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Program Information for 2016B-0177


PI: Yi-Kuan Chiang, U. of Texas, Austin, ykchiang@astro.as.utexas.edu
Address: 2515 Speedway, Stop C1400, Austin, Texas 78712-1205 USA

CoI: Roderik Overzier, Observatorio Nacional Brazil
CoI: Guillermo Blanc, Universidad de Chile
CoI: Karl Gebhardt, U. of Texas, Austin
CoI: Bruna Vajgel, Observatorio Nacional Brazil
CoI: Jun Toshikawa, NAOJ
CoI: Nobunari Kashikawa, NAOJ
CoI: Caitlin Casey, U. of Texas, Austin
CoI: Steven Finkelstein, U. of Texas, Austin

Title: Mapping out the Densest Structures in the COSMOS Field at z~2–3

Abstract: Proto-clusters, the high-redshift ancestor structures of present-day galaxy clusters, are ideal laboratories to study dark matter structure formation, the drivers of galaxy growth, and the cosmic baryon cycle under extreme conditions. However, only a small and heterogeneous sample is known to date. With its rich multiwavelength photometry and large volume at z>2, the 2 degree COSMOS field provides an unique chance to build a standard sample of massive proto-clusters, eventually outweighing the existing sample in size, data quality/homogeneity, and thus science potential. We propose to perform Gemini-GMOS multi-object spectroscopy to confirm 4 of the best candidate proto-clusters in COSMOS at z~2-3, representing the highest photo-z galaxy overdensities in a volume of 2x10^7 Mpc^3. With the spectroscopic redshifts obtained in this proposal, we will estimate the present-day masses of the clusters based on their measured mass overdensities and kinematics. By mapping out their (sub-)Mpc-scale 3D density field, we will study the impact of environmental effects on the galaxies. Combining with the existing 30+ bands photometry, we will measure the total stellar mass and star-formation rate per proto-cluster, and investigate the normalization of the star-forming main sequence in different environments. These results will not only constrain the early formation of massive clusters, but also inform us on the interplay between environmentally driven and internal mechanisms of galaxy formation. This proposal is a resubmission improved upon the program of GS-2015B-Q-33 + GN-2015B-Q-73, which was granted 8.14 hrs of GS (band 2) and 20.36 hrs of GN time (band 3), while only ~2 hrs of data were taken (with GS). We thus subtract 2 hrs from the original time request.

Program Type: Standard/Extragalactic

Scheduled Nights:
Run 1 (2016B):  GEM-NQ/GMOSN -- 12.3hrs band 3 (GN-2016B-Q-64)
Run 2 (2016B):  GEM-SQ/GMOSS -- 2.47hrs band 2 (GS-2016B-Q-38)


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