Properties of the extremely HI-massive galaxy HIZOA J0836-43

TL;DR

This paper investigates the properties of the extremely HI-massive galaxy HIZOA J0836-43, revealing its starburst nature, early stellar mass building, and environment, providing insights into such rare galaxies and their evolution.

Contribution

It presents a detailed multi-wavelength analysis of HIZOA J0836-43, a nearby HI-rich galaxy, highlighting its starburst activity and environmental context, which are novel insights for such massive HI galaxies.

Findings

HIZOA J0836-43 is a luminous starburst galaxy at an early stage of stellar mass assembly.

It resides in a low-density environment with many low stellar mass galaxies.

It is not of low surface brightness, unlike other giant HI galaxies.

Abstract

Little is known about the properties of extremely massive HI-galaxies. They are extremely scarce and are - according to hierarchical structure formation - only forming now (z < 1). The forthcoming deep HI SKA Pathfinders surveys will uncover many more of them. This will lead to a better understanding of their evolution and frequency, and the shape of the bright end of the HI mass function. The recently discovered galaxy HIZOA J0836-43 is one of the most HI-rich galaxies (M(HI)=7.5 x 10^10Msun - and the nearest of its kind. As such it is an ideal local probe of these elusive galaxies. Results from a detailed investigation in the near- (IRSF) and far-infrared (Spitzer) of this local HI-massive galaxy are presented. Unlike other giant HI galaxies, it is not of low surface brightness. The galaxy is found to be a luminous starbursting galaxy at an unexpected early stage of stellar mass building, more typical of star-forming galaxies at higher redshift (z~0.7). With regard to its environment, hence possible clues to its formation, the near infrared imaging survey finds HIZOAJ0836-43 to lie in a region underdense in L* galaxies - consistent with the observation that HI-massive galaxies are preferentially found in low density regions - in the presence, however, of an uncommonly large number of low stellar mass galaxies.