J/MNRAS/465/588 HI 21-cm absorption survey of QSO-galaxy pairs (Dutta+, 2017)
H I 21-cm absorption survey of quasar-galaxy pairs:
distribution of cold gas around z < 0.4 galaxies.
Dutta R., Srianand R., Gupta N., Momjian E., Noterdaeme P., Petitjean P.,
Rahmani H.
<Mon. Not. R. Astron. Soc., 465, 588-618 (2017)>
=2017MNRAS.465..588D 2017MNRAS.465..588D (SIMBAD/NED BibCode)
ADC_Keywords: QSOs ; Galaxies ; H I data ; Redshifts
Keywords: galaxies: ISM - quasars: absorption line
Abstract:
We present the results from our survey of HI 21-cm absorption, using
Giant Metrewave Radio Telescope, Very Large Array and Westerbork Radio
Synthesis Telescope, in a sample of 55 z<0.4 galaxies towards radio
sources with impact parameters (b) in the range ∼0-35kpc. In our
primary sample (defined for statistical analyses) of 40 quasar-galaxy
pairs, probed by 45 sightlines, we have found seven HI 21-cm
absorption detections, two of which are reported here for the first
time. Combining our primary sample with measurements having similar
optical depth sensitivity (∫τdv≤0.3km/s) from the literature,
we find a weak anti-correlation (rank correlation coefficient =-0.20
at 2.42σ level) between ∫τdv and b, consistent with
previous literature results. The covering factor of HI 21-cm absorbers
(C21) is estimated to be 0.24+0.12-0.08 at b≤15kpc and
0.06+0.09-0.04 at b=15-35kpc. ∫τdv and C21 show similar
declining trend with radial distance along the galaxy's major axis and
distances scaled with the effective HI radius. There is also tentative
indication that most of the HI 21-cm absorbers could be co-planar with
the extended HI discs. No significant dependence of ∫τdv and
C21 on galaxy luminosity, stellar mass, colour and star formation
rate is found, though the HI 21-cm absorbing gas cross-section may be
larger for the luminous galaxies. The higher detection rate (by a
factor of ∼4) of HI 21-cm absorption in z<1 damped Lyman-α
systems compared to the quasar-galaxy pairs indicates towards small
covering factor and patchy distribution of cold gas clouds around
low-z galaxies.
Description:
At first we constructed a parent sample of QGPs using the Sloan
Digital Sky Survey (SDSS; York et al., 2000AJ....120.1579Y 2000AJ....120.1579Y) and the
Faint Images of the Radio Sky at Twenty-Centimetres (FIRST; White et
al. 1997, Cat. VIII/92) data bases. To do this we cross-matched
SDSS-Data Release 9 (DR9) galaxies with photometric redshift,
zphot≤0.4, and FIRST radio sources with peak flux density at
1.4GHz≥50mJy within a 40-arcsec search radius.
We obtained the optical spectra of seven galaxies in our sample using
the Robert Stobie Spectrograph (RSS) on SALT in long-slit mode, under
the programmes 2013-2-IUCAA-001, 2014-1-IUCAA-001, 2014-2-SCI-017 (PI:
Dutta). The observations were carried out with a 1.5arcsec slit and
the PG0900 grating (resolution of ∼5Å at 5000Å).
Of the 55 sources that were searched for HI 21-cm absorption by us, 50
were observed with the GMRT, two with the VLA, two with the WSRT, and
one was observed with both the GMRT and the WSRT. The GMRT
observations were carried out using the L-band receiver. Prior to
2011, the sources were observed using the 2MHz baseband bandwidth
split into 128 channels (spectral resolution ∼4km/s/channel; velocity
coverage ∼500km/s). The later observations were carried out using the
4.17MHz baseband bandwidth split into 512 frequency channels (spectral
resolution ∼2km/s/channel; velocity coverage ∼1000km/s). The VLA
observations (Proposal ID: 15A-176) were carried out in
A-configuration (maximum baseline of 36.4km) using a single 8MHz
sub-band in dual polarization split into 4096 channels (spectral
resolution ∼0.5km/s per channel; velocity coverage ∼2000km/s). In the
case of WSRT observations, a total bandwidth of 10MHz split into 2048
spectral channels was used to acquire data in the dual polarization
mode. This corresponds to a total bandwidth of ∼2400km/s and a channel
