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arXiv · 2305.07044

Linking UV spectral properties of MUSE Ly-alpha emitters at z>3 to Lyman continuum escape

I. G. Kramarenko·J. Kerutt·A. Verhamme·P. A. Oesch·L. Barrufet·J. Matthee·H. Kusakabe·I. Goovaerts·T. T. Thai
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Abstract

The physical conditions giving rise to high escape fractions of ionizing radiation (LyC $f_{\rm{esc}}$) in star-forming galaxies - most likely protagonists of cosmic reionization - are not yet fully understood. Using the VLT/MUSE observations of ~1400 Ly$\alpha$ emitters at 2.9 < z < 6.7, we compare stacked rest-frame UV spectra of candidates for LyC leakers and non-leakers selected based on their Ly$\alpha$ profiles. We find that the stacks of potential LyC leakers, i.e. galaxies with narrow, symmetric Ly$\alpha$ profiles with small peak separation, generally show (i) strong nebular OIII]1666, [SiIII]1883, and [CIII]1907+CIII]1909 emission, indicating a high-ionization state of the interstellar medium (ISM); (ii) high equivalent widths of HeII1640 (~1-3 A), suggesting the presence of hard ionizing radiation fields; (iii) SiII*1533 emission, revealing substantial amounts of neutral hydrogen off the line of sight; (iv) high CIV1548,1550 to [CIII]1907+CIII]1909 ratios (CIV/CIII] > 0.75), signalling the presence of low column density channels in the ISM. In contrast, the stacks with broad, asymmetric Ly$\alpha$ profiles with large peak separation show weak nebular emission lines, low HeII1640 equivalent widths (<1 A), and low CIV/CIII] (<0.25), implying low-ionization states and high-neutral hydrogen column densities. Our results suggest that CIV/CIII] might be sensitive to the physical conditions that govern LyC photon escape, providing a promising tool for identification of ionizing sources among star-forming galaxies in the epoch of reionization.

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I. G. Kramarenko, J. Kerutt, A. Verhamme, P. A. Oesch, L. Barrufet, J. Matthee, H. Kusakabe, I. Goovaerts, T. T. Thai. 2023-05-11. Linking UV spectral properties of MUSE Ly-alpha emitters at z>3 to Lyman continuum escape. https://doi.org/10.1093/mnras/stad3853

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