FAST H I 21 cm study of blueberry galaxies

TL;DR

This study investigates the neutral hydrogen content of blueberry galaxies, revealing low gas fractions and short depletion times, which enhances understanding of star formation in local analogs of early universe galaxies.

Contribution

First H I 21 cm study of blueberry galaxies at low redshift, providing new insights into their gas content and star formation properties.

Findings

Detected H I in 2 out of 28 galaxies.

Blueberry galaxies have lower H I-to-stellar mass ratios.

Gas depletion times are about 0.5 Gyr, shorter than main-sequence galaxies.

Abstract

Green Peas (GPs) and blueberry galaxies (BBs) are thought to be local analogs ($z<$0.1) of high redshift Ly$\alpha$ 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 $\gtrsim$10$^{-8}$ yr$^{-1}$) BBs at $z\lesssim$0.05 with the Five-hundred-meter Aperture Spherical radio Telescope. We report significant H I detection towards two BBs namely J1026+0426 and J1132+0809, and discuss possible H I contribution from neighboring galaxies. The median 3$\sigma$ upper limit of $\sim$2.0$\times$10$^{8}$ M$_{\odot}$ 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 ($f_{\rm HI}$) than expected from $f_{\rm HI}$-sSFR and $f_{\rm HI}$-$M_{\ast}$ relations for main-sequence galaxies. The BBs also have a median 3$\sigma$ upper limit on H I gas depletion time scale ($\tau_{\rm HI}$) $\sim$0.5 Gyr, about 1 order of magnitude lower than $\tau_{\rm HI}$ for local main-sequence galaxies. We find a significantly low H I detection rate of 2/28 (7.1$^{+9.4}_{-4.6}$ \%) towards these galaxies, which is similar to previous H I studies of low redshift GPs of high ionization parameter indicator, O32 $\equiv$O[{\sc iii}]$\lambda$5007/O[{\sc ii}]$\lambda$3727 ratios $\gtrsim$10.