J/ApJS/236/48 The Chandra UDS survey (X-UDS) (Kocevski+, 2018)
X-UDS: the Chandra Legacy Survey of the UKIDSS Ultra Deep Survey field.
Kocevski D.D., Hasinger G., Brightman M., Nandra K., Georgakakis A.,
Cappelluti N., Civano F., Li Y., Li Y., Aird J., Alexander D.M.,
Almaini O., Brusa M., Buchner J., Comastri A., Conselice C.J.,
Dickinson M.A., Finoguenov A., Gilli R., Koekemoer A.M., Miyaji T.,
Mullaney J.R., Papovich C., Rosario D., Salvato M., Silverman J.D.,
Somerville R.S., Ueda Y.
<Astrophys. J. Suppl. Ser., 236, 48 (2018)>
=2018ApJS..236...48K 2018ApJS..236...48K
ADC_Keywords: X-ray sources; Surveys; Redshifts
Keywords: galaxies: active ; galaxies: nuclei ; surveys ; X-rays: galaxies
Abstract:
We present the X-UDS survey, a set of wide and deep Chandra
observations of the Subaru-XMM Deep/UKIDSS Ultra Deep Survey
(SXDS/UDS) field. The survey consists of 25 observations that cover a
total area of 0.33deg2. The observations are combined to provide a
nominal depth of ∼600ks in the central 100arcmin2 region of the
field that has been imaged with Hubble/WFC3 by the CANDELS survey and
∼200ks in the remainder of the field. In this paper, we outline the
survey's scientific goals, describe our observing strategy, and detail
our data reduction and point source detection algorithms. Our analysis
has resulted in a total of 868 band-merged point sources detected with
a false-positive Poisson probability of <1x10-4. In addition, we
present the results of an X-ray spectral analysis and provide
best-fitting neutral hydrogen column densities, NH, as well as a
sample of 51 Compton-thick active galactic nucleus candidates. Using
this sample, we find the intrinsic Compton-thick fraction to be
30%-35% over a wide range in redshift (z=0.1-3), suggesting the
obscured fraction does not evolve very strongly with epoch. However,
if we assume that the Compton-thick fraction is dependent on
luminosity, as is seen for Compton-thin sources, then our results are
consistent with a rise in the obscured fraction out to z∼3. Finally,
an examination of the host morphologies of our Compton-thick
candidates shows a high fraction of morphological disturbances, in
agreement with our previous results.
Description:
The X-UDS observations were carried out with Chandra's Advanced CCD
Imaging Spectrometer (ACIS) in the time period 2015 July 6 to 2015
October 4. The observations consist of 25 pointing positions that
cover a total area of roughly 35'x25' in size. A summary of the
observational parameters of the X-UDS exposures is listed in Table 1.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 70 25 Observation log
table4.dat 106 868 Chandra X-UDS source catalog: basic source properties
table5.dat 183 868 Chandra X-UDS source catalog: source fluxes and HRs
table6.dat 73 868 Chandra X-UDS source catalog: best-fit spectral
parameters
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See also:
B/chandra : The Chandra Archive Log (CXC, 1999-2014)
II/319 : UKIDSS-DR9 LAS, GCS and DXS Surveys (Lawrence+ 2012)
J/AJ/126/539 : The Chandra Deep Fields North and South (Alexander+, 2003)
J/MNRAS/356/568 : Deep Chandra survey of the Groth Strip (Nandra+, 2005)
J/ApJS/179/124 : Subaru/XMM-Newton deep survey (SXDS) III. (Ueda+, 2008)
J/ApJS/184/158 : Chandra COSMOS survey I. (Elvis+, 2009)
J/ApJS/180/102 : AEGIS-X: Chandra deep survey (Laird+, 2009)
J/MNRAS/414/3084 : Multi-waveband analysis of 12um galaxies (Brightman+, 2011)
J/A+A/533/A119 : GOODS-Herschel North and South catalogs (Elbaz+, 2011)
J/ApJ/739/57 : Ultra hard X-ray AGNs in the Swift/BAT survey (Koss+, 2011)
J/ApJS/195/10 : The CDF-S survey: 4Ms source catalogs (Xue+, 2011)
