Issue |
A&A
Volume 507, Number 2, November IV 2009
|
|
---|---|---|
Page(s) | 757 - 768 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361/200912546 | |
Published online | 15 September 2009 |
A&A 507, 757-768 (2009)
H I in nearby low-luminosity QSO host galaxies
S. König1 - A. Eckart1,2 - M. García-Marín1 - W. K. Huchtmeier2
1 - I. Physikalisches Institut, Universität zu Köln,
Zülpicher Strasse 77, 50937 Köln, Germany
2 - Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
Received 20 May 2009 / Accepted 2 September 2009
Abstract
We searched for 21 cm H I emission in a sample of 27 previously CO detected nearby galaxies hosting low-luminosity
quasi - stellar objects (QSOs). In this paper we investigate the relationship between the H I
and infrared properties of these host galaxies, compare the atomic and
molecular gas content and look for connections to the optical and FIR
properties. The single dish observations have been made with the
Effelsberg 100-m telescope with a beam size of 9.5.
The sample objects have been drawn from a wide-angle survey for optically bright QSOs (HES), which have declinations
and redshifts up to z = 0.06. 12 host galaxies from the sample have been detected in the H I
21 cm emission line. Eight of them have a spiral geometry, whereas
the other four are bulge dominated and probably of elliptical type
(E/S0). Three of the objects seem to be in a phase of
merging/interaction. The neutral atomic gas masses range from
up to
.
The median H I gas mass in the whole sample is of the order of
,
which is a factor of two higher than the H I content of our galaxy. We find
no strong correlation between H I
mass and IR luminosity. The objects agree well within the expectations
from the Tully-Fisher relation. In the color-color diagram we find all
sources in the estimated locations. With the non-detected sources we
clearly sample an upper envelope of this mass distribution.
Key words: galaxies: active - radio lines: galaxies - galaxies: nuclei - galaxies: Seyfert
1 Introduction
Molecular gas is the fuel for any activity process, whether it is in
the form of vigorous bursts of star formation or an intensively
accreting super massive central black hole (active galactic nuclei,
AGN). The study of its morphology and kinematics is of key importance
to understand the fueling mechanisms that keep the activity alive over
cosmologically significant time scales. As important as studying the
ongoing activity processes is studying the trigger that leads to it in
the first place. It is assumed that galaxy interaction thereby plays a
dominant role, initializing the transport of gas from the outer parts
of the involved galaxies into their centers and so igniting the
starburst and/or AGN activity. Sanders et al. (1988) already suggested early on that there might be even an evolutionary sequence between the onset
of starburst and AGN activity with starbursts as precursors for AGN. This hypothesis is mainly based on the remarkable
resemblance between luminous starburst galaxies (so called ultra-luminous-infrared-galaxies, or ULIRGs) and galaxies
with a pronounced AGN signature (so called QSO host galaxies), such as their enormous amounts of molecular gas.
However, while ULIRGs often exhibit significant signs of galaxy interaction, this is not necessarily true for QSO
host galaxies. In fact, optical studies on QSO host galaxies (e.g., Boyce et al. 1998; Bahcall et al. 1997) find
the majority to be rather morphologically normal without any clear signs of a past or ongoing interaction, though
50% of their sample live with (projected) nearby companions.
Much effort has been invested in studying the molecular gas emission in QSO host galaxies
(e.g., Krips et al. 2006b; Bertram et al. 2007; Scoville et al. 2003; Krips et al. 2006a). Atomic hydrogen, on the other hand, tracing the cold atomic molecular gas, may be
a much better indicator for galaxy interaction. Only little is known so far on the atomic gas content in QSO host galaxies.
Lim & Ho (1999), Lim et al. (2001) and Ho et al. (2008a,b) present one of the first studies of H I
emission in nearby QSO host galaxies. They find that while most of
their observed sources show signs of a past or ongoing tidal
interaction, they do not yet physically merge with another galaxy. This
is in contrast to the proposed sequence by Sanders et al. (1988)
in which QSOs are thought be the merging or merged descendants of
ULIRGs. In this paper we present the study of neutral atomic hydrogen
in 27 nearby low-luminosity quasi-stellar objects. The observations are
part of an ongoing project aimed at enhancing the statistics on nearby
QSOs.
In Sect. 2 we describe the sample selection, Sect. 3 reports on the observations and data reduction. The results of the observations and the conclusions/discussion follow in Sects. 4 and 5.
