Double-peaked Lyman α emission at <i>z</i> = 6.803: a reionization-era galaxy self-ionizing its local H <scp>ii</scp> bubble
R. A. Meyer, Nicolas Laporte, Richard S Ellis, Anne Verhamme, Thibault Garel
Abstract
ABSTRACT We report the discovery of a double-peaked Lyman α profile in a galaxy at z = 6.803, A370p_z1, in the parallel Frontier Field of Abell 370. The velocity separation between the blue and red peaks of the Lyman α profile ($\Delta v=101_{-19}^{+38} (\pm 48)\, \rm km\, \rm s^{-1}$) suggests an extremely high escape fraction of ionizing photons $\gt 59(51){{\ \rm per\ cent}} (2\sigma)$. The spectral energy distribution indicates a young (50 Myr), star-forming ($12\pm 6 \, \rm {M}_\odot \rm {yr}^{-1}$) galaxy with an IRAC excess implying strong [O iii] + H β emission. On the basis of the high escape fraction measured, we demonstrate that A370p_z1 was solely capable of creating an ionized bubble sufficiently large to account for the blue component of its Lyman α profile. We discuss whether A370p_z1 may be representative of a larger population of luminous z ≃ 7 double-peaked Lyman α emitting sources with high escape fractions that self-ionized their surroundings without contributions from associated ultraviolet-fainter sources.