Abstract
We present a study designed to measure the average LyC escape fraction
(⟨fesc⟩) of star-forming galaxies at z=3.5. We assemble a
sample of 148 galaxies from the VANDELS survey at 3.35≤zspec≤3.95, selected to minimize line-of-sight contamination of their
photometry. For this sample, we use ultra-deep, ground-based, U−band imaging
and HST V−band imaging to robustly measure the distribution of
Robs =(LLyC/LUV)obs. We then model
the distribution as a function of ⟨fesc⟩, carefully
accounting for attenuation by dust, and the IGM (and CGM). A maximum likelihood
fit to the Robs distribution returns a best-fitting value of
⟨fesc⟩=0.07±0.02, a result confirmed using an
alternative Bayesian inference technique (both exclude ⟨fesc⟩=0.0 at >3σ). By splitting our sample in two, we find
evidence that ⟨fesc⟩ is positively correlated with
Lyα equivalent width, with high and low sub-samples returning best fits
of ⟨fesc⟩=0.12+0.06−0.04 and ⟨fesc⟩=0.02+0.02−0.01, respectively. In contrast, we find evidence that
⟨fesc⟩ is anti-correlated with intrinsic UV luminosity
and UV dust attenuation; with low UV luminosity and dust attenuation
sub-samples returning best fits in the range 0.10≤⟨fesc⟩≤0.22. We do not find evidence for a clear correlation between
fesc and galaxy stellar mass, suggesting it is not a primary indicator
of leakage. Although larger samples are needed to robustly confirm these
trends, they suggest that it is entirely plausible that the low dust and
metallicity galaxies found at z > 6 will display the ⟨fesc⟩≥0.1 required to drive reionization.
Original language | English |
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Pages (from-to) | 3510-3525 |
Number of pages | 16 |
Journal | Monthly Notices of the Royal Astronomical Society |
Volume | 513 |
Issue number | 3 |
Early online date | 19 Apr 2022 |
DOIs | |
Publication status | Published - 1 Jul 2022 |
Keywords / Materials (for Non-textual outputs)
- galaxies: fundamental parameters
- galaxies: high-redshift
- intergalactic medium