A bottom-up search for Lyman-continuum leakage in the Hubble Ultra Deep Field

Abstract

Context. When studying the production and escape of Lyman Continuum from galaxies, it is standard to rely on array of indirect observational tracers in preselection of candidate leakers. Aims. In this work, we investigate how much ionizing radiation might be missed due to these selection criteria by completely removing them and performing a search selected purely from rest-frame LyC emission; and how that affects our estimates of the ionizing background. Methods. We invert the conventional method and perform a bottom-up search for Lyman-continuum leaking galaxies at redshifts 2 z 3.5. Using archival data from HST and VLT/MUSE, we run source finding software on UV-filter HST images from the HUDF, and subject all detected sources to a series of tests to eliminate those that are inconsistent with being ionizing sources. Results. We find 6 new and one previously identified candidate leakers with absolute escape fractions ranging from 36% to ∼ 100%. Our filtering criteria eliminate one object previously reported as a candidate ionizing emitter in the literature, while we report nondetection in the rest frame Lyman continuum of two other previously reported sources. We find that our candidates make a contribution to the metagalactic ionizing field of log 10 ( ν ) = 25.32 +0.25 −0.21 and 25.29 +0.27 −0.22 erg s −1 Hz −1 cMpc −3 for the full set of candidates and for the 4 strongest candidates only; both values are higher than but consistent with other recent figures in the literature. Conclusions. Our findings suggest that galaxies that do not meet the usual selection criteria may make a non-negligible contribution to the cosmic ionizing field. We recommend that similar searches be carried out on a larger scale in well-studied fields with both UV and large ancillary data coverage, for example in the full set of CANDELS fields.

The Low-Redshift Lyman Continuum Survey: Optically Thin and Thick Mg II Lines as Probes of Lyman Continuum Escape

“…In the last decades, considerable observational efforts have been directed towards studying the escape of Lyman continuum (LyC) photons from galaxies and attempting to explain 2021; Chisholm et al 2022;Flury et al 2022a;Izotov et al 2022;Marques-Chaves et al 2022a;Saldana-Lopez et al 2022;Xu et al 2022), and moderate-to high-redshifted galaxies (z ∼ 2 -4, e.g., Robertson et al 2015;Vanzella et al 2016;de Barros et al 2016;Shapley et al 2016;Bian et al 2017;Marchi et al 2017;Steidel et al 2018;Vanzella et al 2018;Fletcher et al 2019;Rivera-Thorsen et al 2019;Ji et al 2020;Mestrić et al 2020;Vielfaure et al 2020;Naidu et al 2022;Begley et al 2022;Rivera-Thorsen et al 2022;Marques-Chaves et al 2022b). These galaxies are proposed to be analogs of high-redshift (z ∼ 6 -8) ones at EoR (e.g., Schaerer et al 2016;Boyett et al 2022).…”