J/ApJ/900/141 X-ray weak quasars from SDSS & Chandra (Pu+, 2020)
On the fraction of X-ray-weak quasars from the Sloan Digital Sky Survey.
Pu X., Luo B., Brandt W.N., Timlin J.D., Liu H., Ni Q., Wu J.
<Astrophys. J., 900, 141 (2020)>
=2020ApJ...900..141P 2020ApJ...900..141P
ADC_Keywords: QSOs; X-ray sources; Redshifts; Surveys; Active gal. nuclei
Keywords: Galaxy nuclei ; X-ray quasars ; Active galaxies
Abstract:
We investigate systematically the X-ray emission from type 1 quasars
using a sample of 1825 Sloan Digital Sky Survey non-broad absorption
line (non-BAL) quasars with Chandra archival observations. A
significant correlation is found between the X-ray-to-optical
power-law slope parameter (αOX) and the 2500Å monochromatic
luminosity (L2500Å), and the X-ray weakness of a quasar is
assessed via the deviation of its αOX value from that expected
from this relation. We demonstrate the existence of a population of
non-BAL X-ray-weak quasars, and the fractions of quasars that are
X-ray weak by factors of ≥6 and ≥10 are 5.8%±0.7% and 2.7%±0.5%,
respectively. We classify X-ray-weak quasars (X-ray weak by factors of
≥6) into three categories based on their optical spectral features:
weak emission-line quasars (WLQs; CIV rest-frame equivalent width
<16Å), red quasars (Δ(g-i)>0.2), and unclassified X-ray-weak
quasars. The X-ray-weak fraction of 35-9+12% within the WLQ
population is significantly higher than that within non-WLQs,
confirming previous findings that WLQs represent one population of
X-ray-weak quasars. The X-ray-weak fraction of 13-3+5% within the
red quasar population is also considerably higher than that within the
normal quasar population. The unclassified X-ray-weak quasars do not
have unusual optical spectral features, and their X-ray weakness may
be mainly related to quasar X-ray variability.
Description:
The final sample contains 1825 quasars selected via SDSS and BOSS
spectra (see Section 2), and we refer to this sample as sample A which
contains 555 DR7 (Cat. VII/260) quasars and 1270 DR10 (Cat. VII/270)
quasars.
The Chandra X-ray observations for the sample A quasars are listed in
Table 2.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 138 1825 Chandra observations and X-ray photometric properties
table3.dat 101 1825 X-ray and optical properties
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See also:
B/chandra : The Chandra Archive Log (CXC, 1999-2014)
VIII/65 : 1.4GHz NRAO VLA Sky Survey (NVSS) (Condon+ 1998)
II/294 : The SDSS Photometric Catalog, Release 7 (Adelman-McCarthy+, 2009)
VII/260 : The SDSS-DR7 quasar catalog (Schneider+, 2010)
VIII/90 : The FIRST Survey Catalog, Version 12Feb16 (Becker+ 2012)
VII/270 : SDSS quasar catalog: tenth data release (Paris+, 2014)
V/147 : The SDSS Photometric Catalogue, Release 12 (Alam+, 2015)
VII/289 : SDSS quasar catalog, sixteenth data release (DR16Q) (Lyke+, 2020)
J/ApJS/92/53 : Einstein database of quasars. I. (Wilkes+, 1994)
J/AJ/121/2308 : Sloan Digital Sky Survey quasar photometry (Richards+, 2001)
J/AJ/130/387 : SDSS-ROSAT AGN data (Strateva+, 2005)
J/AJ/131/2766 : Quasar luminosity function from SDSS-DR3 (Richards+, 2006)
J/ApJS/165/1 : BAL QSOs from SDSS DR3 (Trump+, 2006)
J/ApJ/685/773 : X-ray-UV relations in SDSS DR5 QSOs (Gibson+, 2008)
J/ApJ/692/758 : BAL QSOs in SDSS-DR5 (Gibson+, 2009)
J/ApJ/696/580 : Properties of weak emission-line QSOs (WLQ) (Shemmer+, 2009)
