Early Results from GLASS-JWST. XXII. Rest-frame UV–Optical Spectral Properties of Lyα Emitting Galaxies at 3 < z < 6
Namrata Roy, Alaina Henry, Tommaso Treu, Tucker Jones, Gonzalo Prieto-Lyon, Charlotte Mason, Tim Heckman, Themiya Nanayakkara, L. Pentericci, Sara Mascia, Maruša Bradač, E. Vanzella, Claudia Scarlata, Kristan Boyett, Michele Trenti, Xin Wang
Abstract
Abstract Ly α emission is possibly the best indirect diagnostic of Lyman continuum (LyC) escape since the conditions that favor the escape of Ly α photons are often the same that allow for the escape of LyC photons. In this work, we present the rest-frame UV–optical spectral characteristics of 11 Ly α emitting galaxies at 3 < z < 6—the redshift range that optimizes between intergalactic medium attenuation effects and temporal proximity to the epoch of reionization. From a combined analysis of JWST/NIRSpec and MUSE data, we present the Ly α escape fraction and study its correlation with other physical properties of galaxies that might facilitate Ly α escape. We find that our galaxies have low masses (80% of the sample with <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>log</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> </mml:msub> <mml:mspace width="0.33em"/> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⋆</mml:mo> </mml:mrow> </mml:msub> <mml:mo><</mml:mo> <mml:mn>9.5</mml:mn> <mml:mspace width="0.33em"/> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> </mml:math> ), compact sizes (median R e ∼ 0.7 kpc), low dust content, moderate [O iii ]/[O ii ] flux ratios (mean ∼ 6.8 ± 1.2), and moderate Ly α escape fractions (mean <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:mspace width="0.33em"/> <mml:mo>∼</mml:mo> </mml:math> 0.11). Our sample shows characteristics that are broadly consistent with low-redshift galaxies with Ly α emission, which are termed as “analogs” of the high-redshift population. We predict the LyC escape fraction in our sample to be low (0.03–0.07), although larger samples in the postreionization epoch are needed to confirm these trends.