HI Imaging of a Blueberry Galaxy Suggests a Merger Origin

TL;DR

This study presents interferometric HI imaging of a Blueberry galaxy, revealing a merger history and high star-formation efficiency, which enhances understanding of their role as local analogues of high-redshift Lyα emitters.

Contribution

First HI 21 cm imaging of a Blueberry galaxy, showing merger evidence and high star-formation efficiency, linking mergers to starburst activity in BBs.

Findings

HI mass of approximately 3×10^8 solar masses

HI-to-stellar mass ratio of about 2.4

Offset of 2 kpc between HI peak and optical center

Abstract

Blueberry galaxies (BBs) are fainter, less massive, and lower redshift counterparts of the Green pea galaxies. They are thought to be the nearest analogues of the high redshift Lyman Alpha (Ly$\alpha$) emitters. We report the interferometric imaging of HI 21 cm emission from a Blueberry galaxy, J1509+3731, at redshift, z = 0.03259, using the Giant Metrewave Radio Telescope (GMRT). We find that this Blueberry galaxy has an HI mass of $M_{\text{HI}} \approx 3\times 10^8 \, M_{\odot}$ and an HI-to-stellar mass ratio $M_{\text{HI}}/M_* \approx$ 2.4. Using SFR estimates from the H$\beta$ emission line, we find that it has a short HI depletion time scale of $\approx 0.2$ Gyr, which indicates a significantly higher star-formation efficiency compared to typical star-forming galaxies at the present epoch. Interestingly, we find an offset of $\approx 2$ kpc between the peak of the HI 21 cm emission and the optical centre which suggests a merger event in the past. Our study highlights the important role of mergers in triggering the starburst in BBs and their role in the possible leakage of Lyman-$\alpha$ and Lyman-continuum photons which is consistent with the previous studies on BB galaxies.