J/ApJ/762/L19 Quasar pairs spectroscopy (Prochaska+, 2013)
A substantial mass of cool, metal-enriched gas surrounding the progenitors of
modern-day ellipticals.
Prochaska J.X., Hennawi J.F., Simcoe R.A.
<Astrophys. J., 762, L19 (2013)>
=2013ApJ...762L..19P 2013ApJ...762L..19P
ADC_Keywords: QSOs ; Redshifts ; Equivalent widths
Keywords: galaxies: halos; quasars: absorption lines
Abstract:
The hosts of luminous z∼2 quasars evolve into today's massive
elliptical galaxies. Current theories predict that the circumgalactic
medium (CGM) of these massive, dark matter halos (MDM∼1012.5M☉)
should be dominated by a T∼107K virialized plasma. We test this
hypothesis with observations of 74 close-projected quasar pairs, using
spectra of the background QSO to characterize the CGM of the
foreground one. Surprisingly, our measurements reveal a cool
(T∼104K), massive (MCGM>1010M☉), and metal-enriched
(Z≳0.1Z☉) medium extending to at least the expected virial
radius (rvir=160kpc). Furthermore, we conservatively estimate that
the quasar CGM has a 64+6-7% covering fraction of optically thick
gas (NHI>1017.2/cm2) within rvir; this covering factor is
twice that of the contemporaneous Lyman break galaxy population. This
unexpected reservoir of cool gas is rarely detected "down-the-barrel"
to quasars, and hence it is likely that our background sight lines
intercept gas that is shadowed from the quasar ionizing radiation by
the same obscuring medium often invoked in models of active galactic
nucleus unification. Because the high-z halos inhabited by quasars
predate modern groups and clusters, these observations are also
relevant to the formation and enrichment history of the
intragroup/intracluster medium.
Description:
Using data-mining techniques suited to large surveys such as the Sloan
Digital Sky Survey (SDSS), we have identified ∼300 projected pairs of
quasars, with redshift difference δv>2000km/s and impact
parameter R<300kpc (e.g., Hennawi et al. 2006, Cat. J/ApJ/651/61;
2006, Cat. J/AJ/131/1 and 2010, Cat. J/ApJ/719/1672). We obtained
deep, high-resolution spectroscopy of the background (b/g) quasar for
49 pairs using the Keck, Gemini, or Magellan telescopes. For an
additional 25 systems, public data sets from the SDSS and BOSS surveys
(Abazajian et al. 2009, Cat. II/294; Ahn et al. 2012, Cat. V/139)
provide b/g spectra with signal-to-noise ratio (S/N) exceeding 10 (per
rest-frame Å) at Lyα, and we use these survey data directly.
The observations and data reduction followed standard procedures;
their details are described elsewhere (J. X. Prochaska et al., in
preparation). Table 1 lists the quasar pair sample and summarizes
several key properties of the pairs and spectral data set. Redshift
estimates and errors for the foreground quasars were derived as
described in Hennawi et al. (2006, Cat. J/ApJ/651/61; see also Shen et
al. 2007, Cat. J/AJ/133/2222), using one or more well-detected
rest-frame UV lines.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 116 74 Sample quasar pairs
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See also:
V/139 : The SDSS Photometric Catalog, Release 9 (Adelman-McCarthy+, 2012)
J/ApJ/755/89 : Metallicities of damped Lyα systems (Rafelski+, 2012)
J/ApJ/740/91 : Lyα & OVI in galaxies around quasars (Prochaska+, 2011)
J/ApJS/194/45 : QSO properties from SDSS-DR7 (Shen+, 2011)
J/ApJ/727/47 : The MgII cross-section of red galaxies (Bowen+, 2011)
J/ApJ/719/1672 : SDSS binary quasars at high redshift. I. (Hennawi+, 2010)
J/ApJ/699/782 : High-redshift SDSS-DR5 QSOs (Diamond-Stanic+, 2009)
J/ApJS/182/378 : HI and OVI absorbers in nearby Universe (Wakker+, 2009)
J/ApJ/679/1144 : Galaxy clusters in LOS to background QSOs. I. (Lopez+, 2008)
J/AJ/133/2222 : Clustering of high-redshift QSOs from SDSS (Shen+, 2007)
J/ApJS/171/29 : UCSD/Keck Lyα Abundance Database (Prochaska+, 2007)
J/AJ/131/1 : Binary quasars in the SDSS (Hennawi+, 2006)
J/ApJ/651/61 : Optically thick absorbers (Hennawi+, 2006)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- FName Foreground QSO identifier (JHHMMSS.ss+DDMMSS.s)
21- 25 F5.3 --- zfg [1.6/3.3] Foreground Quasar redshift estimate
27- 31 F5.3 --- e_zfg [0.002/0.02] Uncertainty in zfg
33- 51 A19 --- BName Background QSO identifier (JHHMMSS.ss+DDMMSS.s)
53- 57 F5.3 --- zbg [1.6/3.8] Background Quasar redshift estimate
59- 61 I3 kpc rho [31/299] Impact parameter ρ
63- 67 A5 --- Inst Spectrum instrument identifier (SDSS, BOSS,
GMOS, LRISb or MagE)
69- 74 F6.4 --- zLya [1.6/3.3] Redshift characterizing Lyα
absorption in the spectrum of the background QSO
76 A1 --- f_logNHI Limit flag on logNHI
78- 82 F5.2 [cm-2] logNHI [18/21.2] Log H I column density
84- 87 F4.2 [cm-2] e_logNHI [0.2/0.4]? Uncertainty in logNHI
89 A1 --- f_W1334 Limit flag on W1334
91- 95 F5.2 0.1nm W1334 [0.04/2.8]? Equivalent width of CII 1334Å line
97-100 F4.2 0.1nm e_W1334 [0.02/0.3]? Uncertainty in W1334
102 A1 --- f_W1548 Limit flag on W1548
104-108 F5.2 0.1nm W1548 [0.09/2.3]? Equivalent width of CIV 1548Å line
110-113 F4.2 0.1nm e_W1548 [0.01/0.3]? Uncertainty in W1548
115-116 I2 --- OT [-1/1]? Optical thickness flag at Lyman limit:
-1=thin, 1=thick, 0=ambiguous
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 08-Oct-2014