Linking UV spectral properties of MUSE Ly α emitters at z ≳ 3 to Lyman continuum escape
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2024-02
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Journal Article
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Abstract
The physical conditions giving rise to high escape fractions of ionizing radiation (LyC fesc) in star-forming galaxies - most likely protagonists of cosmic reionization - are not yet fully understood. Using the VLT/MUSE observations of similar to 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 O III] lambda 1666, [Si III] lambda 1883, and [C III] lambda 1907 + C III] lambda 1909 emission, indicating a high-ionization state of the interstellar medium (ISM); (ii) high equi v alent widths of He II lambda 1640 (similar to 1 - 3 & Aring;), suggesting the presence of hard ionizing radiation fields; (iii) Si II & lowast;lambda 1533 emission, revealing substantial amounts of neutral hydrogen off the line of sight; (iv) high C IV lambda lambda 1548,1550 to [C III] lambda 1907 + C III] lambda 1909 ratios (C IV /C III ] > 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 HeII lambda 1640 equivalent widths ( < 1 & Aring;), and low C IV/C III ] ( < 0.25), implying low-ionization states and high-neutral hydrogen column densities. Our results suggest that C IV/C III ] might be sensitive to the physical conditions that go v ern 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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527 (4)
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9853 - 9871
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Oxford University Press
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galaxies: high-redshift; ISM: lines and bands; dark ages, reionization, first stars; ultraviolet: galaxies; ultraviolet: ISM