2025ApJ...991L..21K

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 ($\approx 5{3}_{-13}^{+16}$%) for the 32 GPs with O32 < 10 than that ($7.{1}_{-4.6}^{+9.4}$%) 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.