 330 |
20 | 34 | 5 | 7 | 44 | 7 | 7 | 39 | 76 | 330 |
31 | 46 | 5 | 5 | 58 | 5 | 7 | 52 | 76 | 330 |
41 | 60 | 5 | 5 | 69 | 5 | 7 | 65 | 76 | 330 |
51 | - | - | - | 79 | 5 | 5 | 79 | 76 | 330 |
U6973 | |||||||||
20 | 162 | 5 | 10 | 179 | 5 | 7 | 170 | 71 | 41 |
30 | 174 | 5 | 7 | 174 | 5 | 7 | 174 | 71 | 41 |
40 | 170 | 5 | 7 | 170 | 5 | 7 | 170 | 71 | 42 |
50 | 170 | 5 | 7 | 170 | 5 | 7 | 170 | 71 | 44 |
61 | 171 | 5 | 7 | 172 | 7 | 7 | 171 | 71 | 45 |
72 | 174 | 5 | 8 | 174 | 8 | 8 | 174 | 71 | 46 |
78 | - | - | - | 177 | 10 | 10 | 177 | 71 | 47 |
84 | 178 | 5 | 8 | - | - | - | 178 | 71 | 47 |
90 | 180 | 5 | 10 | - | - | - | 180 | 71 | 48 |
U6983 | |||||||||
20 | 58 | 10 | 10 | 56 | 10 | 7 | 57 | 49 | 270 |
30 | 93 | 7 | 5 | 82 | 7 | 7 | 87 | 49 | 270 |
40 | 87 | 7 | 7 | 97 | 10 | 7 | 92 | 49 | 270 |
50 | 84 | 7 | 7 | 103 | 7 | 7 | 94 | 49 | 270 |
60 | 93 | 5 | 5 | 103 | 7 | 7 | 98 | 49 | 270 |
70 | 94 | 5 | 5 | 105 | 7 | 7 | 100 | 49 | 270 |
80 | 95 | 5 | 5 | 108 | 5 | 5 | 102 | 49 | 270 |
90 | 100 | 7 | 7 | 113 | 5 | 5 | 107 | 49 | 270 |
100 | 105 | 7 | 7 | 112 | 5 | 5 | 108 | 49 | 270 |
110 | 111 | 7 | 7 | 110 | 5 | 5 | 111 | 49 | 270 |
120 | 113 | 7 | 7 | 112 | 5 | 5 | 113 | 49 | 270 |
130 | 111 | 7 | 7 | 110 | 7 | 7 | 111 | 49 | 270 |
140 | 107 | 7 | 7 | 109 | 7 | 10 | 108 | 49 | 270 |
145 | 102 | 10 | 10 | - | - | - | 102 | 49 | 270 |
150 | - | - | - | 109 | 7 | 10 | 109 | 49 | 270 |
Rad. |
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- - - km s-1 - - - | - - - km s-1 - - - | km s-1 | (![]() |
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U6983 (cont.) | |||||||||
160 | - | - | - | 108 | 10 | 10 | 108 | 49 | 270 |
170 | - | - | - | 108 | 10 | 10 | 108 | 49 | 270 |
180 | - | - | - | 109 | 12 | 12 | 109 | 49 | 270 |
N4051 | |||||||||
20 | - | - | - | 121 | 15 | 15 | 121 | 49 | 310 |
25 | 123 | 15 | 15 | - | - | - | 123 | 49 | 310 |
40 | 119 | 12 | 10 | 114 | 12 | 10 | 116 | 49 | 310 |
60 | 146 | 10 | 10 | 133 | 10 | 10 | 140 | 49 | 310 |
80 | 163 | 7 | 10 | 156 | 10 | 10 | 160 | 49 | 310 |
100 | 158 | 7 | 7 | 165 | 7 | 7 | 162 | 49 | 310 |
115 | - | - | - | 170 | 7 | 7 | 170 | 49 | 310 |
120 | 154 | 7 | 7 | - | - | - | 154 | 49 | 310 |
140 | 153 | 10 | 10 | - | - | - | 153 | 49 | 310 |
N4085 | |||||||||
10 | 35 | 10 | 5 | 50 | 15 | 10 | 42 | 82 | 256 |
20 | 71 | 7 | 5 | 89 | 10 | 10 | 80 | 82 | 256 |
31 | 110 | 12 | 7 | 113 | 7 | 7 | 112 | 82 | 256 |
41 | 126 | 7 | 5 | 127 | 7 | 7 | 127 | 82 | 256 |
51 | 131 | 7 | 7 | 130 | 7 | 5 | 130 | 82 | 256 |
61 | 134 | 7 | 7 | 133 | 5 | 5 | 133 | 82 | 256 |
71 | 136 | 7 | 7 | - | - | - | 136 | 82 | 256 |
N4088 | |||||||||
20 | 92 | 15 | 15 | 78 | 20 | 15 | 85 | 69 | 230 |
40 | 138 | 10 | 15 | 135 | 20 | 10 | 136 | 69 | 230 |
60 | 156 | 7 | 12 | 168 | 15 | 10 | 162 | 69 | 230 |
80 | 167 | 7 | 10 | 191 | 10 | 10 | 179 | 69 | 230 |
100 | 177 | 7 | 10 | 187 | 10 | 7 | 182 | 69 | 230 |
120 | 185 | 7 | 12 | 174 | 10 | 10 | 179 | 69 | 230 |
140 | 187 | 7 | 12 | 162 | 7 | 7 | 174 | 69 | 230 |
160 | 185 | 12 | 12 | 158 | 7 | 7 | 171 | 69 | 230 |
180 | 175 | 10 | 10 | 161 | 7 | 7 | 168 | 69 | 230 |
200 | 171 | 7 | 7 | 160 | 10 | 7 | 165 | 69 | 230 |
210 | - | - | - | 156 | 10 | 7 | 156 | 69 | 229 |
221 | 171 | 10 | 7 | - | - | - | 171 | 69 | 227 |
246 | 174 | 8 | 8 | - | - | - | 174 | 69 | 224 |
N4100 | |||||||||
20 | 67 | 15 | 15 | - | - | - | 67 | 73 | 345 |
30 | 102 | 15 | 20 | 139 | 15 | 7 | 121 | 73 | 345 |
40 | 138 | 12 | 12 | 159 | 10 | 7 | 148 | 73 | 345 |
50 | 164 | 7 | 10 | 173 | 10 | 7 | 168 | 73 | 345 |
60 | 177 | 10 | 7 | 188 | 10 | 7 | 182 | 73 | 345 |
70 | 188 | 7 | 7 | 193 | 7 | 7 | 191 | 73 | 345 |
80 | 193 | 7 | 7 | 195 | 10 | 7 | 194 | 73 | 345 |
90 | 195 | 10 | 7 | 195 | 10 | 7 | 195 | 73 | 345 |
100 | 193 | 5 | 7 | 194 | 7 | 7 | 193 | 73 | 345 |
110 | 192 | 5 | 5 | 192 | 7 | 5 | 192 | 73 | 345 |
120 | 193 | 5 | 5 | 191 | 5 | 5 | 192 | 73 | 345 |
130 | 192 | 5 | 5 | 190 | 7 | 7 | 191 | 73 | 345 |
140 | 188 | 7 | 7 | 189 | 7 | 5 | 189 | 73 | 345 |
150 | 183 | 7 | 10 | 187 | 7 | 5 | 185 | 73 | 345 |
160 | 180 | 7 | 7 | 185 | 5 | 5 | 182 | 73 | 345 |
170 | 175 | 10 | 10 | 183 | 10 | 7 | 179 | 72 | 346 |
180 | 172 | 7 | 10 | 181 | 10 | 7 | 177 | 71 | 346 |
190 | 168 | 10 | 10 | 179 | 10 | 8 | 174 | 71 | 346 |
200 | - | - | - | 178 | 10 | 8 | 178 | 70 | 346 |
210 | - | - | - | 177 | 8 | 5 | 177 | 70 | 347 |
220 | 160 | 5 | 8 | 178 | 10 | 10 | 169 | 69 | 347 |
230 | 158 | 5 | 8 | - | - | - | 158 | 69 | 347 |
241 | 158 | 8 | 8 | - | - | - | 158 | 68 | 348 |
Rad. |
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- - - km s-1 - - - | - - - km s-1 - - - | km s-1 | (![]() |
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N4100 (cont.) | |||||||||
251 | 158 | 8 | 10 | - | - | - | 158 | 68 | 348 |
261 | 159 | 10 | 8 | - | - | - | 159 | 67 | 348 |
N4102 | |||||||||
20 | 179 | 12 | 12 | 184 | 12 | 12 | 181 | 56 | 39 |
30 | 177 | 12 | 10 | 181 | 10 | 12 | 179 | 56 | 39 |
40 | 174 | 12 | 10 | 178 | 10 | 10 | 176 | 56 | 39 |
50 | - | - | - | 178 | 15 | 10 | 178 | 56 | 39 |
N4157 | |||||||||
20 | 66 | 18 | 14 | 127 | 23 | 14 | 96 | 82 | 63 |
40 | 142 | 18 | 14 | 173 | 14 | 14 | 157 | 82 | 63 |
60 | 192 | 9 | 14 | 191 | 11 | 14 | 192 | 82 | 63 |
