Issue |
A&A
Volume 506, Number 3, November II 2009
|
|
---|---|---|
Page(s) | 1541 - 1562 | |
Section | Catalogs and data | |
DOI | https://doi.org/10.1051/0004-6361/200911813 | |
Published online | 03 August 2009 |
A&A 506, 1541-1562 (2009)
PMAS optical integral field spectroscopy of luminous infrared galaxies
I. The atlas
A. Alonso-Herrero1 - M. García-Marín2 - A. Monreal-Ibero3 - L. Colina1 - S. Arribas1 - J. Alfonso-Garzón4 - A. Labiano1
1 - Departamento de Astrofísica Molecular e Infrarroja, Instituto de
Estructura de la Materia, CSIC, Serrano 121, 28006 Madrid, Spain
2 - I. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, 50937 Köln, Germany
3 -
European Organisation for Astronomical Research in the Southern
Hemisphere, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany
4 - Centro de Astrobiología (CSIC-INTA), P.O. Box
78, 28691 Villanueva de la Cañada, Madrid, Spain
Received 9 February 2009 / Accepted 17 July 2009
Abstract
Context. Luminous and ultraluminous infrared galaxies (LIRGs and
ULIRGs) are key cosmological classes since they account for most of the
co-moving star formation rate density at -2.
It is then important to have detailed studies of local samples of their
counterparts for understanding the internal and dynamical processes
taking place at high-z.
Aims. To characterize the two-dimensional morphological,
excitation and kinematic properties of LIRGs and ULIRGs we are carrying
out an optical integral field spectroscopy (IFS) survey of local (z<0.26) samples.
Methods. In this paper we present optical (3800-7200 Å) IFS
with the Potsdam multi-aperture spectrophotometer (PMAS) of the
northern hemisphere portion of a volume-limited
(2750-5200 km s-1) sample of 11 LIRGs. The PMAS IFS observations typically cover the central 5 kpc and are complemented with our own existing HST/NICMOS images.
Results. For most LIRGs in our sample, the peaks of the continuum and gas (e.g., H,
[N II]
6584)
emissions coincide, unlike what is observed in local, strongly
interacting ULIRGs. The only exceptions are galaxies with circumnuclear
rings of star formation where the most luminous H
emitting regions are found in the rings rather than in the nuclei of
the galaxies, and the displacements are well understood in terms of
differences in the stellar populations. A large fraction of the nuclei
of these LIRGs are classified as LINER and intermediate LINER/HII, or
composite objects, which is a combination of starformation and AGN
activity. The excitation conditions of the integrated emission depend
on the relative contributions of H II
regions and the diffuse emission to the line emission over the PMAS
FoV. Galaxies dominated by high surface-brightness H II regions show integrated H II-like excitation. A few galaxies show slightly larger integrated [N II]
6584/H
and [S II]
6717,6731/H
line ratios than the nuclear ones, probably because of more contribution from the diffuse emission. The H
velocity fields over the central few kpc are generally consistent, at
least to first order, with rotational motions. The velocity fields of
most LIRGs are similar to those of disk galaxies, in contrast to the
highly perturbed fields of most local, strongly interacting ULIRGs. The
peak of the H
velocity dispersion coincides with the position of the nucleus and is
likely to be tracing mass. All these results are similar to the
properties of
LIRGs, and they highlight the importance of detailed studies of flux-limited samples of local LIRGs.
Key words: Galaxy: evolution - Galaxy: nucleus - galaxies: Seyfert - galaxies: active - infrared: galaxies
1 Introduction
In recent years deep cosmological surveys have been extremely successful
in identifying large samples of high-z galaxies using specific
wavelengths (e.g., UV, optical, infrared, submillimeter) or combinations of
them. Luminous infrared galaxies (LIRGs, with infrared
m
luminosities
,
see Sanders & Mirabel 1996)
and ultraluminous infrared galaxies (ULIRGs, with IR luminosities
,
see Lonsdale et al. 2006) are significant cosmological classes.
These IR-selected galaxies are the main contributors to the co-moving
star formation rate density of the universe at z > 1
(Elbaz et al. 2002; Le Floc'h et al. 2005; Pérez-González et al. 2005; Caputi et al. 2007).
Table 1: Log of the PMAS observations.
Because these high-z samples are so numerous, most efforts concentrate
on characterizing their integrated properties, such
as stellar masses, star formation rates, average ages, and metallicities.
However, to understand fully how galaxies formed and evolved, one needs
spatially resolved information to study their kinematics, stellar
populations, the star, gas, and dust distributions, as well as the gas
excitation conditions. At high-z this has been done for
optically/UV selected galaxies using integral field spectroscopy
(IFS). These works find clumpy H
morphologies with relatively well-ordered
velocity fields that are consistent with the presence of large disks
at
,
while other systems are better explained as
merger candidates (see e.g.,
Förster-Schreiber et al. 2006; Genzel et al. 2006, 2008; Wright et al. 2009). A similar result is found at intermediate redshifts (Puech et al. 2008; Yan et al. 2008).
In the local universe
LIRGs and ULIRGs are much less numerous than at high-z,
and a large amount of work has already been done to characterize their
properties using optical long-slit spectroscopy (e.g., Heckman et al. 1987; Armus et al. 1989; Kim et al. 1995,
1999; Veilleux et al. 1995, 1999; Wu et al. 1998; Heckman et al. 2000; Rupke et al. 2005; Chen et al. 2009). The majority of optical and near-IR
IFS works have so far focused
on small samples of (U)LIRGs or individual galaxies
(e.g., Arribas et al. 2001;
Murphy et al. 2001;
Lípari et al. 2004a,b; Colina et al. 2005; Monreal-Ibero et al. 2006; García-Marín et al. 2006; Reunanen et al. 2007).
The work of Shapiro et al. (2008)
has recently highlighted the importance of having local templates
for understanding the
internal and dynamical processes taking place at high-z.
We note, however, that care is needed when comparing
local IR luminosity matched galaxies with high-z systems. For
instance, at
the
mid-IR spectra of star-forming ULIRGs are more similar to those of
local starbursts and LIRGs than to those of local ULIRGs (Farrah et al. 2008; Rigby et al. 2008; Alonso-Herrero et al. 2009). One
possible explanation is that in high-z ULIRGs star formation
is taking place over larger scales, a few kpc, than in local ULIRGs
where most of the infrared emission arises from sub-kpc scale regions
(e.g., Soifer et al. 2000). In contrast intermediate
redshift (
)
LIRGs appear to be experiencing similar
starburst phases to those of local LIRGs (Marcillac et al. 2006).
We thus need to understand the spatially-resolved physical processes and properties of local
(U)LIRGs and compare them with those of distant IR-selected galaxies.
We recently started an optical IFS survey of a representative
sample of approximately 70 nearby (
)
LIRGs and ULIRGs (see
Arribas et al. 1998).
The general goal of this survey is to provide a two-dimensional, as
opposed to integrated or nuclear, characterization of the physical
and dynamical processes taking place in local
LIRGs and ULIRGs. As discussed in detail by Arribas et al. (2008),
we are conducting this survey using three different optical IFS
instruments in both the northern and the southern hemispheres. These are:
VIMOS (Le Févre et al. 2003) on the VLT,
the INTEGRAL+WYFFOS system (Arribas et al. 1998; Bingham et al. 1994)
on the William Herschel Telescope, and
the Potsdam multi-aperture spectrophotometer (PMAS, Roth et al. 2005) instrument on the 3.5 m telescope at
Calar Alto (Spain). In this paper
we present an atlas of the IFS observations obtained with
PMAS for the northern hemisphere portion of the volume-limited sample of LIRGs of Alonso-Herrero et al. (2006), which is part of the larger survey of Arribas et al. (2008). Additionally, we are observing a representative sample with near-infrared IFS (Bedregal et al. 2009) using SINFONI (Eisenhauer et al. 2003) on the VLT.
The paper is organized as follows. Sect. 2 gives details on the
sample, the observations and the
data reduction. Sect. 3 presents the analysis of
the PMAS IFS data. Sects. 4, 5, and 6, discuss the general results on the
morphologies of the emission lines and continuum, the nuclear and integrated 1D spectra,
and the kinematics of the ionized gas, respectively. The
discussion and summary of this work are given in Sect. 7.
Throughout this paper we used
.
