FIRST OBSERVATIONAL SUPPORT FOR OVERLAPPING REIONIZED BUBBLES GENERATED BY A GALAXY OVERDENSITY
- INAF—Osservatorio Astronomico di Roma, Via Frascati 33, I-00040 Monte Porzio Catone (RM) (Italy)
- Institute for Computational Cosmology, Department of Physics, University of Durham, South Road, Durham DH1 3LE (United Kingdom)
- Swinburne University of Technology, Hawthorn, VIC 3122 (Australia)
- Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
- INAF—Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, I-34143 Trieste (Italy)
- National Optical Astronomy Observatories, Tucson, AZ 85719 (United States)
- Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126 Pisa (Italy)
- Astronomy Department, University of Massachusetts, Amherst, MA 01003 (United States)
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.
- OSTI ID:
- 22518619
- Journal Information:
- Astrophysical Journal Letters, Vol. 818, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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