Gemini Follow-up of two massive HI clouds discovered with the Australian Square Kilometer Array Pathfinder

TL;DR

This study uses Gemini observations to identify optical counterparts of two massive HI clouds near galaxy IC 5270, revealing high HI mass-to-light ratios and suggesting tidal interactions or ram pressure stripping as their origins.

Contribution

First optical counterparts of these HI clouds are identified, and their high HI mass-to-light ratio is measured, providing new insights into their nature and origin.

Findings

Optical counterparts detected with low surface brightness.

HI mass to light ratio is among the highest reported.

Tidal interactions or ram pressure stripping likely explain the clouds' origin.

Abstract

Using the Gemini Multi Object Spectrograph (GMOS) we search for optical counterparts of two massive (~10^9 solar masses) neutral hydrogen clouds near the spiral galaxy IC 5270, located in the outskirts of the IC 1459 group. These two HI clouds were recently discovered using the Australian Square Kilometer Array Pathfinder (ASKAP). Two low surface brightness optical counterparts to one of these HI clouds are identified in the new Gemini data that reaches down to magnitudes of ~27.5 mag in the g-band. The observed HI mass to light ratio derived with these new data, M_(HI)/L_g =242, is among the highest reported to date. We are also able to rule out that the two HI clouds are dwarf companions of IC 5270. Tidal interactions and ram pressure stripping are plausible explanations for the physical origin of these two clouds.