2 Observations
2.1 The sample
We observed the majority of the northern hemisphere galaxies (see Table 1) from the volume-limited representative sample of local LIRGs of Alonso-Herrero et al. (2006). This sample was
drawn from the IRAS Revised Bright Galaxy Sample (RBGS, Sanders et al. 2003). The Alonso-Herrero et al. (2006) sample is limited in distance
(velocities of
or distances of
Mpc for the assumed cosmology) so that the Pa
emission line at rest-frame wavelength
m could be
observed with the NICMOS F190N narrow band
filter (see Sect. 2.3 and Alonso-Herrero et al. 2000a, 2006 for full
details). Arp 299, the most luminous system in this LIRG sample, was observed with the IFS
INTEGRAL instrument and analyzed in detail by
García-Marín et al. (2006). For the sake of
completeness we will include
Arp 299 (
)
in the discussions presented in Sects. 4, 5, and 6.
Our sample of LIRGs covers a range in infrared
luminosities of
.
The average infrared luminosity of the full sample
(northern and southern hemispheres) is
or
.
Except for Arp 299, which is a strongly interacting system, the
rest of
the northern hemisphere LIRGs in this sample are apparently isolated
galaxies, weakly interacting systems (e.g., NGC 7469,
NGC 7771) and galaxies
with small companions but no clear morphological signs of interaction
(e.g., NGC 6701, see Márquez et al. 1994).
2.2 PMAS optical integral field spectroscopy observations
We obtained optical IFS of 11 LIRGs using PMAS
on the 3.5 m telescope at the German-Spanish
Observatory of Calar Alto
(Spain) during three observing runs: November 2005,
May 2006, and December 2006. The PMAS observations were taken with
the Lens Array Mode configuration which is
made of a
array of microlenses coupled with fibers
called hereafter spaxels. We used the 1
magnification which
provides a field
of view (FoV) of
.
We used the V300 grating with a dispersion of 1.67 Å pixel-1 and an approximate spectral range
of 3400 Å. The wavelength range covered by the observations was
approximately
3800-7200 Å.
The approximate spectral resolution of the spectra in
the
binned mode is
6.8 Å full width half maximum (FWHM, see also Sect. 3.1).
![]() |
Figure 1:
(a) NGC 23. The middle and bottom panels are the PMAS observed (not corrected for extinction) maps of the brightest emission lines: H |
Open with DEXTER |
![]() |
Figure 1: (b) As Fig. 1a but for MCG +12-02-001. |
Open with DEXTER |
![]() |
Figure 1: (c) As Fig. 1a but for UGC 1845. |
Open with DEXTER |
![]() |
Figure 1: (d) As Fig. 1a but for NGC 2388. |
Open with DEXTER |
![]() |
Figure 1: (e) As Fig. 1a but for MCG +02-20-003. |
Open with DEXTER |
![]() |
Figure 1:
(f) As Fig. 1a but for IC 860. The H |
Open with DEXTER |
![]() |
Figure 1: (g) As Fig. 1a but for NGC 5936. |
Open with DEXTER |
![]() |
Figure 1: (h) As Fig. 1a but for NGC 6701. |
Open with DEXTER |
![]() |
Figure 1:
(i) As Fig. 1a but for NGC 7469; there is no HST/NICMOS NIC2 Pa |
Open with DEXTER |
![]() |
Figure 1: (j) As Fig. 1a but for NGC 7591. |
Open with DEXTER |
![]() |
Figure 1:
(k) As Fig. 1a
but for NGC 7771. The PMAS mosaics were constructed with the east
and west pointings done for this galaxy and they cover approximately
the central
|
Open with DEXTER |
2.2.1 Observing procedure
The total integration time for each galaxy was split into three or four
individual galaxy exposures (see Table 1),
each of which having between 400 and 1000 s. Given the relatively
small FoV of PMAS in the Lens Array configuration and the large extent
of the galaxies, we obtained a separate sky integration for each
galaxy, interleaved with the galaxy observations and with a comparable
single exposure time of 900 or 1000 s. For all the galaxies we
obtained one pointing, except for NGC 7771 for which we took two
pointings to cover the approximate
central
region.
Table 1 gives for each target the observing campaign, integration times for the
individual galaxy exposures and number of exposures,
integration time,
seeing conditions for each data set, as well as the airmasses
of the observations. The typical seeing conditions of the observations
varied between 0.8
and 1.7
,
depending on the observing campaign.
During each night we obtained calibration arcs and lamps, and flat-fields. Since PMAS is located at the Cassegrain focus, it is affected by the changing flexures of the telescope when tracking the targets. Therefore, we obtained individual arc and internal lamps exposures for each different pointing, when applicable before and after culmination of the target. The lamps used were a ThAr lamp for the Nov. 2005 and May 2006 campaigns, and a HgNe lamp for the Dec. 2006 campaign. Additionally throughout the nights we observed spectrophotometric standard stars to correct for the instrument response, and to flux calibrate the data. We note, however that conditions were non-photometric for several nights in all the campaigns (see Table 1).
2.2.2 Data reduction
The PMAS data were reduced using a set of customized scripts under the
IRAF
environment.
The first step of the data reduction was to determine and subtract the
bias
level. Next, using reference internal continuum lamp exposures, we
identified and traced the location of each of the 256 spectra along the
dispersion direction of the CCD. Once we extracted the individual
spectra, the third reduction step was the wavelength calibration, which
we carried out using a model obtained from arc lamp exposures. We
checked the wavelength calibration against known sky emission lines
and measured a median standard deviation of 1.8, 2.0, and
1.8 Å for the
Nov. 2005, May 2006, and Dec. 2006 observing runs, respectively. The
fourth step
was to correct for the sensitivity variations by creating a response
image
using internal calibration lamp images and a sky flat exposure. After
that, a
relative flux calibration was performed using standard star
observations. The
next step was to combine the different galaxy exposures (a minimum of
three)
for each individual pointing to improve the signal-to-noise ratio and
to remove cosmic rays. The sky subtraction was done on
a spaxel-by-spaxel basis using for each galaxy its own sky
observation. The final step was to build the data cubes and rotate them
to the north
up, east to the left orientation.
2.3 HST/NICMOS observations
The HST/NICMOS observations were obtained with the NICMOS NIC2
camera, which has a pixel size of 0.076
and a FoV of
.
Details on the observations and data reduction procedures can
be found in Alonso-Herrero et al. (2006). For this paper we make use of the
m continuum observations and
the continuum-subtracted Pa
images for comparison with the PMAS data. The only additional step needed for the NICMOS images was to rotate
and trim them to match the orientation and FoV, respectively, of the PMAS
images. The angular resolution of the NICMOS data is approximately
and
(FWHM) for the
m continuum
and Pa
images, respectively.
3 IFS data analysis
3.1 Spectral maps
We constructed spectral maps of the brightest emission lines by
fitting the lines to Gaussian functions and the adjacent continuum to
straight lines, on a spaxel-by-spaxel basis. To do so we developed our
own routines which make use of the IDL-based MPFITEXPR algorithm
developed by Markwardt (2008) to measure in an automated fashion the central wavelength, the width of
the Gaussian (
), and
integrated flux for each emission line. Using this algorithm we were
also able to fix the relative wavelengths and line
ratios according to atomic parameters when fitting multiple emission
lines ([N II]
6548, H
,
[N
II]
6584, and [S II]
6717,6731).
Additionally for each of the two sets of lines we imposed that the
lines had the same width. We did not attempt to correct the maps of the
H
emission line
for the presence of H
in absorption, which is observed in
most of the spectra of the sample of LIRGs (see also Sect. 3.2).
The spectral maps of the emission line fluxes, as well as the maps of
the central wavelength (or velocity field), and
(or velocity
dispersion) were only constructed for
those spaxels whose integrated line flux was
above the
local continuum, where
was the standard deviation of the
fitted local continuum.
We found that the emission lines of all galaxies were adequately
fitted with one component (Fig. 1), except for NGC 7469, a
well-known Seyfert 1 galaxy, for which we fitted the hydrogen
recombination lines using a broad and a narrow component. The maps of
both components are shown in Fig. 2.
![]() |
Figure 2:
PMAS maps of the H |
Open with DEXTER |
The uncertainties of the measured
velocities and velocity dispersions depend on
the errors in measuring the centroid and width of the emission line, which in
turn depend on
the signal-to-noise of
the spaxel, and the systematic errors (e.g., the wavelength
calibration,
see Sect. 2.2). The typical errors in measuring the widths of the
Gaussians when fitting the H+[N II] lines were 10%.
The maps of the observed H
velocity dispersion
(
)
were corrected for the instrumental
resolution (
)
using
.