80 | 202 | 7 | 9 | 201 | 11 | 11 | 201 | 82 | 63 |
100 | 198 | 11 | 11 | 204 | 9 | 9 | 201 | 82 | 63 |
120 | 192 | 9 | 9 | 197 | 9 | 9 | 195 | 82 | 63 |
140 | 191 | 9 | 9 | 188 | 9 | 7 | 190 | 82 | 63 |
160 | 191 | 9 | 9 | 181 | 9 | 9 | 186 | 82 | 63 |
180 | 192 | 9 | 9 | 176 | 9 | 9 | 184 | 82 | 63 |
200 | 191 | 9 | 9 | 173 | 11 | 11 | 182 | 82 | 63 |
220 | 190 | 7 | 7 | 173 | 14 | 9 | 181 | 82 | 63 |
240 | 189 | 9 | 7 | 177 | 11 | 9 | 183 | 82 | 63 |
260 | 189 | 11 | 7 | 181 | 9 | 9 | 185 | 82 | 63 |
280 | 186 | 11 | 7 | - | - | - | 186 | 82 | 63 |
300 | 186 | 11 | 11 | - | - | - | 186 | 82 | 63 |
320 | 185 | 14 | 14 | - | - | - | 185 | 82 | 63 |
340 | 185 | 14 | 14 | - | - | - | 185 | 82 | 63 |
N4183 | |||||||||
10 | 56 | 12 | 10 | 38 | 15 | 10 | 47 | 82 | 346 |
20 | 71 | 7 | 7 | 61 | 12 | 10 | 66 | 82 | 346 |
30 | 78 | 7 | 7 | 74 | 10 | 7 | 76 | 82 | 346 |
40 | 88 | 7 | 7 | 84 | 10 | 7 | 86 | 82 | 346 |
50 | 97 | 7 | 7 | 97 | 7 | 7 | 97 | 82 | 346 |
60 | 100 | 7 | 7 | 99 | 7 | 7 | 99 | 82 | 346 |
70 | 103 | 7 | 7 | 103 | 7 | 7 | 103 | 82 | 346 |
80 | 106 | 7 | 7 | 107 | 7 | 7 | 107 | 82 | 346 |
90 | 110 | 7 | 7 | 113 | 7 | 7 | 111 | 82 | 346 |
100 | 112 | 7 | 7 | 117 | 10 | 10 | 114 | 82 | 346 |
110 | 112 | 7 | 7 | 118 | 10 | 10 | 115 | 82 | 346 |
120 | 108 | 7 | 7 | 114 | 10 | 7 | 111 | 82 | 346 |
130 | 108 | 7 | 7 | 113 | 10 | 7 | 110 | 82 | 347 |
141 | 111 | 7 | 7 | 112 | 7 | 7 | 111 | 82 | 347 |
151 | 108 | 7 | 5 | 110 | 7 | 7 | 109 | 82 | 347 |
161 | 106 | 5 | 5 | 109 | 7 | 7 | 108 | 82 | 347 |
172 | 109 | 7 | 7 | 109 | 7 | 7 | 109 | 82 | 347 |
183 | 112 | 7 | 7 | 110 | 7 | 7 | 111 | 82 | 348 |
194 | 108 | 5 | 8 | 111 | 8 | 8 | 110 | 82 | 348 |
205 | 106 | 5 | 8 | 111 | 8 | 8 | 109 | 82 | 348 |
217 | 107 | 7 | 8 | 112 | 8 | 8 | 110 | 82 | 348 |
229 | - | - | - | 112 | 10 | 10 | 112 | 82 | 348 |
241 | - | - | - | 113 | 13 | 10 | 113 | 82 | 349 |
N4217 | |||||||||
10 | 38 | 10 | 10 | 57 | 14 | 12 | 48 | 86 | 230 |
20 | 82 | 10 | 12 | 116 | 14 | 10 | 99 | 86 | 230 |
30 | 145 | 10 | 10 | 148 | 14 | 10 | 146 | 86 | 230 |
40 | 162 | 7 | 10 | 165 | 10 | 10 | 164 | 86 | 230 |
50 | 176 | 7 | 10 | 172 | 7 | 10 | 174 | 86 | 230 |
60 | 176 | 7 | 10 | 175 | 10 | 7 | 175 | 86 | 230 |
70 | 189 | 7 | 10 | 179 | 10 | 10 | 184 | 86 | 230 |
80 | 188 | 7 | 10 | 182 | 10 | 10 | 185 | 86 | 230 |
90 | 187 | 5 | 10 | 188 | 12 | 10 | 188 | 86 | 230 |
Rad. |
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i | PA | ||
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- - - km s-1 - - - | - - - km s-1 - - - | km s-1 | (![]() |
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||||
N4217 (cont.) | |||||||||
100 | 188 | 7 | 10 | 192 | 12 | 12 | 190 | 86 | 230 |
110 | 191 | 7 | 10 | 191 | 10 | 10 | 191 | 86 | 230 |
120 | 192 | 7 | 7 | 189 | 10 | 7 | 191 | 86 | 230 |
130 | 191 | 10 | 7 | 187 | 10 | 7 | 189 | 86 | 230 |
140 | 187 | 10 | 7 | 185 | 12 | 10 | 186 | 86 | 230 |
150 | 183 | 10 | 7 | 183 | 10 | 10 | 183 | 86 | 230 |
160 | 180 | 12 | 7 | 178 | 10 | 10 | 179 | 86 | 230 |
170 | 177 | 10 | 10 | 177 | 10 | 12 | 177 | 86 | 230 |
181 | 178 | 12 | 12 | 177 | 10 | 14 | 177 | 86 | 230 |
191 | 178 | 12 | 12 | - | - | - | 178 | 86 | 230 |
N4389 | |||||||||
10 | 30 | 8 | 8 | 25 | 10 | 8 | 27 | 50 | 277 |
20 | 56 | 10 | 8 | 50 | 13 | 8 | 53 | 50 | 277 |
31 | 70 | 13 | 8 | 69 | 10 | 8 | 69 | 50 | 277 |
41 | 79 | 13 | 8 | 88 | 8 | 8 | 84 | 50 | 277 |
51 | 92 | 10 | 10 | 99 | 8 | 8 | 96 | 50 | 277 |
61 | - | - | - | 110 | 8 | 8 | 110 | 50 | 277 |
Rotation curves derived from XV-diagrams only. | |||||||||
N3718 | |||||||||
40 | 228 | 10 | 10 | 228 | 10 | 10 | 228 | 76 | 114 |
80 | 228 | 10 | 10 | 228 | 10 | 10 | 228 | 80 | 130 |
120 | 228 | 10 | 10 | 228 | 10 | 10 | 228 | 84 | 143 |
160 | 228 | 10 | 10 | 228 | 10 | 10 | 228 | 90 | 162 |
200 | 228 | 10 | 10 | 228 | 10 | 10 | 228 | 85 | 175 |
240 | 220 | 10 | 10 | 235 | 10 | 10 | 228 | 80 | 186 |
280 | 225 | 10 | 10 | 239 | 10 | 10 | 232 | 75 | 195 |
320 | 240 | 10 | 10 | 245 | 10 | 10 | 242 | 70 | 196 |
360 | 245 | 10 | 10 | 242 | 10 | 10 | 244 | 65 | 196 |
400 | 235 | 10 | 10 | 240 | 10 | 10 | 237 | 65 | 194 |
420 | 227 | 10 | 10 | - | - | - | - | 65 | 194 |
N3729 | |||||||||
20 | 118 | 34 | 24 | 138 | 12 | 10 | 128 | 48 | 164 |
40 | 157 | 17 | 12 | 141 | 12 | 12 | 149 | 48 | 164 |
50 | - | - | - | 144 | 10 | 10 | 144 | 48 | 164 |
60 | 151 | 12 | 10 | - | - | - | 151 | 48 | 164 |
U6773 | |||||||||
10 | 28 | 10 | 7 | 34 | 10 | 7 | 31 | 60 | 341 |
20 | 38 | 7 | 7 | 48 | 7 | 5 | 43 | 60 | 341 |
30 | 46 | 5 | 5 | 44 | 7 | 7 | 45 | 60 | 341 |
40 | 47 | 5 | 5 | 44 | 10 | 7 | 45 | 60 | 341 |
U6818 | |||||||||
10 | 27 | 7 | 7 | 20 | 10 | 7 | 23 | 79 | 77 |
20 | 28 | 10 | 7 | 28 | 7 | 5 | 28 | 79 | 77 |
30 | 31 | 7 | 5 | 43 | 7 | 5 | 37 | 79 | 77 |
40 | 43 | 7 | 5 | 53 | 7 | 5 | 48 | 79 | 77 |
50 | 66 | 7 | 7 | 61 | 7 | 5 | 63 | 79 | 77 |
60 | 77 | 7 | 10 | 66 | 7 | 5 | 71 | 79 | 77 |
70 | 68 | 7 | 5 | - | - | - | 68 | 79 | 77 |
80 | 74 | 7 | 5 | - | - | - | 74 | 79 | 77 |
N3985 | |||||||||
0 | 8 | 15 | 10 | -8 | 15 | 10 | 0 | 53 | 70 |
10 | 41 | 10 | 7 | 37 | 12 | 7 | 39 | 53 | 70 |
20 | 60 | 7 | 10 | 89 | 15 | 7 | 75 | 53 | 70 |
25 | 68 | 10 | 10 | - | - | - | 68 | 53 | 70 |