Unless otherwise stated,
km s
Mpc
and
are assumed throughout the paper.
Table 1: List of sources observed at 21 cm.
2 The sample
We have selected a volume limited sample of sources. As the sole selection criterion an upper redshift limit of z
< 0.06 was applied. This value has been set to ensure the
observability of the important diagnostic CO (2-0) rotation
vibrational band head absorption line in the K-band. The sources have been selected from the Hamburg / ESO survey of optically
bright QSOs (HES; Wisotzki et al. 2000). These 27 sources, with a declination
(by means of the observability
from the Effelsberg 100-m telescope), have been searched for CO emission with the IRAM 30 m telescope on Pico
Veleta (Spain) and SEST (Swedish ESO-Submillimeter Telescope) in La Silla (Chile). 27 objects (Table 1) were detected in 12CO(1 - 0) and 12CO(2 - 1)
(see Bertram et al. 2007). They feature recession velocities in the range 2500 km s
km s-1.
Bertram et al. (2007) confirmed that the majority of galaxies hosting low-luminosity QSOs are rich in molecular gas. In 2007 and 2008 we
searched this subsample for 21 cm H I emission. This sample complements the study of Ho et al. (2008a). But contrary to their
sample our sources have positions further to the south.
A more detailed description of the ``nearby QSO sample'' can be found in Bertram et al. (2007).
![]() |
Figure 1:
H I spectra of detected host galaxies
from the ``nearby QSO sample'' observed with the Effelsberg 100-m telescope and optical DSS images.
The images in the middle extend over 2 |
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Figure 1: continued. |
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Figure 1: continued. |
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3 Observations and data reduction
The observations of the H I 21 cm emission line were carried out with the Effelsberg 100-m telescope in 2007 and 2008. The
18-21 cm (1.29-1.72 GHz) two - channel L-band
HEMT facility receiver was used as the frontend, in conjunction with
the 8192-channel-autocorrelator (AK 90) and the Fast Fourier
Transform Spectrometer (FFTS) as backends. With bandwidths of
10 MHz (AK 90) and 20 MHz (AK 90 + FFTS), centered
on the redshifted rest frame frequency for each galaxy, we were able to
obtain data with velocity ranges v from
4200 to
21 000 km s
and a velocity resolution between 0.2577
and 2.061 km s
,
depending on the backend and settings. The measurements were done in position - switch mode with
5 mn on and 5 mn off the source positions, with an off - position 45
away. This provides the advantage of better
baselines and the reduction of atmospherical influences. The beam efficiency was
1.15 for a beam size of 9.5
at 21 cm. The on-source integration times range between 30 and
90 minutes. Daily pointing checks were performed using sources
from the Effelsberg Catalog of pointing and flux density calibration (Ott et al. 1994). As flux calibrators we used Holmberg I, NGC 4303,
Sextans B and UGC 2345 (fluxes taken from Tifft & Huchtmeier 1990 and from Springob et al. 2005).
The Effelsberg 100-m telescope site is known for exhibiting low level radio frequency interference (RFI) in the 21 cm band. However as the RFI signals are situated well outside the range of the expected central velocity or can be filtered out, these disturbances have no influence on the observational results.
Table 2: Summary of the H I properties.
![]() |
Figure 2:
H I mass as a function of infrared
luminosity for the nearby QSOs. Stars represent the sample from this
paper. Squares and triangles represent sources taken in order to
enhance the statistics from Ho et al. (2008a): squares represent the
sources from the Ho sample itself and triangles represent a
literature sample assembled by Ho et al. (2008a). Filled squares and
triangles mark available values for
|
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The data were reduced and analyzed with the CLASS package of IRAM's GILDAS
software. All spectra have been averaged, when applicable. To obtain a
better signal to - noise ratio, most of the spectra were
Hanning smoothed. For data taken on different dates the subscans of
each observation were calibrated with respect to a suitable flux
calibrator (see Fig. 1 and Table 1).
Baselines were fitted and subtracted from each subscan individually
before resampling and averaging of the spectra. Another baseline fit
was performed after the final resampling and averaging of all available
data for the source. All polynomial fits to the baselines have been of
the order of one. The errors
for the given intensities I were determined following the procedure from Bertram et al. (2007). The geometric average of the
line error
and the baseline error
were taken into account.
