Ly alpha Escape from Low-mass, Compact, High-redshift Galaxies

We investigate the effects of stellar populations and sizes on Lya escape in 27 spectroscopically confirmed and 35 photometric Ly alpha emitters (LAEs) at z approximate to 2.65 in seven fields of the Bootes region of the NOAO Deep Wide-Field Survey. We use deep HST/WFC3 imaging to supplement ground-based observations and infer key galaxy properties. Compared to typical star-forming galaxies (SFGs) at similar redshifts, the LAEs are less massive (M-* approximate to 10(7)-10(9) M-circle dot), younger (ages less than or similar to 1 Gyr), smaller (r(e) < 1 kpc), and less dust-attenuated (E(B-V) <= 0.26 mag) but have comparable star formation rates (SFRs approximate to 1-100 M-circle dot yr(-1)). Some of the LAEs in the sample may be very young galaxies having low nebular metallicities (Z(neb) less than or similar to 0.2 Z(circle dot)) and/or high ionization parameters (log (U) greater than or similar to -2.4). Motivated by previous studies, we examine the effects of the concentration of star formation and gravitational potential on Ly alpha escape by computing SFR surface density, Sigma(SFR), and specific SFR surface density, Sigma(sSFR). For a given Sigma(SFR), the Ly alpha escape fraction is higher for LAEs with lower stellar masses. The LAEs have a higher Sigma(sSFR), on average, compared to SFGs. Our results suggest that compact star formation in a low gravitational potential yields conditions amenable to the escape of Ly alpha photons. These results have important implications for the physics of Ly alpha radiative transfer and for the type of galaxies that may contribute significantly to cosmic reionization.