J/MNRAS/449/2818 87 radio loud quasars (RLS) with 3.6≤z≤4.4 (Tuccillo+, 2015)
Neural-network selection of high-redshift radio quasars, and the luminosity
function at z∼4.
Tuccillo D., Gonzalez-Serrano J.I., Benn C.R.
<Mon. Not. R. Astron. Soc., 449, 2818-2836 (2015)>
=2015MNRAS.449.2818T 2015MNRAS.449.2818T (SIMBAD/NED BibCode)
ADC_Keywords: Surveys ; QSOs ; Radio sources ; Redshifts
Keywords: surveys - galaxies: active - galaxies: high-redshift -
galaxies: luminosity function, mass function - quasars: general -
cosmology: observations
Abstract:
We obtain a sample of 87 radio-loud quasi-stellar objects (QSOs) in
the redshift range 3.6≤z≤4.4 by cross-correlating sources in the
Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) radio
survey (S1.4GHz>1mJy) with star-like objects having r<20.2 in Sloan
Digital Sky Survey (SDSS) Data Release 7. Of these 87 QSOs, 80 are
spectroscopically classified in previous work (mainly SDSS), and form
the training set for a search for additional such sources. We apply
our selection to 2916 FIRST-DR7 pairs and find 15 likely candidates.
Seven of these are confirmed as high-redshift quasars, bringing the
total to 87. The candidates were selected using a neural-network,
which yields 97 percent completeness (fraction of actual high-z QSOs
selected as such) and an efficiency (fraction of candidates which are
high-z QSOs) in the range of 47-60 percent. We use this sample to
estimate the binned optical luminosity function (LF) of radio-loud
QSOs at z∼4, and also the LF of the total QSO population and its
comoving density. Our results suggest that the radio-loud fraction at
high z is similar to that at low z and that other authors may be
underestimating the fraction at high z. Finally, we determine the
slope of the optical LF and obtain results consistent with previous
studies of radio-loud QSOs and of the whole population of QSOs. The
evolution of the LF with redshift was for many years interpreted as a
flattening of the bright-end slope, but has recently been
re-interpreted as strong evolution of the break luminosity for
high-z QSOs, and our results, for the radio-loud population, are
consistent with this.
Description:
We use the FIRST radio survey and the SDSS DR7 optical survey to
obtain a radio-optical sample of QSO candidates in the redshift range
3.6≤z≤4.4.
We matched each FIRST source, not flagged as possible sidelobe or
nearby bright source (∼3.6 per cent of the sources in the
catalogue have this warning flag), with the closest optical object in
the 'PhotoPrimary' view of the SDSS DR7 catalogue within a
1.5-arcsec radius.
This pre-selection process left us with 9139 star-like objects
coinciding with FIRST radio sources.
The final sample of 87 QSOs with 3.6≤z≤4.4 satisfying our selection
criteria.
This sample includes 72 QSOs (see Section 3.2) from the fifth quasar
catalogue (Schneider et al., 2010AJ....139.2360S 2010AJ....139.2360S, Cat. VII/260) plus
15 QSOs revealed by our NN (8 from Carballo et al. (2008, Cat.
J/MNRAS/391/369) and 7 from this work, see Section 4.1). The magnitude
limit for our sample is rmagAB=20.2.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table4.dat 85 87 Final sample of 87 RLQ with 3.6≤z≤4.4
table5.dat 22 549 K-correction in the SDSS r band
--------------------------------------------------------------------------------
See also:
VII/260 : The SDSS-DR7 quasar catalog (Schneider+, 2010)
VIII/92 : The FIRST Survey Catalog, Version 2014Dec17 (Helfand+ 2015)
J/MNRAS/391/369 : New z≥3.6 QSOs from FIRST-SDSS DR5 (Carballo+, 2008)
Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 A19 --- SDSS SDSS object-ID, JHHMMSS.ss+DDMMSS.s
21- 22 I2 h RAh SDSS right ascension (J2000)
24- 25 I2 min RAm SDSS right ascension (J2000)
27- 31 F5.2 s RAs SDSS right ascension (J2000)
33 A1 --- DE- SDSS declination sign (J2000)
34- 35 I2 deg DEd SDSS declination (J2000)
37- 38 I2 arcmin DEm SDSS declination (J2000)
40- 43 F4.1 arcsec DEs SDSS declination (J2000)
45- 49 F5.2 mag rmag SDSS dereddened PSF r magnitude (AB)
51- 55 F5.3 mag e_rmag Error in PSF r magnitude as given in SDSS
57- 60 F4.2 --- z QSO redshift determined in this work or
from SDSS
62- 67 F6.2 mJy S1.4GHz FIRST peak radio flux density
69- 74 F6.2 mag rMAG Absolute r magnitude
76- 80 F5.2 [W/Hz] logP1.4GHz Radio luminosity at 1.4 GHz
82- 85 A4 --- r_z Indicates the source of the data from which
the redshift was first obtained (1)
--------------------------------------------------------------------------------
Note (1): the two WHT sources are from Benn et al., 2002MNRAS.329..221B 2002MNRAS.329..221B.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
3- 6 F4.2 --- zem Emission redshift
10- 22 E13.10 --- Kcorr K correction
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 08-Dec-2015