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LyC escape from SPHINX galaxies in the Epoch of Reionization

Abstract : We measure escape fractions, fesc, of ionizing radiation from galaxies in the SPHINX suite of cosmological radiation-hydrodynamical simulations of reionization, resolving haloes with $M_{\rm vir}rsim 7.5 \times 10^7 \ {\rm {M}_{\odot }}$ with a minimum cell width of ≍10 pc. Our new and largest 20 co-moving Mpc wide volume contains tens of thousands of star-forming galaxies with halo masses up to a few times 1011 M. The simulated galaxies agree well with observational constraints of the ultraviolet (UV) luminosity function in the Epoch of Reionization. The escape fraction fluctuates strongly in individual galaxies over time-scales of a few Myr, due to its regulation by supernova and radiation feedback, and at any given time a tiny fraction of star-forming galaxies emits a large fraction of the ionizing radiation escaping into the intergalactic medium. Statistically, fesc peaks in intermediate-mass, intermediate-brightness, and low-metallicity galaxies (M* ≍ 107 M, M1500 ≍ -17, Z ≲ 5 × 10-3 Z), dropping strongly for lower and higher masses, brighter and dimmer galaxies, and more metal-rich galaxies. The escape fraction correlates positively with both the short-term and long-term specific star formation rate. According to SPHINX, galaxies too dim to be yet observed, with ${M_{1500}}rsim -17$, provide about 55 per cent of the photons contributing to reionization. The global averaged fesc naturally decreases with decreasing redshift, as predicted by UV background models and low-redshift observations. This evolution is driven by decreasing specific star formation rates over cosmic time.
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Contributor : Olivier Hauss Connect in order to contact the contributor
Submitted on : Monday, August 29, 2022 - 11:29:14 AM
Last modification on : Saturday, September 24, 2022 - 12:02:05 PM

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Joakim Rosdahl, Jérémy Blaizot, Harley Katz, Taysun Kimm, Thibault Garel, et al.. LyC escape from SPHINX galaxies in the Epoch of Reionization. Monthly Notices of the Royal Astronomical Society, 2022, 515, pp.2386-2414. ⟨10.1093/mnras/stac1942⟩. ⟨insu-03763015⟩



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