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Title: The most luminous z ∼ 9-10 galaxy candidates yet found: The luminosity function, cosmic star-formation rate, and the first mass density estimate at 500 Myr

We present the discovery of four surprisingly bright (H {sub 160} ∼ 26-27 mag AB) galaxy candidates at z ∼ 9-10 in the complete HST CANDELS WFC3/IR GOODS-N imaging data, doubling the number of z ∼ 10 galaxy candidates that are known, just ∼500 Myr after the big bang. Two similarly bright sources are also detected in a reanalysis of the GOODS-S data set. Three of the four galaxies in GOODS-N are significantly detected at 4.5σ-6.2σ in the very deep Spitzer/IRAC 4.5 μm data, as is one of the GOODS-S candidates. Furthermore, the brightest of our candidates (at z = 10.2 ± 0.4) is robustly detected also at 3.6 μm (6.9σ), revealing a flat UV spectral energy distribution with a slope β = –2.0 ± 0.2, consistent with demonstrated trends with luminosity at high redshift. Thorough testing and use of grism data excludes known low-redshift contamination at high significance, including single emission-line sources, but as-yet unknown low redshift sources could provide an alternative solution given the surprising luminosity of these candidates. Finding such bright galaxies at z ∼ 9-10 suggests that the luminosity function for luminous galaxies might evolve in a complex way at z > 8. The cosmic starmore » formation rate density still shows, however, an order-of-magnitude increase from z ∼ 10 to z ∼ 8 since the dominant contribution comes from low-luminosity sources. Based on the IRAC detections, we derive galaxy stellar masses at z ∼ 10, finding that these luminous objects are typically 10{sup 9} M {sub ☉}. This allows for a first estimate of the cosmic stellar mass density at z ∼ 10 resulting in log{sub 10} ρ{sub ∗}=4.7{sub −0.8}{sup +0.5} M {sub ☉} Mpc{sup –3} for galaxies brighter than M {sub UV} ∼ –18. The remarkable brightness, and hence luminosity, of these z ∼ 9-10 candidates will enable deep spectroscopy to determine their redshift and nature, and highlights the opportunity for the James Webb Space Telescope to map the buildup of galaxies at redshifts much earlier than z ∼ 10.« less
Authors:
; ;  [1] ; ; ; ;  [2] ; ;  [3] ; ; ; ;  [4] ;  [5] ;  [6] ;  [7] ;  [8] ;  [9]
  1. UCO/Lick Observatory, University of California, Santa Cruz, 1156 High St, Santa Cruz, CA 95064 (United States)
  2. Leiden Observatory, Leiden University, NL-2300 RA Leiden (Netherlands)
  3. Yale Center for Astronomy and Astrophysics, Yale University, New Haven, CT 06520 (United States)
  4. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States)
  5. University of California, Riverside, 900 University Ave, Riverside, CA 92507 (United States)
  6. Institute of Astronomy and Kavli Institute for Cosmology, University of Cambridge, Cambridge CB3 0HA (United Kingdom)
  7. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
  8. South African Astronomical Observatory, P.O. Box 9, Observatory 7935 (South Africa)
  9. Department of Physics and Astronomy, Faculty of Sciences, Macquarie University, Sydney, NSW 2109 (Australia)
Publication Date:
OSTI Identifier:
22356918
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 786; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BRIGHTNESS; DENSITY; DETECTION; EMISSION; ENERGY SPECTRA; EVOLUTION; GALAXIES; LUMINOSITY; MAPS; MASS; RED SHIFT; SPACE; SPECTROSCOPY; STARS; TELESCOPES