For each observing campaign
we measured the instrumental resolution on a spaxel-by-spaxel
basis using the observations of the arc emission lines at a wavelength
close to that of H
.
The median instrumental resolution across
the detector near H
is
Å for all three observing runs.
The H
velocity fields and the maps of the
H
velocity dispersion are shown in the left and right panels,
respectively, of Fig. 3.
Since the emission lines observed in IC 860 are faint, we decided to fit
the H+[N II] and the [S II] lines (H
,
[O III]
5007 and [O I]
6300 were not detected)
manually using splot within IRAF without any
constraints. The spectral maps for this galaxy are shown in
Fig. 1f. As can be seen from this figure, the
H
and [S II] lines are only
detected in the nuclear regions, whereas the [N
II]
6584 emission line is more extended.
In addition to fitting the brightest emission lines for each galaxy,
we constructed a continuum image centered at
Å by
summing up the continuum spectra over a rectangular band width of
approximately 17 Å. Figure 1 shows the
continuum maps for our sample of LIRGs. The peak of the
optical continuum emission is marked with a cross for each galaxy
on the PMAS maps in this figure as well as in Figs. 2 and 3.
As explained in Sect. 2.1.1, for
NGC 7771 we took two separate pointings to cover the approximate
central
region of the galaxy.
The systematic error of telescope offsets with PMAS is given by the
astrometric accuracy of the PMAS Acquisition and Guiding (A&G) system, which has been determined
to be
/pixel (Roth et al. 2005). As the A&G
system is an integral part of the instrument, systematic offset errors
are negligible. The statistical accuracy of the auto-guider is a fraction
of a pixel, and the canonical value is 0.1
rms (Roth 2009, private
communication). Thus, we used the offsets commanded using the PMAS
acquisition images to construct mosaics of the emission line and
continuum maps, as well
as the H
velocity fields and maps of the velocity dispersion.
Figure 1 shows for the 11 LIRGs in our sample the PMAS maps of the
brightest optical emission lines, the HST/NICMOS continuum
subtracted Pa
images, together with images of the
stellar emission at
6200 Å (PMAS) and at
m
(NICMOS). Since the PMAS images do not have astrometry, the PMAS and
NICMOS images were registered by using the peaks and shapes of the
continua for reference. For the typical distances of
our galaxies the FoV of the PMAS observations cover the central
4.3-5.3 kpc, except for NGC 7771 for which the PMAS mosaics cover
approximately the central
.
The maps are shown on a square root scale to maximize the contrast
between diffuse and bright regions.
The observed H
velocity fields for all the LIRGs in our sample
except for IC 860 are shown in Fig. 3. For
NGC 7469 we show the [N II]
6584 velocity field
instead, as that of H
is
affected by the uncertainties associated with fitting the broad and
narrow components.
The zero points of the velocity fields are set at the peak of the
6200 Å continuum emission. The only exception is
NGC 7771 where the zero point
is placed at the position that makes the velocity field gradient
symmetric, and it is approximately coincident with the peak of the
near-infrared continuum. Table 3 gives the measured H
cz for the nuclei of
our sample of LIRGs.
Table 2: Nuclear and Integrated observed (not corrected for extinction) line ratios.
3.2 Extraction of 1D spectra
For each galaxy we extracted two 1D spectra: the nuclear spectrum and the integrated spectrum. The nuclear spectra correspond to the spaxel at the peak of the 6200 Å continuum emission. The physical size covered by the nuclear spectrum is given for each galaxy in Table 2, and it is typically the approximate central 300 pc. For reference the nuclear spectra of Kim et al. (1995) and Veilleux et al. (1995) were extracted with a linear physical size of 2 kpc (see discussion in Sect. 5).
The integrated spectrum of each galaxy was extracted by defining
6200 Å continuum
isophotes and then summing up all the spaxels contained within the
chosen external continuum isophote. The external isophotes (plotted
for all galaxies in Fig. 1) were selected
to cover the PMAS FoV as much as possible, without compromising the quality of the extracted spectra. In Table 2
we give for each galaxy the approximate physical size along the major
axis of the galaxy of the outer continuum isophote used for the
integrated spectra. Note that the term integrated is used in the sense
of integrated spectra over the PMAS FoV, and the integrated spectra do
not encompass the whole galaxy (see e.g. figure.set.8 of Moustakas
& Kennicutt 2006 for a comparison
with one of the galaxies in our sample, NGC 23). Typically our integrated
spectra cover the central
3 to 8 kpc along the major axis of the galaxy, depending on the galaxy, but for most galaxies they include the central
5 kpc (see Table 2).
The integrated spectra of those galaxies
observed under non-photometric conditions (Table 1) may be
affected by imperfect sky
subtraction, but this does not affect the measurements of the brightest
emission lines.
The full nuclear spectra are shown in Fig. 4 for each LIRG
in the sample. In the same figure we present in the insets
the blue part of the integrated spectra to
emphasize the differences between the underlying absorption features and the
H
and [O III]
5007 emission lines in the nuclear
and integrated spectra.
The fluxes of the brightest emission lines of the nuclear and
integrated spectra were measured manually using splot within
IRAF and were compared with the automated flux measurements used for
constructing the spectral maps (see Sect. 3.1), except for NGC 7469.
In the case of the manual measurements we did not impose any
constraints on the line widths and ratios
when measuring the [N II]6548, H
and
[N II]
6584, and the [S II]
6717,6731 lines. For the nuclear and integrated
spectra of NGC 7469 we used the method and restrictions
described in Sect. 3.1.
We find a good agreement between the manual and the automated
measurements of the nuclear values. The largest differences (up to
30%) are for the [O I]
6300/H
line ratio,
whereas for the other line ratios the differences are always of less
than 15%. As done for the spectral maps,
we did not attempt to correct for the presence of H
in absorption. The observed (not corrected for extinction) line ratios
for the nuclear and integrated spectra are given in Table 2.
4 Morphology of the stellar and gas emissions
The optical and near-infrared continuum images (Fig. 1)
reveal the presence of bright nuclei, and a large
number of
star clusters in the nuclear regions as well as along the large scale
spiral arms. The star clusters are only unveiled by the higher angular
resolution of the NICMOS images, which is
typically a few tens of parsecs for our sample of
LIRGs. There is a good overall correspondence, on scales of a few hundred
parsecs (the PMAS spatial resolution), between the optical and the
near-infrared stellar continua as mapped out by the PMAS 6200 Å and the
NICMOS m emissions, respectively. This indicates that
for the majority of these LIRGs the effects of extinction on the
continuum morphologies are not
overly severe, except for the nuclei of the galaxies
(Alonso-Herrero et al. 2006).
This is clearly seen in
NGC 7771 where the peaks of the optical and near-infrared continua
appear displaced by a few arcseconds (see Figs. 1k and 3). This is probably
due to the highly inclined nature of this galaxy, as well as the
diversity of stellar populations and patchy extinction present in the
ring of star formation (Davies et al. 1997; Smith et al. 1999; Reunanen et al. 2000).
Another example with large differences between the
optical and near-infrared continuum emission is Arp 299, and we
refer the reader to Alonso-Herrero et al. (2000a) and
García-Marín et al. (2006) for a full discussion.
The PMAS H
and the NICMOS
Pa
emissions are well correlated, and both trace the
nuclear emission as well as the emission from bright, high
surface-brightness H II regions (Fig. 1). The high angular resolution of the NICMOS Pa
images
resolves with exquisite detail the sites of the youngest star forming
regions in the central regions of LIRGs. These high surface-brightness
H II regions can be either
located in the central 1-2 kpc or spread out throughout the disk of the galaxies (see Alonso-Herrero et al. 2006 for more details).
Since the NICMOS Pa
and nearby continuum
images were taken with narrow-band filters,
and a relatively small pixel size, they are not very sensitive to the diffuse
low surface-brightness emission. This may also be due to the fact that
in LIRGs the diffuse emission suffers much less extinction than the bright
H II regions (see Rieke et al. 2009 and references therein).
The PMAS H
images show emission from
the H II regions, at lower angular resolution than the NICMOS
images. Additionally, for most LIRGs the
PMAS H
images are also sensitive to more diffuse low
surface-brightness
emission. This extended emission can be seen almost over
the entire PMAS FoV (e.g., NGC 5936
Fig. 1g and NGC 6701 Fig. 1h), and beyond, as shown by other works
for a few galaxies in common with our sample (Márquez et al.
1999; Dopita et al. 2002; Hattori et al. 2004).