30 | - | - | - | 93 | 7 | 7 | 93 | 53 | 70 |
U6894 | |||||||||
10 | 28 | 7 | 7 | 28 | 12 | 10 | 28 | 89 | 269 |
20 | 45 | 7 | 7 | 45 | 7 | 7 | 45 | 89 | 269 |
Rad. |
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i | PA | ||
(
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- - - km s-1 - - - | - - - km s-1 - - - | km s-1 | (![]() |
(![]() |
||||
U6894 (cont.) | |||||||||
30 | 56 | 7 | 5 | 56 | 5 | 5 | 56 | 89 | 269 |
40 | 62 | 5 | 5 | 63 | 7 | 7 | 63 | 89 | 269 |
N4013 | |||||||||
65 | - | - | - | 198 | 10 | 10 | 198 | 90 | 245 |
73 | - | - | - | 195 | 5 | 5 | 195 | 90 | 245 |
82 | 193 | 5 | 5 | 195 | 3 | 3 | 194 | 90 | 245 |
91 | 195 | 4 | 4 | 195 | 3 | 3 | 195 | 90 | 245 |
99 | 195 | 3 | 3 | 195 | 3 | 3 | 195 | 90 | 245 |
108 | 195 | 3 | 3 | 193 | 4 | 4 | 195 | 90 | 245 |
117 | 196 | 3 | 3 | 185 | 5 | 5 | 192 | 90 | 245 |
125 | 195 | 3 | 3 | 178 | 5 | 5 | 188 | 90 | 245 |
134 | 190 | 4 | 4 | 178 | 8 | 8 | 186 | 90 | 245 |
143 | 190 | 4 | 4 | - | - | - | 186 | 90 | 245 |
151 | 188 | 5 | 5 | - | - | - | 186 | 90 | 245 |
160 | 187 | 6 | 6 | - | - | - | 185 | 90 | 245 |
168 | 179 | 10 | 10 | - | - | - | 180 | 90 | 243 |
177 | 163 | 8 | 8 | - | - | - | 163 | 90 | 240 |
186 | 161 | 6 | 6 | - | - | - | 162 | 90 | 238 |
194 | 162 | 5 | 5 | - | - | - | 164 | 90 | 236 |
203 | 164 | 5 | 5 | 170 | 5 | 5 | 166 | 90 | 235 |
212 | 164 | 6 | 6 | 168 | 5 | 5 | 166 | 90 | 233 |
220 | 165 | 8 | 8 | 166 | 5 | 5 | 166 | 90 | 232 |
229 | 165 | 7 | 7 | 166 | 5 | 5 | 166 | 90 | 230 |
238 | 169 | 5 | 5 | 168 | 5 | 5 | 168 | 90 | 229 |
246 | 173 | 5 | 5 | - | - | - | 172 | 90 | 228 |
255 | 173 | 5 | 5 | - | - | - | 173 | 90 | 226 |
264 | 172 | 5 | 5 | - | - | - | 171 | 90 | 225 |
272 | 169 | 6 | 6 | 170 | 5 | 5 | 170 | 90 | 224 |
281 | 162 | 10 | 10 | 172 | 5 | 5 | 172 | 90 | 224 |
289 | - | - | - | 174 | 5 | 5 | 173 | 90 | 223 |
298 | - | - | - | 176 | 5 | 5 | 176 | 90 | 222 |
307 | - | - | - | 178 | 5 | 5 | 178 | 90 | 221 |
315 | - | - | - | 180 | 6 | 6 | 180 | 90 | 221 |
324 | - | - | - | 180 | 8 | 8 | 180 | 90 | 220 |
333 | - | - | - | 180 | 5 | 5 | 180 | 90 | 219 |
341 | - | - | - | 180 | 5 | 5 | 180 | 90 | 219 |
350 | - | - | - | 178 | 5 | 5 | 178 | 90 | 218 |
359 | - | - | - | 174 | 5 | 5 | 174 | 90 | 218 |
367 | - | - | - | 170 | 10 | 10 | 170 | 90 | 218 |
U7089 | |||||||||
10 | 25 | 7 | 7 | 17 | 7 | 5 | 21 | 89 | 215 |
20 | 38 | 5 | 5 | 35 | 7 | 7 | 36 | 89 | 215 |
30 | 45 | 5 | 5 | 42 | 7 | 7 | 43 | 89 | 215 |
40 | 51 | 7 | 7 | 51 | 5 | 5 | 51 | 89 | 215 |
50 | 57 | 7 | 5 | 62 | 5 | 5 | 60 | 89 | 215 |
60 | 63 | 10 | 5 | 66 | 5 | 5 | 65 | 89 | 215 |
70 | 66 | 7 | 5 | 69 | 5 | 5 | 68 | 89 | 215 |
75 | - | - | - | 73 | 7 | 7 | 73 | 89 | 215 |
80 | 70 | 7 | 5 | - | - | - | 70 | 89 | 215 |
U7089 (cont.) | |||||||||
90 | 74 | 7 | 5 | - | - | - | 74 | 89 | 215 |
100 | 78 | 7 | 5 | - | - | - | 78 | 89 | 215 |
105 | 79 | 7 | 7 | - | - | - | 79 | 89 | 215 |
U7094 | |||||||||
20 | 32 | 5 | 5 | 32 | 5 | 5 | 32 | 72 | 39 |
40 | 36 | 7 | 5 | 36 | 7 | 5 | 36 | 72 | 39 |
60 | - | - | - | 35 | 7 | 5 | 35 | 72 | 39 |
Rad. |
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i | PA | ||
(
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- - - km s-1 - - - | - - - km s-1 - - - | km s-1 | (![]() |
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N4138 | |||||||||
30 | 178 | 19 | 34 | 181 | 12 | 12 | 179 | 53 | 151 |
60 | 191 | 10 | 10 | 200 | 10 | 10 | 195 | 53 | 151 |
90 | 181 | 10 | 10 | 181 | 15 | 20 | 181 | 53 | 147 |
122 | - | - | - | 162 | 26 | 15 | 162 | 51 | 143 |
154 | 145 | 14 | 14 | 145 | 14 | 14 | 145 | 48 | 140 |
184 | - | - | - | 147 | 18 | 18 | 147 | 43 | 138 |
213 | - | - | - | 150 | 21 | 21 | 150 | 35 | 138 |
N4218 | |||||||||
10 | 51 | 10 | 7 | 70 | 12 | 10 | 60 | 55 | 316 |
20 | 83 | 10 | 5 | 62 | 12 | 10 | 73 | 55 | 316 |
In this section, it will be investigated how the linewidth correction for turbulent motion can be used to match the finally corrected global HI linewidths to the actual rotational velocities measured from the rotation curves.
After the correction for instrumental resolution, the profile widths
are generally corrected for broadening due to turbulent motions of the
HI gas by applying TFq's formula
The generally adopted values for Wc,l are
and
.
The more important
values of Wt,l, however, have been subject of some debate among various
authors. With our new HI synthesis data we can give a meaningful
contribution to this debate.
Bottinelli et al. (1983) came up with an empirical
approach, based on a minimization of the scatter in the TF-relation.
They assumed an anisotropic velocity dispersion of the HI gas of
and a velocity dispersion
perpendicular to the plane of
.
They determined the
values of kl by minimizing the scatter in the TF-relation and found
k20=1.89 and
k50=0.71, indicating deviations from a Gaussian
distribution (broader wings). Due to the assumed velocity anisotropy,
Wt,l has become a function of inclination angle and varies in the
range
45<Wt,20<57 and
17<Wt,50<21 for inclinations
ranging between
.
The same value of
k20=1.89 was adopted by TFq but they
assumed an isotropic velocity dispersion of
and consequently advocate
,
independent of inclination.