4 Analysis
The galaxies observed during this survey do not form a complete sample,
but the results can still be used to improve our knowledge of the
population of nearby AGNs. In order to derive the atomic neutral
hydrogen gas mass
,
the following formula (e.g., Shostak 1978) was applied:



(







These results are summarized in Table 2. Given are the integrated line intensity




5 Results and discussion
In Fig. 1 we show the obtained H I spectra together with the associated DSS images of the region with a diameter of 2 and 9.5
around the source position. The images should serve as a means to
estimate the source confusion. The spectrum of
HE 1248-1356 is remarkable in the sense that the
velocity range 4200-4350 km s-1 shows strong
CO emission (see Bertram et al. 2007) but no H I emission. As this source has a close companion (see the DSS images), it is possible that
the H I
gas was partially more disturbed/stripped/disrupted, by the companion.
This could cause the ``one-sidedness'' of the spectrum indicating that
the part of the host galaxy moving towards us has less neutral atomic
hydrogen than the one receding. Why wasn't the CO affected? It could
just be that the disturbance was only affecting the more outwards lying
H I gas and not yet the molecular CO
in former times. Since then H I was converted into H
(CO) and the H I line in its present shape could be a
remnant signature. The coordinate labels of RA and Dec (J2000), as well as the flux in Jy and the velocity in km s
are
indicating the scales. Each source name is denoted above the spectrum. The H I properties and results are summarized in
Table 2: Integrated line intensities cover a range from 0.5 up to 7.6 Jy km s
.
The intensity upper limits and errors for non-detections represent 3
values.
The line widths (
)
are of the order of hundreds of km s
.
The sources HE 0232-0900
(
km s
)
and HE 2302-0857 (
km s
)
are two special cases:
They both have extraordinary large line widths both in CO (FWZI: 597 km s
and 653 km s
,
from Bertram et al. 2007)
and H I emission. The H I line emission detected from HE 2302-0857 is even more extraordinary if we look at
the full width at zero intensity (FWZI) of the H I line, with a width of 616 km s
,
which is comparable to the
line width (FWZI) in CO (
km s
), although the galaxy is not seen edge-on. For HE 0232-0900
however the H I line is narrower than the CO line. This indicates that the outer regions of the galactic disk were stripped
from H I, or are simply depleted from the atomic gas component. As the DSS images (Fig. 1)
show a peculiar morphology of this object it is also possible that the
current geometry is due to a previous interaction/merger with another
galaxy. The H I masses range between 1.1 and
,
whereas the upper limits for the dynamical masses
have values from
up to
.
Figure 2 shows a plot of the atomic hydrogen mass versus infrared luminosity containing sources from this work and
the work of Ho et al. (2008a). In comparison to Ho et al. (2008b) we concentrate more on the radio - IR properties, rather than the optical
H I relations. The position of the objects in this graph are in good agreement with the work of Young et al. (1989)
about infrared bright galaxies: In general galaxies with high IR
luminosities have high neutral atomic hydrogen masses. Although their
work places an emphasis on even more nearby sources (
Mpc), the mean luminosity distance for the enlarged sample
(this work + Ho et al. 2008a) plotted here was 219.5 Mpc. The comparison of these results shows no evolutionary effect in redshift
due to
or
(see also Table 3 and Haan et al. 2008). The comparison
between the molecular gas content (taken from Bertram et al. 2007) and the atomic one results in a median fraction of
/
for our sample (including the upper limits for the
non-detections). Maiolino et al. (1997) measured a value of 1.79 for their
/
(for galaxy types up to Sy 1.5).
Since we are not sure if Bertram et al. (2007) and Maiolino et al. (1997) used
the same CO - to - H
conversion factor we simply compare the
- to -
ratios. The median
/
value given by the data of Maiolino et al. (1997)
results in 0.14, which is about a factor of two higher than the value obtained for our sample. Since the median CO
luminosity
is about the same in both samples,
for Maiolino et al. (1997) and
(CO data taken from Bertram et al. 2007), the galaxies in their sample are less rich in atomic
hydrogen than the ones in this study. In a more recent publication Haan et al. (2008) compiled a study of H I properties
in AGN host galaxies taken from the NUGA sample. We compared these sources, which lie a step lower in redshift range
(
... 53.9 Mpc, see Table 3), with our sample. They find more ring structures and
dynamically disturbed H I disks in LINERs than in Seyfert host galaxies. Since our sample consists only of Seyfert galaxies
we just account for part of the Haan sample.
Table 3: Sources from Haan et al. (2008).