It is only the two galaxies with the most compact nuclear Pa
emission, IC 860 (Fig. 1f) and to a lesser degree UGC 1845 (Fig. 1c), that also show relatively compact H
emission.
The fact that H
and Pa
morphologies are
in general similar suggests that over the PMAS FoV and with the PMAS
angular resolution the extinction effects on H
are not severe,
except
in the very nuclear regions. Indeed, Alonso-Herrero et al. (2006) for the galaxies in common with this work measured
average extinctions to the gas of
mag over the Pa
emitting regions (a few kpc). Similar values of the extinction were
found by Veilleux et al. (1995) from the Balmer decrement.
The PMAS H
maps are similar to those of H
although they
are more affected by extinction and/or the presence of
H
in absorption, especially in the nuclear regions (e.g., UGC 1845 Fig. 1c, MCG+02-20-003 Fig. 1e, NGC 7591 Fig. 1j).
![]() |
Figure 3:
(a) Maps of the observed H |
Open with DEXTER |
![]() |
Figure 3: (a) continued. |
Open with DEXTER |
![]() |
Figure 3:
(b) As Fig. 3a. The velocity field and the map of the velocity dispersion for NGC 7469 are for the [N II] |
Open with DEXTER |
![]() |
Figure 3: (c) As Fig. 3a. In the case of NGC 7771 the asterisk marks the position that makes the velocity field gradient symmetric, and it is approximately coincident with the peak of the near-infrared continuum and the maximum of the velocity dispersion. |
Open with DEXTER |
In general the overall morphology of the brightest forbidden lines ([N
II]
,
[S II]
6717,6731) shows a
reasonable correlation with that of H
.
On smaller scales,
however,
some differences are already apparent in Fig. 1. For instance, in NGC 23
(Fig. 1a) all the optical
emission lines except for H
and H
peak in the
nucleus, whereas the brightest regions of hydrogen recombination line
emission (H
,
Pa
), which trace the sites of on-going
star formation, are in the circumnuclear ring of star
formation. There are also small scale differences between the
H
and [N
II]
emissions of the nuclei and the H II regions
For example,
some of the extra-nuclear H II regions of NGC 2388 (Fig. 1d)
and MCG +02-20-003 (Fig. 1e) appear to have lower
[N II]
/H
ratios than their nuclei. This
is a well known behavior of galaxies (Veilleux & Osterbrock 1987; Kennicutt et al. 1989; Sarzi et al. 2007).
The small scale differences of the different emission lines
in LIRGs are more apparent from the spatially resolved properties of the optical
line ratios of this sample of LIRGs and will be discussed in detail
in a forthcoming paper (Alonso-Herrero et al. 2009, in preparation).
Although the limited angular resolution of the PMAS continuum and gas
maps does not allow us to resolve all the morphological details seen
in the NICMOS images, the
general behavior is the same. For the majority of the LIRGs in
our sample the peaks of the stellar and the H
gas emissions are
coincident and located in the nuclear region. The few cases of displacements
between the stellar and the H
peaks are found in those
LIRGs with circumnuclear rings of star formation without Seyfert activity. In
NGC 23 (Fig. 1a) and NGC 7771 (Fig. 1k) the stellar emission
peaks in the nuclei, whereas the brightest H
and Pa
emission are
in luminous H II regions in the rings. These displacements
are likely to be due to differences in the stellar populations.
That is, the youngest
regions and thus brightest H
emitting regions are in the rings,
whereas the nuclei contain older stellar populations. The latter is
clearly demonstrated by the presence of strong absorption features
(Balmer line series, H+K CaII lines) in the nuclear spectra of these two galaxies (Fig. 5). In the case of NGC 7469, which also shows a bright circumnuclear ring of star formation (see Genzel et al. 1995; Díaz-Santos et al. 2007, and references therein), the peaks of the stellar and gas emission are coincident with the nuclear AGN.
In contrast to the majority of the LIRGs in this volume-limited
sample, in the interacting LIRG Arp 299 the peaks of the observed
warm ionized gas are displaced from the stellar peaks typically by 1.4 kpc
(see García-Marín et al. 2006).
In local interacting ULIRGs the displacements between the continuum and
gas emissions are common and even larger, typically 2-4 kpc and in
some exceptional cases as large as
8 kpc (Colina et al. 2005; García-Marín et al. 2009). The
differences in the stellar and gas distributions in ULIRGs
are understood in terms of
the more extreme effects produced by the interaction processes on the
spatial distribution of the ionizing sources and the presence of large
amounts of dust in the nuclear regions.
5 Nuclear versus integrated spectral classification
We used the standard optical diagnostic diagrams (BPT diagrams, Baldwin et al. 1981) to classify galaxies into the H II-like, LINER, and Seyfert spectral types. For the spectral classification of the nuclear and integrated activity we used two different sets of boundaries in the optical line ratio diagrams. The first are the classical semi-empirical boundaries of Veilleux & Osterbrock (1987, V&O87 hereafter), which have the added advantage of making the comparison with previous results on these LIRGs easier. The V&O87 boundaries are shown in Fig. 5. The second set includes the latest empirical and theoretical boundaries derived by Kauffmann et al. (2003) and Kewley et al. (2001a, b, 2006), and are shown in Fig. 6. Kewley et al. (2001a, b) modeled AGN and starburst line ratios to provide theoretical boundaries in these diagnostic diagrams. They defined the so-called maximum starburst lines above which the line ratios cannot be explained by pure star formation. Kauffmann et al. (2003) and Kewley et al. (2006) derived empirical boundaries in these diagrams to separate H II, LINERs and Seyfert galaxies using large samples of galaxies drawn from the Sloan Sky Digital Survey (SSDS). We will refer to this second set of boundaries as theoretical/SSDS.
We did not attempt to correct the line ratios for extinction. The effects of extinction on the spectral classifications should be moderately small because the lines involved in the line ratios are in most cases close in wavelength.
The first result worth noticing is that when using the
[O III]5007/H
vs. [N II]
6584/H
diagram and the theoretical/SSDS boundaries (Fig. 6 and Table 3),
a large fraction of the LIRG nuclei are classified as composite, and
thus they are likely to contain a metal-rich stellar population and an
AGN (see Kewley et al. 2006). It is also possible that some of these composite objects have an added contribution
from shock excited emission (from supernovae) associated with an
aging starburst (see Alonso-Herrero et al. 2000b). If we use all three BPT diagrams the fraction of composite
objects appears to be smaller. However, Kauffmann et al. (2003) did
not provide an empirical separation between AGN and star-forming
galaxies in the diagrams involving the [O I]
6300/H
and the [S II]
6717,6731/H
ratios, so we
cannot assess whether galaxies are composite or not using those two diagrams.
Using all three BPT diagrams and the V&O87 classical boundaries (thin lines in Fig. 5) we find that only two nuclei in our sample of LIRGs show pure H II-like excitation (that is, classified as H II using all three BPT diagrams), five have an intermediate LINER/H II classification, two fall in the LINER regions, and one nucleus is classified as a Seyfert galaxy (upper panels of Fig. 5, see also Table 3). This large fraction of composite objects (i.e., star formation and AGN activity) is a well-known property of samples of infrared-bright galaxies (Veilleux et al. 1995; Kewley et al. 2001b; Chen et al. 2009), regardless of what boundaries are used for classifying galaxies.
We
cannot provide a conclusive classification for IC 860 because the
emission lines in the blue part of the spectrum are not detected (note
the strong H
absorption, Fig. 4).
The high [N II]
6584/H
and
[S II]
6717,6731/H
line
ratios could indicate a Seyfert or LINER classification,
but the correction for underlying stellar H
absorption would
decrease significantly the observed line ratios in this galaxy.
A large fraction of the LIRGs in this sample show a strong
contribution from an evolved stellar population as indicated by the
presence of absorption features (Balmer line series, H+K CaII
lines) in the blue part of the spectra
(Fig. 4). Although a detailed modeling of the stellar populations
is beyond the scope of this paper, we can attempt to correct
the [O III]5007/H
ratio for the presence of
an evolved stellar population for those galaxies located near the
AGN/HII boundaries. These are NGC 23, UGC 1845, and NGC 7591
(Fig. 6). Our preliminary modeling indicates
that a combination of intermediate (1-5 Gyr)
and young (<10 Myr) stellar populations with
a measured equivalent width of H
in absorption of
4 Å
would produce acceptable fits to their spectra. This is within the
average H
stellar absorption corrections obtained by Moustakas &
Kennicutt (2006) for a sample of nearby star-forming galaxies.
