ODIN: Searching for LyC emission from Lyman-$\alpha$ emitters at $z=4.5$ in the E-COSMOS and XMM-LSS fields

TL;DR

This study searches for Lyman-continuum emission from a large sample of Lyman-$\alpha$ emitters at $z=4.5$ using deep imaging data, identifying a few candidate LyC leakers but not detecting a significant stacked signal.

Contribution

It presents the largest sample of $z=4.5$ LAEs analyzed for LyC emission, identifying new candidate leakers and exploring their properties with detailed background modeling and photometry.

Findings

12 'gold' LyC-emitting candidates identified

No significant LyC signal detected in the stacked sample

Weak correlations between LyC flux, UV brightness, and Ly$\alpha$ equivalent width

Abstract

We investigated Lyman-continuum (LyC) emission from Lyman-$\alpha$ emitters (LAEs) at $z=4.5$, identified in the One-hundred-deg$^2$ DECam Imaging in Narrowbands (ODIN) survey. Of the 7,498 LAEs (4,101 in COSMOS and 3,397 in XMM-LSS), we excluded LAEs that are either likely low-z objects or contaminated by neighboring sources. Additional background modeling process with thorough quality assessments leaves a final sample of 851 galaxies. We then performed forced photometry on $u/u^*$-band images from the CFHT large area $u$-band deep survey (CLAUDS) to measure their LyC fluxes. This represents the largest sample of $z=4.5$ LAEs searched for such a purpose. Within this sample, we identified 12 `gold' and 39 `silver' LyC-emitting candidates, with LyC fluxes detected of $>3\sigma$ and between $2\sigma$ and $3\sigma$, respectively, in the range of 5.16--55.29 nJy. No LyC signal is detected in the weighted mean stack of the final sample ($0.20 \pm 0.37$ nJy). Given the UVC magnitudes of LAEs in our sample, the expected LyC emission is likely below the detection limit even when stacking the full sample of ODIN LAEs. Nevertheless, having a large sample of LAEs remains valuable for identifying individual LyC leaker candidates. Among the gold and silver candidates, the LyC flux appears to correlate positively with UVC flux and negatively with Ly$\alpha$ equivalent width, although the correlations are weak. A larger sample of LyC leakers will allow a more robust confirmation of these trends and provide better insights into their physical origins.