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

Eunsuk Seo, Hyunmi Song, Lucia Guaita, Kyoung-Soo Lee, Eric Gawiser, Robin Ciardullo, Arjun Dey, Seok-Jun Chang, Nicole Firestone, Stephen Gwyn, Ho Seong Hwang, Sungryong Hong, Sang Hyeok Im, Woong-Seob Jeong, Jaehyun Lee, Seong-Kook Lee, Chanbom Park, Vandana Ramakrishnan, Marcin Sawicki, Yujin Yang, Ann Zabludoff

Abstract

We investigated Lyman-continuum (LyC) emission from Lyman-$α$ 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 $>3σ$ and between $2σ$ and $3σ$, 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$α$ 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.

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

Abstract

We investigated Lyman-continuum (LyC) emission from Lyman- emitters (LAEs) at , identified in the One-hundred-deg 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 -band images from the CFHT large area -band deep survey (CLAUDS) to measure their LyC fluxes. This represents the largest sample of LAEs searched for such a purpose. Within this sample, we identified 12 `gold' and 39 `silver' LyC-emitting candidates, with LyC fluxes detected of and between and , respectively, in the range of 5.16--55.29 nJy. No LyC signal is detected in the weighted mean stack of the final sample ( 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 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.
Paper Structure (2 sections, 2 figures)

This paper contains 2 sections, 2 figures.

Table of Contents

  1. Introduction
  2. Data

Figures (2)

  • Figure 1: The R.A. and Decl. distribution of the ODIN LAEs (gray dots) and of those in the final sample (blue circle, see Section \ref{['sec:LyCflux']}) in the E-COSMOS (left) and XMM-LSS (right) fields. Each field covers an area of $\sim$ 9 deg$^2$. The CLAUDS footprint, where the $u/u^*$-band data is available, is denoted by red lines.
  • Figure 2: Filter transmission for three narrowbands (N419, N501 and N673) and the eight broadbands ($u$, $u^*$ from CFHT/MegaCam, $g$, $r$, $i$, $z$ and $y$ from HSC, and F435W from HST) as a function of wavelength. A composite spectrum of $z=3$ SFGs from Shapley2003, shifted to $z=4.5$, is illustrated in black solid line. The gray solid, dashed and dotted lines mark the rest-frame Lyman limit (912 Å), Ly$\alpha$ (1216 Å), and the UV continuum at 1400 Å, respectively.