The distribution of data points in Fig. 2 shows that we are sampling an upper envelope of the
/
distribution. The sources that we detected in H I emission are those that
have the largest amount of atomic hydrogen, compared to the molecular gas mass, in their hosts. This could be an explanation
for the lack of more H I detections in this work. Upper limits of the non-detected sources show, that with deeper and longer
integrations we would be able to correct for this deficiency in our observations.
![]() |
Figure 3: H I flux vs. CO intensity (taken from Bertram et al. 2007). Crosses mark the upper limits of H I non-detected sources. Filled circles represent the intensities for detected sources. Each object is identified by a number, which is related to the source name given in the figure legend. |
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In Fig. 3 we compare the H I and the CO intensities of the detected sources in our sample. Similar to Fig. 2 it is obvious from Fig. 3 that we have sampled an upper envelope of the H I mass distribution.
If we consider only the certain H I detected sources from this work then a high H I
mass is present almost independently of the molecular mass content.
Remarkable about this plot is, that the two sources with the largest CO
intensity values (HE 0433-1028 and
HE 1108-2813) are not detected in atomic hydrogen. This
could mean that most of the available neutral atomic gas was already
converted to molecular gas, i.e. H
(CO). The number of upper limits in the H I
line strength is larger for galaxies with low molecular gas content.
This implies that a correlation may be present, such that low molecular
gas mass also implies a low atomic gas mass. On a statistical basis the
H I detection fraction above and below the median value of the
molecular gas masses (taken from Bertram et al. 2007) could give a hint for the confidence limit of this trend in our sample. The median
value results in
.
Then we studied the distribution of the H I masses of the
sources above the median of the molecular gas mass and below it. The median H I mass above the median molecular gas mass is
and the median H I mass below the
median molecular gas mass is
.
These calculations do not take the non-detections into account. We
defined estimated values for error bars by determining the median
deviation from the medians of the H I masses. Taking these error bars into account, we find that the sources above the median
molecular mass also have the larger H I masses, the sources below the median molecular gas mass have lower H I masses. Within the
error bars the two populations of H I detected sources do not overlap. Nonetheless our sample is very small and hence not suitable
for making statistically significant statements.
5.1 Source confusion
We can not exclude the possibility of source confusion (see Fig. 1). The half power beam width (HPBW) at 21 cm
is 9.5.
Since the whole beam lobe is (reduced) sensitive for radio signals out to twice the primary beam diameter, an
H I rich galaxy at, the appropriate red shift, can cause disturbances out to angular distances of up to 18
.
Asymmetries in the line profiles could possibly indicate the presence
of companions or phases of merging that influence the host galaxies.
One help to shed light on this matter may also be provided by the DSS
images (see Fig. 1). Here we can
look for indications for interactions or companions within a field of view representing the 9.5
Effelsberg beam size. An
outstanding example for this circumstance is the source HE 0150-0344. Its H I
spectrum shows two emission lines close in velocity. In the DSS image
the source shows an elongated structure with two peaks, indicating two
very close by sources. With the large Effelsberg beam we are not able
to distinguish between the objects. Due to the close proximity of the
sources interferometrical data would be needed to achieve the
differentiation. Source confusion has a strong influence on the line
shape, as well as on the line width, as mentioned earlier. Two objects,
which exhibit emission at the observed frequency, close in redshift,
hence also in recession velocity would cause a broadening of the
studied emission line (always under the assumption that the two objects
are galaxies). Therefore the target source would feature a much broader
line width than it shows in reality (see Fig. 1,
HE 0150-0344). This would then cause wrong numbers for
the observed intensity and the resulting gas mass. Cross-checking with
other observational tools, for e.g., optical images, is therefore
essential to get the right result.
5.2 Morphology
A comparison of the shape of the spectra shows good agreement between line shape and associated morphology in e.g., the optical (Fig. 1, Tables 1, 2): for 11 of the 12 detected sources (the exception is HE 1248-1356) we find that the morphology from the optical DSS images and the line shape determined from the H I spectra are the same. But one has to remark that the asymmetry of the line shape in some of the spectra makes it difficult to achieve an accurate differentiation. From the optical DSS images (Fig. 1) we find spiral morphology in 15 (55%) host galaxies, elliptical morphology in 11 (41%) host galaxies and a ring morphology in 1 (4%) host galaxy. In 33% of the sources the H I spectra show triangular shaped line profiles, that is expected for turbulent line-of-sight dispersion (as in elliptical galaxies), and 67% have boxy or double-horn shaped line profiles, which is an indicator for emission from an inclined, rotating disk (as in spirals). In comparison Haan et al. (2008) find that 44% of the sources in their AGN sample are of spiral morphology, 28% are centrally peaked, 22% ringed and 5% of their host galaxies show a warped geometry. This hints at a preference for spirals in terms of morphological properties of QSO host galaxies. In their Seyfert subsample a slight excess of galaxies with a spiral geometry is evident.
