Mapping A Distant Protocluster Anchored by A Luminous Quasar in the Epoch of Reionization
Abstract
Theoretical models predict luminous quasars should reside in the most massive dark matter halos acting as signposts for large overdensities of galaxies in the young Universe. But despite two decades of searching, proto-clusters traced by quasars have not yet been uncovered in the epoch of reionization (EoR). Recent ALMA/JCMT sub-mm observations and Subaru narrow/broad band imaging of a luminous quasar at z=6.63 have revealed a spectacular overdensity of [CII] emitters, sub-mm galaxies (SMGs), and Lyman alpha emitters (LAEs), suggesting that it is the the most distant known proto-cluster harboring quasar activity, and the first such system discovered in the EoR. With two HST pointings we will map the inner region of this large scale structure, covering the quasar, six [CII] emitters, two LAEs, and seven SMGs. The high-resolution WFC3 images will measure the spectral energy distribution and the sizes of these galaxies, and resolve two putative galaxy merger systems. It will also enable accurate PSF subtraction to study the assembly of the massive and very large (>1 arcsec, from ALMA) quasar host galaxy. On larger scales, the combination of HST and Subaru deep imaging will identify more than 20 Lyman-break galaxies (LBGs) at z~6.6, and reveal the distribution of star forming galaxies. These rest-frame UV HST observations will trace the unobscured star formation, highly complimentary to the dust and gas emission traced by ALMA and JCMT. In addition, our proposed observations provide data essential for planning future JWST NIRSpec/MSA and IFU observations of this unique system to understand galaxy formation and evolution in the densest environments in the EoR.
- Publication:
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HST Proposal
- Pub Date:
- May 2020
- Bibcode:
- 2020hst..prop16187W