Escape Fractions from Unattenuated Ly <i>α</i> Emitters around Luminous <i>z</i> &gt; 6 Quasars

Abstract Ionized proximity zones around luminous quasars provide a unique laboratory to characterize the Ly α emission lines from z &gt; 6 galaxies without significant attenuation from the intergalactic medium (IGM). However, Ly α line measurements for galaxies within high-redshift quasars’ proximity zones have been rare so far. Here we present deep spectroscopic observations obtained with the NIRSpec/Micro-Shutter Assembly (MSA) instrument on the James Webb Space Telescope of galaxies in two z &gt; 6 quasar fields. We measure the Ly α line fluxes for 50 galaxies at 6 &lt; z &lt; 7 with UV absolute magnitude M UV &lt; −19 (median M UV = −19.97), among which 15 are located near the luminous quasars, i.e., within Δ v &lt; 2500 km s −1 . We find that galaxies near the quasars show significant flux blueward of the systemic Ly α wavelength, and have higher Ly α equivalent width compared to galaxies at similar redshifts that are not located within the quasars’ environment. Our result indicates little or no redshift evolution for the Ly α emitter fraction from z ∼ 6.4 to z ∼ 5. Leveraging the low IGM opacity in the quasars’ vicinity, we evaluate the Ly α escape fraction ( <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:mtext>esc</mml:mtext> <mml:mspace width="0.1em"/> </mml:mrow> <mml:mrow> <mml:mspace width="0.1em"/> <mml:mtext>Ly</mml:mtext> <mml:mi>α</mml:mi> </mml:mrow> </mml:msubsup> </mml:math> ) of high-redshift galaxies. Our analysis suggests that galaxies at 〈 z 〉 ≈ 6.4 have an average <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:mtext>esc</mml:mtext> <mml:mspace width="0.1em"/> </mml:mrow> <mml:mrow> <mml:mspace width="0.1em"/> <mml:mtext>Ly</mml:mtext> <mml:mi>α</mml:mi> </mml:mrow> </mml:msubsup> <mml:mo>=</mml:mo> <mml:mn>0.14</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.04</mml:mn> </mml:math> . This value is consistent with reionization models where the Lyman continuum escape fraction is low <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo stretchy="false">(</mml:mo> <mml:msubsup> <mml:mrow> <mml:mi>f</mml:mi> </mml:mrow> <mml:mrow> <mml:mtext>esc</mml:mtext> <mml:mspace width="0.1em"/> </mml:mrow> <mml:mrow> <mml:mspace width="0.1em"/> <mml:mtext>LyC</mml:mtext> </mml:mrow> </mml:msubsup> <mml:mo>≲</mml:mo> <mml:mn>0.1</mml:mn> <mml:mo stretchy="false">)</mml:mo> </mml:math> for luminous galaxies, and where the most luminous galaxies have only a minor contribution to the total ionizing photon budget.