Lyman continuum leaker candidates at z ∼ 3–4 in the HDUV based on a spectroscopic sample of MUSE LAEs

Abstract

In recent years, a number of Lyman continuum (LyC) leaker candidates have been found at intermediate redshifts, providing insight into how the Universe was reionised at early cosmic times. There are now around 100 known LyC leakers at all redshifts, which enables us to analyse their properties statistically. Here, we identify new LyC leaker candidates at $z 3-4.5$ and compare them to objects from the literature to get an overview of the different observed escape fractions and their relation to the properties of the Lyman alpha (Lyalpha ) emission line. The aim of this work is to test the indicators (or proxies) for LyC leakage suggested in the literature and to improve our understanding of the kinds of galaxies from which LyC radiation can escape. We used data from the Hubble Deep Ultraviolet (HDUV) legacy survey to search for LyC emission based on a sample of $ 2000$ Lyalpha emitters (LAEs) detected previously in two surveys with the Multi-Unit Spectroscopic Explorer (MUSE), namely MUSE-Deep and MUSE-Wide. Based on the redshifts and positions of the LAEs, we look for potential LyC leakage in the WFC3/UVIS F336W band of the HDUV survey. The escape fractions are measured and compared in different ways, including spectral energy distribution (SED) fitting performed using the CIGALE software. We add 12 objects to the sample of known LyC leaker candidates (5 highly likely leakers and 7 potential ones), 1 of which was previously known, and compare their Lyalpha properties to their escape fractions. We find escape fractions of between $ 20<!PCT!>$ and $ 90<!PCT!>$, assuming a high transmission in the intergalactic medium (IGM). We present a method whereby the number of LyC leaker candidates we find is used to infer the underlying average escape fraction of galaxies, which is $ 12<!PCT!>$. Based on their Lyalpha properties, we conclude that LyC leakers are not very different from other high-z LAEs and suggest that most LAEs could be leaking LyC even if this cannot always be detected because of the direction of emission and the transmission properties of the IGM.

Cosmic Reionization in the JWST Era: Back to AGNs?

“…) has been detected by Naidu et al (2018) in a stack of extreme [O III] emitters (a "Green Pea" subgroup known to have an elevated fesc,H at low redshifts; e.g., Izotov et al 2018) or in low-mass lensed galaxies at 1.3 z 3.0 (Jung et al 2024). In a sample of 621 Lyαemitting galaxies at z = 3.0-4.5, Kerutt et al (2024) recently identified only 5 likely LyC leakers but argued that this detection rate was consistent with a global escape fraction of 12%. Using an alternative approach to constrain fesc,H empirically at 1.6 < z < 6.7 via spectroscopy of long-duration gamma-ray burst afterglows, Tanvir et al (2019) estimated an average escape fraction of 0.7% at the Lyman limit.…”