J/MNRAS/441/1802 Low-redshift QSOs in SDSS Stripe 82 (Karhunen+, 2014)
Low-redshift quasars in the SDSS Stripe 82. The local environments.
Karhunen K., Kotilainen J.K., Falomo R., Bettoni D.
<Mon. Not. R. Astron. Soc., 441, 1802-1816 (2014)>
=2014MNRAS.441.1802K 2014MNRAS.441.1802K
ADC_Keywords: QSOs ; Active gal. nuclei ; Redshifts ; Magnitudes
Keywords: galaxies: active - galaxies: nuclei - quasars: general
Abstract:
We study the environments of low-redshift (z<0.5) quasars based on a
large and homogeneous data set from the Stripe 82 region of the Sloan
Digital Sky Survey (SDSS). We have compared the <1Mpc scale
environments of 302 quasars that were resolved in our recent study to
those of 288 inactive galaxies with closely matched redshifts.
Crucially, the luminosities of the inactive galaxies and the quasar
host galaxies are also closely matched, unlike in most previous
studies. The environmental overdensities were studied by measuring the
number density of galaxies within a projected distance of 200kpc to
1Mpc. The galaxy number density of the quasar environments is
comparable to that of the inactive galaxies with similar luminosities,
both classes of objects showing significant excess compared to the
background galaxy density for distances <400kpc. There is no
significant dependence of the galaxy number density on redshift,
quasar or host galaxy luminosity, black hole mass or radio loudness.
This suggests that the fuelling and triggering of the nuclear activity
is only weakly dependent on the local environment of quasars, and the
quasar phase may be a short-lived common phase in the life cycle of
all massive galaxies.
Description:
The quasar sample was extracted from the fifth release of the SDSS
Quasar Catalog (Schneider et al., 2010AJ....139.2360S 2010AJ....139.2360S, Cat. VII/260),
which uses data from the SDSS DR7 (Abazajian et al.,
2009ApJS..182..543A 2009ApJS..182..543A). The catalogue consists of quasars fainter than
i∼15.0, with an absolute magnitude of Mi←22.0 and a reliably measured
redshift. Additionally, the quasars either have at least one emission
line with full width at half-maximum (FWHM)>1000km/s or show
complex/interesting absorption lines. The full catalogue contains
∼106000 spectroscopically confirmed quasars. In this work, we only
used objects in the Stripe 82 (Annis et al., 2014ApJ...794..120A 2014ApJ...794..120A)
region.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 57 416 Table of all quasars in the full quasar sample (FQS)
table2.dat 55 580 Table of all galaxies in the full control galaxy
sample (FCGS)
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See also:
VII/260 : The SDSS-DR7 quasar catalog (Schneider+, 2010)
J/MNRAS/440/476 : Low-redshift quasars in SDSS Stripe 82 (Falomo+, 2014)
Byte-by-byte Description of file: table1.dat table2.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq Object sequential number, within the table (1)
5- 23 A19 --- Name Name of object (JHHMMSS.ss+DDMMSS.s)
25- 28 F4.2 --- z [0.5/0.5] Redshift
30- 31 I2 --- N0.25 [0/98] Number of galaxies detected
within 0.25Mpc
33- 37 F5.2 arcmin-2 n0.25 [0/25] Galaxy density within 0.25Mpc
39- 42 F4.2 arcmin-2 nbg [1/9.5] Average background galaxy density
44- 47 F4.2 arcmin-2 e_nbg rms uncertainty on nbg
49- 53 F5.2 mag ithr [20.7/23.3] Apparent i-band magnitude threshold
determined for the frame
55- 57 A3 --- Notes Sample(s) the source belongs to (2)
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Note (1): For table1.dat (FQS), the sequential number is from Falomo et al.,
2014 (J/MNRAS/440/476).
Note (2): Notes ad follows:
r = object is part of the resolved quasar sample (RQS, 302 objects)
q = object is part of the radio-quiet quasars (RQQ) sample
l = object is part of the radio-loud quasars (RLQ) sample
m = object is part of the matched control galaxy sample (MCGS)
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 06-Feb-2015