J/ApJ/696/924 : UV and X-Ray radio-quiet QSOs (Gibson+, 2009)
J/ApJ/699/782 : High-redshift SDSS-DR5 QSOs (Diamond-Stanic+, 2009)
J/ApJ/699/800 : Mass functions of active black holes (Vestergaard+, 2009)
J/A+A/493/339 : XMM-Newton serendipitous Survey. V. (Watson+, 2009)
J/MNRAS/405/2302 : Improved redshifts for SDSS quasar spectra (Hewett+, 2010)
J/A+A/512/A34 : XMM-COSMOS Type 1 AGNs (Lusso+, 2010)
J/AJ/139/390 : BL Lac objects from SDSS-DR7 (Plotkin+, 2010)
J/ApJ/726/20 : X-ray emission from quasars (Miller+, 2011)
J/ApJS/194/45 : QSO properties from SDSS-DR7 (Shen+, 2011)
J/ApJS/195/10 : The CDF-S survey: 4Ms source catalogs (Xue+, 2011)
J/ApJ/746/54 : Chandra X-ray observations of SDSS-DR5 QSOs (Gibson+, 2012)
J/A+A/548/A66 : SDSS Quasar Catalog, DR9Q (Paris+, 2012)
J/ApJ/747/10 : X-ray and multiwavelength properties of 11 WLQs (Wu+, 2012)
J/AJ/149/203 : Reddening of ∼35000 quasars from SDSS (Krawczyk+, 2015)
J/ApJ/805/122 : X-ray properties of PHL1811 analogs and WLQs (Luo+, 2015)
J/ApJ/819/154 : SDSS-DR7 QSOs with X-ray and UV luminosities (Lusso+, 2016)
J/ApJ/831/145 : 6Ms Chandra long-term analyses of AGNs (Yang+, 2016)
J/ApJS/228/2 : Chandra Deep Field-South survey: 7Ms sources (Luo+, 2017)
J/MNRAS/469/3163 : Properties of BAL quasars (McGraw+, 2017)
J/A+A/616/A114 : CIV BAL disappearance in SDSS QSOs (De Cicco+, 2018)
J/A+A/619/A95 : X-ray/UV ratio of AGN (Chiaraluce+, 2018)
J/ApJ/862/22 : CIV broad abs. line SDSS QSO with Gemini (Rogerson+, 2018)
J/MNRAS/492/719 : Chandra obs. of 2106 radio-quiet QSOs (Timlin+, 2020)
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 A18 --- SDSS SDSS designation
(HHMMSS.ss+DDMMSS.s; J2000) (G1)
20- 21 I2 --- DR [7/10] SDSS Data release
23- 28 F6.4 --- z [1.7/2.7] Redshift (1)
30- 34 I5 --- ObsID [323/17627] Chandra observation identifier
36- 40 F5.1 ks Exp [0.6/166] Chandra effective exposure time in
the broad band
42 A1 --- l_CtsBB Limit flag on CtsBB (2)
44- 48 F5.1 ct CtsBB [1.9/841] Broad-band (0.5-7keV) net counts in
source region (2)
50- 54 F5.1 ct e_CtsBB [1.3/39.5]? Lower uncertainty on CtsBB
56- 60 F5.1 ct E_CtsBB [2.7/41]? Upper uncertainty on CtsBB
62 A1 --- l_CtsSB Limit flag on CtsSB (2)
64- 68 F5.1 ct CtsSB [1.9/721] Soft-band (0.5-2keV) net counts in
source region (2)
70- 74 F5.1 ct e_CtsSB [1.3/29.1]? Lower uncertainty on CtsSB
76- 80 F5.1 ct E_CtsSB [2.7/30.1]? Upper uncertainty on CtsSB
82 A1 --- l_CtsHB Limit flag on CtsHB (2)
84- 88 F5.1 ct CtsHB [1.9/212.8] Hard-band (2-7keV) net counts in
source region (2)
90- 94 F5.1 ct e_CtsHB [1.3/22.4]? Lower uncertainty on CtsHB
96- 100 F5.1 ct E_CtsHB [2.7/23.6]? Upper uncertainty on CtsHB
102- 106 F5.2 --- BRatio [0.04/10.25]? Band ratio, hard-band to
soft-band counts (3)
108- 112 F5.2 --- e_BRatio [0.02/9]? Lower uncertainty on BRatio
114- 119 F6.2 --- E_BRatio [0.03/84]? Upper uncertainty on BRatio
121- 124 F4.1 --- Gamma [-1.4/4] 0.5-7keV effective power-law photon
index (4)
126- 129 F4.1 --- e_Gamma [0.1/4.6]? Lower uncertainty on Gamma
131- 134 F4.1 --- E_Gamma [0.1/2.3]? Upper uncertainty on Gamma
136 I1 --- SamB [0/1] Member of sample B (5)
138 I1 --- SamC [0/1] Member of sample C (5)
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Note (1): The improved redshifts from Hewett & Wild (2010, J/MNRAS/405/2302)
and reported in the Shen+ (2011, J/ApJS/194/45) catalog are listed
for the DR7 quasars.
