Securing a sample of exceptionally bright z> 9 galaxies to prepare for JWST and probe early galaxy assembly
Abstract
Especially massive galaxies are thought to be rare in the high-redshift universe, so the discovery of one very bright z=11.1 galaxy (GN-z11) within the original CANDELS program (0.25 sq. deg) was quite a surprise. Most theoretical models suggested a 10-50x larger area would be required to identify such a source. While such a discovery could suggest high-mass galaxies form particularly efficiently at early times, it could also be a "lucky" find. To determine which and to probe the properties of the most massive assembled galaxies in the early universe, we search a much larger volume for bright z>8.5 galaxies and discovered 4 very bright, high-probability z~9-10 candidate galaxies over that 6 square degree area with the deepest optical, near-IR, and Spitzer/IRAC data. The extreme luminosities of these sources demands that we urgently try to confirm their nature as secure z>8 galaxies with deeper follow-up observations given the implications for the formation efficiency of massive galaxies in the early universe and the proximity of the JWST cycle 1 deadline. With just 1 orbit of HST imaging data at 0.1 micron, these candidates would be detected at 10 sigma if at z<7, or be found to be secure >99.9999%-probability z>8 galaxies if undetected. Thanks to the very large volumes we search, we will likely confirm 1 of these extreme sources as robust, and potentially more if galaxy formation is especially efficient at early times. Our resultant sample of exceptionally bright z~9-10 galaxies should serve as high value targets for deep spectroscopy in the near future with JWST, ALMA, and also with the ELTs.
- Publication:
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HST Proposal
- Pub Date:
- October 2019
- Bibcode:
- 2019hst..prop16037S