J/A+A/655/A109 Chandra view of the LX-LUV relation in quasars (Bisogni+, 2021)
The Chandra view of the relation between X-ray and UV emission in quasars.
Bisogni S., Lusso E., Civano F., Nardini E., Risaliti G., Elvis M.,
Fabbiano G.
<Astron. Astrophys. 655, A109 (2021)>
=2021A&A...655A.109B 2021A&A...655A.109B (SIMBAD/NED BibCode)
ADC_Keywords: QSOs ; Active gal. nuclei ; Redshifts ; X-ray sources ;
Ultraviolet ; Optical; Surveys; Spectroscopy; Photometry
Keywords: galaxies: active - galaxies: nuclei - quasars: general -
quasars: supermassive black holes
Abstract:
We present a study of the relation between X-rays and ultraviolet
emission in quasars for a sample of broad-line, radio-quiet objects
obtained from the cross-match of the Sloan Digital Sky Survey DR14
with the latest Chandra Source Catalog 2.0 (2332 quasars) and the
Chandra COSMOS Legacy survey (273 quasars). The non-linear relation
between the ultraviolet (at 2500Å, LUV) and the X-ray (at 2keV, LX)
emission in quasars has been proved to be characterised by a smaller
intrinsic dispersion than the observed one, as long as a homogeneous
selection, aimed at preventing the inclusion of contaminants in the
sample, is fulfilled. By leveraging on the low background of Chandra,
we performed a complete spectral analysis of all the data available
for the SDSS-CSC2.0 quasar sample (i.e. 3430 X-ray observations), with
the main goal of reducing the uncertainties on the source properties
(e.g. flux, spectral slope). We analysed whether any evolution of the
LX-LUV relation exists by dividing the sample in narrow redshift
intervals across the redshift range spanned by our sample, z~=0.5-4.
We find that the slope of the relation does not evolve with redshift
and it is consistent with the literature value of 0.6 over the
explored redshift range, implying that the mechanism underlying the
coupling of the accretion disc and hot corona is the same at the
different cosmic epochs. We also find that the dispersion decreases
when examining the highest redshifts, where only pointed observations
are available. These results further confirm that quasars are
'standardisable candles', that is we can reliably measure cosmological
distances at high redshifts where very few cosmological probes are
available.
Description:
Optical and X-ray properties of the 3430 X-ray observations,
corresponding to 2332 SDSS DR14 sources, analysed. For each entry we
list SDSS name, redshift, Chandra observation identifier, off-axis
angle in the X-ray observation, exposure time in the X-ray
observation, number of the SDSS Data Release, UV rest-frame
monochromatic fluxes at 2500 Angstroem, X-ray rest-frame monochromatic
fluxes at 2keV, photon index, rest-frame 2keV flux limit per
observation, raw counts in the soft band (0.5-2keV), raw counts in
the hard band (2-7keV), signal-to-noise in the soft band
(0.5-2keV), signal-to-noise in the hard band (2-7keV).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 172 3430 Properties of the 3430 X-ray observations
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See also:
VII/286 : SDSS quasar catalog, fourteenth data release (Paris+, 2018)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 18 A18 --- Name Quasar name in DR14,
HHMMSS.ss+DDMMSS.s
20- 27 F8.6 --- z Redshift
29- 33 I5 --- ObsId Chandra Observation Identifier
35- 43 F9.7 [arcmin] theta Off-axis angle of source
in X-ray observation
45- 53 F9.2 [s] ExpTime Exposure time of X-ray obs.
55- 58 A4 --- DRflag Number of SDSS Data Release,
DR7, DR12 or DR14
60- 67 F8.4 [mW/m2/Hz] logF2500A Rest-frame fluxes at 2500 Angstroem (1)
69- 74 F6.4 [mW/m2/Hz] e_logF2500A Error on rest-frame fluxes at 2500Å
76- 83 F8.4 [mW/m2/Hz] logF2keV Rest-frame fluxes at 2keV
85- 91 F7.4 [mW/m2/Hz] e_logF2keV Lower error on fluxes at 2keV
93- 98 F6.4 [mW/m2/Hz] E_logF2keV Upper error on fluxes at 2keV
100-107 F8.6 --- Gamma Photon index
109-116 F8.5 --- e_Gamma Lower error on photon index
118-125 F8.5 --- E_Gamma Upper error on photon index
126-134 F9.4 --- logF2keVlim ? Rest-frame 2keV flux limit
per observation
136 A1 --- n_logF2keVlim [I] I for -Infinity
137-144 F8.3 --- Cts Raw counts in soft band (0.5-2keV)
146-153 F8.3 --- Cth Raw counts in hard band (2-7keV)
155-162 F8.5 --- SNs SN in the soft band (0.5-2keV)
164-172 F9.6 --- SNh ? SN in hard band (2-7keV)
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Note (1): Fluxes are in units of log(erg/s/cm2/Hz).
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Acknowledgements:
Susanna Bisogni, susanna.bisogni(at)inaf.it
(End) Patricia Vannier [CDS] 08-Sep-2021