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AR 16606 (Archival Research)

Mon Jul 15 05:12:53 GMT 2024

Principal Investigator: Cody Carr
PI Institution: Zhejiang University (ZJU)
Investigators (xml)

Title: Modeling the Mg II-Lyman Alpha Relation as a Calibrator of the Lyman Continuum Escape Fraction
Cycle: 29

Abstract
Understanding the reionization of the universe is a major focus of upcoming ground- and space-based facilities. One major source of uncertainty is the escape of hydrogen ionizing (LyC) photons during the epoch of reionization (EoR). This quantity *cannot* be measured at z>6, so local indirect indicators are being calibrated using local galaxies. HST has invested hundreds of hours in the effort of 1) identifying LyC emitters and measuring their escape fraction of LyC radiation (fesc), and 2) calibrating indirect estimators of fesc to use at z>6. Among the various indirect tracers of fesc, Lyman alpha (Lya) and Mg II promise to be the most informative, as they carry information about the density, velocity and distribution of the neutral gas. What is missing, and what we are proposing here, is a full modeling effort to link Mg II emission to Lya and LyC, properly accounting for the nebular emission and the continuum scattering component. Specifically, we will 1) perform detailed radiation transfer calculations of the propagation of Mg~II and Lya through the interstellar and circum-galactic media, for general geometries and velocity fields. These models will be 2) used to infer the neutral gas properties in confirmed LyC emitters identified by local Hubble surveys. In addition to interpreting Hubble data, our work will be crucial to make the most out of upcoming JWST programs that will observe EoR galaxies in Lya and MgII to estimate fesc and, ultimately, constrain the EoR. We will make our calculations publicly available as a resource for the community to interpret JWST observations by early 2022.