Understanding Large-scale Structure in the SSA22 Protocluster Region Using Cosmological Simulations
Abstract
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 }b,{gal}=4.8+/- 1.8 and {δ }r,{gal}=9.5+/- 2.0 for the blue and red peaks, respectively, and {δ }t,{gal}=7.6+/- 1.4 for the entire region. These overdensities correspond to masses of {M}b=(0.76+/- 0.17)× {10}15{h}-1 {M}⊙ , {M}r=(2.15+/- 0.32)× {10}15{h}-1 {M}⊙ , and {M}t=(3.19+/- 0.40)× {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 7.4{h}3 {{{Gpc}}}-3.
Based on data obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration, and was made possible by the generous financial support of the W.M. Keck Foundation.- Publication:
-
The Astrophysical Journal
- Pub Date:
- January 2018
- DOI:
- 10.3847/1538-4357/aa9f0f
- arXiv:
- arXiv:1709.06572
- Bibcode:
- 2018ApJ...852..134T
- Keywords:
-
- galaxies: clusters: individual: SSA22;
- galaxies: formation;
- galaxies: high-redshift;
- galaxies: starburst;
- large-scale structure of universe;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 13 pages, 8 figures, Accepted to ApJ