They did not address the situation at the 50% level.
Fouqué et al. (1990) also assumed isotropy but adopted
.
They determined kl in a more direct way by
comparing the corrected line width to the observed maximum rotational
velocity
as derived from HI velocity
fields. They found
k20=1.96 and
k50=1.13, indicating a
near-Gaussian distribution, contrary to the findings of Bottinelli
et al. Consequently, Fouqué et al. advocate the much larger values of
and
respectively.
A similar procedure was followed by Broeils (1992) using a
sample of 21 galaxies with well defined HI velocity fields. Broeils made
no a priori assumptions about the intrinsic velocity dispersion and did
not decouple kl and .
He did, however, recognize that
may exceed
and he determined for each galaxy the
values of
and
for which the
differences
Finally, Rhee (1996a) performed the same investigation using 28
galaxies, most of them in common with Broeils' (1992)
sample. Not surprisingly, he found
![]() |
Figure 2:
Comparison of the global profile widths WR,l, corrected for instrumental broadening and
random motions, with
![]() ![]() ![]() ![]() |
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Here, with our new and independent dataset, we follow the same strategy
as Broeils and Rhee by investigating which values of Wt,l allow an
accurate retrieval of
and
from the broadened global profile. For
this purpose we will only consider those 22 galaxies in our Ursa Major
sample that show a flat part in their rotation curves (with a
significant amount of HI gas) and that are free from a major change in
inclination angle. Of these 22, there are 6 galaxies with
.
Note
that both Broeils and Rhee used Bottinelli et al.'s prescription to
correct for instrumental broadening which we are forced to adopt here to
ensure a valid comparison between their and our results. We calculated
the values of
and
for which the average values
Our results are illustrated in Fig. 2 where we show, for each of the
22 galaxies, the deviations
(upper panels) and
(lower
panels) as a function of
.
Galaxies with
are
indicated by filled symbols, galaxies with
are indicated by open symbols. The upper two
panels in each block show the
results one obtains when using Broeil's adopted values of
Wt,20=38 and
.
From the upper panels in the upper block it is clear that the maximum
rotational velocity as derived from the corrected global profiles is
severely underestimated when using the values of Wt,l derived by
TFq and adopted by Broeils. This systematic underestimation disappears
when Wt,20 is decreased from 38 to 22 km s-1 and Wt,50 is
decreased from 14 to 5 km s-1. The upper two panels in the lower block
show that if one is interested in the amplitude of the flat part, which
is smaller than the maximum rotational velocity for galaxies with a
declining rotation curve (open symbols), the average offset becomes less
significant simply because the open symbols scatter upward. In this
case, to obtain an average zero offset, we find similar values for
Wt,l as those adopted by Broeils. However, we find the curious
situation that the corrected width of the global profile systematically
overestimates
for galaxies with a
declining rotation curve (open symbols) and systematically
underestimates
for galaxies with a purely
flat rotation curve (filled symbols).
From this we can conclude that, in a statistical sense, the maximum
rotational velocity of a galaxy can be reasonably well retrieved from
the width of the global profile when using
Wt,20=22 or
.
The amplitude of the flat part can not be retrieved
consistently for a mixed sample containing galaxies with declining
rotation curves. Note that we have explored only a restricted range of
rotational velocities:
.
Our results also indicate a non-Gaussian distribution of random
velocities in the sense that
.
Interpreting Wt,20 and Wt,50 in terms of velocity dispersions
it follows that
Present day instrumentation allows accurate measurements of the luminosities and global HI profiles of galaxies. In general, the observed scatter in the TF-relation is larger than can be explained by the observational uncertainties in these measured parameters alone. However, the uncertainty in corrections sensitive to inclination contribute significantly to the observed scatter. For a sample of randomly oriented galaxies more inclined than 45 degrees, an uncertainty of 1, 3 or 5 degrees in the inclination angle contributes respectively 0.04, 0.12 or 0.19 magnitudes to the scatter due to the uncertainty in line widths alone, assuming a slope in the TF-relation of -10. Therefore, it is important to determine the inclination angle of a galaxy as accurate as possible and this issue deserves some special attention.
From the photometric and HI synthesis data available, three independent
measurements of the inclination angle of a galaxy can in principle be
obtained;
from the optical axis ratio,
from the apparent ellipticity of the HI disk, and
from fitting tilted rings to the
HI velocity field. Each of these methods has its own systematic
limitations which are important to recognize when estimating the actual
inclination of a galaxy. In the following discussion we will briefly
address those limitations and make an intercomparison of
,
,
and
.
The most widely used formula to infer the inclination angle from the
observed optical axis ratio
was provided by
Hubble (1926):
![]() |
Figure 3:
Intercomparison of the three independently determined inclination angles
![]() ![]() ![]() ![]() ![]() |
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Apart from the oblate stellar disk, the HI disk can also be used to
determine the inclination. In general, the HI disk is much thinner than
the stellar disk and its intrinsic thickness is of no concern. However,
its patchiness, lopsidedness and the existence of warps and tidal tails
may complicate the interpretation of the results from fitting ellipses
to a certain HI isophote. Here, no correction for the intrinsic
thickness of the HI layer was applied. However, the relatively large
synthesized beams of imaging arrays at 21 cm may smear the observed HI
disks to a rounder appearance. Therefore, a simple correction for beam
smearing was applied to our measurements and the inclination of the HI disk was determined according to
The inclination angle of an HI disk can also be measured by fitting
tilted-rings to its velocity field (Begeman 1989). However,
the inclination angle and the rotational velocity are strongly coupled
and reasonable results can only be obtained for inclination angles
between roughly 50 and 75 degrees. This procedure requires accurate
velocity fields with high signal-to-noise ratios as well as many
independent points along a ring. The advantage that velocity fields
offer is the possibility to identify warps and to check the kinematic
regularity of the HI disk. For instance, the optical appearance of a
galaxy may look very regular while the outer regions of the HI disk may
be strongly warped toward edge-on (e.g. N3726). Such a warp would broaden
the global profile and an inclination correction based on the optical
axis ratio would lead to an overestimate of the rotational velocity when
dividing the "warp-broadened'' line width by
.
Note that the inclination measurement of a tilted ring may be affected by
non-circular motions due to spiral arms, bars and lopsidedness.
For the comparison between the three differently inferred inclination angles we considered only those 27 galaxies with fully reduced HI data for which the velocity fields and integrated HI maps are available. We excluded the interacting galaxies (N3769, N3893, U6973) because their outer isophotes (optical and HI) are affected by tidal tails. We also excluded galaxies with perturbed or inadequately sampled velocity fields (N4088, U6969, N4389), galaxies with excessively patchy HI maps (N4102) and obviously lopsided galaxies (N4051). These eliminations leave us with 19 galaxies that have smooth outer isophotes, well filled HI disks and regular HI velocity fields.
Figure 3 presents the comparison between the three differently inferred
inclination angles using two different values for q0. When
calculating mean differences and scatters using
,
only galaxies with
are considered because kinematic inclinations of highly inclined galaxies are
systematically underestimated. The error bars on
are based on the variations
in
between the various fitted rings but are not
considered any further here.
The upper most panel compares
with
.
No significant offset is found for the
14 galaxies that meet the above-mentioned criteria. Assuming that
and
contribute
equally to the scatter of 3.1 degrees implies that the inclination angle
can be determined with an accuracy of 2.2 degrees from either the
velocity fields or from the inclined HI disk. Note that the correlation
turns up for
due to the
systematic underestimation of
for highly
inclined disks.
Comparing
with
and
does show a significant offset of
roughly 3 degrees when assuming q0=0.20 (middle panels). This offset
is biggest toward edge-on as would be expected in case of an
overestimate of the intrinsic thickness. Note that there are several
galaxies with an observed optical axis ratio less than 0.20 which have
been assigned an inclination angle of
.
This 3
offset disappears when q0=0.09 is used (lower panels)
and the rms scatter is reduced to only 1.9 degrees for
versus
but is
still 4.0 degrees in case of
versus
.
In the latter case, the scatter is caused
by a few nearly edge-on systems for which the higher uncertainties have
no influence on the deprojection of the rotational velocities.
The adopted inclinations and their errors, listed in Col. 11 of Table 1 are best estimates based on all the information available for a particular galaxy, including the morphology of dust lanes if present. For galaxies which lack fully reduced HI synthesis data, the inclination angles were inferred from the optical axis ratios using q0=0.09 for galaxies of type Sc and later and q0=0.24 for galaxies of type Sbc and earlier. The latter value of q0 seemed justified by the observed axis ratios of the (nearly) edge-on systems N4013, N4026 and N4111 of types Sb, S0 and S0 respectively. Unfortunately, there are not enough suitable galaxies available to determine q0 as a function of morphology.
