Kavli Affiliate: Michael D. Gladders
| First 5 Authors: Erik Solhaug, Hsiao-Wen Chen, Mandy C. Chen, Fakhri Zahedy, Max Gronke
| Summary:
The hydrogen Lyman-alpha (Lya) emission line, the brightest spectral feature
of a photoionized gas, is considered an indirect tracer of the escape of Lyman
continuum (LyC) photons, particularly when the intergalactic medium is too
opaque for direct detection. However, resonant scattering complicates
interpreting the empirical properties of Lya photons, necessitating radiative
transfer simulations to capture their strong coupling with underlying gas
kinematics. In this study, we leverage the exceptional spatial resolution from
strong gravitational lensing to investigate the connection between Lya line
profiles and LyC leakage on scales of a few 100 pc in the Sunburst Arc galaxy
at $zsim2.37$. New optical echelle spectra obtained using Magellan MIKE show
that both the LyC leaking and non-leaking regions exhibit a classic double-peak
Lya feature with an enhanced red peak, indicating outflows at multiple
locations in the galaxy. Both regions also show a central Gaussian peak atop
the double peaks, indicating directly escaped Lya photons independent of LyC
leakage. We introduce a machine learning-based method for emulating Lya
simulations to quantify intrinsic dynamics ($sigma_{mathrm{int}}$), neutral
hydrogen column density ($N_{mathrm{HI}}$), outflow velocity
($v_{mathrm{exp}}$), and effective temperature ($T$) across continuous
parameter spaces. By comparing the spatially and spectrally resolved Lya lines
in Sunburst, we argue that the directly escaped Lya photons originate in a
volume-filling, warm ionized medium spanning $sim1$ kpc, while the LyC leakage
is confined to regions of $lesssim200$ pc. These sub-kpc variations in Lya
profiles highlight the complexity of interpreting integrated properties in the
presence of inhomogeneous mixtures of gas and young stars, emphasizing the need
for spatially and spectrally resolved observations of distant galaxies.
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