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 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 &lt; 0.05, with 19 detections and 41 nondetections of H i 21 cm emission and with stellar masses in the range 10 6 –10 9 M ⊙ . We use the line luminosity ratio O32 ≡ [O iii ] λ 5007 + λ 4959/[O ii ] λ 3727,3729 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 ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>≈</mml:mo> <mml:mn>5</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>3</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>13</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>16</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> %) for the 32 GPs with O32 &lt; 10 than that ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>7</mml:mn> <mml:mo>.</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>1</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>4.6</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>9.4</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> %) for the 28 GPs with O32 &gt; 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 &gt; 10 are lower than the corresponding values for GPs with O32 &lt; 10. Earlier studies have shown that galaxies with O32 &gt; 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 Ly α emission signals, due to the paucity of H i in the strongest LyC and Ly α leakers.