Haojing Yan, Steven L. Finkelstein, Kuang-Han Huang, Russell E. Ryan, Henry C. Ferguson, Anton M. Koekemoer, Norman A. Grogin, Mark Dickinson, Jeffrey A. Newman, Rachel S. Somerville, Romeel Dave, S. M. Faber, Casey Papovich, Yicheng Guo, Mauro Giavalisco, Kyoung-soo Lee, Naveen Reddy, Asantha R. Cooray, Brian D. Siana, Nimish P. Hathi, Giovanni G. Fazio, Matthew Ashby, Benjamin J. Weiner, Ray A. Lucas, Avishai Dekel, Laura Pentericci, Christopher J. Conselice
One key goal of the Hubble Space Telescope Cosmic Assembly Near-Infrared Deep
Extragalactic Legacy Survey is to track galaxy evolution back to z ~ 8. Its
two-tiered "wide and deep" strategy bridges significant gaps in existing
near-infrared surveys. In this Letter we report on eight z ~ 8 galaxy
candidates selected as F105W-band dropouts in one of its deep fields, which
covers ~ 62.9 sq.arcmin to 4 ks per filter depth in the Great Observatories
Origins Deep Survey southern field. Three of our candidates have J<26.2 mag,
and are at least ~ 1 mag brighter than any previously known F105W-dropouts. We
derive constraints on the bright-end of the rest-frame ultraviolet luminosity
function of galaxies at z ~ 8, and show that the number density of such very
bright objects is higher than expected from the previous Schechter luminosity
function estimates at this redshift. Two of our candidates, one of which is
among the top three brightest, are securely detected in Spitzer Infrared Array
Camera images, which are the first such detections at z ~ 8. Their derived
stellar masses are on the order of 10^{9.3-10.2} Msun, from which we obtain the
first measurement of the high-mass end of the galaxy stellar mass function at z
~ 8. The high number density of very luminous and very massive galaxies at z ~
8, if real, could imply a large stellar-to-halo mass ratio and an efficient
conversion of baryons to stars at such an early time.
View original:
http://arxiv.org/abs/1112.6406
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