FIRST OBSERVATIONAL SUPPORT for OVERLAPPING REIONIZED BUBBLES GENERATED by A GALAXY OVERDENSITY

M. Castellano, P. Dayal, L. Pentericci, A. Fontana, A. Hutter, G. Brammer, E. Merlin, A. Grazian, S. Pilo, R. Amorin, S. Cristiani, M. Dickinson, A. Ferrara, S. Gallerani, E. Giallongo, M. Giavalisco, L. Guaita, A. Koekemoer, R. Maiolino, D. ParisP. Santini, L. Vallini, E. Vanzella, J. Wagg

Research output: Contribution to journalArticlepeer-review

53 Citations (Scopus)

Abstract

We present an analysis of deep Hubble Space Telescope (HST) multi-band imaging of the BDF field specifically designed to identify faint companions around two of the few Lyα emitting galaxies spectroscopically confirmed at z ∼ 7. Although separated by only 4.4 proper Mpc these galaxies cannot generate H ii regions large enough to explain the visibility of their Lyα lines, thus requiring a population of fainter ionizing sources in their vicinity. We use deep HST and VLT-Hawk-I data to select z ∼ 7 Lyman break galaxies around the emitters. We select six new robust z ∼ 7 LBGs at Y ∼ 26.5-27.5 whose average spectral energy distribution is consistent with the objects being at the redshift of the close-by Lyα emitters. The resulting number density of z ∼ 7 LBGs in the BDF field is a factor of approximately three to four higher than expected in random pointings of the same size. We compare these findings with cosmological hydrodynamic plus radiative transfer simulations of a universe with a half neutral IGM: we find that indeed Lyα emitter pairs are only found in completely ionized regions characterized by significant LBG overdensities. Our findings match the theoretical prediction that the first ionization fronts are generated within significant galaxy overdensities and support a scenario where faint, "normal" star-forming galaxies are responsible for reionization.

Original languageEnglish
Article numberL3
JournalAstrophysical Journal Letters
Volume818
Issue number1
DOIs
Publication statusPublished - 10 Feb 2016
Externally publishedYes

Keywords

  • dark ages, reionization, first stars
  • galaxies: high-redshift

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Fingerprint

Dive into the research topics of 'FIRST OBSERVATIONAL SUPPORT for OVERLAPPING REIONIZED BUBBLES GENERATED by A GALAXY OVERDENSITY'. Together they form a unique fingerprint.

Cite this