J/ApJ/923/44 Galaxy-absorber pairs for low-z QSO sightlines (Scott+, 2021)
Identifying circumgalactic medium absorption in QSO spectra: a Bayesian
approach.
Scott J.E., Shoemaker E.S., Hamill C.D.
<Astrophys. J., 923, 44 (2021)>
=2021ApJ...923...44S 2021ApJ...923...44S
ADC_Keywords: Intergalactic medium; QSOs; Spectra, ultraviolet; Redshifts;
Equivalent widths; Photometry, SDSS; Magnitudes, absolute;
Galaxies, optical
Keywords: Circumgalactic medium ; Intergalactic medium ;
Galactic and extragalactic astronomy
Abstract:
We present a study of candidate galaxy-absorber pairs for
43 low-redshift QSO sightlines (0.06<z<0.85) observed with the Hubble
Space Telescope/Cosmic Origins Spectrograph that lie within the
footprint of the Sloan Digital Sky Survey with a statistical approach
to match absorbers with galaxies near the QSO lines of sight using
only the SDSS Data Release 12 photometric data for the galaxies,
including estimates of their redshifts. Our Bayesian methods combine
the SDSS photometric information with measured properties of the
circumgalactic medium to find the most probable galaxy match, if any,
for each absorber in the line-of-sight QSO spectrum. We find
∼630 candidate galaxy-absorber pairs using two different statistics.
The methods are able to reproduce pairs reported in the targeted
spectroscopic studies upon which we base the statistics at a rate of
72%. The properties of the galaxies comprising the candidate pairs
have median redshift, luminosity, and stellar mass, all estimated from
the photometric data, z=0.13, L=0.1L*, and log(M*/M☉)=9.7. The
median impact parameter of the candidate pairs is ∼430kpc, or
∼3.5 times the galaxy virial radius. The results are broadly
consistent with the high Lyα covering fraction out to this
radius found in previous studies. This method of matching absorbers
and galaxies can be used to prioritize targets for spectroscopic
studies, and we present specific examples of promising systems for
such follow-up.
Description:
Of the 82 QSOs with HST COS spectra in the sample of
Danforth+ (2016, J/ApJ/817/111) and archived in the Mikulski Archive
for Space Telescopes (MAST), 43 of them, and their surrounding fields,
overlap with the footprint of the SDSS DR12 (V/147). Table 1 lists
these QSOs, which constitute our sample.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 63 43 HST/COS QSO sample in SDSS footprint
table4.dat 153 1073 Galaxy-absorber pairs: P(rvir)
table5.dat 153 1039 Galaxy-absorber pairs: P(M*)
table6.dat 124 81 Galaxy-absorber pairs in the literature
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See also:
V/147 : The SDSS Photometric Catalogue, Release 12 (Alam+, 2015)
J/ApJ/508/200 : QSO low-z Lyα absorbers (Tripp+, 1998)
J/ApJ/559/654 : Lyα absorption systems. V. (Chen+, 2001)
J/ApJ/701/1219 : Galaxy survey in 3 QSO fields (Chen+, 2009)
J/ApJS/182/378 : HI and OVI absorbers in nearby Universe (Wakker+, 2009)
J/ApJS/193/28 : Galaxy survey around 20 UV-bright quasars (Prochaska+, 2011)
J/ApJ/740/91 : Lya & OVI in galaxies around quasars (Prochaska+, 2011)
J/MNRAS/445/2061 : Abs. in multiphase circumgalactic medium (Liang+, 2014)
J/MNRAS/437/2017 : HI-galaxy cross-correlation at z≲1 (Tejos+, 2014)
J/ApJ/815/91 : z<0.16 CIV absorbers from HST/COS QSOs sp. (Burchett+, 2015)
J/MNRAS/452/2553 : Sample of foreground-background QSO pairs (Johnson+, 2015)
J/ApJ/817/111 : HST/COS survey of z<0.9 AGNs. I. (Danforth+, 2016)
J/A+A/590/A68 : AGN data and absorption-line measurements (Richter+, 2016)
J/ApJS/230/6 : HST-COS & -STIS absorption-line sp. II. (Keeney+, 2017)
J/ApJS/237/11 : Gal. z survey near HST/COS AGN sight lines (Keeney+, 2018)
J/MNRAS/486/21 : QSO Sightline and Galaxy Evolution Survey I (Bielby+, 2019)
J/ApJ/883/78 : Column densities of CGM absorption lines (Pointon+, 2019)
J/ApJS/243/24 : The CASBaH galaxy redshift survey (Prochaska+, 2019)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 24 A24 --- Name Full Quasar name
26- 32 A7 --- QSO Short name for QSO as used in Tables 4 and 5
34- 35 I2 h RAh Hour of Right Ascension (J2000)
37- 38 I2 min RAm Minute of Right Ascension (J2000)
40- 44 F5.2 s RAs Second of Right Ascension (J2000)
46- 46 A1 --- DE- Sign of the Declination (J2000)