![]() |
Figure 4:
Infrared luminosity
|
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In 1980 Dressler discovered a morphology-density ()
relation for galaxies: the fraction of elliptical like
(E + S0) galaxies increases strongly with increasing local
galaxy density, whereas the numbers of spiral galaxies decrease (see
e.g., Table 1 in Pimbblet 2003). In good agreement with further studies of this relationship he also derives values for different
environments: from galaxies in the field over poor and rich groups to clusters. Furthermore Dressler et al. (1997) report a redshift
evolution in the
relation: an additional increase of the fraction of S0 galaxies with redshift whilst the number of
elliptical galaxies stays nearly constant. The distribution of spiral, elliptical (E) and lenticular (S0) galaxies in our
H I data is comparable to the numbers for field galaxies or poor groups. Dressler et al. (1985)
expand the statistical studies of clusters by also looking at emission
line galaxies. They find a much higher emission line frequency in field
galaxies than in cluster galaxies. AGN occur at a rate of
5% in field galaxies whereas in clusters only
1% of the galaxies
harbor an AGN. Martini et al. (2006) searched for low-luminosity AGN in low redshift clusters. They determined an AGN fraction of
5%, in clusters arguing that through X-ray emission more AGN towards lower luminosities can be identified. They concluded
that if the AGN fraction in the field is indeed 5 times the AGN cluster fraction they would identify
25% of the field
galaxy population to show characteristics of AGN. On the other hand, Popesso & Biviano (2006) find an average AGN fraction of 18% in clusters.
They, too, argue that their estimate includes low-luminosity AGN, probably missed in previous studies. Scaling the
relation from Dressler (1980)
to AGN this would, by a strong simplification, mean that most AGN in
our sample reside in host galaxies of spiral morphological type,
whereas in clusters the fraction of AGN in elliptical and lenticular
hosts would increase significantly.
For analytical purposes we introduce an estimate for the
compactness of gas confined to the host galaxies within our sample by
the derivation of the fraction of the CO line width to the H I line width as follows:
![]() |
(5) |

As another analytical tool we use the surface mass density:
![]() |
(6) |
The area of the sources again was estimated from the DSS images (Fig. 1, see Sect. 4 again for the description of the area extraction process). The sample sources show areas between 55 and 76 000










![]() |
Figure 5:
Blue magnitude |
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![]() |
Figure 6:
IRAS color-color diagram according to
Helou (1986). The underlying model was taken from Desert (1986).
Filled circles show H I detected sources from this work,
unfilled ones mark H I non-detected sources with available
IRAS fluxes. Arrows are indicators for upper limits. Each object is
identified by a number, which is related to the source name given in
the figure legend. The location of our sample sources in the plot
shows that almost all of them are starburst dominated hosts that
have high dust temperatures (sources to the upper left).
The
galaxies to the lower right of the plot have colors that are often
found for elliptical galaxies. The two sources
HE 0150-0344 and HE 0212-0059 are such
objects. These objects are dominated by the 100 |
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5.3 IRAS color-color diagram
Figure 6 represents an IRAS color-color diagram of the sources from this sample after Helou (1986), overlaid
with the computations of Desert (1986). Our sample sources fit well into the model by Desert (1986).
The location of our sample sources in the IRAS color-color plot shows
that almost all of them exhibit signs which are typical for starburst
dominated hosts that have elevated dust temperatures i.e. show bright
60 m emission compared to their 100
m emission, and show faint
12
m emission compared to their 25
m emission. The far-IR color is particularly sensitive to foreground Galactic
``cirrus'' emission, which can cause artificially small values of
(60)/
(100). Only 2 objects
(HE 0150-0344, HE 0212-0059) are dominated by the 100
m
emission implying lower dust temperatures. They have colors that are
often found for elliptical galaxies. A visual inspection of their
images shows that an identification with an elliptical host is
plausible. Objects to the upper left of this plot are thought to be
starburst galaxies.
