J/ApJ/716/1514 Galaxies as tracers of the circumgalactic gas (Yao+, 2010)
The dearth of chemically enriched warm-hot circumgalactic gas.
Yao Y., Wang Q.D., Penton S.V., Tripp T.M., Shull J.M., Stocke J.T.
<Astrophys. J., 716, 1514-1521 (2010)>
=2010ApJ...716.1514Y 2010ApJ...716.1514Y
ADC_Keywords: Active gal. nuclei ; Galaxies, nearby ; Redshifts ; X-ray sources
Keywords: cosmology: observations - intergalactic medium -
quasars: absorption lines - X-rays: general
Abstract:
The circumgalactic medium (CGM) around galaxies is believed to record
various forms of galaxy feedback and contain a significant portion of
the "missing baryons" of individual dark matter halos. However, clear
observational evidence for the existence of the hot CGM is still
absent. We use intervening galaxies along 12 background active
galactic nuclei (AGNs) as tracers to search for X-ray absorption lines
produced in the corresponding CGM. Stacking Chandra grating
observations with respect to galaxy groups and different luminosities
of these intervening galaxies, we obtain spectra with signal-to-noise
ratios of 46-72 per 20mÅ spectral bin at the expected OVIIKα
line. We find no detectable absorption lines of CVI, NVII, OVII,
OVIII, or NeIX. The high spectral quality allows us to tightly
constrain upper limits to the corresponding ionic column densities (in
particular log[NOVII(cm-2)]≤14.2-14.8). These nondetections are
inconsistent with the Local Group hypothesis of the X-ray absorption
lines at z∼0 commonly observed in the spectra of AGNs. These results
indicate that the putative CGM in the temperature range of
105.5-106.3K may not be able to account for the missing baryons
unless the metallicity is less than 10% solar.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 32 12 Background AGNs, Chandra observations, and
intervening galaxies
table2.dat 62 144 Intervening galaxies along the 12 sight lines
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See also:
B/chandra : The Chandra Archive Log (CXC, 1999-2012)
IX/19 : X-ray lightcurves of bright AGNs from Ginga (Hayashida+ 1998)
J/A+A/539/A149 : Multiwavelength view of blazar PKS 2155-304 (Abramowski+,
2012)
J/MNRAS/392/1181 : BV(RI)c photometry of 3C 273 (Dai+, 2009)
J/ApJS/182/378 : HI and OVI absorbers in nearby Universe (Wakker+, 2009)
J/ApJ/701/1219 : Galaxy survey in 3 QSO fields (Chen+, 2009)
J/ApJS/155/351 : Absorption toward PG 1116+215 (Sembach+, 2004)
J/ApJ/508/200 : QSO low-z Lyα absorbers (Tripp+, 1998)
J/PAZh/23/409 : Spectrophotometry of Mrk 509 (Chuvaev+, 1997)
J/PASP/106/646 : HST quasar absorption-line key project. VIII. (Kirhakos+,
1994)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Name Source name for sight line
14- 18 F5.3 --- zAGN AGN redshift
20- 21 I2 --- No Number of Chandra grating observations
23- 26 I4 ks Exp Total exposure time
28- 29 I2 --- Ng Number of intervening galaxies along the sight
line
31- 32 I2 --- Nb Number of intervening galaxies with reported
B magnitudes. (1)
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Note (1): Only these galaxies were used in this work. The information on the
intervening galaxies was extracted from the same galaxy database as
used by Stocke et al. (2006ApJ...641..217S 2006ApJ...641..217S). This database was
assembled from several galaxy redshift surveys and has been updated
with SDSS DR7 (Cat. II/294). Only those galaxies with reported B-band
magnitudes were used, and the K-correction of Fukugita et al.
(1995PASP..107..945F 1995PASP..107..945F) had been applied to obtain the absolute
magnitude of these galaxies.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Name Source name for sight line
14- 20 F7.3 deg RAdeg Right Ascension in decimal degrees (J2000)
22- 28 F7.3 deg DEdeg Declination in decimal degrees (J2000)
30- 37 F8.6 --- zGal Spectroscopic redshift zigal
39- 44 F6.2 arcsec Dtheta Angular distance
46- 50 F5.1 kpc b Impact distance (riρ; see eq. (1))
52- 56 F5.2 mag Bmag ?=99.9 The B band magnitude
58- 62 F5.3 --- L/L* ?=0 The B band luminosity relative to L*
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 04-Jun-2012