J/MNRAS/493/2745 GALEX EUV quasar colours of SDSS QSOs DR14 (Vanden Berk+, 2020)
Extreme ultraviolet quasar colours from GALEX observations of the
SDSS DR14Q catalog.
Vanden Berk D.E., Wesolowski S.C., Yeckley M.J., Marcinik J.M.,
Quashnock J.M., Machia L.M., Wu J.
<Mon. Not. R. Astron. Soc. 493, 2745 (2020)>
=2020MNRAS.493.2745V 2020MNRAS.493.2745V (SIMBAD/NED BibCode)
ADC_Keywords: Surveys ; QSOs ; Photometry, ultraviolet
Keywords: methods: statistical - catalogues - quasars: general -
ultraviolet: general
Abstract:
The rest-frame far to extreme ultraviolet (UV) colour-redshift
relationship has been constructed from data on over 480,000 quasars
carefully cross-matched between SDSS Data Release 14 and the final
GALEX photometric catalog. UV matching and detection probabilities are
given for all the quasars, including dependencies on separation,
optical brightness, and redshift. Detection limits in the UV bands are
also provided for all objects. The UV colour distributions are skewed
redward at virtually all redshifts, especially when detection limits
are accounted for. The median GALEX far-UV minus near-UV (FUV-NUV)
colour-redshift relation is reliably determined up to z∼2.8,
corresponding to rest-frame wavelengths as short as 400Å.
Extreme-UV (EUV) colours are substantially redder than found
previously, when detection limits are properly accounted for. Quasar
template spectra were forward modeled through the GALEX bandpasses,
accounting for intergalactic opacity, intrinsic reddening, and
continuum slope variations. Intergalactic absorption by itself cannot
account for the very red EUV colours. The colour-redshift relation is
consistent with no intrinsic reddening, at least for SMC-like
extinction. The best model fit has a far-UV continuum power-law slope
of -0.34±0.03 consistent with previous results, but an EUV slope
of -2.90±0.04 that is much redder and inconsistent with any
previous composite value (all >-2.0). The EUV slope difference can be
attributed in part to the tendency of previous studies to
preferentially select UV brighter and bluer objects. The weak EUV flux
suggests quasar accretion disc models that include outflows such as
disc winds.
Description:
GALEX UV photometric quantities for 483161 quasars in the SDSS Data
Release 14 quasar catalog (DR14Q). DR14Q Quasars not observed by GALEX
are included with default values, so that the catalog is a
line-by-line match to the 526356 quasar entries published in the
DR14Q catalog. Matching separations, GALEX FUV and NUV magnitudes,
magnitude uncertainties, lower magnitude limits (when no GALEX
detection exists), and GALEX effective exposure times are included
among the catalogued quantities. The information allows subsamples to
be selected in the same way as described in the paper.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
dr14quv.dat 189 526356 GALEX UV data for SDSS DR14Q
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See also:
II/335 : Revised catalog of GALEX UV sources, GUVcat_AIS GR6+7 (Bianchi+ 2014)
VII/286 : SDSS DR14Q catalog (Paris+, 2019)
Byte-by-byte Description of file: dr14quv.dat
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Bytes Format Units Label Explanations
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1- 6 I6 --- SeqQSO SDSS DR14Q catalog sequential row number
8- 25 A18 --- DR14Qo SDSS DR14Q coordinate-based name,
HHMMSS.ss+DDMMSS.s
27- 44 A18 --- DR14Q SDSS DR14Q coordinate-based name,
HHMMSS.ss+DDMMSS.s, corrected by CDS
46- 55 F10.6 deg RAdeg ? GALEX right ascension (J2000) (1)
57- 66 F10.6 deg DEdeg ? GALEX declination (J2000) (1)
68- 72 F5.3 --- z SDSS DR14Q redshift
74 A1 --- BAL Broad absorption line flag [YN]
76- 81 F6.3 mag FUVmag ?=99.999 GALEX FUV magnitude
83- 88 F6.3 mag e_FUVmag ?=9.999 GALEX FUV magnitude uncertainty
90- 95 F6.3 mag NUVmag ?=99.999 GALEX NUV magnitude
97-102 F6.3 mag e_NUVmag ?=9.999 GALEX NUV magnitude uncertainty
104-109 F6.3 mag umag ?=99.999 SDSS DR14Q u PSF magnitude
110-116 F7.3 mag e_umag ?=9.999 SDSS DR14Q u PSF magnitude uncertainty
118-123 F6.3 mag FUVmaglim ?=99.999 GALEX FUV magnitude lower limit
125-130 F6.3 mag NUVmaglim ?=99.999 GALEX NUV magnitude lower limit
132-135 F4.2 arcsec sepCoord ?=9.99 SDSS and GALEX coordinate separation
137-141 F5.2 arcmin dCent ?=99.99 Distance to tile center
143-147 I5 --- tile-FUV ?=-999 GALEX FUV tile number
149-153 I5 --- tile-NUV ?=-999 GALEX NUV tile number
155-163 F9.2 s tEff-FUV ?=-99999.99 FUV effective exposure time
165-173 F9.2 s tEff-NUV ?=-99999.99 NUV effective exposure time
175-176 I2 --- numNbr15 Number of SDSS neighbors within 15 arcsec
178-182 F5.2 arcsec dNNbr15 ?=99.99 Distance to nearest SDSS neighbor
(if within 15 arcseconds)
184-189 F6.3 mag uNbr15 ?=99.999 u magnitude of brightest SDSS
neighbor (if within 15 arcseconds)
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Note (1): 103725 SDSS QSO DR14 without GALEX counterpart.
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Acknowledgements:
Daniel E. Vanden Berk, daniel.vandenberk(at)stvincent.edu
References:
Paris et al., 2018A&A...613A..51P 2018A&A...613A..51P, Cat. VII/286
(End) D. Vanden Berk [Saint Vincent College], P. Vannier [CDS] 10-Feb-2020