The Atomic Gas Properties of Green Pea Galaxies: Connections to Lyman Continuum Leakage

We have used the Green Bank Telescope to search for H i 21 cm emission from 30 Green Pea galaxies (GPs) at z ≈ 0.012–0.045, obtaining 7 detections of H i 21 cm emission and 17 upper limits on the H i mass. Including GPs from the literature, we obtain a sample of 60 GPs at z < 0.05, with 19 detections and 41 nondetections of H i 21 cm emission and with stellar masses in the range 106–109M⊙. We use the line luminosity ratio O32 ≡ [O iii]λ5007 + λ4959/[O ii]λ3727,3729 as an indicator of Lyman continuum (LyC) leakage and examine the dependence of the H i properties of the 60 GPs on the O32 ratio. We obtain a far higher H i 21 cm detection rate ( %) for the 32 GPs with O32 < 10 than that ( %) for the 28 GPs with O32 > 10. We find statistically significant evidence that the H i mass, the H i-to-stellar mass ratio, and the H 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 i in such galaxies, with most of the H i consumed in the starburst. Our results further suggest that H i 21 cm studies of the galaxies that reionized the Universe at z ≳ 6 are likely to find an anticorrelation between the H i 21 cm and Lyα emission signals, due to the paucity of H i in the strongest LyC and Lyα leakers.