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Understanding Large-scale Structure in the SSA22 Protocluster Region Using Cosmological Simulations

Topping, Michael W. and Shapley, Alice E. and Steidel, Charles C. and Naoz, Smadar and Primack, Joel R. (2018) Understanding Large-scale Structure in the SSA22 Protocluster Region Using Cosmological Simulations. Astrophysical Journal, 852 (2). Art. No. 134. ISSN 1538-4357. doi:10.3847/1538-4357/aa9f0f.

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We investigate the nature and evolution of large-scale structure within the SSA22 protocluster region at z = 3.09 using cosmological simulations. A redshift histogram constructed from current spectroscopic observations of the SSA22 protocluster reveals two separate peaks at z = 3.065 (blue) and z = 3.095 (red). Based on these data, we report updated overdensity and mass calculations for the SSA22 protocluster. We find δ_( = 4.8 ± 1.8 and δ_( = 9.5 ± 2.0 for the blue and red peaks, respectively, and δ_( = 7.6 ± 1.4 for the entire region. These overdensities correspond to masses of M_b = (0.76 ± 0.17) x 10^(15)h^(-1) M_⊙ M_r = (2.15 ± 0.32) x 10^(15)h^(-1) M_⊙, and M_t = (3.19 ± 0.40) x 10^(15)h^(-1),M_⊙ for the red, blue, and total peaks, respectively. We use the Small MultiDark Planck (SMDPL) simulation to identify comparably massive z ~ 3 protoclusters, and uncover the underlying structure and ultimate fate of the SSA22 protocluster. For this analysis, we construct mock redshift histograms for each simulated z ~ 3 protocluster, quantitatively comparing them with the observed SSA22 data. We find that the observed double-peaked structure in the SSA22 redshift histogram corresponds not to a single coalescing cluster, but rather the proximity of a ~ 10^(15)h^(-1) M_⊙ protocluster and at least one 〉 10^(14)h^(-1) M_⊙ cluster progenitor. Such associations in the SMDPL simulation are easily understood within the framework of hierarchical clustering of dark matter halos. We finally find that the opportunity to observe such a phenomenon is incredibly rare, with an occurrence rate of 7.4h^3 Gpc^(-3).

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Shapley, Alice E.0000-0003-3509-4855
Steidel, Charles C.0000-0002-4834-7260
Naoz, Smadar0000-0002-9802-9279
Primack, Joel R.0000-0001-5091-5098
Additional Information:© 2018 The American Astronomical Society. Received 2017 September 18. Accepted 2017 December 2. Published 2018 January 16. The authors gratefully acknowledge the Gauss Centre for Supercomputing e.V. ( and the Partnership for Advanced Supercomputing in Europe (PRACE, for funding the MultiDark simulation project by providing computing time on the GCS Supercomputer SuperMUC at Leibniz Supercomputing Centre (LRZ, The Bolshoi simulations have been performed within the Bolshoi project of the University of California High-Performance AstroComputing Center (UC-HiPACC) and were run at the NASA Ames Research Center. We wish to extend special thanks to those of Hawaiian ancestry on whose sacred mountain we are privileged to be guests. Without their generous hospitality, most of the observations presented herein would not have been possible. S.N. acknowledges partial support from a Sloan Foundation Fellowship. C.C.S. acknowledges support from NSF grants AST-0908805 and AST-1313472.
Group:Astronomy Department
Funding AgencyGrant Number
Alfred P. Sloan FoundationUNSPECIFIED
Subject Keywords:galaxies: clusters: individual (SSA22) ; galaxies: formation; galaxies: high-redshift; galaxies: starburst; large-scale structure of universe
Issue or Number:2
Record Number:CaltechAUTHORS:20180118-133854987
Persistent URL:
Official Citation:Michael W. Topping et al 2018 ApJ 852 134
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:84392
Deposited By: Ruth Sustaita
Deposited On:18 Jan 2018 22:15
Last Modified:15 Nov 2021 20:19

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