J/AJ/159/216 Ions density in the CGM of low mass galaxy groups (Pointon+, 2020)
Low-mass group environments have no substantial impact on the circumgalactic
medium metallicity.
Pointon S.K., Kacprzak G.G., Nielsen N.M., Murphy M.T., Muzahid S.,
Churchill C.W., Charlton J.C.
<Astron. J., 159, 216 (2020)>
=2020AJ....159..216P 2020AJ....159..216P
ADC_Keywords: Intergalactic medium; QSOs; Galaxies; Spectra, ultraviolet;
Spectra, optical; Redshifts; Abundances
Keywords: Circumgalactic medium ; Quasar absorption line spectroscopy ;
Metallicity ; Galaxy environments
Abstract:
We explore how environment affects the metallicity of the
circumgalactic medium (CGM) using 13 low-mass galaxy groups (two to
five galaxies) at <zabs≥0.25 identified near background quasars.
Using quasar spectra from the Hubble Space Telescope/Cosmic Origins
Spectrograph (HST/COS) and from Keck/High Resolution Echelle
Spectrometer (Keck/HIRES) or the Very Large Telescope/Ultraviolet and
Visual Echelle Spectrograph (VLT/UVES), we measure column densities of
or determine limits on CGM absorption lines. We use a Markov Chain
Monte Carlo approach with Cloudy to estimate metallicities of cool
(T∼104K) CGM gas within groups and compare them to CGM metallicities
of 47 isolated galaxies. Both group and isolated CGM metallicities
span a wide range (-2<[Si/H]<0), where the mean group (-0.54±0.22)
and isolated (-0.77±0.14) CGM metallicities are similar. Group and
isolated environments have similar distributions of HI column
densities as a function of impact parameter. However, contrary to
isolated galaxies, we do not find an anticorrelation between HI column
density and the nearest group galaxy impact parameter. We additionally
divided the groups by member luminosity ratios (i.e., galaxy-galaxy
and galaxy-dwarf groups). While there was no significant difference in
their mean metallicities, a modest increase in sample size should
allow one to statistically identify a higher CGM metallicity in
galaxy-dwarf groups compared to galaxy-galaxy groups. We conclude that
either environmental effects have not played an important role in the
metallicity of the CGM at this stage and expect that this may only
occur when galaxies are strongly interacting or merging or that some
isolated galaxies have higher CGM metallicities due to past
interactions. Thus, environment does not seem to be the cause of the
CGM metallicity bimodality.
Description:
In order to study the circumgalactic medium (CGM) of the group
environments, we use the "Multiphase Galaxy Halos" Survey, which is
comprised of UV Hubble Space Telescope/Cosmic Origins Spectrograph
(HST/COS) spectra from our program (PID 13398), as well as data taken
from the literature (Chen+, 2001, J/ApJ/559/654; Chen & Mulchaey,
2009, J/ApJ/701/1219; Meiring+, 2011ApJ...732...35M 2011ApJ...732...35M; Werk+,
2012ApJS..198....3W 2012ApJS..198....3W; Johnson+, 2013, J/MNRAS/434/1765).
All quasars in the sample have COS UV spectra (R∼20000), while two
also have reduced UV spectra from the Far-Ultraviolet Spectroscopic
Explorer (FUSE) telescope (R∼30000).
Eight quasars have optical spectra from High Resolution Echelle
Spectrometer (Keck/HIRES) and Very Large Telscope/Ultraviolet and
Visual Echelle Spectrograph (VLT/UVES) with a resolving power of
R∼40000.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 85 11 Quasar observations
table4.dat 39 140 Measured column densities
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See also:
J/ApJ/508/200 : QSO low-z Lyα absorbers (Tripp+, 1998)
J/ApJ/559/654 : Lyα absorption systems. V. (Chen+, 2001)
J/ApJ/679/1144 : Galaxy clusters in LOS to background QSOs. I. (Lopez+, 2008)
J/ApJ/701/1219 : Galaxy survey in 3 QSO fields (Chen+, 2009)
J/ApJ/714/1521 : Spectroscopy of galaxies around distant QSOs (Chen+, 2010)
J/ApJ/724/L176 : MgII absorbing gas around galaxies (Chen+, 2010)
J/ApJ/710/613 : Broad HI absorbers (Danforth+, 2010)
J/ApJ/740/91 : Lyα and OVI galaxies around quasars (Prochaska+, 2011)
J/ApJ/774/40 : Galaxy clusters aligned with quasars. III. (Andrews+, 2013)
J/MNRAS/434/1765 : Catalog of galaxies around PKS 0405-123 (Johnson+, 2013)
J/ApJ/770/138 : Metallicities of Lyman limit systems and DLA (Lehner+, 2013)
J/ApJ/776/114 : MAGIICAT. I. MgII Absorber-Galaxy Catalog (Nielsen+, 2013)
J/ApJ/796/140 : Circumgalactic medium surrounding z∼2 QSOs (Prochaska+,2014)
J/ApJ/804/79 : HST/COS obs. of QSOs within 600kpc of M31 (Lehner+, 2015)
J/MNRAS/449/3263 : Extended galaxy halo gas through HI and OVI (Johnson+, 2015)
J/ApJ/866/33 : The COS CGM compendium. I. Initial results (Lehner+, 2018)
J/ApJ/871/35 : HST/COS spectra of QSOs with SiIV data (Zheng+, 2019)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- QSO J-Name of the quasar
7- 11 F5.3 --- z [0.17/1.08] Quasar redshift
13- 14 I2 h RAh [1/11] Hour of right ascension (J2000)
16- 17 I2 min RAm Minute of right ascension (J2000)
19- 23 F5.2 s RAs Second of right ascension (J2000)
25 A1 --- DE- [-+] Sign of declination (J2000)
26- 27 I2 deg DEd Degree of declination (J2000)
29- 30 I2 arcmin DEm Arcminute of declination (J2000)
32- 36 F5.2 arcsec DEs Arcsecond of declination (J2000)
38- 46 A9 --- InstUV Instrument used for UV observations (1)
48- 59 A12 --- GratCOS Grating for COS instrument
61- 65 I5 --- PIDCOS [11541/13398] PID(s) for COS instrument
67- 71 A5 --- Instopt Instrument used for optical observations (1)
73- 85 A13 --- PIDopt PID for optical instrument
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Note (1): Instruments as follows:
COS = Cosmic Origins Spectrograph on Hubble Space Telescope
(11 occurrences)
FUSE = Far-Ultraviolet Spectroscopic Explorer telescope (2 occurrences)
UVES = Ultraviolet and Visual Echelle Spectrograph on Very Large
Telescope (2 occurrences)
HIRES = High Resolution Echelle Spectrometer on Keck telescope
(5 occurrences)
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Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- QSO J-Name of the quasar
7- 14 F8.6 --- z [0.05/0.38] Galaxy redshift
16- 21 A6 --- Ion Ion identifier (C, Ca, Fe, H, Mg, N, O and Si
ions)
23- 23 A1 --- l_logN [<>]Limit flag on logN
24- 28 F5.2 [cm-2] logN [10.85/19.58] log column density (1)
30- 34 F5.2 [cm-2] uplogN [19]? Upper limit on logN (1)
36- 39 F4.2 [cm-2] e_logN [0.01/7.8]? Uncertainty in logN
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Note (1): Some of the HI column densities are given as ranges. In these cases
the logN is the lower range and uplogN is the upper range.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 17-Sep-2020