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Title: Young galaxy candidates in the Hubble Frontier Fields. I. A2744

We report the discovery of 24 Lyman-break candidates at 7 ≲ z ≲ 10.5, in the Hubble Frontier Fields (HFF) imaging data of A2744 (z = 0.308), plus Spitzer/IRAC data and archival ACS data. The sample includes a triple image system with a photometric redshift of z ≅ 7.4. This high redshift is geometrically confirmed by our lens model corresponding to deflection angles that are 12% larger than the lower-redshift systems used to calibrate the lens model at z = 2.019. The majority of our high-redshift candidates are not expected to be multiply lensed given their locations in the image plane and the brightness of foreground galaxies, but are magnified by factors of ∼1.3-15, so that we are seeing further down the luminosity function than comparable deep-field imaging. It is apparent that the redshift distribution of these sources does not smoothly extend over the full redshift range accessible at z < 12, but appears to break above z = 9. Nine candidates are clustered within a small region of 20'' across, representing a potentially unprecedented concentration. Given the poor statistics, however, we must await similar constraints from the additional HFF clusters to properly examine this trend. The physical properties ofmore » our candidates are examined using the range of lens models developed for the HFF program by various groups including our own, for a better estimate of underlying systematics. Our spectral-energy-distribution fits for the brightest objects suggest stellar masses of ≅ 10{sup 9} M {sub ☉}, star formation rates of ≅ 4 M {sub ☉} yr{sup –1}, and a typical formation redshift of z ≲ 19.« less
Authors:
; ;  [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [7] ; ;  [8] ;  [9] ;  [10]
  1. Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States)
  2. CEA Saclay, DSM/Irfu/Service d'Astrophysique, Orme des Merisiers, F-91191 Gif-sur-Yvette Cedex (France)
  3. Department of Physics and Astronomy, Siena College, Loudonville, NY 12211 (United States)
  4. Cahill Center for Astronomy and Astrophysics, California Institute of Technology, MS 249-17, Pasadena, CA 91125 (United States)
  5. Department of Theoretical Physics, University of Basque Country UPV/EHU, Bilbao (Spain)
  6. Instituto de Astrofísica de Andalucía-CSIC, Glorieta de la Astronomía, s/n. E-18008 Granada (Spain)
  7. IFCA, Instituto de Física de Cantabria, UC-CSIC, s/n. E-39005 Santander (Spain)
  8. Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile 306, Santiago 22 (Chile)
  9. The Observatories of the Carnegie Institution for Science, Pasadena, CA 91101 (United States)
  10. Leiden Observatory, Leiden University, NL-2300 RA Leiden (Netherlands)
Publication Date:
OSTI Identifier:
22370277
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 795; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABUNDANCE; BRIGHTNESS; COMPARATIVE EVALUATIONS; CONCENTRATION RATIO; COSMOLOGY; DISTRIBUTION; ENERGY SPECTRA; GALAXIES; GALAXY CLUSTERS; GRAVITATIONAL LENSES; IMAGES; LUMINOSITY; MASS; RED SHIFT; STARS; STATISTICS