J/ApJ/685/773 X-ray-UV relations in SDSS DR5 QSOs (Gibson+, 2008)
Are optically selected quasars universally X-ray luminous?
X-ray-UV relations in Sloan Digital Sky Survey quasars.
Gibson R.R., Brandt W.N., Schneider D.P.
<Astrophys. J., 685, 773-786 (2008)>
=2008ApJ...685..773G 2008ApJ...685..773G
ADC_Keywords: Surveys ; QSOs ; X-ray sources ; Ultraviolet ; Redshifts
Keywords: galaxies: active - galaxies: nuclei - quasars: absorption lines -
quasars: emission lines - X-rays: general
Abstract:
We analyze archived Chandra and XMM-Newton X-ray observations of 536
Sloan Digital Sky Survey (SDSS) Data Release 5 (DR5) quasars (QSOs) at
1.7≤z≤2.7 in order to characterize the relative UV and X-ray
spectral properties of QSOs that do not have broad UV absorption lines
(BALs). We constrain the fraction of X-ray-weak, non-BAL QSOs and find
that such objects are rare; for example, sources underluminous by a
factor of 10 comprise ≲2% of optically selected SDSS QSOs. X-ray
luminosities vary with respect to UV emission by a factor of ≲2 over
several years for most sources. UV continuum reddening and the
presence of narrow-line absorbing systems are not strongly associated
with X-ray weakness in our sample. X-ray brightness is significantly
correlated with UV emission-line properties, so that relatively
X-ray-weak, non-BAL QSOs generally have weaker, blueshifted CIV
λ1549 emission and broader CIII] λ1909 lines. The CIV
emission-line strength depends on both UV and X-ray luminosity,
suggesting that the physical mechanism driving the global Baldwin
effect is also associated with X-ray emission.
Description:
In this study we consider the 536 SDSS QSOs at redshifts 1.7≤z≤2.7
that have been observed with Chandra or XMM-Newton. The lower limit on
redshift ensures that the SDSS spectrum reaches to ∼1400Å allowing
good coverage of any potential high-velocity CIV absorption, up to
~-30000km/s. The upper redshift limit ensures that the 2500Å
continuum is in view so that we can determine the UV continuum flux
accurately.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 111 536 Source information
table2.dat 55 536 UV emission line measurements
--------------------------------------------------------------------------------
See also:
VII/252 : SDSS-DR5 quasar catalog (Schneider+, 2007)
J/AJ/133/313 : AGN from RASS and SDSS DR5 (Anderson+, 2007)
http://www.sdss.org : SDSS Home Page
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 A19 --- SDSS SDSS source name JHHMMSS.ss+DDMMSS.s
21- 24 F4.2 --- z Spectroscopic redshift
26- 35 I10 --- ObsId Chandra or XMM observation identification
number (1)
37- 41 F5.1 ks Expo X-ray exposure time (2)
43- 46 I4 ct Scts Observed-frame soft (0.5-2keV) counts
in source region
48- 50 I3 ct Hcts Observed-frame hard (2-8keV) counts
in source region
52 I1 --- X [0/1] X-ray detected? (1=yes)
54 I1 --- B [0/1] Source in sample B? (1=yes)
56 A1 --- l_logR* Limit flag on logR*
58- 62 F5.2 [-] logR* Radio-loudness parameter (5)
64- 68 I5 km/s CIV.0 Rest-frame balnicity index
for CIV absorption (6)
70 I1 --- Mg Number of narrow Mg II absorption systems (7)
72- 76 F5.2 [10-7W/Hz] L1400 Log of monochromatic luminosity at
1400Å (8)
78- 82 F5.2 [10-7W/Hz] L2500 Log of monochromatic luminosity at
2500Å (8)
84 A1 --- l_L2keV Limit flag on log2keV
86- 90 F5.2 [10-7W/Hz] L2keV Log of monochromatic luminosity at 2keV (8)
92 A1 --- l_a.OX Limit flag on a.OX
94- 98 F5.2 --- a.OX X-ray/optical spectral index (9)
100-103 F4.2 --- e_a.OX ? Uncertainty in a.OX (10)
105 A1 --- l_Da.OX Limit flag on Da.OX
107-111 F5.2 --- Da.OX Relative X-ray brightness (11)
--------------------------------------------------------------------------------
Note (1): The Chandra or XMM-Newton observation identification number.
Ten-digit numbers correspond to XMM-Newton observations, while shorter
numbers correspond to Chandra observations.
Note (2): Reported by the CIAO or SAS toolchains for the extraction of the
source region.
Note (5): Where log(R*)=log[Lν(5GHz)/Lν(2500Å)]. We classify
sources with log(R*)≥1 as "radio-loud" and all other sources as
"radio-quiet".
Note (6): Similar to the traditional "balnicity index", BI, of Weymann et
al. (1991ApJ...373...23W 1991ApJ...373...23W), except that it is integrated from velocity
offsets -25000km/s to 0km/s from the QSO rest frame.
Note (7): Found using the method described in Section 2.2.
Note (8): Where the luminosity is in units of erg/s/Hz.
Note (9): Where a.OX = αOX = 0.3838*log(L(2keV)/L(2500Å)).
Note (10): Errors assumed to be dominated by the error on X-ray luminosity.
Note (11): Relative to "ordinary" QSOs. Where
Da.OX = ΔαOX = αOX -
(-0.217±0.036)*log(L2500Å)+(5.075±1.118).
(for instance, a value of -0.5 corresponds to X-ray weakness
by a factor of ∼20 compared to QSOs with the same UV luminosity)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 A19 --- SDSS SDSS source identification, JHHMMSS.ss+DDMMSS.s
21- 25 F5.1 0.1nm C4EW Equivalent width of CIV (1549Å)
27- 32 F6.1 0.1nm C4Wave Central wavelength of CIV (1549Å)
34- 37 F4.1 0.1nm C4FWHM Full-Width at Half-Maximum of CIV (1549Å)
39- 42 F4.1 0.1nm C3EW ? Equivalent width of CIII] (1909Å) (1)
44- 49 F6.1 0.1nm C3Wave ? Central wavelength of CIII] (1909Å) (1)
51- 55 F5.1 0.1nm C3FWHM ? Full-Width at Half-Maximum of
CIII] (1909Å) (1)
--------------------------------------------------------------------------------
Note (1): Blank entries indicate that the C III] emission line could not be
fit because the spectrum was bad in that region.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 03-Sep-2009