J/MNRAS/445/2061 Absorption in multiphase circumgalactic medium (Liang+, 2014)
Mining circumgalactic baryons in the low-redshift universe.
Liang C.J., Chen H.-W.
<Mon. Not. R. Astron. Soc., 445, 2061-2081 (2014)>
=2014MNRAS.445.2061L 2014MNRAS.445.2061L
ADC_Keywords: QSOs ; Galaxies, nearby ; Equivalent widths
Keywords: survey - galaxies: dwarf - galaxies: haloes - intergalactic medium -
quasars: absorption lines
Abstract:
This paper presents an absorption-line study of the multiphase
circumgalactic medium (CGM) based on observations of Lyα, CII,
CIV, SiII, SiIII, and SiIV absorption transitions in the vicinities of
195 galaxies at redshift z<0.176. The galaxy sample is established
based on a cross-comparison between public galaxy and quasi-stellar
object (QSO) survey data and is characterized by a median redshift of
=0.041, a median projected distance of =362kpc to the sightline
of the background QSO, and a median stellar mass of
log(Mstar/M☉)=9.7±1.1. Comparing the absorber features
identified in the QSO spectra with known galaxy properties has led to
strong constraints for the CGM absorption properties at z≲0.176.
First, abundant hydrogen gas is observed out to d∼500kpc, well beyond
the dark matter halo radius Rh of individual galaxies, with a mean
covering fraction of ∼60 percent. In contrast, no heavy elements are
detected at d≳0.7Rh from either low-mass dwarfs or high-mass
galaxies. The lack of detected heavy elements in low- and
high-ionization states suggests that either there exists a chemical
enrichment edge at d∼0.7Rh or gaseous clumps giving rise to the
observed absorption lines cannot survive at these large distances.
Considering all galaxies at d>Rh leads to a strict upper limit for
the covering fraction of heavy elements of ∼3% (at a 95% confidence
level) over d=(1-9)Rh. At d<Rh, differential covering fraction
between low- and high-ionization gas is observed, suggesting that the
CGM becomes progressively more ionized from d<0.3Rh to larger
distances. Comparing CGM absorption observations at low and high
redshifts shows that at a fixed fraction of Rh the CGM exhibits
stronger mean absorption at z=2.2 than at z∼0, and that the
distinction is most pronounced in low-ionization species traced by CII
and SiII absorption lines. We discuss possible pseudo-evolution of the
CGM as a result of misrepresentation of halo radius, and present a
brief discussion on the implications of these findings.
Description:
We have assembled a large sample (ngal∼300) of spectroscopically
identified galaxies that occur at small projected distances ≲500kpc
from the sightline of a background UV bright QSO. This galaxy sample
is ideal for characterizing extended gaseous haloes around galaxies
based on the absorption features imprinted in the spectra of the
background QSOs.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 101 195 Summary of galaxy properties
table2.dat 76 96 Summary of observations of QSOs
table4.dat 114 195 Summary of individual halo absorption properties
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1 A1 --- n_Galaxy [*] Unexplained flag
2- 30 A29 --- Galaxy Galaxy name
33- 43 F11.7 deg RAdeg Right ascension (J2000)
45- 56 F12.8 deg DEdeg Declination (J2000)
59- 69 F11.9 --- zsp [0.002/0.18] Spectroscopic redshift
71- 75 F5.2 [Msun/yr] log(SFR) ?=-9.99 SFR derived from GALEX NUV band (1)
78- 81 F4.1 [Msun] log(M*) Stellar mass
83- 86 F4.1 [Msun] log(Mh) Halo mass (2)
88- 92 F5.1 kpc Rh [23/391] Halo radius (2)
94- 99 F6.2 mag rMAG Absolute r band magnitude in SDSS (3)
101 A1 --- n_Rh [0/1] How the halo parameters are derived (2)
--------------------------------------------------------------------------------
Note (1): Star formation rate derived from GALEX Near UV band with
λeff2267Å. -9.99 if no measurements available.