width of ∼1.2km/s before Hanning smoothing.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 104 62 Details of the QGPs observed by us
tableb1.dat 101 24 Details of the QGPs searched for HI 21-cm
absorption in the literature that are included
in this work
tablec1.dat 102 7 Details of the galaxy spectra obtained using SALT
tabled1.dat 93 67 Radio observation log of the sources observed
by us
tablee1.dat 59 62 Parameters derived from radio observations
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Byte-by-byte Description of file: tablea1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1 A1 --- Sample [PSM] Sample (G1)
3- 12 A10 --- QGP QGP name (JHHMM+DDMM)
13- 14 A2 --- m_QGP Multiplicity index on QGP (G2)
16- 34 A19 --- RName Radio source name (JHHMMSS.ss+DDMMSS.s)
36- 37 A2 --- l_zrad [≥ ] Limit flag on zrad
38- 42 F5.3 --- zrad ?=- Redshift of radio source
43 A1 --- n_zrad [ab] Note on zrad (3)
45 A1 --- Type [QGU] Type of radio source (G3)
47 A1 --- Morph [CR] Morphology of radio source at
arcsecond-scale (G4)
49- 67 A19 --- Galaxy Galaxy name (JHHMMSS.ss+DDMMSS.s)
69- 75 F7.5 --- zgal ?=- Galaxy redshift
77 I1 --- r_zgal ? Reference for zgal (6)
79- 82 F4.2 mag g-r ?=- Rest-frame SDSS g-r colour of galaxy
84- 87 F4.1 [Msun] logM* ?=- log of stellar mass of galaxy from kcorrect
(Blanton & Roweis, 2007AJ....133..734B 2007AJ....133..734B)
89- 92 F4.1 [Lsun] logLB ?=- log of B-band luminosity
94 A1 --- l_b Limit flag on b
95- 98 F4.1 kpc b Projected separation or impact parameter
between radio sightline and centre of galaxy
100-101 I2 deg i ?=- Galaxy inclination
103-104 I2 --- phi ?=- Orientation of radio sightline with respect
to galaxy's major axis
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Note (3): Note on zrad as follows:
a = Based on SDSS and WISE colours (see text for details)
b = Photometric redshift
Note (6): source of galaxy redshift as follows:
1 = Jonas (2009, IEEE Proc, 97, 1522)
2 = SDSS
3 = APO observations (Gupta et al., 2009MNRAS.398..201G 2009MNRAS.398..201G)
4 = SALT observations (this work)
5 = Schombert, Pildis & Eder (1997ApJS..111..233S 1997ApJS..111..233S)
6 = identified by us as GOTOQ
7 = Epinat et al. (2008, Cat. J/MNRAS/388/500)
8 = Womble (1993PASP..105.1043W 1993PASP..105.1043W)
9 = CaII absorption identified by us in SDSS quasar spectra
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Byte-by-byte Description of file: tableb1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 A19 --- RName Radio source name (JHHMMSS.ss+DDMMSS.s)
21- 25 F5.3 --- zrad ?=- Redshift of radio source
26 A1 --- n_zrad [p] Note on zrad, p for photometric redshift
28 A1 --- Type [QGU] Type of radio source (G3)
30 A1 --- Morph [CR] Morphology of radio source at
arcsecond-scale (G4)
32- 50 A19 --- Galaxy Galaxy name (JHHMMSS.ss+DDMMSS.s)
52- 58 F7.5 --- zgal ?=- Galaxy redshift
60- 63 F4.2 mag g-r ?=- Rest-frame SDSS g-r colour of galaxy
65- 68 F4.1 [Msun] logM* ?=- log of stellar mass of galaxy from kcorrect
(Blanton & Roweis, 2007AJ....133..734B 2007AJ....133..734B)
70- 73 F4.1 [Lsun] logLB ?=- log of B-band luminosity
75- 78 F4.1 kpc b Projected separation or impact parameter
between radio sightline and centre of galaxy
80- 81 I2 deg i ?=- Galaxy inclination
83- 84 I2 deg phi ?=- Orientation of radio sightline with respect
to galaxy's major axis
86- 87 A2 --- l_Itdv3s [≤ ] Limit flag on Itdv3s
88- 92 F5.3 km/s Itdv3s 3σ upper limit on integrated HI 21-cm
optical depth from spectra smoothed to 10km/s
94- 97 F4.2 km/s Itdv ?=- Integrated HI 21-cm optical depth in the
case of detections at the observed spectral
resolution
98 A1 --- n_Itdv [b] Note on Itdv (1)
100-101 I2 --- Ref Reference for the HI 21-cm optical depth
measurements (2)
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Note (1): b: itdv corresponds to stronger of the two absorption components
separated by 250km/s.