The approximate effects of correcting the observed
[O III]
5007/H
for underlying stellar
absorption are shown as arrows in the upper panel of Fig. 6. The
corrections for the other line ratios involving H
would be
smaller. As can be
seen from this figure, this correction does not change fundamentally
the result that these nuclei appear to be composite in nature.
![]() |
Figure 4: PMAS spectra
(plotted in arbitrary units) of the nuclei of the galaxies in the
sample. Additionally, for each LIRG the inset shows the blue part of
the integrated spectrum so that the absorption features as well as the H |
Open with DEXTER |
![]() |
Figure 4: continued. |
Open with DEXTER |
![]() |
Figure 5: BPT diagrams for the PMAS nuclear ( upper panels) and the integrated ( lower panels) emission of the LIRGs in our sample. The thin lines are the classical boundaries of Veilleux & Osterbrock (1987) for the H II region, LINER, and Seyfert excitation. |
Open with DEXTER |
![]() |
Figure 6:
Same as Fig. 5 but showing
the so-called ``maximum starburst lines'' (thick solid lines),
defined by Kewley et al. (2001a) from theoretical modeling as the lines above which line ratios cannot be explained by star formation alone.
We also show the empirical separation between AGN and H
II regions of Kauffmann et al. (2003), and between Seyfert and LINER of Kewley et al. (2006), as thick dashed lines. In the upper panel, the arrows represent the result of correcting the H |
Open with DEXTER |
Table 3: Spectral classifications of the nuclear and integrated spectra.
We have seven galaxies in common with the work of Veilleux et al. (1995). Our
nuclear classifications
are in good agreement with theirs. The only two exceptions are
NGC 23 and NGC 6701, which we would classify as
LINER/HII with the V&O87 boundaries, or as composite using the
theoretical/SSDS boundaries. As explained in Sect. 3.2 we extracted
our nuclear spectra with
the smallest possible physical sizes allowed by the PMAS spaxels
(300 pc, Table 2), whereas
Veilleux et al. (1995) used linear sizes of 2 kpc for
extracting their nuclear spectra. As can be seen from Figs. 1a and 1h, the Veilleux et al. (1995) apertures included a large number of H II
regions in the ring of star formation of NGC 23 and in the inner
spiral structure of NGC 6701. This readily explains the H II-like classification given by Veilleux et al. (1995).
The BPT diagrams for the integrated emission over the PMAS FoV are
presented in the lower panels of Figs. 5 and 6.
The integrated line ratios of the four galaxies whose nuclei
are classified as LINERs using the V&O87 boundaries
now fall in the H II region or in the
intermediate LINER/H II region. A similar situation is
seen for NGC 7469 for which the integrated line ratios move toward
the composite area in all diagrams. This is well understood in
terms of the increased contribution of extra-nuclear high surface-brightness
H II regions (see Hmorphologies in Fig. 1) to their integrated emission. For the other
galaxies there is no general trend, as the integrated line
ratios depend on the
relative contribution of H II regions and diffuse emission to
the total line
emission over the PMAS FoV (Alonso-Herrero et al. 2009, in
preparation). For instance, the integrated line ratios of NGC 7771
show larger [N II]
6584/H
and
[S II]
6717,6731/H
line
ratios than the nuclear ones, whereas the nuclear and integrated line
ratios of other galaxies (e.g., MCG+02-20-003) remain approximately
constant or slightly more similar to those of H II regions.
Finally, we show an example of the power of optical IFS in identifying
different excitation conditions. For NGC 7469 we also
extracted the spectrum of an H II region in
the circumnuclear ring of star formation, located at about 2
west from the nucleus (Fig. 4). It is clear that the line ratios are typical of H II-like
excitation and are not contaminated by the nearby Seyfert 1
nucleus (i.e., no broad components are present in the hydrogen
recombination lines).
Summarizing, the
comparison of the nuclear and integrated activity classifications,
together with the spatial distribution of the bright emission lines
(in particular H)
allowed us to isolate and quantify the different
ionization sources
(nuclei, and circumnuclear H II regions and diffuse emission)
contributing to the observed emission in galaxies (see also
Alonso-Herrero et al. 2009, in preparation).
6 Ionized gas kinematics
The velocity fields of the emission lines over the
central few kpc (typically 5 kpc) are mostly consistent with rotation
(see Fig. 3) for all the galaxies in the sample. We note that even
on the physical scales probed by PMAS (300 pc),
some velocity fields appear to show some peculiarities.
However, it is clear that these velocity fields are more similar to
those of disk galaxies (Falcón-Barroso et al. 2006: Daigle et al. 2006) than to those of local ULIRGs (Colina et al. 2005; Monreal-Ibero et al. 2006).
The large scale continuum major photometric axis and the H
major kinematic
axis are broadly in agreement with each other (seen in
projection) in the majority of our LIRGs. The ionized gas peak-to-peak velocities of LIRGs (over the central
5 kpc) are typically between 200 and
(see Table 4), whereas in ULIRGs with tidally induced flows the gas peak-to-peak velocities can be as high as
(Colina et al. 2005).
Three galaxies in our sample show circumnuclear rings of star
formation. The central H
velocity field of NGC 23
is consistent with
rotation, with the major kinematic axis aligned with the major axis of
the galaxy rather than with the orientation of the ring of star formation
as seen in H
(Fig. 1a).
A similar situation is observed for
NGC 7469, where the [N II]
6584 velocity field has a
major axis similar to that of the continuum, although it is
asymmetric towards the north-west direction. This asymmetry was
already reported in the rotation curve along the major axis of the
galaxy by Márquez & Moles (1994). In both galaxies, it
is likely that most of the mass in the central region is in relatively evolved stars
rather than in young ionizing stars (see also Díaz-Santos et al. 2007 for NGC 7469).
The H
velocity field of the inner
of NGC 7771 has a major kinematic axis aligned with the approximate
orientation of the circumnuclear ring of star formation (east-west
direction), whereas the outer velocity
field appears to have a major kinematic axis in better agreement with that
of the large scale continuum emission. This kind of velocity fields with
symmetric distortions can be associated with the presence of a warped
disk. It is also worth mentioning that there is dynamical evidence
that NGC 7771 is weakly interacting with NGC 7770 (Keel 1993) and is located in a group of galaxies.
Another example of a central H
velocity field that deviates from
perfect rotation is that
of NGC 6701. This galaxy shows a complex overall
morphology, with the presence of a large
scale bar, an inner isophote twist produced by a spiral like inner ring
(see Márquez et al. 1996, and the continuum
m image in
Fig. 1h), a perturbed rotation curve,
and a small companion likely to be responsible for some of these
properties (Márquez et al. 1996). As seen in other galaxies in our sample, the
major kinematic axis of the H
velocity field appears to be better
aligned with the photometric axis of the galaxy (PA
,
Vogt et al. 2004) rather than with the orientation of the nuclear high
surface-brightness emission Pa
emission, which is seen in an
almost north-south orientation.
Arp 299 the most luminous galaxy in our sample and a strongly interacting system shows very complicated velocity fields (both of neutral and ionized gas, see García-Marín et al. 2006), not only at the interface between the two galaxies, but also in the nuclear regions of the two members of the system. Moreover, the velocity fields of the ionized gas in Arp 299 do not appear to be dominated by ordered virialized motions, probably as a result of the interaction between the two galaxies, as is the case of most ULIRGs.
Table 4: Gas kinematic results.
As can be seen from Fig. 3 for most LIRGs in our sample the
peak of the H
velocity
dispersion coincides with the peak of the optical and near-infrared
continuum emission (i.e., the nucleus), and thus the velocity
dispersion is likely to be tracing mass. The nuclear H
velocity dispersions are between 66 and 144
(Table 4). The largest velocity dispersions
of the ionized gas are associated with three of the nuclei classified
as LINERs and the Seyfert galaxy NGC 7469.
In the case of galaxies with circumnuclear rings of star formation, we find that the gas velocity dispersions in the rings are less than in the nuclear regions. This is consistent with the findings of Falcón-Barroso et al. (2006) for the same type of galaxies and was interpreted as an indication for the presence of large amounts of cold gas from which stars have recently formed.
There are only a few measurements of the stellar velocity
dispersion of LIRGs. From near-infrared CO
absorption features the stellar velocity dispersions are between 60 and
160
(Shier et al. 1996; Hinz & Rieke
2006), similar to the range of H
velocity
dispersions measured for our LIRGs. The only LIRG in our sample with a
stellar velocity dispersion measurement is NGC 7469, for which
Onken et al. (2004) obtained
from the calcium triplet, in
good
agreement with our measurement from the ionized gas.
