The atomic gas properties of Green Pea galaxies: Connections to Lyman continuum leakage

Abstract: We have used the Green Bank Telescope to search for H{\sc{i}} 21\,cm emission from 30 Green Pea galaxies (GPs) at $z\approx0.012-0.045$, obtaining 7 detections of H{\sc{i}} 21\,cm emission and 17 upper limits on the H{\sc{i}} mass. Including GPs from the literature, we obtain a sample of 60 GPs at $z<0.05$, with 19 detections and 41 non-detections of H{\sc{i}} 21\,cm emission, and with stellar masses in the range $10^6-10^9\,\rm{M_{\odot}}$. We use the line luminosity ratio O32~$\equiv$~[O{\sc iii}]$\lambda 5007+\lambda 4959$/[O{\sc ii}]$\lambda$3727,3729 as an indicator of Lyman continuum (LyC) leakage, and examine the dependence of the H{\sc{i}} properties of the 60 GPs on the O32 ratio. We obtain a far higher H{\sc{i}} 21\,cm detection rate ($\approx53^{+16}_{-13}$\%) for the 32 GPs with O32~$<10$ than that ($7.1^{+9.4}_{-4.6}$\%) for the 28 GPs with O32~$>10$. We find statistically significant evidence that the H{\sc{i}} mass, the H{\sc{i}}-to-stellar mass ratio, and the H{\sc{i}} gas depletion timescale of GPs with O32~$>10$ are lower than the corresponding values for GPs with O32~$<10$. Earlier studies have shown that galaxies with O32~$>10$ tend to show significant LyC leakage: our results indicate that this is due to the lack of H{\sc{i}} in such galaxies, with most of the H{\sc{i}} consumed in the starburst. Our results further suggest that H{\sc{i}} 21\,cm studies of the galaxies that reionized the Universe at $z\gtrsim6$ are likely to find an anti-correlation between the H{\sc{i}} 21\,cm and Ly$\alpha$ emission signals, due to the paucity of H{\sc{i}} in the strongest LyC and Ly$\alpha$ leakers.