NEW CONSTRAINTS ON COSMIC REIONIZATION FROM THE 2012 HUBBLE ULTRA DEEP FIELD CAMPAIGN
- Department of Astronomy and Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States)
- Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States)
- UPMC-CNRS, UMR7095, Institut d'Astrophysique de Paris, F-75014, Paris (France)
- Department of Astrophysics, California Institute of Technology, MC 249-17, Pasadena, CA 91125 (United States)
- Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh EH9 3HJ (United Kingdom)
- Space Telescope Science Institute, Baltimore, MD 21218 (United States)
- Institute for Cosmic Ray Research, University of Tokyo, Kashiwa City, Chiba 277-8582 (Japan)
Understanding cosmic reionization requires the identification and characterization of early sources of hydrogen-ionizing photons. The 2012 Hubble Ultra Deep Field (UDF12) campaign has acquired the deepest infrared images with the Wide Field Camera 3 aboard Hubble Space Telescope and, for the first time, systematically explored the galaxy population deep into the era when cosmic microwave background (CMB) data indicate reionization was underway. The UDF12 campaign thus provides the best constraints to date on the abundance, luminosity distribution, and spectral properties of early star-forming galaxies. We synthesize the new UDF12 results with the most recent constraints from CMB observations to infer redshift-dependent ultraviolet (UV) luminosity densities, reionization histories, and electron scattering optical depth evolution consistent with the available data. Under reasonable assumptions about the escape fraction of hydrogen-ionizing photons and the intergalactic medium clumping factor, we find that to fully reionize the universe by redshift z {approx} 6 the population of star-forming galaxies at redshifts z {approx} 7-9 likely must extend in luminosity below the UDF12 limits to absolute UV magnitudes of M{sub UV} {approx} -13 or fainter. Moreover, low levels of star formation extending to redshifts z {approx} 15-25, as suggested by the normal UV colors of z {approx_equal} 7-8 galaxies and the smooth decline in abundance with redshift observed by UDF12 to z {approx_equal} 10, are additionally likely required to reproduce the optical depth to electron scattering inferred from CMB observations.
- OSTI ID:
- 22126800
- Journal Information:
- Astrophysical Journal, Vol. 768, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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