![]() |
Figure 4: Layout of the HI atlas pages for the 30 galaxies with fully reduced data. All the data for these galaxies are presented on two facing pages. Results for the 13 galaxies with partially reduced data are presented on a single page per galaxy and include only the channel maps, the global profile and the XV-diagram. The linear scale is 5.4 kpc per arcminute |
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The atlas is presented in Appendix B and consists of two parts. The first part presents the data for the 30 galaxies which have been fully reduced and analyzed. The second part gives a less elaborate presentation of the remaining 13 galaxies which have been only partially reduced.
The reduction procedures described in Sect. 3 were applied to the data at all three angular resolutions. However, to facilitate the intercomparison of various results for a galaxy, it was decided to present the data of a particular galaxy at the same angular resolution as much as possible. The rotation curves are in some cases a combination of the rotation curves at various resolutions, the inner parts at the highest spatial resolution and the outer parts from data of lower resolution but higher signal-to-noise ratio. The channel maps are sometimes presented at a lower angular resolution than the other data.
Figure 4 shows the graphical layout for each of the 30 galaxies in the first part of the atlas. The data for each of the 13 galaxies in the second part of the atlas are presented on a single page which contains the tables and notes as well as the mosaic of channel maps, the global profile and the XV-diagram along the major axis. The contents of the various tables and panels are described below.
Tables and Notes - There are three tables presented for each galaxy. The upper left table contains information on the observations like date, integration time and correlator settings. The lower left table presents some of the quantities derived from the HI data like global profile widths, integrated HI flux, systemic velocity etc. The upper right table provides the noise and contour levels for the maps in the various panels. The contours in the channel maps, 21 cm continuum maps and XV-diagrams are always drawn at levels which are related to the rms noise.
The notes contain information about specific aspects of a particular galaxy like optical and HI appearance.
Channel maps - The channel maps show how the
HI emission behaves as a function of velocity. From these maps it is
possible to recognize the presence of warps, non-circular motions and
HI-bridges between interacting galaxies like N3769/1135+48 and
N3893/N3896. The contours are drawn at levels of -3, -1.5 (dashed),
1.5, 3, 4.5, 6, 9, 12, 15, ....
The value of the rms noise level
is given in the upper right table. In each panel, the cross
indicates the adopted dynamical center of the galaxy. The ellipse in
the upper left panel is centered on this position and the position angle
is set at the kinematic major axis of the inner regions. The
ellipticity represents the inclination as derived from the optical axis
ratio and the major axis diameter is equal to
Db,i25. The
synthesized beam at half power is shown in the lower left corners of the
left panels. The panel at the lower right shows the subtracted,
"dirty'' continuum map.
Optical image - The optical image of a galaxy was scanned from the blue POSS plates. In the upper left corner, the morphological type according to the RC3 is given. CCD images of far superior quality can be found in Paper I. An example is given for N3726 in which case the CCD image is pasted into the POSS image.
Radio continuum map - The cleaned 21 cm radio
continuum map is plotted at the same scale as the optical image. The
contours are drawn at levels of -4, -2 (dashed), 2, 4, 8, 16, 32,
64, ....
The value of the rms noise
is given in the
upper right table. The ellipse represents the optical image as in the
upper left panel in the channels maps. The synthesized beam is plotted
in the lower left corner and the small cross indicates the adopted
position of the center of rotation.
Global profile - Each point in the global HI profile gives the primary-beam corrected, total HI flux density integrated over a single channel map. The errors are derived as explained in Sect. 3.2. The vertical arrow indicates the systemic velocity (lower left table on the first page) as derived from the HI velocity field and does not necessarily indicate the center of the global HI profile. A significant offset from the center could indicate non-circular motions or a strong lopsidedness. These anomalies can often be traced in the individual channel maps.
Surface density profile - The open and filled symbols indicate the azimuthally averaged radial surface densities for the approaching and receding sides. The solid line follows the average value. At the adopted distance of 18.6 Mpc, 1 arcmin corresponds to 5.4 kpc. The vertical arrow indicates R25b,i. The profile becomes unreliable for highly inclined systems since no correction for beam smearing was applied.
XV-diagrams - The position-velocity diagrams
are shown for two orthogonal cuts through the adopted center of rotation
along the kinematic major (left) and minor (right) axes. The position
angles of these two axes are printed in the upper right corner of each
panel. Note that the quoted position angles refer to the positive
offset axes. Consequently, the position angle of the major axis refers
to the receding side which also can be inferred from the channel maps.
The vertical dashed line indicates the position of the center of
rotation. The horizontal dashed line indicates the systemic velocity as
derived from either the velocity field for galaxies with fully reduced
data, or from the XV-diagram for galaxies in the second part of the
atlas. The two vertical arrows show where the ellipse with major axis
diameter
D25b,i intersects the XV-slice. The horizontal arrows
in the left panel show the systemic velocity
derived from the
global profile and
where WR,I is the width of
the global profile at the 20% level of peak flux, corrected for
instrumental broadening (see Sect. 3.2) and turbulent motions
according to TFq.
Contours are at levels of -3, -1.5 (dashed), 1.5, 3, 4.5, 6, 9, 12,
15, ....
The value of the rms noise
is given in the
upper right table. The cross in the lower left corners indicates the
angular and velocity resolutions. An offset of 1 arcmin corresponds to
a projected distance of 5.4 kpc from the center.
The crosses give the projected rotational velocities as derived from the tilted rings fit. In some cases, at large radii, a cross can be found without any underlying signal in the XV-diagram. In such cases, the rotational velocity at that radius is defined by points in the velocity field away from the major axis. The open and filled circles indicate the projected rotational velocity estimated directly from these XV-diagrams. These points must be deprojected using the appropriate inclination and position angles to obtain the actual rotation curve for both halves of the galaxy.
Total HI map - All pixels in the total HI
map with a positive signal have a greyscale value assigned. Because the
signal-to-noise ratio along a contour is not constant, the
"3-contour'' is not defined. Section 3.3 and the appendix explain
why and how the noise varies across an integrated HI map.
The second contour in the total HI maps corresponds to the average
value of all pixels with a signal-to-noise ratio between 2.75 and 3.25
and this contour can thus be considered as a pseudo 3-contour.
Wherever a contour goes through an area with
,
the
contour is plotted much thinner. Consequently, the lowest contour,
plotted at the "1.5
'' level, is plotted thin over most of its
stretch. The various contour levels in atoms cm-2 are given in
the upper right table. The size of the synthesized beam is plotted in
the lower left corner. The beamwidths are the same as in the channel
maps unless specified otherwise in the note. The small cross indicates
the adopted position of the center of rotation (1 arcmin corresponds to
5.4 kpc).
Velocity fields - The greyscales indicate the pixels where a radial velocity was measured. Darker greyscales and white isovelocity contours indicate the receding side. The thick first black contour adjacent to the white ones indicates the adopted systemic velocity. In the ideal case of circular motion and no noise, this thick contour should be a straight line through the center and coinciding with the kinematic minor axis of the galaxy. The isovelocity contours are plotted with constant velocity intervals as given by the upper right table. The synthesized beam is plotted in the lower left corner.
The observed velocity field was modeled by fitting tilted rings to it. The orientation and rotational velocity of each ring were then used to construct the model velocity field. The model velocity field is plotted with the same orientation and on the same scale as the observed velocity field. The isovelocity contours are plotted at the same velocities in the observed as in the model velocity fields. For nearly edge-on systems, the model velocity field is only one or two pixels wide in which case no contours could be drawn.
The residual velocity field was made by subtracting the model from the observed velocity field. White contours indicate positive residuals, black contours indicate negative residuals. The contour levels are ..., -15, -10, -5, 5, 10, 15, ... km s-1.
Tilted-ring fits - The three combined panels show the results from the tilted-ring fits to the observed velocity field. The upper panel shows the inclination angle, the middle panel the position angle and the lower panel the rotational velocity.
The crosses with errorbars in the panels for inclination and position angle are the results from the second step of the fitting procedure as explained in Sect. 3.6.1. The dashed lines, mostly coinciding with the solid lines, in these upper two panels indicate the final values of the inclination and position angles kept fixed when the rotational velocity was fitted. The resulting rotation curve is shown by crosses with errorbars in the lower panel. The errorbars indicate the formal errors, as given by the least squares minimization algorithm.
The horizontal arrows in the upper two panels indicate the inclination and position angles as derived from the optical isophotes in the outer regions. The diamonds indicate the inclination and position angles as determined from the total HI maps. When the total HI maps are very patchy, these diamonds are very uncertain. The horizontal arrow in the lower panel indicates the rotational velocity as derived from the width of the global HI profile corrected for instrumental broadening, turbulent motion and inclination. The adopted inclination is representative for the outer parts. The vertical arrow in the lower panel indicates R25b,i.
