THE ABUNDANCE OF STAR-FORMING GALAXIES IN THE REDSHIFT RANGE 8.5-12: NEW RESULTS FROM THE 2012 HUBBLE ULTRA DEEP FIELD CAMPAIGN
- Department of Astrophysics, California Institute of Technology, MS 249-17, Pasadena, CA 91125 (United States)
- Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh EH9 3HJ (United Kingdom)
- Department of Astronomy and Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States)
- Institute for Cosmic Ray Research, University of Tokyo, Kashiwa City, Chiba 277-8582 (Japan)
- Space Telescope Science Institute, Baltimore, MD 21218 (United States)
- UPMC-CNRS, UMR7095, Institut d'Astrophysique de Paris, F-75014 Paris (France)
We present the results of the deepest search to date for star-forming galaxies beyond a redshift z {approx_equal} 8.5 utilizing a new sequence of near-infrared Wide-Field Camera 3 (WFC3/IR) images of the Hubble Ultra Deep Field (UDF). This 'UDF12' campaign completed in 2012 September doubles the earlier exposures with WFC3/IR in this field and quadruples the exposure in the key F105W filter used to locate such distant galaxies. Combined with additional imaging in the F140W filter, the fidelity of high-redshift candidates is greatly improved. Using spectral energy distribution fitting techniques on objects selected from a deep multi-band near-infrared stack, we find seven promising z > 8.5 candidates. As none of the previously claimed UDF candidates with 8.5 < z < 10 are confirmed by our deeper multi-band imaging, our campaign has transformed the measured abundance of galaxies in this redshift range. Although we recover the candidate UDFj-39546284 (previously proposed at z = 10.3), it is undetected in the newly added F140W image, implying that it lies at z = 11.9 or is an intense emission line galaxy at z {approx_equal} 2.4. Although no physically plausible model can explain the required line intensity given the lack of Ly{alpha} or broadband UV signal, without an infrared spectrum we cannot rule out an exotic interloper. Regardless, our robust z {approx_equal} 8.5-10 sample demonstrates a luminosity density that continues the smooth decline observed over 6 < z < 8. Such continuity has important implications for models of cosmic reionization and future searches for z >10 galaxies with James Webb Space Telescope.
- OSTI ID:
- 22078329
- Journal Information:
- Astrophysical Journal Letters, Vol. 763, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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