47- 48 I2 deg DEd Degree of Declination (J2000)
50- 51 I2 arcmin DEm Arcminute of Declination (J2000)
53- 56 F4.1 arcsec DEs Arcsecond of Declination (J2000)
58- 63 F6.4 --- zem [0.063/0.852] QSO emission redshift
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Byte-by-byte Description of file: table[45].dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- QSO Short name for QSO
9- 18 A10 --- Ptot Total Probability (1)
20- 26 F7.3 kpc Impact [18.9/500] Galaxy-absorber projected
separation (2)
28- 38 A11 --- Ion Ion, in TeX format
40- 48 A9 --- zabs Absorber redshift
50- 57 F8.3 0.1pm Wrest [5.39/2797] Absorber rest equivalent width,
in milli-Angstroms
59- 65 F7.3 0.1pm e_Wrest [0.89/575] Wrest uncertainty
67- 75 A9 --- P(Ion) Probability for ion (3)
77- 85 A9 --- zphot Galaxy photometric redshift from SDSS
87- 93 F7.3 deg RAdeg [0.48/358.4] Galaxy Right Ascension (J2000)
95- 100 F6.3 deg DEdeg [-1.21/66] Galaxy Declination (J2000)
102- 107 F6.3 mag rmag [14.14/21.54] Galaxy extinction corrected AB
magnitude from SDSS
109- 115 F7.3 mag rMag [-23.04/-15.9] Galaxy absolute r magnitude
117- 123 F7.3 kpc Rad [45.5/241] Galaxy virial radius (4)
125- 130 F6.3 [Msun] logMs [8/11.71] Galaxy stellar mass (5)
132- 150 I19 --- SDSS Galaxy SDSS DR12 objID
152- 153 A2 --- Flag Absorption flag (6)
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Note (1): Full probability from Equation 1 using virial radius method for
absorption system, all ions within deltav=300km/s
Note (2): Proper separation of galaxy and absorber assuming absorber redshift
in Col. 5
Note (3): Probability from Equation 1 using virial radius method for ion
listed in Col. 4
Note (4): Virial radius estimated from Richter+ (2016, J/A+A/590/A68)
parameterization
Note (5): Stellar mass estimated from Taylor+ (2011MNRAS.418.1587T 2011MNRAS.418.1587T)
parameterization
Note (6): Absorption flag as in Keeney+ (2018, J/ApJS/237/11). Code as follows:
-1 = object has z<0.001 and is likely a star;
0 = galaxy is not within 1000km/s of an absorber;
1 = galaxy is within 1000km/s of an absorber but is not the closest galaxy;
2 = galaxy is closest in this Table to an absorber, but a closer galaxy
is known from SDSS or other sources;
3 = closest known galaxy to an absorber.
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
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1- 24 A24 --- Name QSO name
26- 29 I4 kpc rho [12/1742] galaxy-absorber impact parameter
31- 55 A25 --- Galaxy Galaxy name
57- 60 F4.1 mag omag [10.2/22.4] Observed magnitude in Filt
61- 62 A2 --- Filt Filter for omag
64- 70 F7.5 --- zgal [0.00137/0.241] Galaxy redshift
72- 78 F7.5 --- zabs [0.00137/0.241] Absorber redshift
80- 86 F7.2 0.1pm EW [6/1630] Equivalent width Lyman line,
in milli-Angstroms (1)
88- 88 A1 --- f_EW Lyman line flag (1)
90- 95 F6.2 0.1pm e_EW [0.1/173]? Uncertainty in EW
97-107 A11 --- r_EW Reference(s) for EW (2)
109-109 I1 --- n_Galaxy [1/4] SDSS Note (3)
113-114 I2 --- R-rvir [1/10]? Rank of galaxy-absorber pair, r_vir (4)
116-117 I2 --- R-MI [1/10]? Rank of galaxy-absorber pair, M* (4)
119-124 F6.4 --- zphot [0.01/0.4]? Photometric redshift
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Note (1): Equivalent width is of the Lyman α line except where flagged
(f_EW=5) when it is the Lyman β line.
Note (2): References for EW as follows:
B97 = Bowen et al. (1997MNRAS.284..599B 1997MNRAS.284..599B);
T98 = Tripp et al. (1998, J/ApJ/508/200);
P02 = Penton et al. (2002ApJ...565..720P 2002ApJ...565..720P);
C05 = Cote et al. (2005ApJ...618..178C 2005ApJ...618..178C);
WS09 = Wakker & Savage (2009, J/ApJS/182/378);
S13 = Stocke et al. (2013ApJ...763..148S 2013ApJ...763..148S);
LC14 = Liang & Chen (2014, J/MNRAS/445/2061);
M14 = Mathes et al. (2014ApJ...792..128M 2014ApJ...792..128M);
D16 = Danforth et al. (2016, J/ApJ/817/111)
Note (3): SDSS Note as follows:
1 = Galaxy is present in SDSS catalog;
2 = Galaxy is not in SDSS catalog, r<14;
3 = photometric redshift cut;
4 = no photometric redshift.
Note (4): No entry for the Rank indicates that this galaxy is not recovered in
top 10 highest probability matches to the absorber for that method.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 16-May-2023