J/ApJ/768/105 z∼5 QSO luminosity function from SDSS Stripe 82 (McGreer+, 2013)
The z = 5 quasar luminosity function from SDSS stripe 82.
McGreer I.D., Jiang L., Fan X., Richards G.T., Strauss M.A., Ross N.P.,
White M., Shen Y., Schneider D.P., Myers A.D., Brandt W.N., Degraf C.,
Glikman E., Ge J., Streblyanska A.
<Astrophys. J., 768, 105 (2013)>
=2013ApJ...768..105M 2013ApJ...768..105M
ADC_Keywords: QSOs ; Redshifts ; Spectroscopy ; Photometry, SDSS ;
Photometry, infrared
Keywords: quasars: general
Abstract:
We present a measurement of the Type I quasar luminosity function at
z=5 using a large sample of spectroscopically confirmed quasars
selected from optical imaging data. We measure the bright end
(M1450←26) with Sloan Digital Sky Survey (SDSS) data covering
∼6000deg2, then extend to lower luminosities (M1450←24) with
newly discovered, faint z∼5 quasars selected from 235deg2 of deep,
coadded imaging in the SDSS Stripe 82 region (the celestial equator in
the Southern Galactic Cap). The faint sample includes 14 quasars with
spectra obtained as ancillary science targets in the SDSS-III Baryon
Oscillation Spectroscopic Survey, and 59 quasars observed at the MMT
and Magellan telescopes. We construct a well-defined sample of
4.7<z<5.1 quasars that is highly complete, with 73 spectroscopic
identifications out of 92 candidates. Our color selection method is
also highly efficient: of the 73 spectra obtained, 71 are
high-redshift quasars. These observations reach below the break in the
luminosity function (M1450*~-27). The bright-end slope is steep
(β≲-4), with a constraint of β←3.1 at 95% confidence. The
break luminosity appears to evolve strongly at high redshift,
providing an explanation for the flattening of the bright-end slope
reported previously. We find a factor of ∼2 greater decrease in the
number density of luminous quasars (M1450←26) from z=5 to z=6 than
from z=4 to z=5, suggesting a more rapid decline in quasar activity at
high redshift than found in previous surveys. Our model for the quasar
luminosity function predicts that quasars generate ∼30% of the
ionizing photons required to keep hydrogen in the universe ionized at
z=5.
Description:
We obtain spectroscopic identifications of our candidates from
multiple sources by utilizing the dense SDSS/BOSS spectroscopic
coverage of Stripe 82 combined with our own observations. We have
obtained spectra for additional candidates (extending much fainter
than the SDSS and BOSS spectroscopic observations) using the MMT and
Magellan telescopes.
We first observed four candidates at the Magellan Clay 6.5m on 2011
June 11-13 using the Magellan Echellette spectrograph. MAGE provides
full coverage from 3100Å to 1um at a resolution of ∼5800 using the
0.7" slit.
The bulk of our spectroscopic observations occurred at the MMT 6.5m
telescope using the Red Channel spectrograph (5500-9700Å with
resolutions of R∼640 and R∼430 for 1" and 1.5" slit, respectively).