The solid lines in the upper and middle panels show the inclination and position angles that were adopted to deproject the radial velocities determined from the XV-diagrams. This deprojection results in the rotation curves plotted as open and filled circles in the lower panel (same symbols as in the XV-diagrams). Note that although the rotational velocities at a certain radius may be different for the approaching and receding sides, both sides were assumed to have the same inclination and position angles at that radius. The solid line in the lower panel shows the mean rotation curve derived from the XV-diagram. 1 arcmin on the horizontal axis corresponds to 5.4 kpc.
Tabulated data - The various parameters derived from the HI data presented here are summarized in Table 5.
Column (1) gives the NGC or UGC numbers.
Columns (2)-(5) give the uncorrected widths with formal errors of the global profiles at
20% and 50% of the peak flux.
Column (6) gives the instrumental velocity resolution at which the global profiles were
observed.
Columns (7) and (8) contain the heliocentric systemic velocities and their uncertainties as
derived from the global profiles.
Name | ![]() |
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Res. |
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shape |
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||||||||
- - - - - - - - km s-1 - - - - - - - - | Jy km s-1 | - mJy - | (![]() |
(![]() |
- km s-1 - | - - - - km s-1 - - - - | ||||||||||||||
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) | (11) | (12) | (13) | (14) | (15) | (16) | (17) | (18) | (19) | (20) | (21) |
Galaxies with fully reduced HI data: | ||||||||||||||||||||
U6399 | 188.1 | 1.4 | 172.5 | 2.9 | 8.3 | 791.5 | 0.6 | 10.5 | 0.3 | <2.5 | 1.68 | 1.50 | 88 | 5 | R/F | 88 | 5 | 88 | 5 | |
U6446 | 154.1 | 1.0 | 131.9 | 1.2 | 5.0 | 644.3 | 0.8 | 40.6 | 0.5 | <7.2 | 2.96 | 2.93 | 80 | 11 | F L | 82 | 4 | 82 | 4 | |
N3726 | 286.5 | 1.6 | 260.6 | 1.8 | 5.0 | 865.6 | 0.9 | 89.8 | 0.8 | 49.7 | 5.0 | 4.24 | 6.22 | 167 | 15 | F/(D) | 162 | 9 | 162 | 9 |
N3769 | 265.3 | 6.7 | 230.5 | 3.6 | 8.3 | 737.3 | 1.8 | 62.3 | 0.6 | 12.1 | 2.9 | 4.31 | 7.10 | 113 | 11 | F/(D) | 122 | 8 | 122 | 8 |
U6667 | 187.5 | 1.4 | 178.1 | 1.9 | 5.0 | 973.2 | 1.2 | 11.0 | 0.4 | <2.7 | 1.64 | 1.50 | 86 | 3 | R L | 86 | 3 | 86 | 3 | |
N3877 | 373.4 | 5.0 | 344.5 | 6.2 | 33.2 | 895.4 | 3.8 | 19.5 | 0.6 | 35.6 | 2.4 | 2.19 | 2.17 | 169 | 7 | F L | 167 | 11 | 167 | 11 |
N3893 | 310.9 | 1.0 | 277.9 | 4.1 | 5.0 | 967.2 | 1.0 | 69.9 | 0.5 | 137.4 | 2.9 | 3.98 | 3.88 | 148 | 19 | F/(D) | 188 | 11 | 188 | 11 |
N3917 | 294.5 | 1.9 | 279.1 | 2.1 | 8.3 | 964.6 | 1.4 | 24.9 | 0.6 | <7.2 | 2.69 | 2.83 | 137 | 8 | F | 135 | 3 | 135 | 3 | |
N3949 | 286.5 | 1.4 | 258.3 | 1.7 | 8.3 | 800.2 | 1.2 | 44.8 | 0.4 | 134.1 | 3.6 | 2.62 | 1.35 | 169 | 8 | F L | 164 | 7 | 164 | 7 |
N3953 | 441.9 | 2.4 | 413.9 | 3.2 | 33.1 | 1052.3 | 2.0 | 39.3 | 0.8 | 50.9 | 2.5 | 3.32 | 3.00 | 215 | 10 | F | 223 | 5 | 223 | 5 |
N3972 | 281.2 | 1.4 | 260.7 | 5.5 | 8.3 | 852.2 | 1.4 | 16.6 | 0.4 | <5.8 | 1.92 | 1.67 | 134 | 5 | R L | 134 | 5 | ... | .. | |
U6917 | 208.9 | 3.2 | 189.6 | 1.6 | 8.3 | 910.7 | 1.4 | 26.2 | 0.3 | <4.4 | 2.42 | 2.00 | 111 | 7 | R/F | 104 | 4 | 104 | 4 | |
U6923 | 166.8 | 2.4 | 147.1 | 4.5 | 10.0 | 1061.6 | 2.2 | 10.7 | 0.6 | <2.6 | 1.29 | 1.02 | 81 | 5 | R L | 81 | 5 | ... | .. | |
U6930 | 136.5 | 0.5 | 122.1 | 0.7 | 8.3 | 777.2 | 0.4 | 42.7 | 0.3 | <5.8 | 3.20 | 3.17 | 108 | 7 | R/F | 107 | 4 | 107 | 4 | |
N3992 | 478.5 | 1.4 | 461.4 | 2.4 | 10.0 | 1048.2 | 1.2 | 74.6 | 1.5 | 30.2 | 7.6 | 4.75 | 6.67 | 237 | 9 | F/D | 272 | 6 | 242 | 5 |
U6940 | 59.3 | 3.8 | 40.6 | 7.8 | 10.0 | 1118.0 | 1.7 | 2.1 | 0.3 | <1.3 | 0.61 | 0.33 | 37 | 4 | R | 37 | 4 | ... | .. | |
U6962 | 220.3 | 6.6 | 182.4 | 3.7 | 8.3 | 807.4 | 3.2 | 10.0 | 0.3 | 13.4 | 1.7 | 1.38 | 1.00 | 171 | 7 | R L | 171 | 7 | ... | .. |
N4010 | 277.7 | 1.0 | 264.1 | 1.2 | 8.3 | 901.9 | 0.8 | 38.2 | 0.3 | 16.9 | 1.6 | 3.36 | 2.00 | 122 | 2 | (R)/F L | 128 | 9 | 128 | 9 |
U6969 | 132.1 | 6.4 | 123.5 | 2.9 | 10.0 | 1118.5 | 2.4 | 6.1 | 0.5 | <3.8 | 0.95 | 0.85 | 79 | 5 | R | 79 | 5 | ... | .. | |
U6973 | 367.8 | 1.8 | 350.4 | 1.2 | 8.3 | 700.5 | 1.0 | 22.9 | 0.2 | 127.5 | 2.1 | 2.21 | 1.50 | 180 | 8 | F/(D) | 173 | 10 | 173 | 10 |
U6983 | 188.4 | 1.3 | 173.0 | 1.1 | 5.0 | 1081.9 | 0.8 | 38.5 | 0.6 | <5.4 | 3.07 | 3.00 | 109 | 12 | F | 107 | 7 | 107 | 7 | |
N4051 | 255.4 | 1.8 | 224.6 | 1.5 | 5.0 | 700.3 | 1.2 | 35.6 | 0.8 | 26.5 | 2.6 | 2.89 | 2.33 | 153 | 10 | R/F L | 159 | 13 | 159 | 13 |
N4085 | 277.4 | 6.6 | 255.4 | 7.8 | 19.8 | 745.7 | 5.0 | 14.6 | 0.9 | 44.1 | 1.3 | 1.94 | 1.18 | 136 | 7 | R/F L | 134 | 6 | 134 | 6 |
N4088 | 371.4 | 1.7 | 342.1 | 1.9 | 19.8 | 756.7 | 1.2 | 102.9 | 1.1 | 222.3 | 1.9 | 4.25 | 4.10 | 174 | 8 | F/(D) L | 173 | 14 | 173 | 14 |
N4100 | 401.8 | 2.0 | 380.5 | 1.8 | 19.9 | 1074.4 | 1.3 | 41.6 | 0.7 | 54.3 | 1.7 | 3.45 | 4.35 | 159 | 9 | F/D | 195 | 7 | 164 | 13 |
N4102 | 349.8 | 2.0 | 322.4 | 8.5 | 8.3 | 846.3 | 2.0 | 8.0 | 0.2 | 276.0 | 1.5 | 1.16 | 0.83 | 178 | 12 | F | 178 | 11 | 178 | 11 |
N4157 | 427.6 | 2.2 | 400.7 | 3.1 | 19.9 | 774.4 | 1.8 | 107.4 | 1.6 | 179.6 | 2.3 | 4.60 | 5.67 | 185 | 14 | F/D | 201 | 7 | 185 | 10 |
N4183 | 249.6 | 1.2 | 232.5 | 1.5 | 8.3 | 930.1 | 1.0 | 48.9 | 0.7 | <5.8 | 3.07 | 4.02 | 113 | 11 | F/D L | 115 | 6 | 109 | 4 | |
N4217 | 428.1 | 5.1 | 395.6 | 3.8 | 33.2 | 1027.0 | 3.0 | 33.8 | 0.7 | 115.6 | 2.2 | 3.19 | 3.17 | 178 | 12 | F/D | 191 | 6 | 178 | 5 |
N4389 | 184.0 | 1.5 | 164.9 | 1.6 | 8.3 | 718.4 | 1.2 | 7.6 | 0.2 | 23.3 | 1.2 | 1.30 | 1.02 | 110 | 8 | R | 110 | 8 | ... | .. |
Galaxies with partially reduced HI data: | ||||||||||||||||||||
N3718 | 492.8 | 1.0 | 465.7 | 1.0 | 33.2 | 993.0 | 0.8 | 140.9 | 0.9 | 11.4 | 0.4 | 6.67 | 223 | 12 | F | 232 | 11 | 232 | 11 | |
N3729 | 270.8 | 1.5 | 253.2 | 3.9 | 33.2 | 1059.8 | 1.4 | 5.5 | 0.3 | 18.0 | 0.9 | 1.00 | 151 | 11 | F | 151 | 11 | 151 | 11 | |
U6773 | 110.4 | 2.3 | 91.1 | 2.2 | 8.3 | 923.6 | 1.6 | 5.6 | 0.4 | <2.6 | 0.67 | 45 | 5 | R L | 45 | 5 | ... | .. | ||
U6818 | 166.9 | 2.3 | 141.9 | 5.7 | 8.3 | 808.1 | 2.1 | 13.9 | 0.2 | 2.4 | 1.0 | 1.33 | 74 | 7 | R/(F) L | 73 | 5 | 73 | 5 | |
U6894 | 141.8 | 1.1 | 132.2 | 1.5 | 8.3 | 848.6 | 1.8 | 5.8 | 0.2 | <2.7 | 0.67 | 63 | 5 | R | 63 | 5 | ... | .. | ||
N3985 | 160.2 | 3.7 | 88.0 | 2.4 | 8.3 | 948.2 | 2.0 | 15.7 | 0.6 | 9.7 | 1.4 | 0.50 | 93 | 7 | R | 93 | 7 | ... | .. | |
