J/ApJ/740/37 Obscured AGN at z∼0.5-1 in the CDFS (Luo+, 2011)
Revealing a population of heavily obscured active galactic nuclei at
z∼0.5-1 in the Chandra Deep Field-South.
Luo B., Brandt W.N., Xue Y.Q., Alexander D.M., Brusa M., Bauer F.E.,
Comastri A., Fabian A.C., Gilli R., Lehmer B.D., Rafferty D.A.,
Schneider D.P., Vignali C.
<Astrophys. J., 740, 37 (2011)>
=2011ApJ...740...37L 2011ApJ...740...37L
ADC_Keywords: Active gal. nuclei ; Infrared sources ; Redshifts ; Extinction
Keywords: cosmic background radiation - galaxies: active - X-rays: galaxies -
galaxies: photometry - galaxies: starburst - infrared: galaxies -
Abstract:
We identify a numerically significant population of heavily obscured
AGNs at z∼0.5-1 in the Chandra Deep Field-South (CDF-S) and Extended
Chandra Deep Field-South by selecting 242 X-ray undetected objects
with infrared-based star-formation rates (SFRs) substantially higher
(a factor of 3.2 or more) than their SFRs determined from the UV after
correcting for dust extinction. An X-ray stacking analysis of 23
candidates in the central CDF-S region using the 4Ms Chandra data
reveals a hard X-ray signal with an effective power-law photon index
of Γ=0.6+0.3-0.4, indicating a significant contribution from
obscured AGNs. Based on Monte Carlo simulations, we conclude that
74%±25% of the selected galaxies host obscured AGNs, within which
∼95% are heavily obscured and ∼80% are Compton-thick (CT;
NH>1.5x1024cm-2).
Description:
In this paper, we improve the IR SFR excess (ISX) selection method
(Daddi et al. 2007ApJ...670..173D 2007ApJ...670..173D) and utilize it to search for
X-ray undetected, heavily obscured AGNs at z∼0.5-1 in the Chandra Deep
Field-South (CDF-S; Giacconi et al. 2002, Cat. J/ApJS/139/369; Luo et
al. 2008, Cat. J/ApJS/179/19; Xue et al. 2011, Cat. J/ApJS/195/10) and
Extended Chandra Deep Field-South (E-CDF-S; Lehmer et al. 2005, Cat.
J/ApJS/161/21).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 77 81 List of ISX (IR SFR excess) and ISN (IR SFR
normal) sources in the X-ray stacking analysis
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See also:
B/chandra : The Chandra Archive Log (CXC, 1999-2012)
II/253 : Chandra Deep Field South: multi-colour data (Wolf+, 2008)
J/ApJS/195/10 : The CDF-S survey: 4Ms source catalogs (Xue+, 2011)
J/ApJ/727/1 : IRAC/MUSYC SIMPLE survey (Damen+, 2011)
J/ApJS/191/124 : 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/A+A/512/A12 : VLT/VIMOS spectroscopy in GOODS-South field (Balestra+, 2010)
J/ApJ/702/441 : Obscured active galaxies (Greene+, 2009)
J/A+A/507/1277 : Multiwavelength photometry of CDFS X-ray sources (Brusa+,
2009)
J/ApJS/179/19 : CDFS survey: 2 Ms source catalogs (Luo+, 2008)
J/A+A/478/83 : GOODS-South Field VLT/FORS2 redshifts. III. (Vanzella+, 2008)
J/A+A/465/1099 : Redshift catalog of 691 objects in CDFS (Ravikumar+, 2007)
J/ApJ/642/673 : IR-selected obscured AGN candidates (Polletta+, 2006)
J/ApJ/642/L13 : ECDFS MUSYC galaxies UBVRIzNB5000 photometry (Gawiser+, 2006)
J/A+A/449/951 : GOODS-MUSIC sample: multicolour catalog (Grazian+, 2006)
J/ApJS/161/21 : Extended Chandra Deep Field-South survey (Lehmer+, 2005)
J/A+A/437/883 : K20 survey: spectroscopic catalogue (Mignoli+, 2005)
J/A+A/428/1043 : Redshifts from VIMOS VLT Deep Survey (Le Fevre+, 2004)
J/ApJS/155/271 : CDF-S: Optical spectroscopy (Szokoly+, 2004)
J/ApJS/139/369 : Chandra Deep Field South. 1 Ms catalog (Giacconi+, 2002)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- Sample Sample (ISN or ISX) (1)
5- 6 I2 h RAh [3] Hour of Right Ascension (J2000)
8- 9 I2 min RAm [32] Minute of Right Ascension (J2000)
11- 15 F5.2 s RAs Second of Right Ascension (J2000)
17 A1 --- DE- [-] Sign of the Declination (J2000)
18- 19 I2 deg DEd [27] Degree of Declination (J2000)
21- 22 I2 arcmin DEm [43/54] Arcminute of Declination (J2000)
24- 27 F4.1 arcsec DEs Arcsecond of Declination (J2000)
29- 33 F5.3 --- z [0.5/1] Redshift (2)
35- 39 F5.2 --- b_z ?=-1 The 1σ lower limit on z (3)
41- 45 F5.2 --- B_z ?=-1 The 1σ upper limit on z (3)
47- 49 F3.1 mag Av [0/2.7] V-band dust extinction (4)
51- 55 F5.1 uJy F24 Spitzer/MIPS 24 micron band flux density
57- 61 F5.2 [Lsun] logLIR [10.21/11.51] Log of integrated 8-1000um
luminosity (5)
63- 66 F4.1 Msun/yr SFRI+U IR and UV based Star Formation Rate
68- 71 F4.1 Msun/yr SFRUc [0.6/97] UV corrected based Star Formation Rate
73- 77 F5.2 [-] RSFR Log of IR- to UV- based Star Formation Rates
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Note (1): We define "ISX" (IR SFR excess) sources using the same criterion as
in Daddi et al. (2007ApJ...670..173D 2007ApJ...670..173D): RSFR>0.5. For comparison, we
define IR SFR normal ("ISN") sources as those having RSFR<0.2.
Note (2): Spectroscopic redshifts are denoted by having three decimal places,
while photometric redshifts only have two. The Photometric redshifts
and limits were derived using ZEBRA (Zurich Extragalactic Bayesian
Redshift Analyzer; Feldmann et al. 2006MNRAS.372..565F 2006MNRAS.372..565F).
Note (3): For photometric redshifts only. For the spectroscopic redshifts
"-1.00" is used as a placeholder.
Note (4): Derived from ZEBRA SED fitting.
Note (5): Estimated based on the observed 24 micron flux.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 30-Jan-2013