The velocity dispersions of LIRGs are in
general similar to or slightly less than the typical nuclear gas
and stellar velocity dispersions of ULIRGs (Colina et al. 2005; Dasyra et al. 2006).
This suggests that at least some LIRGs have comparable dynamical masses
to those of ULIRGs, although a detailed modeling is needed to assess
this issue.
7 Discussion and summary
This is the first paper in a series presenting PMAS optical IFS
observations of the northern hemisphere portion of the volume-limited
(
)
sample of local LIRGs defined by Alonso-Herrero et al. (2006). This
sample is in turn part of the larger IFS survey of nearby (z<0.26) LIRGs and ULIRGs assembled by Arribas et al. (2008). In this paper
we presented the observations and
data reduction of the PMAS observations. The PMAS observations cover
the central
(typically the central
5 kpc) with spaxels of 1
in size, and a spectral range
3800-7200 Å. The PMAS IFS data were complemented
with our own existing near-infrared HST/NICMOS observations of
the
m continuum and the Pa
emission line. The main goal of this paper is to present
an atlas of the observations and
the general IFS results of the sample of LIRGs
and compare them with local ULIRGs.
On the physical scales probed by the PMAS IFS (300 pc) the optical and near-infrared stellar morphologies
are similar for most galaxies, indicating that extinction is not
playing a major role for this sample of LIRGs, except in the innermost regions. Similarly,
there are no major morphological differences between
Pa
and H
.
The HST/NICMOS Pa
and PMAS H
observations are
complementary, with the former
revealing in great detail (physical scales of a few
tens of parsecs) the morphologies of the
high surface-brightness H II regions, and the latter
being sensitive not only to H II regions but also to
diffuse emission with lower surface brightness.
In the majority of the LIRGs in our sample
the peaks of the continuum and gas (e.g., H,
[N
II]
6584) emissions coincide. This contrasts with
local interacting ULIRGs, where the extreme effects of the interaction
processes on the ionizing mechanisms and the distribution of dust
can
cause displacements between the peaks of continuum and gas emission of
typically 2-4 kpc (Colina et al. 2005: García-Marín et al. 2009). The only exceptions in the LIRG sample are galaxies with
circumnuclear rings of star formation (NGC 23 and NGC 7771)
and the strongly interacting galaxy Arp 299. In the case of the
galaxies with circumnuclear rings of star formation, the most luminous
H
emitting regions are found in the rings rather
than in the nuclei of the galaxies, and the displacements are well
understood in terms of differences in the
stellar populations. In Arp 299 the displacements are due to the high
extinctions suffered by the nuclear regions (see Alonso-Herrero et al. 2000a; García-Marín et al. 2006).
Using standard BPT diagrams we compared the excitation conditions of
the nuclear and
integrated (over the PMAS FoV) 1D spectra of the LIRGs in our
sample. Only two nuclei show
pure H II-like excitation using the classical
V&O87 boundaries, and one
has a Seyfert nucleus.
The rest are classified as LINER or intermediate LINER/H II,
using the V&O87 boundaries, or alternatively as composite
objects using the
theoretical/SSDS boundaries. We also found that a large
fraction of the nuclei show evidence
for a strong contribution from an
evolved stellar population (absorption features).
There is no general trend for the excitation
conditions of the integrated emission when compared with the nuclear
excitation, as the former depends on the
relative contributions of H II regions and the diffuse emission
to the line emission over the PMAS FoV (Alonso-Herrero et al. 2009, in preparation). That is, galaxies dominated by high surface-brightness
H II regions show integrated H II-like excitation,
whereas galaxies with more diffuse low surface-brightness
emission tend to show
slightly larger [N II]6584/H
and
[S II]
6717,6731/H
line ratios.
The H
velocity fields over the central few kpc covered by the
PMAS observations are generally consistent, at least to first order, with
rotational motions.
The observed H
velocity amplitudes (peak-to-peak) are between 200 and
.
Although the velocity fields of some LIRGs show some
peculiarities, they are not as perturbed as those of most local,
strongly interacting ULIRGs. In that respect, the velocity fields of
the emission lines of our sample resemble those of disk galaxies
(Falcón-Barroso et al. 2006: Daigle et al. 2006).
In most LIRGs in our sample the peak of the H
velocity
dispersion coincides with the peak of the optical and near-infrared
continuum emission (i.e., the nucleus). Thus, the velocity
dispersion is likely to be tracing mass and provides further support
for rotation. The nuclear H
velocity dispersions are in the range
and
are similar to the stellar values measured from
near-infrared CO absorption features measured for other LIRGs.
The LIRG nuclei with the largest H
velocity dispersions are
those classified as LINERs and the Seyfert 1 nucleus of NGC 7469.
Throughout this paper we discussed the ionized gas and stellar
distributions, excitation conditions and kinematics of a volume
limited sample of LIRGs. We also showed that the properties of this
sample of LIRGs, and in particular, their kinematics,
are more similar to those of disk galaxies, rather than to
those of local, strongly interacting ULIRGs.
Our LIRGs are part of a flux and volume limited sample
drawn from the IRAS RBGS of
Sanders et al. (2003). As a consequence, our
sample is predominantly composed of
low-luminosity LIRGs with an average IR luminosity of
for the full sample (northern and southern hemispheres, see
Alonso-Herrero et al. 2006). Sanders & Ishida (2004) demonstrated that
marks the
transition between samples being dominated by
disk galaxies and merger dominated samples. In the
Sanders & Ishida (2004) sample of LIRGs, most
objects at
are spiral galaxies with no signatures of a
major interaction and pairs of galaxies, whereas at
most objects are
strongly interacting equal mass galaxies with overlapping disks.
The similarities of our sample with normal disk
galaxies are then well understood because our sample
is mostly composed of disk galaxies and galaxy pairs not undergoing a
strong interaction (Sect. 2.1).
At intermediate redshifts ()
LIRGs are the main contributors to the
star formation rate density
(Elbaz et al. 2002; Le Floc'h et al. 2005; Pérez-González et al. 2005;
Caputi et al. 2007). Moreover, these
LIRGs
are mostly classified as spiral galaxies
(Bell et al. 2005; Melbourne et al. 2005, 2008)
with the star formation smoothly distributed in the disks of the
galaxies as seen for our sample of LIRGs. There is also a strong
evolution in galaxy kinematics at z<1, but still about half of
the line emitting population at these redshifts, which are mostly
LIRGs, have rotating disks (Puech et al. 2008; Yan et al. 2008).
While local and distant LIRGs may have self regulated star formation as in disk galaxies (see Bell et al. 2005), it is clear that their star formation
rates are at least a factor of ten or
more higher than in spirals.
Locally the central regions of LIRGs are found to contain a large
population of giant HII regions not observed in normal spiral galaxies
(see Alonso-Herrero et al. 2006). This, together with a higher
star formation efficiency of the dense gas in local LIRGs (Graciá-
Carpio et al. 2008) may explain
the high star formation rates of LIRGs when compared to normal disk
galaxies.
Studying the spatially resolved properties of flux-limited
complete samples of local LIRGs may help us understand if the
similarities with
LIRGs stem from the same physical
processes and comparable evolutionary states.
Summarizing, we demonstrated the ability of optical IFS to spatially resolve the different ionization sources contributing to the observed emission of LIRGs, as well as to study their kinematic properties. Full detailed studies of the extinction, excitation conditions, stellar populations, and kinematics of LIRGs and ULIRGs will be presented in forthcoming papers.
AcknowledgementsWe are grateful to the Calar Alto staff, and in particular to S. Sánchez, A. Guijarro, L. Montoya, and N. Cardiel, for their support during the PMAS observing campaigns. We thank Martin Roth for interesting and useful discussions about the PMAS instrument, and J. Rodríguez Zaurín for advice on stellar populations. We thank the referee for his/her constructive comments.This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.
A.A.-H., L.C., S.A., A.L., and J.A.-.G acknowledge support from the Spanish Plan Nacional del Espacio under grants ESP2005-01480 and ESP2007-65475-C02-01. A.A.-H. also acknowledges support for this work from the Spanish Ministry of Science and Innovation through Proyecto Intramural Especial under grant number 200850I003. M.G.-M. is supported by the German Federal Department of Education and Research (BMBF) under project numbers: 50OS0502 and 50OS0801. A.M.-I. is supported by the Spanish Ministry of Science and Innovation (MICINN) under program ``Specialization in International Organisms'', ref. ES2006-0003.
