Published in

Cambridge University Press (CUP), Proceedings of the International Astronomical Union, A29B(11), p. 804-807, 2015

DOI: 10.1017/s174392131600689x

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The First Half Billion Years (z > 9): Results from the Frontier Fields

Journal article published in 2015 by Dan A. Coe ORCID, Larry D. Bradley ORCID
This paper was not found in any repository, but could be made available legally by the author.
This paper was not found in any repository, but could be made available legally by the author.

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Data provided by SHERPA/RoMEO

Abstract

AbstractWe present z > 9 candidates identified in Hubble Frontier Fields imaging of the first four clusters and blank parallel fields (two-thirds of the complete program). Based on the deeper Hubble imaging, we revise the redshift estimate of the CLASH z ~ 9.6 candidate MACS1149-JD to z = 9.2+0.2-0.5 (95% C.L.). We identify a new possible fainter z ~ 9 companion 3” away (~1 kpc in the source plane). And we discover a new z ~ 9.2 candidate in the MACS1149 parallel field. Combined with previously published candidates at z ~ 9.8 and 9.1 (in A2744 and its parallel field, respectively), these five z > 9 candidates fall below our published expectation of 8 – 47 at this stage in the program. We attribute some of this shortfall to incompleteness, which we have yet to quantify. At z ~ 8 (7.5 – 8.5), we detect 26 candidates down to F160W H < 28.7 AB, roughly one-third the ~82 we expect. If our z > 9 incompleteness is similar (~68%), our results would support the sharp drop in z > 9 number counts claimed by some (but not all) previous works and supported by several (but not all) theoretical models. Properly quantifying our incompleteness will require adding simulated high-redshift galaxies into the images and testing our recovery rate. Additionally, incorporating the deep Spitzer imaging into our analysis could potentially significantly improve our identification of z > 9 candidates by rejecting low-redshift (z ~ 2) interlopers. Data from the full Frontier Fields program will provide strong evidence for or against accelerated evolution and a sharp drop in the cosmic star formation rate density at z > 9.

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