FAST H i 21 cm Study of Blueberry Galaxies

Abstract

Green Peas (GPs) and blueberry galaxies (BBs) are thought to be local analogs ( z < 0.1) of high redshift Ly α emitters. H i study of these can help us understand the star formation in the primordial Universe. In this Letter, we present the results of H i 21 cm study of 28 high specific star formation rate (sSFR ≳ 10 ^−8 yr ^−1 ) BBs at z ≲ 0.05 with the Five-hundred-meter Aperture Spherical radio Telescope. We report significant H i detection towards two BBs, namely J1026+0426 and J1132+0809, and discuss possible H i contribution from neighboring galaxies. The median 3 σ upper limit of ∼2.0 × 10 ^8 M _⊙ was obtained on H i mass for galaxies with nondetections. We find BBs tend to have lower H i -to-stellar-mass ratio or gas fraction ( f _H _i ) than expected from f _H _i –sSFR and f _H _i – M _* relations for main-sequence galaxies. The BBs also have a median 3 σ upper limit on H i gas depletion timescale ( τ _H _i ) ∼ 0.5 Gyr, about 1 order of magnitude lower than τ _H _i for local main-sequence galaxies. We find a significantly low H i detection rate of 2/28 (7.1 ${}_{-4.6}^{+9.4}$ %) towards these galaxies, which is similar to previous H i studies of low redshift GPs of high ionization parameter indicator, O32 ≡ O[ iii ] λ 5007/O[ ii ] λ 3727 ratios ≳10.

Keywords

• Blue compact dwarf galaxies
• Starburst galaxies
• Galaxies
• Radio spectroscopy
• H I line emission