Overdensities of Y-dropout Galaxies from the Brightest-of-Reionizing Galaxies Survey: A Candidate Protocluster at Redshift z~8

Abstract

Theoretical and numerical modeling of dark-matter halo assembly predicts that the most luminous galaxies at high redshift are surrounded by overdensities of fainter companions. We test this prediction with HST observations acquired by our Brightest of Reionizing Galaxies (BoRG) survey, which identified four very bright z~8 candidates as Y-dropout sources in four of the 23 non-contiguous WFC3 fields observed. We extend here the search for Y-dropouts to fainter luminosities (M_* galaxies with M_AB\sim-20), with detections at >5sigma confidence (compared to >8sigma confidence adopted earlier) identifying 17 new candidates. We demonstrate that there is a correlation between number counts of faint and bright Y-dropouts at >99.84% confidence. Field BoRG58, which contains the best bright z\sim8 candidate (M_AB=-21.3), has the most significant overdensity of faint Y-dropouts. Four new sources are located within 70arcsec (corresponding to 3.1 comoving Mpc at z=8) from the previously known brighter z\sim8 candidate. The overdensity of Y-dropouts in this field has a physical origin to high confidence (p>99.975%), independent of completeness and contamination rate of the Y-dropout selection. We modeled the overdensity by means of cosmological simulations and estimate that the principal dark matter halo has mass M_h\sim(4-7)x10^11Msun (\sim5sigma density peak) and is surrounded by several M_h\sim10^11Msun halos which could host the fainter dropouts. In this scenario, we predict that all halos will eventually merge into a M_h>2x10^14Msun galaxy cluster by z=0. Follow-up observations with ground and space based telescopes are required to secure the z\sim8 nature of the overdensity, discover new members, and measure their precise redshift.

arXiv commentMinor revision: ApJ accepted [17 pages (emulateapj style), 7 figures, 2 tables]

References in corpus (56)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Interpretation
• Linking halo mass to galaxy luminosity
• UV Luminosity Functions at z~4, 5, and 6 from the HUDF and other Deep HST ACS Fields: Evolution and Star Formation History
• Near-Infrared Photometry and Spectroscopy of L and T Dwarfs: the Effects of Temperature, Clouds, and Gravity
• UV Luminosity Functions from 132 z~7 and z~8 Lyman-Break Galaxies in the ultra-deep HUDF09 and wide-area ERS WFC3/IR Observations
• Keck Spectroscopy of Faint 3<z<7 Lyman Break Galaxies: - I. New constraints on cosmic reionisation from the luminosity and redshift-dependent fraction of Lyman-alpha emission
• Spectroscopic Confirmation of Three z-Dropout Galaxies at z = 6.844 - 7.213: Demographics of Lyman-Alpha Emission in z ~ 7 Galaxies
• Cosmic Variance and Its Effect on the Luminosity Function Determination in Deep High z Surveys
• A candidate redshift z ~ 10 galaxy and rapid changes in that population at an age of 500 Myr
• Cosmic Variance in the Great Observatories Origins Deep Survey
• A massive proto-cluster of galaxies at a redshift of z {\approx} 5.3
• Spectroscopic confirmation of z~7 LBGs: probing the earliest galaxies and the epoch of reionization
• Keck Spectroscopy of Faint 3<z<8 Lyman Break Galaxies:- Evidence for a Declining Fraction of Emission Line Sources In the Redshift Range 6<z<8
• z~7 Galaxies in the HUDF: First Epoch WFC3/IR Results
• A Counts-in-Cells Analysis of Lyman-break Galaxies at z~3
• Very blue UV-continuum slopes of low luminosity z~7 galaxies from WFC3/IR: Evidence for extremely low metallicities?
• Galaxies at z = 6 - 9 from the WFC3/IR imaging of the HUDF
• The Discovery of Primeval Large-Scale Structures with Forming Clusters at Redshift 6
• Very Strong Emission-Line Galaxies in the WISP Survey and Implications for High-Redshift Galaxies
• The Contribution of High Redshift Galaxies to Cosmic Reionization: New Results from Deep WFC3 Imaging of the Hubble Ultra Deep Field
• On the Stellar Populations and Evolution of Star-Forming Galaxies at 6.3 < z < 8.6
• Star formation rates and stellar masses of z=7-8 galaxies from IRAC observations of the WFC3/IR ERS and the HUDF field
• The Large-scale and Small-scale Clustering of Lyman-Break Galaxies at 3.5 < z< 5.5 from the GOODS survey
• The Galaxy Luminosity Function during the Reionization Epoch
• The Brightest Of Reionizing Galaxies Survey: Design and Preliminary Results
• An overdensity of galaxies at z=5.9 +/-0.2 in the Ultra Deep Field confirmed using the ACS grism
• Smoothly-Rising Star Formation Histories During the Reionization Epoch
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• Discovery of six Ly alpha emitters near a radio galaxy at z ~ 5.2
• Expanded Search for z~10 Galaxies from HUDF09, ERS, and CANDELS Data: Evidence for Accelerated Evolution at z>8?
• LCDM predictions for galaxy protoclusters I: the relation between galaxies, protoclusters and quasars at z~6
• The UDF05 Follow-up of the HUDF: I. The Faint-End Slope of the Lyman-Break Galaxy Population at z~5
• Mapping the Dark Matter From UV Light at High Redshift: An Empirical Approach to Understand Galaxy Statistics
• Probing Very Bright End of Galaxy Luminosity Function at z >~ 7 Using Hubble Space Telescope Pure Parallel Observations
• The UDF05 Follow-up of the HUDF: II. Constraints on Reionization from z-dropout Galaxies
• Clustering of Star-forming Galaxies Near a Radio Galaxy at z=5.2
• An Overdensity of Galaxies near the Most Distant Radio-Loud Quasar
• Seeing Through the Trough: Outflows and the Detectability of Lyman Alpha Emission from the First Galaxies
• A Large Number of z > 6 Galaxies around a QSO at z = 6.43: Evidence for a Protocluster?
• Assessing the redshift evolution of massive black holes and their hosts
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• Probing $\sim L_{\ast }$ Lyman-break Galaxies at $z\approx 7$ in GOODS-South with WFC3 on HST
• Constraining the Minimum Mass of High-Redshift Galaxies and Their Contribution to the Ionization State of the IGM
• Spectroscopy of luminous z>7 galaxy candidates and sources of contamination in z>7 galaxy searches
• How well do cosmological simulations reproduce individual-halo properties?
• A Brighter Past: Galaxy Luminosity Function At High Redshifts
• Clustering of i-dropout galaxies at z=6 in GOODS and the UDF
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• The Density Contrast of the Shapley Supercluster
• Verifying the Identity of High-Redshift Massive Galaxies Through the Clustering of Lower Mass Galaxies Around Them
• Galaxy Statistics in Pencil-beam Surveys at High Redshifts
• A Candidate Brightest Proto-Cluster Galaxy at z = 3.03

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• Observational determination of the galaxy bias from cosmic variance with a random pointing survey: Clustering of z~2 galaxies from Hubble's BoRG survey
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• Photometrically Selected Protocluster Candidates at z~9-10 in the JWST COSMOS-Web field
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