J/ApJ/758/129 4Ms Chandra Deep Field South 6-8keV galaxies (Xue+, 2012)
Tracking down the source population responsible for the unresolved cosmic
6-8 keV background.
Xue Y.Q., Wang S.X., Brandt W.N., Luo B., Alexander D.M., Bauer F.E.,
Comastri A., Fabian A.C., Gilli R., Lehmer B.D., Schneider D.P.,
Vignali C., Young M.
<Astrophys. J., 758, 129 (2012)>
=2012ApJ...758..129X 2012ApJ...758..129X
ADC_Keywords: Active gal. nuclei ; Redshifts ; Photometry, infrared ;
X-ray sources ; Magnitudes, absolute ; Surveys
Keywords: diffuse radiation; galaxies: active; surveys;
X-rays: diffuse background; X-rays: galaxies
Abstract:
Using the 4Ms Chandra Deep Field-South (CDF-S) survey, we have
identified a sample of 6845 X-ray-undetected galaxies that dominates
the unresolved ~20%-25% of the 6-8keV cosmic X-ray background
(XRB). This sample was constructed by applying mass and color cuts to
sources from a parent catalog based on GOODS-South Hubble Space
Telescope z-band imaging of the central 6' radius area of the 4Ms
CDF-S. The stacked 6-8keV detection is significant at the 3.9σ
level, but the stacked emission was not detected in the 4-6keV band,
which indicates the existence of an underlying population of highly
obscured active galactic nuclei (AGNs). Further examinations of these
6845 galaxies indicate that the galaxies on the top of the blue cloud
and with redshifts of 1≲z≲3, magnitudes of 25≲z850≲28, and
stellar masses of 2x108≲M{sstarf}/M☉≲2x109 make the
majority contributions to the unresolved 6-8keV XRB. Such a population
is seemingly surprising given that the majority of the X-ray-detected
AGNs reside in massive (≳1010M☉) galaxies. We discuss
constraints upon this underlying AGN population, supporting evidence
for relatively low mass galaxies hosting highly obscured AGNs, and
prospects for further boosting the stacked signal.
Description:
The Luo et al. (2011, Cat. J/ApJ/740/37) sample of 18272
X-ray-undetected GOODS-S HST z-band sources is located within 6' of
the 4Ms CDF-S (Cat. J/ApJS/195/10) average aim point
(RAJ2000=03:32:28.06, DEJ2000=-27:48:26.4) and outside of twice the
90% encircled-energy (in the 0.5-2keV band) aperture radius of any 4Ms
CDF-S main-catalog source (the resultant total stacking area is
0.027deg2). We reduce the size of this sample to 18035 (after
discarding the 160 sources with a low signal-to-noise ratio and the 77
stars spectroscopically identified in Dahlen et al.
2010ApJ...724..425D 2010ApJ...724..425D) and refer to this reduced sample as "Sample A".
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4.dat 133 18035 Derived properties for the sources in sample A
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See also:
B/chandra : The Chandra Archive Log (CXC, 1999-2014)
II/253 : Chandra Deep Field South: multi-colour data (Wolf+, 2008)
J/ApJS/207/24 : GOODS-S CANDELS multiwavelength catalog (Guo+, 2013)
J/A+A/556/A114 : AGNs in XMM deep survey in CDF-S (Castello-Mor+, 2013)
J/A+A/555/A42 : The XMM-CDFS catalogues (Ranalli+, 2013)
J/MNRAS/420/2190 : ECDFS sources with radio counterparts (Vattakunnel+, 2012)
J/ApJ/748/124 : AGN X-ray variability in the 4Ms catalog (Young+, 2012)
J/A+A/534/A110 : Type-2 AGN from XMM-COSMOS bolometric output (Lusso+, 2011)
J/ApJS/195/10 : The CDF-S survey: 4Ms source catalogs (Xue+, 2011)
J/ApJ/742/61 : Phot. redshift of AGNs from XMM- and C-COSMOS (Salvato+ 2011)
J/ApJ/742/3 : Photometric catalogs for ECDF-S and CDF-N (Rafferty+, 2011)
J/ApJ/740/37 : Obscured AGN at z∼0.5-1 in the CDFS (Luo+, 2011)