References
- Alonso-Herrero, A., Rieke, G. H., Rieke, M. J., et al. 2000a, ApJ, 532, 845 [NASA ADS] [CrossRef]
- Alonso-Herrero, A., Rieke, M. J., Rieke, G. H., et al. 2000b, ApJ, 530, 688 [NASA ADS] [CrossRef]
- Alonso-Herrero, A., Rieke, G. H., Rieke, M. J., et al. 2006, ApJ, 650, 835 [NASA ADS] [CrossRef]
- Alonso-Herrero, A., Rieke, G. H., Colina, L., et al. 2009, ApJ, 697, 660 [NASA ADS] [CrossRef]
- Armus, L., Heckman, T. M., & Miley, G. K. 1989, ApJ, 347, 727 [NASA ADS] [CrossRef]
- Arribas, S., Carter, D., Cavaller, L. et al. 1998, SPIE, 3355, 821 [NASA ADS]
- Arribas, S., Colina, L., & Clements, D. 2001, ApJ, 560, 160 [NASA ADS] [CrossRef]
- Arribas, S., Colina, L., Monreal-Ibero, A., et al. 2008, A&A, 479, 687 [NASA ADS] [CrossRef] [EDP Sciences]
- Baldwin, J. A., Phillips, M. M., & Terlevich, R. 1981, PASP, 93, 5 [NASA ADS] [CrossRef]
- Bedregal, A. G., Colina, L., Alonso-Herrero, A., et al. 2009, ApJ, 698, 1852 [NASA ADS] [CrossRef]
- Bell, E., Papovich, C., Wolf, C., et al. 2005, ApJ, 625, 23 [NASA ADS] [CrossRef]
- Bingham, R. G., Gellatly, D. W., Jenkins, C. R., et al. 1994, Proc. SPIE, 2198, 56 [NASA ADS]
- Caputi, K., Lagache, G., Yan, L., et al. 2007, ApJ, 660, 97 [NASA ADS] [CrossRef]
- Chen, X. Y., Liang, Y. C., Hammer, F., Zhao, Y. H., & Zhong, G. H. 2009, A&A, 495, 457 [NASA ADS] [CrossRef] [EDP Sciences]
- Colina, L., Arribas, S., & Monreal-Ibero, A. 2005, ApJ, 621, 725 [NASA ADS] [CrossRef]
- Daigle, O., Carignan, C., Amram, P., et al. 2006, MNRAS, 367, 469 [NASA ADS] [CrossRef]
- Dasyra, K. M., Tacconi, L. J., Davies, R. I. et al. 2006, ApJ, 638, 745 [NASA ADS] [CrossRef]
- Davies, R. I., Alonso-Herrero, A., & Ward, M. J. 1997, MNRAS, 291, 557 [NASA ADS]
- Díaz-Santos, T., Alonso-Herrero, A., Colina, L., Ryder, S. D., & Knapen, J. H. 2007, ApJ, 661, 149 [NASA ADS] [CrossRef]
- Dopita, M. A., Pereira, M., Kewley, L. J., et al. 2002, ApJS, 143, 47 [NASA ADS] [CrossRef]
- Eisenhauer, F., Abuter, R., Bickert, K., et al. 2003, SPIE, 4841, 1548 [NASA ADS]
- Elbaz, D., Cesarsky, C. J., Chandal, P., et al. 2002, A&A, 384, 848 [NASA ADS] [CrossRef] [EDP Sciences]
- Falcón-Barroso, J., Bacon, R., Bureau, M., et al. 2006, MNRAS, 369, 529 [NASA ADS] [CrossRef]
- Farrah, D., Lonsdale, C. J., Weedman, D. W., et al. 2008, ApJ, 677, 957 [NASA ADS] [CrossRef]
- Förster-Schreiber, N. M., Genzel, R., Lehnert, M. D., et al. 2006, ApJ, 645, 1062 [NASA ADS] [CrossRef]
- García-Marín, M., Colina, L., Arribas, S., Alonso-Herrero, A., & Mediavilla, E. 2006, ApJ, 650, 850 [NASA ADS] [CrossRef]
- García-Marín, M., Colina, L., Arribas, S., & Monreal-Ibero, A. 2009, A&A, 505, 1319 [CrossRef] [EDP Sciences]
- Genzel, R., Weitzel, L., Tacconi-Garman, L. E., et al. 1995, ApJ, 444, 129 [NASA ADS] [CrossRef]
- Genzel, R., Tacconi, L.J., Eisenhauer, F., et al. 2006, Nature, 442, 786 [NASA ADS] [CrossRef]
- Genzel, R., Burkert, A., Bouché, N., et al. 2008, ApJ, 687, 59 [NASA ADS] [CrossRef]
- Graciá-Carpio, J., García-Burillo, S., Planesas, P., Fuente, A., & Usero, A. 2008, A&A, 479, 703 [NASA ADS] [CrossRef] [EDP Sciences]
- Hattori, T., Yoshida, M., Ohtani, H., et al. 2004, AJ, 127, 736 [NASA ADS] [CrossRef]
- Heckman, T. M., Armus, L., & Miley, G. K. 1987, AJ, 93, 276 [NASA ADS] [CrossRef]
- Heckman, T. M., Lehnert, M. D., Strickland, D. K., et al. 2000, ApJS, 129, 493 [NASA ADS] [CrossRef]
- Hinz, J. L., & Rieke, G. H. 2006, ApJ, 646, 872 [NASA ADS] [CrossRef]
- Kauffmann, G., Heckman, T. M., Tremonti, C., et al. 2003, MNRAS, 346, 1055 [NASA ADS] [CrossRef]
- Keel, W. C. 1993, AJ, 106, 1771 [NASA ADS] [CrossRef]
- Kennicutt, R. C. Jr., Keel, W. C., & Blaha, C. A. 1989, AJ, 97, 1022 [NASA ADS] [CrossRef]
- Kewley, L. J., Dopita, M. A., Sutherland, R. S., Heisler, C. A., & Trevena, J. 2001a, ApJ, 556, 121 [NASA ADS] [CrossRef]
- Kewley, L. J., Heisler, C. A., Dopita, M. A., et al. 2001b, ApJS, 132, 37 [NASA ADS] [CrossRef]
- Kewley, L. S., Groves, B., Kauffmann, G., et al. 2006, MNRAS, 372, 961 [NASA ADS] [CrossRef]
- Kim, D.-C., Sanders, D. B., Veilleux, S., Mazzarella, J. M., & Soifer, B. T. 1995, ApJS, 98, 129 [NASA ADS] [CrossRef]
- Kim, D.-C., Veilleux, S., & Sanders, D. B. 1998, ApJ, 508, 627 [NASA ADS] [CrossRef]
- Law, D. R., Steidel, C. C., Erb, D. K., et al. 2007, ApJ, 669, 929 [NASA ADS] [CrossRef]
- LeFevre, O., Saisse, M., Mancini, D., et al. 2003, SPIE, 4841, 1670 [NASA ADS]
- Le Floc'h, E., Papovich, C., Dole, H., et al. 2005, ApJ, 632, 169 [NASA ADS] [CrossRef]
- Lípari, S., Mediavilla, E., Garcia-Lorenzo, B., et al. 2004a, MNRAS, 355, 641 [NASA ADS] [CrossRef]
- Lípari, S., Mediavilla, E., Díaz, R. J., et al. 2004b, MNRAS, 348, 369 [NASA ADS] [CrossRef]
- Lonsdale, C. J., Farrah, D., & Smith, H. E. 2006, in Astrophysics Update 2, ed. J. W. Mason (Germany, Heidelberg: Springer Verlag)
- Marcillac, D., Elbaz, D., Charlot, S., et al. 2006, A&A, 458, 369 [NASA ADS] [CrossRef] [EDP Sciences]
- Markwardt, C. B. 2008, ``Non-Linear Least Squares Fitting in IDL with MPFIT'', in proc. Astronomical Data Analysis Software and Systems XVIII, Quebec, Canada, ed. D. Bohlender, P. Dowler, & D. Durand (ASP: San Francisco), ASP Conf. Ser., TBD, in press [arXiv:0902.2850]
- Márquez, I., & Moles, M. 1994, AJ, 108, 90 [NASA ADS] [CrossRef]
- Márquez, I., Masegosa, J., & Moles, M. 1996, A&A, 310, 401 [NASA ADS]
- Melbourne, J., Koo, D. C., & Le Floc'h, E. 2005, ApJ, 632, 65 [NASA ADS] [CrossRef]
- Melbourne, J., Desai, V., Armus, Lee, et al. 2008, AJ, 136, 1110 [NASA ADS] [CrossRef]
- Monreal-Ibero, A., Arribas, S., & Colina, L. 2006, ApJ, 637, 138 [NASA ADS] [CrossRef]
- Moustakas, J., & Kennicutt, R. C. Jr. 2006, ApJS, 164, 81 [NASA ADS] [CrossRef]
- Murphy, T. W. Jr., Soifer, B. T., Matthews, K., et al. 2001, ApJ, 559, 201 [NASA ADS] [CrossRef]
- Onken, C. A., Ferrarese, L., Merritt, D., et al. 2004, ApJ, 615, 645 [NASA ADS] [CrossRef]
- Pérez-González, P. G., Rieke, G. H., Egami, E., et al. 2005, ApJ, 630, 82 [NASA ADS] [CrossRef]
