No strong dependence of Lyman continuum leakage on physical properties of star-forming galaxies at $\mathbf{3.1 \lesssim z \lesssim 3.5}$

Abstract

We present Lyman continuum (LyC) radiation escape fraction ( 𝑓 esc ) measurements for 183 spectroscopically confirmed starforming galaxies in the redshift range 3.11 < 𝑧 < 3.53 in the Chandra Deep Field South. We use ground-based imaging to measure 𝑓 esc , and use ground-and space-based photometry to derive galaxy physical properties using spectral energy distribution (SED) fitting. We additionally derive [O ] + H𝛽 equivalent widths (that fall in the observed 𝐾 band) by including nebular emission in the SED fitting. After removing foreground contaminants, we report the discovery of 11 new candidate LyC leakers, with absolute LyC escape fractions, 𝑓 esc in the range 0.07 − 0.52. Most galaxies in our sample (≈ 94%) do not show any LyC leakage, and we place 1𝜎 upper limits of 𝑓 esc < 0.07 through weighted averaging, where the Lyman-break selected galaxies have 𝑓 esc < 0.07 and 'blindly' discovered galaxies with no prior photometric selection have 𝑓 esc < 0.10. We additionally measure 𝑓 esc < 0.09 for extreme emission line galaxies in our sample with rest-frame [O ] + H𝛽 equivalent widths > 300 Å. For the candidate LyC leakers, we do not find a strong dependence of 𝑓 esc on their stellar masses and/or specific star-formation rates, and no correlation between 𝑓 esc and EW 0 ([O ] + H𝛽). We suggest that this lack of correlations may be explained by viewing angle and/or non-coincident timescales of starburst activity and periods of high 𝑓 esc . Alternatively, escaping radiation may predominantly occur in highly localised star-forming regions, thereby obscuring any global trends with galaxy properties. Both hypotheses have important consequences for models of reionisation.

SDSS-IV MaNGA: an observational evidence of density bounded region in a Lyman-$α$ emitter

“…6, we bring the stellar mass and gasphase metallicity of the leaky systems while discussing these correlations. We find that f esc LyC and [SII]-deficiency correlation is unlikely to depend on the host stellar mass, consistent with earlier findings (Izotov et al 2021;Saxena et al 2021). Moreover, this also supports the finding of Wang et al (2021) that there is no link between [SII]-deficiency and stellar-mass.…”

CLEAR: Boosted Ly$α$ Transmission of the Intergalactic Medium in UV bright Galaxies

“…Particularly, they find a higher Lyα detection rate at z 7 from massive galaxies with strong [O III]+Hβ emission, which reflects enhanced ionizing photo production rates (e.g., Roberts-Borsani et al 2016;Tang et al 2019Tang et al , 2021aEndsley et al 2021b), arguing for higher Lyα equivalentwidths (EWs) from the strong [O III]+Hβ emitting population as similar as shown at lower redshifts of z 2 -3 (Tang et al 2021b). This may be related to the galaxies' specific star-formation rates (sSFRs) and ionization (Backhaus et al 2021, Papovich et al, in prep), although this remains tenuous as there is not yet any conclusive evidence for a significant enhancement of Lyman continuum escape fraction found for galaxies with higher [O III]+Hβ galaxies at z ∼ 3 (Saxena et al 2021). Therefore, it is prudent to look for indications that evolution of Lyα emission in galaxies depends on UV luminosity in the epoch of reionization.…”

Properties of High-Redshift GRBs

“…An increase in ionizing photon production from an evolving initial mass function could relieve tension in reionization models where large escape fractions of ionizing photons from galaxies (> 10%) are required at high redshift to complete reionization by z ≈ 5.5 − 6. Observations of galaxies at z < 4, where escape fractions of ionizing photons can be measured, predominantly report low escape fractions (< 10%) (Siana et al 2010;Sandberg et al 2015;Rutkowski et al 2017;Grazian et al 2017;Pahl et al 2021;Saxena et al 2021), though recently higher escape fractions have been measured in some galaxies (Steidel et al 2018;Fletcher et al 2019;Marques-Chaves et al 2021;Izotov et al 2021;Saxena et al 2021). Higher Lyman continuum photon production efficiencies in galaxies at high redshift are favored in Finkelstein et al (2019) where they consider scenarios for reionization with empirically-supported low galaxy ionizing photon escape fractions.…”