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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
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 <z≥0.041, a median projected distance of <d≥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). 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
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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