N4013 | 425.0 | 0.9 | 395.0 | 0.8 | 33.0 | 831.3 | 0.6 | 41.5 | 0.2 | 36.3 | 0.8 | 6.12 | 170 | 10 | F/D | 195 | 3 | 177 | 6 | |
U7089 | 156.7 | 1.7 | 97.7 | 3.0 | 10.0 | 770.0 | 1.5 | 17.0 | 0.6 | <3.4 | 1.75 | 79 | 7 | R L | 79 | 7 | ... | .. | ||
U7094 | 83.7 | 1.7 | 71.9 | 5.5 | 10.0 | 779.6 | 1.6 | 2.9 | 0.2 | <2.6 | 1.00 | 35 | 6 | R L | 35 | 6 | ... | .. | ||
N4117 | 289.4 | 7.5 | 260.3 | 5.2 | 10.0 | 934.0 | 1.5 | 6.9 | 1.1 | 3.7 | 1.2 | ? | ||||||||
N4138 | 331.6 | 4.5 | 266.0 | 7.8 | 19.9 | 893.8 | 3.9 | 19.2 | 0.7 | 16.7 | 4.6 | 3.55 | 150 | 21 | F/D | 195 | 7 | 147 | 12 | |
N4218 | 138.0 | 5.0 | 79.9 | 1.9 | 8.3 | 729.9 | 1.7 | 7.8 | 0.2 | 6.3 | 0.8 | 0.33 | 73 | 7 | R | 73 | 7 | ... | .. | |
N4220 | 438.1 | 1.3 | 423.3 | 3.3 | 33.1 | 914.2 | 1.2 | 4.4 | 0.3 | <4.9 | ? |
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Figure 5:
Correlations between HI mass-to-light ratios and absolute ![]() |
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Columns (9) and (10) provide the integrated HI flux and the uncertainty in
Jy km s-1.
Columns (11) and (12) contain the 21 cm continuum flux density and its uncertainty in mJy.
In case no continuum flux was detected, a 3
upper limit for extended emission is given.
Column (13) gives the radius of the HI disk,
in arcmin, at
the azimuthally averaged surface density of
,
measured from the radial
surface density profiles.
Column (14) gives the radius
of the last measured point of the rotation
curve in arcmin. The differences between
and
depend on the sensitivity of the
measurement and the distribution of the HI gas along the kinematic major axis.
Columns (15) and (16) give the rotational velocity of the last measured point
and its uncertainty.
Column (17) contains information on the overal shape of the rotation curve; R: rising
rotation curve, F: the rotation curve shows a flat part, D: the rotation curve shows a declining part, L:
lopsided.
Columns (18) and (19) give the maximum observed rotational velocity
and its
uncertainty. For galaxies with a rising rotation curve (R)
.
Columns (20) and (21) give the average rotational velocity of the flat part of the
rotation curve
and its uncertainty. For galaxies with a flat rotation curve (F)
may deviate from
because
was averaged
over the flat part of the rotation curve while
was measured at a single
point.
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Figure 6:
Ratio of HI-to-optical diameter as a function of ![]() ![]() |
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The HI survey of the Ursa Major cluster presented here provides not only the kinematical information necessary for the study of the Tully-Fisher relation and of the dark and luminous matter for a well defined sample of galaxies. It also serves to investigate the general HI properties of disks and to make a comparison with galaxies in the field and with galaxies in denser environments. The HI studies of the Virgo cluster galaxies by Warmels (1988a, 1988b) and especially by Cayatte et al. (1990) have shown that the spiral galaxies in the central parts of the cluster have smaller HI disks of lower surface density. In the Hydra Cluster McMahon (1993) did not find any such significant HI deficiency. She did find, however, a surprisingly large number of isolated HI-rich dwarf galaxies near the center of the cluster. Dickey (1997) surveyed the more distant Hercules SuperCluster and found a similar HI deficiency of spirals near the X-ray gas as in the case of Virgo.
The Ursa Major cluster differs from those just mentioned. It has no central concentration, no X-ray emitting gas and contains mainly spirals of late morphological types. In many respects its conditions are very similar to those of a field environment. For this reason it is useful to compare the properties of the Ursa Major spirals not only with those of galaxies in dense cluster environments but also with those of field galaxies as found in various recent studies (see e.g. Broeils 1992; Puche & Carignan 1991; Rhee 1996a; Swaters 1999).
Here we give only a brief description of the global parameters and of the main properties of the HI disks of the Ursa Major galaxies. A more detailed discussion and a comparison with results from previous work is beyond the scope if this data paper.
Integral properties and global parameters of spiral galaxies have been derived for a large number of objects from single-dish observations (cf. Roberts & Haynes 1994). In recent years also synthesis observations (Broeils 1992; Rhee 1996a) have been used to obtain similar information for smaller samples of galaxies.
The
ratios obtained for the galaxies of
the Ursa Major sample listed in Table 5 are shown here in Fig. 5 as a
function of absolute magnitude and of morphological type. It is well
known (see refs. above) that the
ratio of
galaxies depends on luminosity and morphological type. The present
sample of galaxies shows a clear increase of the HI mass fraction with
decreasing luminosity and from early to late morphological types. The
correlation is clearly stronger for the
-band magnitudes which
is a better tracer of the stellar mass.
Detailed information on the sizes and radial distributions of HI disks has been obtained recently from synthesis observations of limited samples of field and cluster galaxies (Broeils & Van Woerden 1994; Cayatte et al. 1994; Rhee 1996a and 1996b). Here we present only some of the main results on the comparison of HI and optical diameters, on the relation between HI mass and diameter and on the radial density profiles for the Ursa Major sample.
Figure 6 shows the ratio of the HI diameter
(defined at an HI surface density of
)
to the
optical diameter
D25b,i as a function of
luminosity, morphological type and disk scale-length. The diagrams do
not indicate any clear trend or dependence of the diameter ratio on any
of those quantities. The spread is large. There may be a hint of a
slight increase of the ratio from early to later types and from more
luminous to less luminous systems. For almost all galaxies
is larger than
Db,i25.
As shown in previous investigations (see refs. above), there is a tight correlation between HI mass and HI diameter as illustrated in Fig. 7. This implies a nearly constant mean HI surface density regardless of size. The HI mass correlates also with the optical diameter, but, as in previous work, with a much larger scatter.
