CLEAR: Boosted Ly Transmission of the Intergalactic Medium in UV-bright Galaxies Academic Article uri icon


  • Abstract Reionization is an inhomogeneous process, thought to begin in small ionized bubbles of the intergalactic medium (IGM) around overdense regions of galaxies. Recent Ly studies during the epoch of reionization show evidence that ionized bubbles formed earlier around brighter galaxies, suggesting higher IGM transmission of Ly from these galaxies. We investigate this problem using IR slitless spectroscopy from the Hubble Space Telescope (HST) Wide-Field Camera 3 (WFC3) G102 grism observations of 148 galaxies selected via photometric redshifts at 6.0 < z < 8.2. These galaxies have spectra extracted from the CANDELS Ly Emission at Reionization (CLEAR) survey. We combine the CLEAR data for 275 galaxies with the Keck Deep Imaging Multi-Object Spectrograph and MOSFIRE data set from the Texas Spectroscopic Search for Ly Emission at the End of Reionization Survey. We constrain the Ly equivalent width (EW) distribution at 6.0 < z < 8.2, which is described by an exponential form, dN / d EW exp ( EW ) / W 0 , with the characteristic e-folding scale width (W 0). We confirm a significant drop in the Ly strength (i.e., W 0) at z > 6. Furthermore, we compare the redshift evolution of W 0 between galaxies at different UV luminosities. UV-bright (M UV < 21 [i.e., L UV > L*]) galaxies show weaker evolution with a decrease of 0.4 ( 0.2) dex in W 0 at z > 6, while UV-faint (M UV > 21 [L UV < L*]) galaxies exhibit a significant drop of 0.70.8 (0.2) dex in W 0 from z < 6 to z > 6. If the change in W 0 is proportional to the change in the IGM transmission for Ly photons, then this is evidence that the transmission is boosted around UV-brighter galaxies, suggesting that reionization proceeds faster in regions around such galaxies.

published proceedings

  • The Astrophysical Journal

author list (cited authors)

  • Jung, I., Papovich, C., Finkelstein, S. L., Simons, R. C., Estrada-Carpenter, V., Backhaus, B. E., ... Trump, J. R.

complete list of authors

  • Jung, Intae||Papovich, Casey||Finkelstein, Steven L||Simons, Raymond C||Estrada-Carpenter, Vicente||Backhaus, Bren E||Cleri, Nikko J||Finlator, Kristian||Giavalisco, Mauro||Ji, Zhiyuan||Matharu, Jasleen||Momcheva, Ivelina||Straughn, Amber N||Trump, Jonathan R

publication date

  • July 2022