J/A+A/590/A68 AGN data and absorption-line measurements (Richter+, 2016)
An HST/COS legacy survey of intervening SiIII absorption in the extended gaseous
halos of low-redshift galaxies.
Richter P., Wakker B.P., Fechner C., Herenz P., Tepper-Garcia T., Fox A.J.
<Astron. Astrophys. 590, A68 (2016)>
=2016A&A...590A..68R 2016A&A...590A..68R (SIMBAD/NED BibCode)
ADC_Keywords: QSOs; Positional data; Redshifts; Spectroscopy; Equivalent widths
Keywords: galaxies: halos - galaxies: formation - intergalactic medium -
quasars: absorption lines
Abstract:
Doubly ionized silicon (SiIII) is a powerful tracer of diffuse ionized
gas inside and outside of galaxies.It can be observed in the local
Universe in ultraviolet (UV) absorption against bright extragalactic
background sources. We here present an extensive study of intervening
SiIII-selected absorbers and study the properties of the warm
circumgalactic medium (CGM) around low-redshift (z<0.1) galaxies.
We analyzed the UV absorption spectra of 303 extragalactic background
sources, as obtained with the Cosmic Origins Spectrograph (COS)
on-board the Hubble Space Telescope (HST). We developed a geometrical
model for the absorption-cross section of the CGM around the local
galaxy population and compared the observed SiIII absorption
statistics with predictions provided by the model. We also compared
redshifts and positions of the absorbers with those of ∼64,000
galaxies using archival galaxy-survey data to investigate the relation
between intervening SiIII absorbers and the CGM.
Along a total redshift path of Δz∼24, we identify 69 intervening
SiIII systems that all show associated absorption from other low and
high ions (e.g., HI, SiII, SiIV, CII, CIV). We derive a bias-corrected
number density of dN/dz(SiIII)=2.5±0.4 for absorbers with column
densities log N(SiIII)>12.2, which is ∼3 times the number density of
strong MgII systems at z=0. This number density matches the expected
cross section of a SiIII absorbing CGM around the local galaxy
population with a mean covering fraction of <fc≥0.69. For the
majority (∼60 percent) of the absorbers, we identify possible host
galaxies within 300km/s of the absorbers and derive impact parameters
ρ<200kpc, demonstrating that the spatial distributions of SiIII
absorbers and galaxies are highly correlated.
Our study indicates that the majority of SiIII-selected absorbers in
our sample trace the CGM of nearby galaxies within their virial radii
at a typical covering fraction of ∼70 percent. We estimate that
diffuse gas in the CGM around galaxies, as traced by SiIII contains
substantially more (more than twice as much) baryonic mass than their
neutral interstellar medium.
Description:
Names, positions and emission redshifts for 303 QSOs are provided in
Table A.1. Table A.2 summarizes the absorption-line measurements for
59 intervening SiIII absorbers including absorption redshifts,
equivalent-widths, and column densities for various different ions.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 89 303 QSO names, coordinates, and emission redshifts
tablea2.dat 65 426 Absorption-line measurements for 59 QSOs
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq [1/303] QSO number
4 A1 --- n_Seq [*] Note (1)
6- 31 A26 --- Name1 QSO name (COS)
33- 63 A31 --- Name2 QSO name (NED)
65- 70 F6.2 deg RAdeg Right ascension (J2000.0)
72- 77 F6.2 deg DEdeg Declination (J2000.0)
79- 83 F5.3 --- zem QSO emission redshift
85- 89 F5.3 --- dz Absorption redshift path for z<0.1
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Note (1): QSO number 6: spectrum shows no QSO characteristics; possibly wrong
source (white dwarf) observed; object/spectrum not considered in study.
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Byte-by-byte Description of file: tablea2.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- No Row number
5- 30 A26 --- Name1 QSO name (COS)
32- 36 F5.3 --- zabs Absorption redshift
38- 42 A5 --- Ion Ion (1)
44 A1 --- l_EWrest Limit flag on EWrest
45- 48 I4 0.1pm EWrest ? Restframe equivalent width (or limit)
50- 53 I4 0.1pm e_EWrest ? Sigma restframe equivalent width
55 A1 --- l_logN Limit flag on logN
56- 60 F5.2 [cm-2] logN ? Logarithmic column density
62- 65 F4.2 [cm-2] e_logN ? Sigma logarithmic column density
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Note (1): Used ion transitions: HI 1215, SiII 1260, SiIII 1206, SiIV 1393,
CII 1334, and CIV 1548.
One line per transition.
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Acknowledgements:
Philipp Richter, prichter(at)astro.physik.uni-potsdam.de
(End) P. Richter [Univrsitaet Potsdam, Germany], P. Vannier [CDS] 30-Mar-2016