Bibcode
McGreer, Ian D.; Jiang, Linhua; Fan, Xiaohui; Richards, Gordon T.; Strauss, Michael A.; Ross, Nicholas P.; White, Martin; Shen, Yue; Schneider, Donald P.; Myers, Adam D.; Niel Brandt, W.; DeGraf, Colin; Glikman, Eilat; Ge, Jian; Streblyanska, A.
Referencia bibliográfica
The Astrophysical Journal, Volume 768, Issue 2, article id. 105, 25 pp. (2013).
Advertised on:
5
2013
Revista
Número de citas
202
Número de citas referidas
189
Descripción
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 (M 1450
<–26) with Sloan Digital Sky Survey (SDSS) data covering ~6000
deg2, then extend to lower luminosities (M 1450
<–24) with newly discovered, faint z ~ 5 quasars selected from
235 deg2 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 (M_{1450}^*\approx -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 (M
1450 <–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.
Observations reported here were obtained at the MMT Observatory, a joint
facility of the Smithsonian Institution and the University of Arizona.
This paper also includes data gathered with the 6.5 m Magellan
telescopes located at Las Campanas Observatory, Chile.
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