J/ApJS/201/30 : The Chandra COSMOS survey. III. (Civano+, 2012)
J/ApJ/769/80 : Spitzer/IRAC observations of five deep fields (Ashby+, 2013)
J/ApJS/206/10 : CANDELS multiwavelength catalog (Galametz+, 2013)
J/MNRAS/443/1999 : X-ray spectral analysis of AGNs (Brightman+, 2014)
J/ApJ/802/89 : Luminosity function of X-ray-selected AGNs (Buchner+, 2015)
J/ApJS/220/10 : AEGIS-X Deep survey of EGS (AEGIS-XD) (Nandra+, 2015)
J/ApJ/815/L13 : Compton-thick AGNs from 70-month Swift/BAT (Ricci+, 2015)
J/ApJS/224/15 : Improved 2Ms and 250ks Chandra catalogs (Xue+, 2016)
J/ApJS/235/17 : NuSTAR Extragalactic Surveys: UDS field (Masini+, 2018)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Field Field name
9-13 I5 --- ObsID [17287/17311] Chandra ObsID
15-16 I2 h RAh [2] Hour of right ascension (J2000)
18-19 I2 min RAm [16/18] Minute of right ascension (J2000)
21-25 F5.2 s RAs Second of right ascension (J2000)
27 A1 --- DE- [-] Sign of declination (J2000)
28-29 I2 deg DEd [5] Degree of declination (J2000)
31-32 I2 arcmin DEm [5/15] Arcminute of declination (J2000)
34-38 F5.2 arcsec DEs Arcsecond of declination (J2000)
40-58 A19 "date" Start Start time (UT)
60-64 F5.2 ks Exp [44.6/51.2] Exposure time
66-70 F5.1 deg Roll [70.2/106.2] Roll angle
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- --- [xuds_]
6- 8 I03 --- XUDS [1/868] Internal identifier
(<[KHB2018] xuds NNN> in Simbad)
10- 25 A16 --- CXOUDS Chandra X-UDS catalog identifier
(JHHMMSS.s+DDMMSS)
27- 35 F9.6 deg RAdeg [34/34.8] Right Ascension (J2000)
37- 45 F9.6 deg DEdeg [-5.5/-4.9] Declination (J2000)
47- 50 F4.2 arcsec ePos [0.1/1.4] Positional uncertainty
52- 56 F5.2 arcmin OAA [3.4/12.1] Off axis angle
58- 61 I4 ct FBcts [6/5859] Full 0.5-10keV band counts
63- 66 F4.1 ct FBbck [1.9/65] Background counts in 0.5-10keV band
68- 71 I4 ct SBcts [0/3720] Soft 0.5-2keV band counts
73- 76 F4.1 ct SBbck [0.5/16] Background counts in 0.5-2keV band
78- 81 I4 ct HBcts [2/2069] Hard 2-10keV band counts
83- 86 F4.1 ct HBbck [1.5/56] Background counts in 2-10keV band
88- 90 I3 ct UBcts [1/675] Ultra hard 5-10keV band counts
92- 95 F4.1 ct UBbck [0.9/38.5] Background counts in 5-10keV band
97-100 A4 --- Det Detection code (1)
102-106 F5.2 [-] logP [-8/-4] log minimum Poisson false
detection probability (2)
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Note (1): Where bands are full (f), soft (s), hard (h), and ultrahard (u).
Note (2): Among the four analysis bands. Probabilities lower than 1e-8
are listed as -8.0.
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- --- [xuds_]
6- 8 I03 --- XUDS [1/868] Internal identifier
(<[KHB2018] xuds NNN> in Simbad)
10 A1 --- l_FbF 68% upper limit flag on FbF
11- 16 F6.2 10-18W/m2 FbF [0.1/497] Full 0.5-10keV Bayesian flux (3)
18- 21 F4.2 10-18W/m2 E_FbF [0/10]? Upper uncertainty in FbF
23- 26 F4.2 10-18W/m2 e_FbF [0/9]? Lower uncertainty in FbF
28 A1 --- l_FbS 68% upper limit flag on FbS
29- 34 F6.2 10-18W/m2 FbS [0.03/152] Soft 0.5-2keV Bayesian flux (3)
36- 39 F4.2 10-18W/m2 E_FbS [0/5]? Upper uncertainty in FbS
41- 44 F4.2 10-18W/m2 e_FbS [0/5]? Lower uncertainty in FbS
46 A1 --- l_FbH 68% upper limit flag on FbS
47- 52 F6.2 10-18W/m2 FbH [0.1/281] Hard 2-10keV Bayesian flux (3)
54- 58 F5.2 10-18W/m2 E_FbH [0/11]? Upper uncertainty in FbH
60- 63 F4.2 10-18W/m2 e_FbH [0/10]? Lower uncertainty in FbH
65 A1 --- l_FbU 68% upper limit flag on FbU
66- 71 F6.2 10-18W/m2 FbU [0.2/141] Ultra hard 5-10keV Bayesian
flux (3)
73- 77 F5.2 10-18W/m2 E_FbU [0.3/12]? Upper uncertainty in FbU
79- 83 F5.2 10-18W/m2 e_FbU [0.4/11]? Lower uncertainty in FbU
85 A1 --- l_FcF 68% upper limit flag on FcF
