The Lyα Dependence on Nebular Properties from the HETDEX and MOSDEF Surveys

Abstract Investigating the impact of galaxy properties on emergent Ly α emission is crucial for reionization studies, given the sensitivity of Ly α to neutral hydrogen. This study presents an analysis of the physical characteristics of 155 star-forming galaxies, 29 with Ly α detected, and 126 with Ly α not detected with Ly α EW &lt; 20 Å, at z = 1.9–3.5, drawn from the MOSFIRE Deep Evolution Field survey, that have overlapping observations from the Hobby–Eberly Telescope Dark Energy Experiment survey. To unravel the interstellar medium (ISM) conditions in our sample, we developed a custom nebular line modeling algorithm based on the MAPPINGS V photoionization model grid and the emcee framework. Combining nebular-based ISM properties with photometry-based global properties, constrained via Bagpipes , we explore distinctions in the stellar and gas properties between Ly α -detected and Ly α -nondetected galaxies. Our analysis reveals statistically significant differences between the two samples in terms of stellar mass and dust attenuation ( A V ) at &gt;2 σ significance, as determined via a Kolmogorov–Smirnov test. Moreover, there are weaker (≲1 σ significance) indications that the ionization parameter and metallicity differ between the two samples. Our results demonstrate that the escape fraction of Ly α ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mi>f</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>esc</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>Ly</mml:mi> <mml:mi>α</mml:mi> </mml:mrow> </mml:msubsup> </mml:math> ) is inversely correlated with stellar mass, star formation rate, and dust attenuation, while it is positively correlated with the ionization parameter, with significance levels exceeding 2 σ . Our findings suggest that the interstellar environments of Ly α -detected galaxies, characterized by low mass, low dust, low gas-phase metallicity, and high ionization parameters, play a pivotal role in promoting the escape of Ly α radiation.