Note (2): References for the HI 21-cm optical depth measurements as follows:
1 = Borthakur et al. (2011ApJ...727...52B 2011ApJ...727...52B)
2 = Hwang & Chiou (2004ApJ...600...52H 2004ApJ...600...52H)
3 = Carilli & van Gorkom (1992ApJ...399..373C 1992ApJ...399..373C)
4 = Zwaan et al. (2015MNRAS.453.1268Z 2015MNRAS.453.1268Z)
5 = Keeney et al. (2005ApJ...622..267K 2005ApJ...622..267K)
6 = Borthakur (2016ApJ...829..128B 2016ApJ...829..128B)
7 = Borthakur et al. (2014ApJ...795...98B 2014ApJ...795...98B)
8 = Reeves et al. (2016MNRAS.457.2613R 2016MNRAS.457.2613R)
9 = Keeney et al. (2011AJ....141...66K 2011AJ....141...66K)
10 = Haschick & Burke (1975ApJ...200L.137H 1975ApJ...200L.137H)
11 = Corbelli & Schneider (1990ApJ...356...14C 1990ApJ...356...14C)
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Byte-by-byte Description of file: tablec1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 A19 --- Galaxy Galaxy name (JHHMMSS.ss+DDMMSS.s)
21- 26 F6.4 --- zgal Galaxy redshift
28- 33 F6.4 --- e_zgal rms uncertainty on zgal
35- 73 A39 --- EmLines Emission lines detected in the SALT spectrum
75-102 A28 --- AbsLines Absorption lines detected in the SALT spectrum
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Byte-by-byte Description of file: tabled1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1 A1 --- Sample [PSM] Sample (G1)
3- 21 A19 --- RName Radio source name (JHHMMSS.ss+DDMMSS.s)
23- 41 A19 --- Galaxy Galaxy name (JHHMMSS.ss+DDMMSS.s)
43- 49 F7.5 --- zgal ?=- Galaxy redshift
51- 54 A4 --- Tel Telescope used for radio observation
56- 65 A10 "date" Date Date of observation
67- 69 F3.1 km/s dv ?=- Spectral resolution in km/s per channel
71- 73 F3.1 h Timeon Time on source
75- 78 F4.1 arcsec Beam1 ? Size of the restoring beam of the continuum
image
79 A1 -- --- [x]
80- 83 F4.1 arcsec Beam2 ? Size of the restoring beam of the continuum
image
85- 88 F4.1 kpc Spres1 ? Spatial resolution corresponding to the beam
size at the redshift of the galaxy
89 A1 --- --- [x]
90- 93 F4.1 kpc Spres2 ? Spatial resolution corresponding to the beam
size at the redshift of the galaxy
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Byte-by-byte Description of file: tablee1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1 A1 --- Sample [PSM] Sample (G1)
3- 12 A10 --- QGP QGP name (JHHMM+DDMM)
13- 14 A2 --- m_QGP Multiplicity index on QGP (G2)
16- 19 I4 mJy/beam Speak Peak flux density
21- 23 F3.1 km/s dv Spectral resolution in km/s per channel
25- 27 F3.1 mJy/beam rms Spectral rms (1)
29- 33 F5.3 --- sigmatau Standard deviation of the HI 21-cm
optical depth (1)
35- 38 F4.2 --- sigmap ?=- Maximum HI 21-cm optical depth in the
case of HI 21-cm detections (1)
40- 41 A2 --- l_Itdv3s [≤ ] Limit flag on Itdv3s
42- 46 F5.3 km/s Itdv3s 3σ upper limit on integrated HI 21-cm
optical depth from spectra smoothed
to 10km/s
48- 52 F5.2 km/s Itdv ?=- Integrated HI 21-cm optical depth in the
case of detections at the observed spectral
resolution (1)
54- 57 F4.2 km/s e_Itdv ?=- rms uncertainty on Idtv
59 I1 --- Ref References (2)
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Note (1): the values are at the spectral resolution specified in Column dv.
Note (2): References as follows:
1 = Dutta et al. (2016MNRAS.456.4209D 2016MNRAS.456.4209D)
2 = This work
3 = Gupta et al. (2010MNRAS.408..849G 2010MNRAS.408..849G)
4 = Gupta et al. (2013A&A...558A..84G 2013A&A...558A..84G)
5 = Srianand et al. (2013MNRAS.428.2198S 2013MNRAS.428.2198S)
6 = Srianand et al. (2015MNRAS.451..917S 2015MNRAS.451..917S)
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Global notes:
Note (G1): Sample as follows:
P = Primary sample
S = Supplemantary sample
M = Miscellaneous sample
Note (G2): in the case of multiple radio sightlines for the same QGP, the name
is suffixed with N, S, E, W or C (denoting north, south, east, west and
centre, respectively) to indicate the radio sightline; in the case of two
galaxies around the same radio sightline, the name is suffixed with _1 and _2
to differentiate the two QGPs.
Note (G3): Type of radio source as follows:
Q = quasar
G = radio galaxy
U = unknown (U).
Note (G4): Morphology of radio source at arcsecond-scale as follows:
C = compact
R = resolved
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 15-Jun-2018