A Survey of [CLC][ITAL]z[/ITAL][/CLC] > 5.8 Quasars in the Sloan Digital Sky Survey. I. Discovery of Three New Quasars and the Spatial Density of Luminous Quasars at [CLC][ITAL]z[/ITAL][/CLC] ∼ 6

Abstract

We present the results from a survey of i-dropout objects selected from D1550 deg2 of multicolor imaging data from the Sloan Digital Sky Survey to search for luminous quasars at Objects with z Z 5.8. i*[z* [ 2.2 and z* \ 20.2 are selected, and follow-up J-band photometry is used to separate L-and T-type cool dwarfs from high-redshift quasars. We describe the discovery of three new quasars, SDSSp J083643.85]005453.3 (z \ 5.82), J130608.26]035626.3 (z \ 5.99), and J103027.10]052455.0 (z \ 6.28). The quasar SDSSp J083643.85]005453.3 is a radio source with Ñux of 1.1 mJy at 20 cm. The spectra of all three quasars show strong and broad Lya ] N V emission lines and very strong Lya forest absorption, with a mean continuum decrementThe ARC 3.5 m spectrum of SDSSp D A[ 0.90. J103027.10]052455.0 shows that over a range of D300 immediately blueward of the Lya emission, Ó the average transmitted Ñux is only 0.003^0.020 times that of the continuum level, consistent with zero Ñux over a D300 range of the Lya forest region and suggesting a tentative detection of the complete Ó Gunn-Peterson trough. The existence of strong metal lines in the quasar spectra suggests early metal enrichment in the quasar environment. The three new objects, together with the previously published z \ 5.8 quasar SDSSp J104433.04[012502.2, form a complete color-selected Ñux-limited sample at z Z 5.8. We estimate the selection function of this sample, taking into account the estimated variations in the quasar spectral energy distribution, as well as observational photometric errors. We Ðnd that at z \ 6, 2 This paper is dedicated to the memory of Arthur Davidsen, who was a pioneer of the study of the intergalactic medium and who showed great leadership as chairman of the Advisory Council of the Sloan Digital Sky Survey.3 Institute for Advanced Study, Olden Lane, Princeton, NJ 08540. 4 Princeton University Observatory, Princeton, NJ 08544. . This is a factor of D2 lower than that at z D 5 and is consistent with an extrapolation of the observed quasar evolution at z \ 5. Using the current sample, we discuss the constraint on the shape of the quasar luminosity function and the implications for the contribution of quasars to the ionizing background at z D 6. The luminous quasars discussed in the paper have central black hole masses of several times 109 by the Eddington argument, with likely dark halo masses on the order M _ of 1013Their observed space density provides a sensitive test of models of quasar and galaxy for-M _ . mation at high redshift.

Galaxy UV-luminosity function and reionization constraints on axion dark matter

“…6. Observations of the Gunn-Peterson trough in quasar spectra at z > 6 (Fan et al 2006) and transmission in the Lyα forest for z < 6 (Becker et al 2001;Djorgovski et al 2001;Fan et al 2001) suggests the epoch of reionization ends at z ∼ 6 (QHII(z ∼ 6) > 0.99). These constraints on the neutral fraction of hydrogen at the end of reionization rely on detailed modelling of both the IGM and ionizing sources making their accuracy (and therefore the exact end of reionization) the subject of debate (Becker, Rauch & Sargent 2007;Furlanetto & Mesinger 2009;Mesinger 2010;McGreer, Mesinger & Fan 2011;Robertson et al 2013).…”

Simulating the growth of intermediate-mass black holes

“…If successful, this strategy would not only represent a breakthrough in the study of the first luminous objects in the Universe, but it would also shed some light on the puzzles provided by the interpretation of the formation of SMBHs (see e.g. Fan et al 2001;Mortlock et al 2011;Petri et al 2012) and the excess recently found in the power spectrum of the cosmic Near Infrared Background fluctuations (for an overview, see Yue et al 2013). These issues will be discussed in more details in Sec.…”

Observational Comparison of Star Formation in Different Galaxy Types

“…Surprisingly, even the very young quasars discovered at a redshift of z ∼ 6 (age of the Universe: ∼ 900 Myr) reveal metal absorption lines that translate into supersolar metallicities, indicating very rapid, early enrichment. These objects may be the precursors of giant ellipticals (Fan et al 2001). The masses of the central black holes in z ∼ 6 QSOs are estimated to range from several 10 8 to several 10 9 M .…”