6 Conclusions
We present results on the neutral atomic gas content of 27 nearby
low-luminosity QSO host galaxies. 12 of the target sources were
detected in H I emission. The atomic gas masses cover a range from
up to
with a median mass of the order of
.
Considering the upper limits for non-detections this value changes to
.
Taking this median H I mass
for the whole sample into account, the atomic hydrogen mass is a factor of two higher for our sample than the H I content of the Milky
Way (Hartmann & Burton 1997,
).
Though it is not possible to discuss the nature of the objects without
high resolution imaging in more detail, we were able to draw some
interesting conclusions with the help of the profiles of the H I
spectra and optical DSS images. For several galaxies we found possible
companions in the vicinity, as well as indications for
merger / interactions. We find no distinct correlation
between the IR luminosity of a galaxy and its H I gas content. In general galaxies with high IR luminosities
have high neutral atomic hydrogen masses. The compactness for objects with spiral features seems to be lower (the CO
emitting regions have a smaller extension than H I emitting ones) as they have a larger outspread than the ones showing an
elliptical geometry. Only for our sample there are CO and H I measurements done for the sample together. For other samples, like e.g.,
for the Haan et al. sample, there exist CO measurements with different telescopes/techniques in the literature by separate authors.
To our knowledge an estimated number of about 50 sources have H I
and CO data taken. Therefore our sample contributes to the, at the
moment, rather small contingency of hosts with atomic and molecular
masses. The observed median surface mass density is about a factor two
lower than the values for our Milky Way (50-
pc
). From the Tully-Fisher relation we deduced a median inclination of
30
,
in good agreement with the assumption of nearly face-on morphology. Interferometrical data
through follow-up observations for two out of the twelve H I detected sources have been obtained. For the other ten sources
these follow-up observations are in planning.
M.G.-M. is supported by the German federal department for education and research (BMBF) under the project numbers: 50OS0502 & 50OS0801. Based on observations with the 100-m telescope of the MPIfR (Max-Planck-Institut für Radioastronomie) at Effelsberg. 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.
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Footnotes
- ... GILDAS
- http://www.iram.fr/IRAMFR/GILDAS
All Tables
Table 1: List of sources observed at 21 cm.
Table 2: Summary of the H I properties.
Table 3: Sources from Haan et al. (2008).
All Figures
![]() |
Figure 1:
H I spectra of detected host galaxies
from the ``nearby QSO sample'' observed with the Effelsberg 100-m telescope and optical DSS images.
The images in the middle extend over 2 |
Open with DEXTER | |
In the text |
![]() |
Figure 1: continued. |
Open with DEXTER | |
In the text |
![]() |
Figure 1: continued. |
Open with DEXTER | |
In the text |
![]() |
Figure 2:
H I mass as a function of infrared
luminosity for the nearby QSOs. Stars represent the sample from this
paper. Squares and triangles represent sources taken in order to
enhance the statistics from Ho et al. (2008a): squares represent the
sources from the Ho sample itself and triangles represent a
literature sample assembled by Ho et al. (2008a). Filled squares and
triangles mark available values for
|
Open with DEXTER | |
In the text |
![]() |
Figure 3: H I flux vs. CO intensity (taken from Bertram et al. 2007). Crosses mark the upper limits of H I non-detected sources. Filled circles represent the intensities for detected sources. Each object is identified by a number, which is related to the source name given in the figure legend. |
Open with DEXTER | |
In the text |
![]() |
Figure 4:
Infrared luminosity
|
Open with DEXTER | |
In the text |
![]() |
Figure 5:
Blue magnitude |
Open with DEXTER | |
In the text |
![]() |
Figure 6:
IRAS color-color diagram according to
Helou (1986). The underlying model was taken from Desert (1986).
Filled circles show H I detected sources from this work,
unfilled ones mark H I non-detected sources with available
IRAS fluxes. Arrows are indicators for upper limits. Each object is
identified by a number, which is related to the source name given in
the figure legend. The location of our sample sources in the plot
shows that almost all of them are starburst dominated hosts that
have high dust temperatures (sources to the upper left).
The
galaxies to the lower right of the plot have colors that are often
found for elliptical galaxies. The two sources
HE 0150-0344 and HE 0212-0059 are such
objects. These objects are dominated by the 100 |
Open with DEXTER | |
In the text |
Copyright ESO 2009
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