J/ApJS/191/124 : Opt. spectroscopy of ECDF-S X-ray sources (Silverman+, 2010)
J/ApJS/189/270 : MUSYC optical imaging in ECDF-S (Cardamone+, 2010)
J/ApJS/187/560 : Photometric redshifts of the 2Ms CDF-S (Luo+, 2010)
J/ApJ/720/368 : Color-magnitude relations of galaxies in CDFs (Xue+, 2010)
J/ApJ/708/137 : Broad-line AGNs in zCOSMOS survey (Merloni+, 2010)
J/MNRAS/398/1165 : AGN in nearby galaxies (Goulding+, 2009)
J/A+A/507/1277 : Multiwavelength phot. of CDFS X-ray sources (Brusa+, 2009)
J/A+A/497/81 : Variability-selected AGN in CDFS (Boutsia+, 2009)
J/ApJ/693/1713 : Spectroscopy of X-ray sources in ECDF-S (Treister+, 2009)
J/ApJS/179/19 : CDFS survey: 2 Ms source catalogs (Luo+, 2008)
J/AJ/135/1505 : CDFs AGNs X-ray power-law photon index (Saez+, 2008)
J/A+A/488/73 : Variability-selected AGN in Chandra DFS (Trevese+, 2008)
J/A+A/466/823 : Hard 2-10kev X-ray selected sources (Georgantopoulos+, 2007)
J/A+A/451/457 : X-ray properties of AGN in CDFS (Tozzi+, 2006)
J/ApJ/640/167 : AGNs and ULIRGs in the CDF-South (Alonso-Herrero+, 2006)
J/AJ/131/2373 : Extended Chandra Deep Field-South survey (Virani+, 2006)
J/ApJS/161/21 : Extended Chandra Deep Field-South survey (Lehmer+, 2005)
J/ApJS/155/271 : CDF-South: Optical spectroscopy (Szokoly+, 2004)
J/ApJS/155/73 : Photometric redshifts of X-ray sources in CDF-S (Zheng+, 2004)
J/AJ/126/539 : The Chandra Deep Fields North and South (Alexander+, 2003)
J/ApJS/139/369 : Chandra Deep Field South. 1 Ms catalog (Giacconi+, 2002)
Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- Seq [1/18035] Source running sequence number
7- 14 F8.5 deg RAdeg [53.009/53.23] Right ascension (J2000)
16- 24 F9.5 deg DEdeg [-27.91/-27.7] Declination (J2000)
26- 31 F6.3 --- zsp [0.07/5.9]?=-1 Spectroscopic redshift
33- 37 F5.3 --- zph [0.03/7] Photometric redshift
39- 43 F5.3 --- e_zph 1-σ lower limit on zph
45- 49 F5.3 --- E_zph 1-σ upper limit on zph
51- 56 F6.2 mag UMag [-25.1/-9] Rest-frame absolute U-band Vega
magnitude (1)
58- 63 F6.2 mag BMag Rest-frame absolute B-band Vega magnitude (1)
65- 70 F6.2 mag VMag Rest-frame absolute V-band Vega magnitude (1)
72- 77 F6.2 mag redMag [-26.6/-13.6] Reddest rest-frame absolute
Vega magnitude (1)
79 I1 --- f_redMag [1/7] Flag of reddest rest-frame coverage (2)
81- 85 F5.2 [Msun] Mass [5.8/13] Log stellar-mass estimate adopted here
87- 91 F5.2 [Msun] MassF Log stellar-mass estimate calculated by FAST
93- 98 F6.2 mag Ymag [16.6/28.9]?=-99 CANDELS HST/WFC3 F105W
Y-band AB magnitude
100-105 F6.2 mag e_Ymag [0/1]?=-99 1-σ uncertainty in Ymag
107-112 F6.2 mag Jmag [16.5/29]?=-99 CANDELS HST/WFC3 F125W
J-band AB magnitude
114-119 F6.2 mag e_Jmag ?=-99 1-σ uncertainty in Jmag
121-126 F6.2 mag Hmag [16.4/29.8]?=-99 CANDELS HST/WFC3 F160W
H-band AB magnitude
128-133 F6.2 mag e_Hmag ?=-99 1-σ uncertainty in Hmag
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Note (1): The conversion between Vega and AB rest-frame absolute magnitudes is:
MAB=MVega+mconv, where
mconv=0.628/-0.102/0.029/0.264/0.501/0.914/1.381/1.839 for
rest-frame U/B/V/R/I/J/H/K-band, respectively; we derived these
mconv values using a K-correction package (kcorrect.v4 1 4;
Blanton & Roweis 2007AJ....133..734B 2007AJ....133..734B).
Note (2): This flag shows which stellar-mass estimate is adopted as the
final estimate. "Fred"=(1, 2, 3, 4, 5, 6, 7) means that
redMag=MB/V/R/I/J/H/K and
Massstellar,B/V/R/I/J/H/K are adopted, respectively.
See section 2.3 for further explanations on stellar mass estimations.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 08-Jul-2014