- Puech, M., Flores, H., Hammer, F., et al. 2008, A&A, 484, 173 [NASA ADS] [CrossRef] [EDP Sciences]
- Reunanen, J., Kotilainen, J. K., Laine, S., et al. 2000, ApJ, 529, 853 [NASA ADS] [CrossRef]
- Reunanen, J., Tacconi-Garman, L. E., & Ivanov, V. D. 2007, MNRAS, 382, 951 [NASA ADS]
- Rieke, G. H., Alonso-Herrero, A., Weiner, B. J., et al. 2009, ApJ, 692, 556 [NASA ADS] [CrossRef]
- Roth, M. M., Kelz, A., Fechner, Th., et al. 2005, PASP, 117, 620 [NASA ADS] [CrossRef]
- Rupke, D. S., Veilleux, S., & Sanders, D. B. 2005, ApJS, 160, 115 [NASA ADS] [CrossRef]
- Sanders, D. B., & Ishida, C. M. 2004, ASPC, 320, 230 [NASA ADS]
- Sanders, D. B., & Mirabel, I. F. 1996, ARA&A, 34, 749 [NASA ADS] [CrossRef]
- Sanders, D. B., Mazzarella, J. M., Kim, D.-C., Surace, J. A., & Soifer, B. T. 2003, AJ, 126, 1607 [NASA ADS] [CrossRef]
- Sarzi, M., Allard, E., Knapen, J. H., et al. 2007, MNRAS, 380, 949 [NASA ADS] [CrossRef]
- Shapiro, K. L., Genzel, R., Förster S. N M., et al. 2008, ApJ, 682, 231 [NASA ADS] [CrossRef]
- Shier, L. M., Rieke, M. J., & Rieke, G. H. 1996, ApJ, 470, 222 [NASA ADS] [CrossRef]
- Smith, D. A., Herter, T., Haynes, M. P., et al. 1999, ApJ, 510, 669 [NASA ADS] [CrossRef]
- Soifer, B. T., Neugebauer, G., Matthews, K., et al. 2000, AJ, 119, 509 [NASA ADS] [CrossRef]
- Veilleux, S., & Osterbrock, D. E. 1987, ApJS, 63, 295 [NASA ADS] [CrossRef]
- Veilleux, S., Kim, D.-C., Sanders, D. B., Mazzarella, J. M., & Soifer, B. T. 1995, ApJS, 98, 171 [NASA ADS] [CrossRef]
- Veilleux, S., Kim, D.-C., & Sanders, D. B. 1999, ApJ, 522, 113 [NASA ADS] [CrossRef]
- Vogt, N. P., Haynes, M. P., Herter, T., et al. 2004, AJ, 127, 3273 [NASA ADS] [CrossRef]
- Wright, S. A., Larkin, J. E., Law, D. R., et al. 2009, ApJ, 699, 421 [NASA ADS] [CrossRef]
- Wu, H., Zou, Z. L., Xia, X. Y., et al. 1998, A&AS, 132, 181 [NASA ADS] [CrossRef] [EDP Sciences]
- Yang, Y., Flores, H., Hammer, F., et al. 2008, A&A, 477, 789 [NASA ADS] [CrossRef] [EDP Sciences]
Footnotes
- ... atlas
- Based on observations collected at the German-Spanish Astronomical Center, Calar Alto, jointly operated by the Max-Planck-Institut für Astronomie Heidelberg and the Instituto de Astrofísica de Andalucía (CSIC).
- ...
IRAF
- IRAF software is distributed by the National Optical Astronomy Observatory (NOAO), which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., in cooperation with the National Science Foundation.
- ... algorithm
- http://www.purl.com/net/mpfit
All Tables
Table 1: Log of the PMAS observations.
Table 2: Nuclear and Integrated observed (not corrected for extinction) line ratios.
Table 3: Spectral classifications of the nuclear and integrated spectra.
Table 4: Gas kinematic results.
All Figures
![]() |
Figure 1:
(a) NGC 23. The middle and bottom panels are the PMAS observed (not corrected for extinction) maps of the brightest emission lines: H |
Open with DEXTER | |
In the text |
![]() |
Figure 1: (b) As Fig. 1a but for MCG +12-02-001. |
Open with DEXTER | |
In the text |
![]() |
Figure 1: (c) As Fig. 1a but for UGC 1845. |
Open with DEXTER | |
In the text |
![]() |
Figure 1: (d) As Fig. 1a but for NGC 2388. |
Open with DEXTER | |
In the text |
![]() |
Figure 1: (e) As Fig. 1a but for MCG +02-20-003. |
Open with DEXTER | |
In the text |
![]() |
Figure 1:
(f) As Fig. 1a but for IC 860. The H |
Open with DEXTER | |
In the text |
![]() |
Figure 1: (g) As Fig. 1a but for NGC 5936. |
Open with DEXTER | |
In the text |
![]() |
Figure 1: (h) As Fig. 1a but for NGC 6701. |
Open with DEXTER | |
In the text |
![]() |
Figure 1:
(i) As Fig. 1a but for NGC 7469; there is no HST/NICMOS NIC2 Pa |
Open with DEXTER | |
In the text |
![]() |
Figure 1: (j) As Fig. 1a but for NGC 7591. |
Open with DEXTER | |
In the text |
![]() |
Figure 1:
(k) As Fig. 1a
but for NGC 7771. The PMAS mosaics were constructed with the east
and west pointings done for this galaxy and they cover approximately
the central
|
Open with DEXTER | |
In the text |
![]() |
Figure 2:
PMAS maps of the H |
Open with DEXTER | |
In the text |
![]() |
Figure 3:
(a) Maps of the observed H |
Open with DEXTER | |
In the text |
![]() |
Figure 3: (a) continued. |
Open with DEXTER | |
In the text |
![]() |
Figure 3:
(b) As Fig. 3a. The velocity field and the map of the velocity dispersion for NGC 7469 are for the [N II] |
Open with DEXTER | |
In the text |
![]() |
Figure 3: (c) As Fig. 3a. In the case of NGC 7771 the asterisk marks the position that makes the velocity field gradient symmetric, and it is approximately coincident with the peak of the near-infrared continuum and the maximum of the velocity dispersion. |
Open with DEXTER | |
In the text |
![]() |
Figure 4: PMAS spectra
(plotted in arbitrary units) of the nuclei of the galaxies in the
sample. Additionally, for each LIRG the inset shows the blue part of
the integrated spectrum so that the absorption features as well as the H |
Open with DEXTER | |
In the text |
![]() |
Figure 4: continued. |
Open with DEXTER | |
In the text |
![]() |
Figure 5: BPT diagrams for the PMAS nuclear ( upper panels) and the integrated ( lower panels) emission of the LIRGs in our sample. The thin lines are the classical boundaries of Veilleux & Osterbrock (1987) for the H II region, LINER, and Seyfert excitation. |
Open with DEXTER | |
In the text |
![]() |
Figure 6:
Same as Fig. 5 but showing
the so-called ``maximum starburst lines'' (thick solid lines),
defined by Kewley et al. (2001a) from theoretical modeling as the lines above which line ratios cannot be explained by star formation alone.
We also show the empirical separation between AGN and H
II regions of Kauffmann et al. (2003), and between Seyfert and LINER of Kewley et al. (2006), as thick dashed lines. In the upper panel, the arrows represent the result of correcting the H |
Open with DEXTER | |
In the text |
Copyright ESO 2009
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.