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Figure 7: Correlations between HI mass and the isophotal diameters of the stellar (triangles) and HI disks (circles). Solid lines indicate fits to the plotted data points while the dashed lines represent the fits found by Broeils (1992). Filled symbols indicate HSB galaxies and open symbols denote galaxies of the LSB type. Triangles are offset by 0.3 dex to the left |
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Name |
Type | Warped | Lopsided | Inter- | |
HI distr. | HI kin. | acting | |||
U6399 |
Sm | ![]() |
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U6446 | Sd | ![]() |
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N3718 | Sa | ![]() |
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N3726 | SBc | ![]() |
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N3729 | SBab | ||||
N3769 | SBb | ![]() |
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||
U6667 | Scd | ![]() |
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N3877 | Sc | ![]() |
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U6773 | Sm | ![]() |
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N3893 | Sc | ![]() |
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N3917 | Scd | ![]() |
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U6818 | Sd | ![]() |
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N3949 | Sbc | ![]() |
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||
N3953 | SBbc | ||||
U6894 | Scd | ||||
N3972 | Sbc | ![]() |
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U6917 | SBd | ![]() |
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N3985 | Sm | ![]() |
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U6923 | Sdm | ![]() |
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||
U6930 | SBd | ![]() |
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N3992 | SBbc | ||||
U6940 | Scd | ||||
N4013 | Sb | ![]() |
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U6962 | SBcd | ![]() |
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||
N4010 | SBd | ![]() |
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U6969 | Sm | ||||
U6973 | Sab | ![]() |
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U6983 | SBcd | ||||
N4051 | SBbc | ![]() |
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N4085 | Sc | ![]() |
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N4088 | Sbc | ![]() |
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|
U7089 | Sdm | ![]() |
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N4100 | Sbc | ![]() |
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U7094 | Sdm | ![]() |
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N4102 | SBab | ||||
N4117 | S0 | ||||
N4138 | Sa | ![]() |
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||
N4157 | Sb | ![]() |
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N4183 | Scd | ![]() |
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N4218 | Sm | ||||
N4217 | Sb | ||||
N4220 | Sa | ||||
N4389 | SBbc |
The radial distributions of the HI surface densities are shown in
Fig. 8. Only galaxies with fully reduced data, more inclined than
80 degrees and with
1 arcmin are considered in
order to avoid the most severe cases of beam smearing. There is clearly
a considerable diversity of shapes and intensities. The upper row shows
the profiles grouped for galaxies of similar morphological types. The
dotted lines represent low surface brightness galaxies. No obvious trend
with morphological type or surface brightness can be discerned. However,
in the lower row, the profiles are grouped according to the galaxy
properties as listed in Table 6. In this case, a clear trend is visible
in the sense that galaxies with high HI surface densities in their inner
regions are either involved in interactions, are lopsided or display a
warped HI disk. Especially in the case of interacting and strongly
lopsided systems, no longlived stable gas orbits can be expected and
evidently, the cold gas becomes concentrated toward the inner regions of
the disk. Note that some galaxies appear in more than one panel.
![]() |
Figure 8:
Azimuthally averaged deprojected radial HI surface density
profiles of galaxies with fully reduced data, less inclined than
80 degrees and with
![]() ![]() ![]() ![]() |
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Warps are thought to be a quite common feature of the outer HI layers of spiral galaxies. But, in spite of attempts made in recent years (Bosma 1991), a good statistics on their occurrence does not exist yet. The information on HI warps provided by the present survey of the Ursa Major sample is somewhat limited mainly because of the already noted small radial extent of the HI layers with respect to the optical. There are pronounced HI warps like the well-known ones found in NGC 3718 (Schwarz 1985) and NGC 4013 (Bottema 1995) and those seen in other galaxies (N3726, N3985 N4010, N4157, N4183). In most cases the warps are visible in the outer parts beyond the optical bright disk and are present in normal, regular, not interacting disks. But there are also systems, like NGC 4088, which are strongly distorted in their optical appearance and also in their kinematics. Similar distortions are found in clearly interacting systems like NGC 3769. In the sample of 43 galaxies (Table 6) there are at least 13 objects with clear indications of warping.
Also asymmetries are thought to occur frequently in field spirals (Richter & Sancisi 1994). In the present sample we see a large number of objects (at least half, see Table 6) with a lopsided HI distribution and/or kinematics. The majority shows kinematical asymmetries: on one side of the disk the rotation curve rises more slowly and reaches its flat part at a larger radius than on the other side (see for example NGC 3877, 3949, 4051). Note that this occurs in the inner parts of non-interacting, regular, normal systems.
Finally, there are four galaxies in this sample of 43 which have close companions and show clear HI signs of tidal interactions. A few more objects (examples NGC 3718, 4088) show distortions or peculiar structures in their density and velocity maps.
This data paper has presented the results of an extensive HI synthesis imaging survey with the WSRT of a well-defined complete equidistant sample of spiral galaxies in the nearby Ursa Major cluster. Figures B.1 and B.2 show a compilation of all the available HI maps. Individual galaxies are at their proper position on the sky but they are individually four times enlarged. Some galaxies had to be shifted to avoid overlapping maps. Rotation curves have been derived for most galaxies as well as detailed information on the kinematical state of the galaxy disks as indicated by the presence of global perturbations, warps, interactions and lopsidedness. Since the galaxies were not selected on the basis of their HI size or content, the quality of the kinematical data varies widely from galaxy to galaxy. Nevertheless, these data will be useful for an analysis of the statistical properties of the Tully-Fisher relation and the rotation curves may be decomposed into contributions from the main dynamical constituents like the stellar and gaseous disks, the bulge and the dark matter halo. These issues will be addressed in forthcoming papers.
Those who would like to use the rotation curves for their own purposes are advised not to take the rotation curves at face value but to check their validity against the actual data and to take notice of the comments provided on the atlas pages. It should be realized that the rotation curves presented here are derived from the kinematics of the HI gas which is assumed to be a tracer of a galaxy's potential. There are some caveats to be aware of like the projection effects of streaming motions and partially filled HI disks of edge-on systems.
Finally, optical long-slit spectroscopy is already available for nearly all galaxies in the sample. These high resolution optical rotation curves will be used to supplement the HI rotation curves in the inner regions, allowing for better decompositions and maximum-disk constraints.
Acknowledgements
The Westerbork Synthesis Radio Telescope is operated by the Netherlands Foundation for Research in Astronomy (NFRA/ASTRON), with financial support by The Netherlands Organization for Scientific Research (NWO). This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, Caltech, under agreement with the National Aeronautics and Space Association. The results presented in this paper were obtained during MV's thesis research at the Kapteyn Institute of the University of Groningen, The Netherlands. This paper was finalized at the National Radio Astronomy Observatory which is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. This research has been supported by NATO Collaborative Research Grant 940271.
This Appendix explains how the noise in a total HI map can be calculated. A total HI map is usually constructed from a 3 dimensional datacube containing a number of so called channelmaps. Each channelmap shows an HI image of the galaxy at a certain velocity. A total HI map is made by adding those channelmaps which contain the HI signal. Before adding the channel maps the signal in each channelmap should be isolated. When the signal is not isolated one merely adds noise to the total HI map because the location of the signal in a channel map varies with velocity due to the galactic rotation. The signals can be isolated interactively by blotting away the surrounding noise or in a more objective way by taking a certain contour level in the smoothed maps as a mask. As a consequence of adding channel maps with isolated regions, the noise in the total HI map is not constant but varies from pixel to pixel. The noise at a certain pixel in the total HI map depends on the number N of non-blank pixels at the same position in the individual channel maps that were added.
In case the data cube was obtained with an uniform taper during the
observation, the noise
in two channelmaps will be
independent. The noise equivalent bandwidth Bu in a uniform
tapered spectrum is equal to the channel separation b. When adding Nuniform tapered channelmaps at a certain pixel the noise
at the same pixel position in the total HI map will be
increased by a factor
:
Because the noise is correlated, adding N adjacent
hanning tapered channelmaps does not give an increase of the noise with
a factor
but with a factor
as is shown below. First the total signal HN is
calculated.
Channel | Ui-1 | Ui | Ui+1 | ![]() |
Ui+N-2 | Ui+N-1 | Ui+N | |
i | 1/4 | 1/2 | 1/4 | |||||
i+1 | 1/4 | 1/2 | ![]() |
|||||
i+2 | 1/4 | ![]() |
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i+N-3 | ![]() |
1/4 | ||||||
i+N-2 | ![]() |
1/2 | 1/4 | |||||
i+N-1 | 1/4 | 1/2 | 1/4 | + | ||||
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![]() |
Ui+1 | ![]() |
Ui+N-2 |
![]() |
![]() |
and thus
![]() |
Figure B.2: Same as Fig. B.1, displayed here in grayscale. Note the interacting pairs N3769/1135+48, N3893/N3896 and U6962/U6973. The galaxies N3718, N3726, N4010, N4013, N4088 and N4138 are strongly warped. It is clear that the integrated column density strongly depends on inclination. Many of the more face-on galaxies show a depletion of the HI gas in their inner regions |