Observations were conducted on 2011 June 23-24, 2011 October 1-4, and
2012 May 27-28.
At the time the initial candidate selection was performed, the
publicly available UKIDSS data on Stripe 82 did not extend to
RA<21:36. We imaged some of the candidates lacking J coverage on 2011
October 14-15 with the MMT Smithsonian Widefield Infrared Camera (SWIRC).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 113 84 Stripe 82 high-redshift quasar catalog
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See also:
II/319 : UKIDSS-DR9 LAS, GCS and DXS Surveys (Lawrence+ 2012)
V/139 : The SDSS Photometric Catalog, Release 9 (Adelman-McCarthy+, 2012)
VII/269 : SDSS Quasar Catalog, DR9Q (Paris+, 2012)
VII/260 : The SDSS-DR7 quasar catalog (Schneider+, 2010)
II/294 : The SDSS Photometric Catalog, Release 7 (Adelman-McCarthy+, 2009)
J/ApJS/199/3 : The quasars MMT-BOSS pilot survey (Ross+, 2012)
J/ApJ/746/169 : Luminosity function of broad-line quasars (Shen+, 2012)
J/ApJ/743/125 : Likelihood method for QSOs selection (Kirkpatrick+, 2011)
J/ApJ/728/23 : GALEX UV-bright high-redshift quasars (Worseck+, 2011)
J/A+A/525/A37 : QSO variability indexes in SDSS Stripe 82 (Meusinger+, 2011)
J/ApJ/710/1498 : QSO luminosity function at z∼4 (Glikman+, 2010)
J/ApJ/699/782 : High-redshift SDSS-DR5 QSOs (Diamond-Stanic+, 2009)
J/ApJ/693/8 : High-redshift QSOs in the COSMOS survey (Brusa+, 2009)
J/ApJ/675/49 : High-redshift QSOs in the SWIRE survey (Siana+, 2008)
J/AJ/133/2222 : Clustering of high-redshift QSOs from SDSS (Shen+, 2007)
J/AJ/131/2766 : Quasar luminosity function from SDSS-DR3 (Richards+, 2006)
J/ApJ/633/630 : Low-mass stars found in CFHTLS (Willott+, 2005)
J/AJ/125/1711 : Broad Absorption Line Quasars from SDSS (Reichard+, 2003)
J/AJ/121/2308 : Sloan Digital Sky Survey quasar photometry (Richards+, 2001)
J/AJ/121/31 : High-redshift quasars in SDSS (Fan+, 2001)
http://www.sdss3.org/ : SDSS-III home page
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 2 I2 h RAh Hour of right ascension (J2000)
4- 5 I2 min RAm Minute of right ascension (J2000)
7- 11 F5.2 s RAs Second of right ascension (J2000)
13 A1 --- DE- Sign of declination (J2000)
14- 15 I2 deg DEd Degree of declination (J2000)
17- 18 I2 arcmin DEm Arcminute of declination (J2000)
20- 23 F4.1 arcsec DEs Arcsecond of declination (J2000)
25- 29 F5.2 mag gmag [22.6/26.7]? SDSS g-band AB magnitude (1)
31- 34 F4.2 mag e_gmag [0.02/1]? gmag uncertainty
36- 40 F5.2 mag rmag [20.4/25.5] SDSS r-band AB magnitude (1)
42- 45 F4.2 mag e_rmag [0/0.5] rmag uncertainty
47- 51 F5.2 mag imag [18.9/23.1] SDSS i-band AB magnitude (1)
53- 56 F4.2 mag e_imag [0/0.07] imag uncertainty
58- 62 F5.2 mag zmag [18.7/22.2] SDSS z-band AB magnitude (1)
64- 67 F4.2 mag e_zmag [0.01/0.2] zmag uncertainty
69- 73 F5.2 mag Jmag [18.8/22.1]? UKIDSS J-band AB magnitude (1)
75- 78 F4.2 mag e_Jmag [0.05/0.9]? Jmag uncertainty
80 A1 --- f_Jmag [ce] c: J magnitude from MMT/SWIRC;
e: lack of coverage
82- 87 F6.2 mag M1450 [-28/-23] Monochromatic luminosity at
rest-frame 1450Å
89- 92 F4.2 --- z [4.3/5.9] Redshift
94- 98 F5.2 --- Prob [0/1]?=-1 Selection probability p(M,z) of
spectroscopically confirming this object (2)
100-113 A14 --- Notes Notes (3)
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Note (1): Magnitudes are on the AB system (Oke & Gunn 1983ApJ...266..713O 1983ApJ...266..713O) and
have been corrected for extinction. Blank entries indicate objects
for which Sextractor did not report a magnitude in that band (due to
negative fluxes); objects that are not formally detected but have
measurements from Sextractor are included with their uncertainties.
Note (2): The selection probability p(M,z) of spectroscopically confirming this
object, including all sources of incompleteness (see Section 6.1.2).
A value of -1 indicates an object not included in the uniform sample.
Note (3): Spectroscopic identifications from MMT/Magellan show the UT date of
the observation; those from BOSS give the plate-MJD-fiber of the
observation.
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 27-Nov-2014