86- 91 F6.2 10-18W/m2 FcF [0.05/497] Full 0.5-10keV classical flux (4)
93- 96 F4.2 10-18W/m2 E_FcF [0.2/10]? Upper uncertainty in FcF
98-101 F4.2 10-18W/m2 e_FcF [0.2/9]? Lower uncertainty in FcF
103 A1 --- l_FcS 68% upper limit flag on FcS
104-109 F6.2 10-18W/m2 FcS [0.04/152] Soft 0.5-2keV classical flux (4)
111-114 F4.2 10-18W/m2 E_FcS [0.08/5]? Upper uncertainty in FcS
116-119 F4.2 10-18W/m2 e_FcS [0.06/5]? Lower uncertainty in FcS
121 A1 --- l_FcH 68% upper limit flag on FcH
122-127 F6.2 10-18W/m2 FcH [0.1/281] Hard 2-10keV classical flux (4)
129-133 F5.2 10-18W/m2 E_FcH [0.3/14]? Upper uncertainty in FcH
135-138 F4.2 10-18W/m2 e_FcH [0.3/10]? Lower uncertainty in FcH
140 A1 --- l_FcU 68% upper limit flag on FcH
141-146 F6.2 10-18W/m2 FcU [0.2/142] Ultra hard 5-10keV classical
flux (4)
148-152 F5.2 10-18W/m2 E_FcU [0.5/20]? Upper uncertainty in FcU
154-158 F5.2 10-18W/m2 e_FcU [0.4/12]? Lower uncertainty in FcU
160-164 F5.2 --- HRb [-1/1] Bayesian hardness ratio (5)
166-169 F4.2 --- E_HRb [0.01/0.9] Upper 1σ uncertainty in HRb
171-174 F4.2 --- e_HRb [0.01/0.8] Lower 1σ uncertainty in HRb
176-181 F6.2 --- HRc [-99/1] Classical hardness ratio (5)
183 I1 --- Phot [0/2]? Photometric quality flag (6)
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Note (3): Using the Bayesian methodology of (Laird+, 2009, J/ApJS/180/102).
In units of 1e-15erg/cm2/s. Not corrected for intrinsic source
absorption.
Note (4): Using the classical method of converting count rates to fluxes.
Not corrected for intrinsic source absorption.
Note (5): HR=(H-S)/(H+S) where "H" is the hard 2-10keV band and
"S" is the soft 0.5-2keV band. A -99 indicates the hardness
ratio could not be determined.
Note (6): Flag as follows:
1 = possible contamination from a nearby source;
2 = likely contamination from a nearby source;
0 = no contamination.
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- --- [xuds_]
6- 8 I03 --- XUDS [1/868] Internal identifier
(<[KHB2018] xuds NNN> in Simbad)
10- 13 I4 ct Cts [2/5824] Full 0.5-10keV band counts from best fit
15- 18 F4.2 --- zsp [0.01/5.8]?=0 Optical counterpart spectroscopic
redshift (7)
20- 24 F5.2 [cm-2] logNH [20/26] log HI column density
26- 31 F6.2 [cm-2] e_logNH [0.06/2]?=-99 Lower 90% uncertainty in logNH (8)
33- 38 F6.2 [cm-2] E_logNH [0.09/3]?=-99 Upper 90% uncertainty in logNH (8)
40- 44 F5.2 --- gamma [1.2/10] Best-fit power law index
46- 51 F6.2 --- e_gamma [0.05/5]?=-99 Lower 90% uncertainty in gamma (8)
53- 58 F6.2 --- E_gamma [0.05/8]?=-99 Upper 90% uncertainty in gamma (8)
60- 65 F6.2 [mW/m2] logF [-25.2/-12.4] log observed 0.5-8keV band flux;
in units of erg/s/cm-2.
68- 73 F6.2 [10-7W] logL [32.7/53.6]?=-99 log 2-10keV rest-frame
luminosity absorption-corrected;
in units of erg/s
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Note (7): The redshift of each X-ray source was obtained from the best
near-infrared counterpart in the CANDELS H-band catalog
(Galametz+ 2013, J/ApJS/206/10) or UKIDSS DR10 K-band catalog and is
a combination of spectroscopic and photometric redshifts. Counterpart
matching was done using the likelihood ratio technique of
Sutherland & Saunders (1992MNRAS.259..413S 1992MNRAS.259..413S), following the procedure
described by Civano+ (2012, J/ApJS/201/30). Further details of this
matching will be provided in a forthcoming paper
(G. Hasinger et al. 2018, in preparation).
Note (8): A -99 indicates that the uncertainty calculation hit the hard
lower and upper limits of the model, which are 1e+20 cm-2 and
1e+26 cm-2, respectively for logNH and 1.0 and 3.0, respectively,
for gamma.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 22-Aug-2018