Kavli Affiliate: Michael D. Gladders
| First 5 Authors: M. Riley Owens, Keunho J. Kim, Matthew B. Bayliss, T. Emil Rivera-Thorsen, Keren Sharon
| Summary:
We investigate the Lyman-$alpha$ (Ly$alpha$) and Lyman continuum (LyC)
properties of the Sunburst Arc, a $z=2.37$ gravitationally lensed galaxy with a
multiply-imaged, compact region leaking LyC and a triple-peaked Ly$alpha$
profile indicating direct Ly$alpha$ escape. Non-LyC-leaking regions show a
redshifted Ly$alpha$ peak, a redshifted and central Ly$alpha$ peak, or a
triple-peaked Ly$alpha$ profile. We measure the properties of the Ly$alpha$
profile from different regions of the galaxy using $Rsim5000$ Magellan/MagE
spectra. We compare the Ly$alpha$ spectral properties to LyC and narrowband
Ly$alpha$ maps from Hubble Space Telescope (HST) imaging to explore the
subgalactic Ly$alpha-$LyC connection. We find strong correlations (Pearson
correlation coefficient $r>0.6$) between the LyC escape fraction ($f_{rm
esc}^{rm LyC}$) and Ly$alpha$ (1) peak separation $v_{rm{sep}}$, (2) ratio
of the minimum flux density between the redshifted and blueshifted Ly$alpha$
peaks to continuum flux density $f_{rm{min}}/f_{rm{cont}}$, and (3)
equivalent width. We favor a complex ion{H}{1} geometry to explain the
Ly$alpha$ profiles from non-LyC-leaking regions and suggest two ion{H}{1}
geometries that could diffuse and/or rescatter the central Ly$alpha$ peak from
the LyC-leaking region into our sightline across transverse distances of
several hundred parsecs. Our results emphasize the complexity of Ly$alpha$
radiative transfer and its sensitivity to the anisotropies of ion{H}{1} gas on
subgalactic scales. Large differences in the physical scales on which we
observe spatially variable direct escape Ly$alpha$, blueshifted Ly$alpha$,
and escaping LyC photons in the Sunburst Arc underscore the importance of
resolving the physical scales that govern Ly$alpha$ and LyC escape.
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