Note (2): The halo mass Mh and halo radius Rh are estimated following the
prescription described in Section 4.3. The flag is:
1 = mass obtained using Eq. (1) of the paper
0 = mass obtained from NASA-Sloan Atlas
Note (3): Absolute r-band magnitude estimated from Sergic + Exponential light
profile fit (Bernadi et al., 2013MNRAS.436..697B 2013MNRAS.436..697B). Assumed cosmology:
h=0.7 (H0=70km/s/Mpc), Ωmatter=0.3, ΩΛ=0.7.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 23 A23 --- QSO QSO Name
25- 34 F10.6 deg RAdeg Right ascension (J2000)
36- 45 F10.6 deg DEdeg Declination (J2000)
48- 55 F8.6 --- zsp [0.05/1.5] Spectroscopic redshift
57- 61 I5 --- PID [8015/12264] Program ID
63- 66 I4 --- S/N1 [2/29]?=-999 Median signal-to-noise in
COS(G130M grating) (1150-1450Å)
68- 71 I4 --- S/N2 [2/20]?=-999 Median signal-to-noise in
COS(G160M grating) (1450-1750Å)
73- 76 I4 --- S/N3 [5/48]?=-999 Median signal-to-noise in STIS
(1200-1700Å)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1 A1 --- n_Galaxy [*] Unexplained flag
2- 30 A29 --- Galaxy Galaxy Name
32- 37 F6.1 arcsec Sep [29/9198] Angular separation QSO-galaxy
39- 43 F5.1 kpc d [32/499] Impact parameter (projected distance)
45- 50 F6.4 --- zGal [0.002/0.18] Galaxy redshift
52- 58 F7.4 --- zLya [0/0.18]?=-1 Redshift of Lyα detection
60- 61 A2 --- l_EW(Lya) [≤ ] Limit flag on EW(Lya) (2σ)
62- 65 I4 0.1pm EW(Lya) [8/1397]?=0 Lyα equivalent width
(1215Å) (4)
67- 69 I3 0.1pm e_EW(Lya) [3/94]? rms uncertainty on EW(Lya)
71- 72 A2 --- l_EW(1206) [≤ ] Limit flag on EW(1206) (2σ)
73- 75 I3 0.1pm EW(1206) [1/290]?=0 SiIII 1206Å equivalent width (4)
77- 78 I2 0.1pm e_EW(1206) [2/12]? rms uncertainty on EW(1206)
80- 81 A2 --- l_EW(1260) [≤ ] Limit flag on EW(260) (2σ)
82- 84 I3 0.1pm EW(1260) [2/146]?=0 SiII 1260Å equivalent width (4)
86- 87 I2 0.1pm e_EW(1260) [2/8]? rms uncertainty on EW(1260)
89- 90 A2 --- l_EW(1393) [≤ ] Limit flag on EW(1393) (2σ)
91- 93 I3 0.1pm EW(1393) [3/166]?=0 SiIV 1393Å equivalent width (4)
95- 96 I2 0.1pm e_EW(1393) [4/16]? rms uncertainty on EW(1393)
98- 99 A2 --- l_EW(1334) [≤ ] Limit flag on EW(1334) (2σ)
100-102 I3 0.1pm EW(1334) [2/221]?=0 CII 1334Å equivalent width (4)
104-105 I2 0.1pm e_EW(1334) [4/19]? rms uncertainty on EW(1334)
107-108 A2 --- l_EW(1548) [≤ ] Limit flag on EW(1548) (2σ)
109-111 I3 0.1pm EW(1548) [6/586]?=0 CIV 1548Å equivalent width (4)
113-114 I2 0.1pm e_EW(1548) [4/33]? rms uncertainty on EW(1548)
--------------------------------------------------------------------------------
Note (4): 0 if no measurements available due to contamination, bad data,
or lack of data.
--------------------------------------------------------------------------------
History:
* 09-Oct-2015: From electronic version of the journal
* 03-Feb-2016: 2 SDSS names corrected in tables 1 and 4
(End) Patricia Vannier [CDS] 18-May-2015