By clearing neutral gas away from a young starburst, superwinds may regulate the escape of Lyman continuum (LyC) photons from star-forming galaxies. However, models predict that superwinds may not launch in the most extreme, compact starbursts. We explore the role of outflows in generating low optical depths in the Green Peas (GPs), the only known star-forming population with several confirmed and candidate LyC-leaking galaxies. With Hubble Space Telescope UV spectra of 25 low-redshift GPs, including new observations of 13 of the most highly ionized GPs, we compare the kinematics of UV absorption lines with indirect H i optical depth diagnostics: Lyα escape fraction, Lyα peak separation, or low-ionization absorption line equivalent width. The data suggest that high-ionization kinematics tracing superwind activity may correlate with low optical depth in some objects. However, the most extreme GPs, including many of the best candidate LyC emitters with weak low-ionization absorption and strong, narrow Lyα profiles, show the lowest velocities. These results are consistent with models for suppressed superwinds, which suggests that outflows may not be the only cause of LyC escape from galaxies.
Bibliographical noteFunding Information:
We thank the referee for a helpful response and thank Crystal Martin for useful discussions. A.E.J. acknowledges support by NASA through Hubble Fellowship grant HST-HF2-51392 and STScI grant HST-GO-14080. M.S.O. acknowledges support from NASA through grant HST-GO-14080 from STScI. STScI is operated by AURA under NASA contract NAS-5-26555. T.D. acknowledges support from the Massachusetts Space Grant Consortium. Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the U.S. Department of Energy Office of Science. SDSS-III is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS-III Collaboration.
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- dark ages, reionization, first stars
- galaxies: ISM
- galaxies: dwarf
- galaxies: evolution
- galaxies: star clusters: general
- galaxies: starburst