TY - JOUR
T1 - The prevalence of galaxy overdensities around UV-luminous Lyman α emitters in the Epoch of Reionization
AU - Leonova, E.
AU - Oesch, P. A.
AU - Qin, Y.
AU - Naidu, R. P.
AU - Wyithe, J. S.B.
AU - De Barros, S.
AU - Bouwens, R. J.
AU - Ellis, R. S.
AU - Endsley, R. M.
AU - Hutter, A.
AU - Illingworth, G. D.
AU - Kerutt, J.
AU - Labbé, I.
AU - Laporte, N.
AU - Magee, D.
AU - Mutch, S. J.
AU - Roberts-Borsani, G. W.
AU - Smit, R.
AU - Stark, D. P.
AU - Stefanon, M.
AU - Tacchella, S.
AU - Zitrin, A.
N1 - Funding Information: We would like to thank the referee for their insightful comments that have helped clarify and improve this manuscript. We acknowledge support from the Swiss National Science Foundation through the SNSF Professorship grant 190079 (PAO, JK). The Cosmic Dawn Center (DAWN) is funded by the Danish National Research Foun- dation under grant No. 140. This research was supported by the Australian Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), through project number CE170100013. Part of this w ork w as performed on the OzSTAR national facility at Swinburne University of Technology, which is funded by Swinburne University of Technology and the National Col- laborative Research Infrastructure Strategy (NCRIS). ST is supported by the 2021 Research Fund 1.210134.01 of UNIST (Ulsan National Institute of Science & Technology). RSE acknowledges funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement No 669253). RJB and MS acknowledge support from TOP grant TOP1.16.057. RS acknowledges support from a STFC Ernest Rutherford Fello wship (ST/S004831/1). AH ackno wledges support from the European Research Council's starting grant ERC StG- 717001 (DELPHI). AZ acknowledges support by Grant No. 2020750 from the United States-Israel Binational Science Foundation (BSF) and Grant No. 2109066 from the United States National Science Foundation (NSF), and by the Ministry of Science and Technology, Israel. Publisher Copyright: © 2022 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.
PY - 2022/10/1
Y1 - 2022/10/1
N2 - Before the end of the Epoch of Reionization, the Hydrogen in the Universe was predominantly neutral. This leads to a strong attenuation of Ly α lines of z ≳ 6 galaxies in the intergalactic medium. Nevertheless, Ly α has been detected up to very high redshifts (z ∼9) for several especially UV luminous galaxies. Here, we test to what extent the galaxy's local environment might impact the Ly α transmission of such sources. We present an analysis of dedicated Hubble Space Telescope (HST) imaging in the CANDELS/EGS field to search for fainter neighbours around three of the most UV luminous and most distant spectroscopically confirmed Ly α emitters: EGS-zs8-1, EGS-zs8-2, and EGSY-z8p7 at zspec = 7.73, 7.48, and 8.68, respectively. We combine the multiwavelength HST imaging with Spitzer data to reliably select z ∼7-9 galaxies around the central, UV-luminous sources. In all cases, we find a clear enhancement of neighbouring galaxies compared to the expected number in a blank field (by a factor ∼3-9×). Our analysis thus reveals ubiquitous overdensities around luminous Ly α emitting sources in the heart of the cosmic reionization epoch. We show that our results are in excellent agreement with expectations from the Dragons simulation, confirming the theoretical prediction that the first ionized bubbles preferentially formed in overdense regions. While three UV luminous galaxies already have spectroscopic redshifts, the majority of the remaining fainter, surrounding sources are yet to be confirmed via spectroscopy. JWST follow-up observations of the neighbouring galaxies identified here will thus be needed to confirm their physical association and to map out the ionized regions produced by these sources.
AB - Before the end of the Epoch of Reionization, the Hydrogen in the Universe was predominantly neutral. This leads to a strong attenuation of Ly α lines of z ≳ 6 galaxies in the intergalactic medium. Nevertheless, Ly α has been detected up to very high redshifts (z ∼9) for several especially UV luminous galaxies. Here, we test to what extent the galaxy's local environment might impact the Ly α transmission of such sources. We present an analysis of dedicated Hubble Space Telescope (HST) imaging in the CANDELS/EGS field to search for fainter neighbours around three of the most UV luminous and most distant spectroscopically confirmed Ly α emitters: EGS-zs8-1, EGS-zs8-2, and EGSY-z8p7 at zspec = 7.73, 7.48, and 8.68, respectively. We combine the multiwavelength HST imaging with Spitzer data to reliably select z ∼7-9 galaxies around the central, UV-luminous sources. In all cases, we find a clear enhancement of neighbouring galaxies compared to the expected number in a blank field (by a factor ∼3-9×). Our analysis thus reveals ubiquitous overdensities around luminous Ly α emitting sources in the heart of the cosmic reionization epoch. We show that our results are in excellent agreement with expectations from the Dragons simulation, confirming the theoretical prediction that the first ionized bubbles preferentially formed in overdense regions. While three UV luminous galaxies already have spectroscopic redshifts, the majority of the remaining fainter, surrounding sources are yet to be confirmed via spectroscopy. JWST follow-up observations of the neighbouring galaxies identified here will thus be needed to confirm their physical association and to map out the ionized regions produced by these sources.
KW - dark ages, reionization, first stars
KW - galaxies: abundances
KW - galaxies: formation
KW - galaxies: groups: general
KW - galaxies: high-redshift
UR - http://www.scopus.com/inward/record.url?scp=85141037070&partnerID=8YFLogxK
U2 - https://doi.org/10.1093/mnras/stac1908
DO - https://doi.org/10.1093/mnras/stac1908
M3 - Article
SN - 0035-8711
VL - 515
SP - 5790
EP - 5801
JO - MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
JF - MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
IS - 4
ER -