Note (2): A 3σ confidence level upper limit on the source counts is
given if the source is undetected.
Note (3): An blank (null) entry indicates that the source is undetected in
both hard- and soft- bands.
Note (4): Gamma is fixed at 1.8 will null errors for any source that is
undetected in both the soft and hard bands (see Section 3).
Note (5): Sample selection as in Table 1:
-----------------------------------------------------------------------
Sample B = in Sample A + In DR7 quasar catalog; mi<19.6;
effective exposure time >2.5ks; off-axis angle <9.8'
-----------------------------------------------------------------------
Sample C = in Sample A + In DR10 quasar catalog; mi<21.1;
effective exposure time >6.3ks; off-axis angle <8.2'
-----------------------------------------------------------------------
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 A18 --- SDSS SDSS designation
(HHMMSS.ss+DDMMSS.s; J2000) (G1)
20- 25 F6.2 mag iMag [-29.7/-22.8] Absolute i-band magnitude
27 A1 --- l_F2keV Limit flag for f2keV
29- 33 F5.2 10-32mW/m2/Hz F2keV [0.01/95] Rest-frame 2keV flux
density, 10-32erg/cm2/s/Hz (6)
35 A1 --- l_F0.5-7 Limit flag for F0.5-7
37- 41 F5.2 10-14mW/m2 F0.5-7 [0.1/54] Observed-frame 0.5-7keV flux,
10-14erg/cm2/s (7)
43 A1 --- l_logLX Limit flag for logLX
45- 49 F5.2 10-7W logLX [43.2/46] Logarithm of the rest-frame
2-10 keV luminosity, erg/s (7)
51- 55 F5.2 10-27mW/m2/Hz F2500 [0.02/12.4] Rest-frame 2500Å flux
density, 10-27erg/cm2/s/Hz
57 A1 --- l_aOX Limit flag for aOX
59- 63 F5.2 --- aOX [-2.5/-0.9] Measured X-ray-to-optical
power-law slope (6)
65 A1 --- l_DaOX Limit flag for DaOX
67- 71 F5.2 --- DaOX [-1/0.43] Difference between the
measured and expected aOX (8)
73 A1 --- l_fweak Limit flag for fweak
75- 79 F5.1 --- fweak [0.1/415] X-ray weakness factor
measured from DaOX
81- 85 F5.1 0.1nm REW [0.9/479.1] Rest-frame equivalent
width, CIV1549Å emission line
87- 91 F5.2 mag D(g-i) [-0.97/2.67] Relative g-i color index
93 A1 --- l_R Limit flag on R
95- 99 F5.1 --- R [1.3/247.2] Radio-loudness parameter (9)
101 I1 --- XWeak [0/1] X-ray weak flag (10)
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Note (6): A 3σ confidence level upper limit is provided for F2keV and
aOX if the source is undetected.
Note (7): BBFlux and logLX both calculated using F2keV and Gamma (see Table 2).
Note (8): difference between the measured aOX and that expected from our
best-fit aOXL2500Å_ relation.
Note (9): The radio-loudness parameter is defined as R=F5GHz/F2500Å,
where F5GHz is the flux density at rest-frame 5GHz. The F5GHz values
(or their upper limits) were converted from the observed 1.4GHz flux
densities assuming a radio power-law slope of αr=-0.5.
See Section 2.4.
Note (10): An entry of "1" indicates that the object is X-ray weak. We adopted
ΔaOX=-0.3 to be the threshold separating X-ray normal and X-ray weak
quasars (see Section 4.2)
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Global notes:
Note (G1): SDSS J09119.173+173740.4, SDSS J12567.933+214417.1 &
SDSS J13317.78-020312.0 are misprints for SDSS J091109.17+173740.4,
SDSS J125607.93+214417.1 & SDSS J133107.77-020312.0 (corrected in
SDSS DR16, Cat. VII/289 but not in DR10, Cat. VII/270); corrected
here by CDS.
History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 03-Jan-2022