Discovery of a Protocluster Associated with a Lyα Blob Pair at z = 2.3

Journal Article · Sun Aug 20 04:00:00 EDT 2017 · Astrophysical Journal

DOI:https://doi.org/10.3847/1538-4357/AA8220· OSTI ID:22875886

Bădescu, Toma; Yang, Yujin; Bertoldi, Frank; Karim, Alexander; Magnelli, Benjamin ^[1]; Zabludoff, Ann ^[2]

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1. Argelander Institut für Astronomie, Universität Bonn, Auf dem Hügel 71, D-53121 Bonn (Germany)
2. Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)

Bright Lyα blobs (LABs)—extended nebulae with sizes of ∼100 kpc and Lyα luminosities of ∼10{sup 44} erg s{sup −1}—often reside in overdensities of compact Lyα emitters (LAEs) that may be galaxy protoclusters. The number density, variance, and internal kinematics of LABs suggest that they themselves trace group-like halos. Here, we test this hierarchical picture, presenting deep, wide-field Lyα narrowband imaging of a 1° × 0.°5 region around a LAB pair at z = 2.3 discovered previously by a blind survey. We find 183 Lyα emitters, including the original LAB pair and three new LABs with Lyα luminosities of (0.9--1.3)×10{sup 43} erg s{sup −1} and isophotal areas of 16–24 arcsec{sup 2}. Using the LAEs as tracers and a new kernel density estimation method, we discover a large-scale overdensity (Boötes J1430+3522) with a surface density contrast of δ{sub Σ}=2.7, a volume density contrast of δ ∼10.4, and a projected diameter of ≈20 comoving Mpc. Comparing with cosmological simulations, we conclude that this LAE overdensity will evolve into a present-day Coma-like cluster with log(M/M{sub ⊙}) ∼ 15.1 ± 0.2. In this and three other wide-field LAE surveys re-analyzed here, the extents and peak amplitudes of the largest LAE overdensities are similar, not increasing with survey size, and implying that they were indeed the largest structures then and today evolve into rich clusters. Intriguingly, LABs favor the outskirts of the densest LAE concentrations, i.e., intermediate LAE overdensities of δ{sub Σ}=1--2. We speculate that these LABs mark infalling protogroups being accreted by the more massive protocluster.

• OSTI ID: 22875886
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 845; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
AUGMENTATION
COMPARATIVE EVALUATIONS
COMPUTERIZED SIMULATION
CONCENTRATION RATIO
DENSITY
GALACTIC EVOLUTION
GALAXIES
GALAXY CLUSTERS
LUMINOSITY
LYMAN LINES
NEBULAE
RED SHIFT
SURFACES
UNIVERSE