Speaker
Description
A key unknown in our understanding of cosmic reionization is the feedback mechanisms that enabled Lyman continuum (LyC) to escape in the earliest starbursts. One clue comes from Green Pea (GP) galaxies, the largest class of local (z ~ 0.3) LyC emitters. Most GPs show broad nebular emission-line wings of unknown origin, reaching 200-1000 km/s. The broad-wing velocity has been shown to correlate with the LyC escape fraction, indicating a link between LyC escape and feedback. We now investigate whether the broad wings of Low-redshift Lyman Continuum Survey (LzLCS) galaxies trace radiation-driven superwinds, as proposed by Komarova et al. 2021 (K21). Using Magellan/MIKE, WHT/ISIS, and VLT/X-Shooter spectra of 28 LzLCS galaxies, we relate the broad-wing parameters to galaxy and LyC properties. We find that broader, brighter wings are correlated with high star formation rate density, high $O_{32}$, young age, and low metallicity, consistent with radiation-driven winds. The broad-wing velocity and luminosity moreover correlate with the leaking LyC luminosity, in agreement with superwinds accelerated by LyC/Ly$\alpha$ photons. Indeed, based on the K21 model, we show that most of the observed broad-wing velocities can only be explained with H I opacity, or LyC/Ly$\alpha$-driving. So, radiation-accelerated, and in particular LyC/Ly$\alpha$-driven, superwinds may be an important feature tracing LyC escape. Given the abundance of metal-poor, high-ionization starbursts in the early universe revealed by JWST, such superwinds are likely to be common in the reionization era.
