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Title: New observations of z ∼ 7 galaxies: evidence for a patchy reionization

We present new results from our search for z ∼ 7 galaxies from deep spectroscopic observations of candidate z dropouts in the CANDELS fields. Despite the extremely low flux limits achieved by our sensitive observations, only two galaxies have robust redshift identifications, one from its Lyα emission line at z = 6.65, the other from its Lyman break, i.e., the continuum discontinuity at the Lyα wavelength consistent with a redshift of 6.42 but with no emission line. In addition, for 23 galaxies we present deep limits in the Lyα equivalent width derived from the nondetections in ultradeep observations. Using this new data as well as previous samples, we assemble a total of 68 candidate z ∼ 7 galaxies with deep spectroscopic observations, of which 12 have a line detection. With this much enlarged sample we can place solid constraints on the declining fraction of Lyα emission in z ∼ 7 Lyman-break galaxies compared to z ∼ 6, both for bright and faint galaxies. Applying a simple analytical model, we show that the present data favor a patchy reionization process rather than a smooth one.
Authors:
; ; ; ; ; ; ;  [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [7] ;  [8] ; ;  [9] ;  [10] ;  [11] ;  [12]
  1. INAF Osservatorio Astronomico di Roma, Via Frascati 33, I-00040 Monteporzio (RM) (Italy)
  2. INAF Osservatorio Astronomico di Bologna (Italy)
  3. Department of Physics, University of California, Santa Barbara, CA 93106-9530 (United States)
  4. Scuola Normale Superiore,Piazza dei Cavalieri 7, I-56126 Pisa (Italy)
  5. Max-Planck-Institut fur Astrophysik, Karl-Schwarzschild-Str. 1, D-85741 Garching (Germany)
  6. Department of Physics, University of California, Davis, CA 95616 (United States)
  7. School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom)
  8. INAF Osservatorio Astronomico di Trieste, Via G.B.Tiepolo 11, I-34131 Trieste (Italy)
  9. Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh EH9 3HJ (United Kingdom)
  10. Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States)
  11. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
  12. Kavli Institute for Cosmology, University of Cambridge, Madingley Road, Cambridge, CB3 0HA (United Kingdom)
Publication Date:
OSTI Identifier:
22370543
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 793; 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; COMPARATIVE EVALUATIONS; DETECTION; DISTANCE; EMISSION; GALAXIES; LYMAN LINES; RED SHIFT; WAVELENGTHS