SPECTROSCOPY OF LUMINOUS z > 7 GALAXY CANDIDATES AND SOURCES OF CONTAMINATION IN z > 7 GALAXY SEARCHES
- Spitzer Science Center, 314-6 Caltech, 1201 East California Boulevard, Pasadena, CA 91125 (United States)
- Department of Physics and Astronomy, University of California, Riverside, CA 92521 (United States)
- Department of Astronomy, 249-17 Caltech, 1201 East California Boulevard, Pasadena, CA 91125 (United States)
- Institut d'Astrophysique de Paris, UMR7095 CNRS, Universite Pierre et Marie Curie, 98 bis Boulevard Arago, 75014 Paris (France)
- Laboratoire d'Astrophysique de Marseille, BP 8, Traverse du Siphon, F-13376 Marseille Cedex 12 (France)
- Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)
- AIM-Unite Mixte de Recherche CEA-CNRS-Universite Paris VII-UMR 7158, F-91191 Gif-sur-Yvette (France)
- National Radio Astronomy Observatory, P.O. Box 0, Socorro, NM 87801-0387 (United States)
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
- Astronomy Department, University of Massachusetts, Amherst, MA 01003 (United States)
- Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)
- LBNL and Berkeley Center for Cosmological Physics, University of California, Berkeley, CA 94720 (United States)
- Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
- Laboratoire d'Astrophysique de Marseille, CNRS-Universite Aix-Marseille, 38 rue F. Joliot-Curie, 13388 Marseille Cedex 13 (France)
- Max-Planck-Institut fr Astronomie, Knigstuhl 17, D-69117 Heidelberg (Germany)
We present three bright z{sup +}-dropout candidates selected from deep near-infrared (NIR) imaging of the COSMOS 2 deg{sup 2} field. All three objects match the 0.8-8 {mu}m colors of other published z > 7 candidates but are 3 mag brighter, facilitating further study. Deep spectroscopy of two of the candidates covering 0.64-1.02 {mu}m with Keck-DEIMOS and all three covering 0.94-1.10 {mu}m and 1.52-1.80 {mu}m with Keck-NIRSPEC detects weak spectral features tentatively identified as Ly{alpha} at z = 6.95 and z = 7.69 in two of the objects. The third object is placed at z {approx} 1.6 based on a 24 {mu}m and weak optical detection. A comparison with the spectral energy distributions of known z < 7 galaxies, including objects with strong spectral lines, large extinction, and large systematic uncertainties in the photometry, yields no objects with similar colors. However, the {lambda} > 1 {mu}m properties of all three objects can be matched to optically detected sources with photometric redshifts at z {approx} 1.8, so the non-detection in the i {sup +} and z {sup +} bands is the primary factor which favors a z > 7 solution. If any of these objects are at z {approx} 7, the bright end of the luminosity function is significantly higher at z > 7 than suggested by previous studies, but consistent within the statistical uncertainty and the dark matter halo distribution. If these objects are at low redshift, the Lyman break selection must be contaminated by a previously unknown population of low-redshift objects with very strong breaks in their broadband spectral energy distributions and blue NIR colors. The implications of this result on luminosity function evolution at high redshift are discussed. We show that the primary limitation of z > 7 galaxy searches with broad filters is the depth of the available optical data.
- OSTI ID:
- 21574861
- Journal Information:
- Astrophysical Journal, Vol. 730, Issue 2; Other Information: DOI: 10.1088/0004-637X/730/2/68; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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