The connection between galactic outflows and the escape of ionizing photons

Kavli Affiliate: Michael D. Gladders

| First 5 Authors: Ramesh Mainali, Jane R. Rigby, John Chisholm, Matthew Bayliss, Rongmon Bordoloi

| Summary:

We analyze spectra of a gravitationally lensed galaxy, known as the Sunburst
Arc, that is leaking ionizing photons, also known as the Lyman continuum (LyC).
Magnification from gravitational lensing permits the galaxy to be spatially
resolved into one region that leaks ionizing photons, and several that do not.
Rest-frame ultraviolet and optical spectra from Magellan target ten different
regions along the lensed Arc, including six multiple images of the LyC leaking
region, as well as four regions that do not show LyC emission. The rest-frame
optical spectra of the ionizing photon emitting regions reveal a blue-shifted
($Delta V$=27 km s$^{-1}$) broad emission component (FWHM=327 km s$^{-1}$)
comprising 55% of the total [OIII] line flux, in addition to a narrow component
(FWHM = 112 km s$^{-1}$), suggesting the presence of strong highly ionized gas
outflows. This is consistent with the high-velocity ionized outflow inferred
from the rest-frame UV spectra. In contrast, the broad emission component is
less prominent in the non-leaking regions, comprising $sim$26% of total [OIII] line flux. The high ionization absorption lines are prominent in both leaker
and non-leaker but low ionization absorption lines are very weak in the leaker,
suggesting that the line of sight gas is highly ionized in the leaker. Analyses
of stellar wind features reveal that the stellar population of the LyC leaking
regions is considerably younger ($sim$3 Myr) than the non-leaking regions
($sim$12 Myr), highlighting that stellar feedback from young stars may play an
important role in ionizing photon escape.

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