2 The sample

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 $\approx$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 $M_B\approx-16.8$, 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 $i_{\rm opt}$ 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 $K^\prime$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 $K^\prime$ passbands toward face-on $A_\lambda^{i\rightarrow 0}$, calculated according to Tully et al. (1998):

$$A_\lambda^{i\rightarrow 0} = \gamma_\lambda \; \log (a/b)$$

where a/b is the observed axis ratio of the galaxy as an indication of inclination while $\gamma_\lambda$ depends on the luminosity and is calculated according to

$$\gamma_{B} = 1.57 + 2.75 ({\rm log} W^i_{R,I}-2.5) \\$$

$$\gamma_{R} = 1.15 + 1.88 ({\rm log} W^i_{R,I}-2.5) \\$$

$$\gamma_{I}\, = 0.92 + 1.63 ({\rm log} W^i_{R,I}-2.5) \\$$

$$\gamma_{K^\prime} = 0.22 + 0.40 ({\rm log} W^i_{R,I}-2.5) \\$$

where Wⁱ_R,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 W_t,20=22 km s^-1 as motivated in Sect. 4 and corrected for inclination using $i_{\rm adopt}$ from Table 1. For dwarf galaxies with Wⁱ_R,I<85 km s^-1 and for lenticulars with no dust features, the value of $\gamma_\lambda$ is set to zero at all passbands.
Columns (11)-(14) give the total absolute B, R, I and $K^\prime$ 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:

$$M^{b,i}_\lambda=m^{\rm tot}_\lambda-A_\lambda^b-A_\lambda^{i\rightarrow 0}- 31.35$$

where the Galactic extinction A_B^b is taken from SFD as listed in Table 1. Extinction corrections in the other passbands are made according to the Galactic reddening law given by Cardelli et al. (1989) as summarized by SFD under the Landolt filters in their Table 6. It's given by A^b_R/A^b_B=0.62, A^b_I/A^b_B=0.45 and $A^b_{K^\prime}/A^b_{B}=0.08$.
Column (15) gives the diameter of the 25th mag arcsec^-2 blue isophote corrected for both galactic and internal extinction and projection according to TFq:

$$\mbox{Log}(D^{b,i}_{25}) = \mbox{Log}(D_{25}) - 0.22\;\mbox{Log}(D_{25}/d_{25}) + 0.09\;A^b_{B}$$

where d₂₅ is the minor axis diameter at the 25th mag arcsec^-2 blue isophote and A^b_B is taken from SFD.