ALFALFA and WSRT Imaging of Extended HI Features in the Leo Cloud of Galaxies

TL;DR

This study uses ALFALFA and WSRT observations to reveal extensive, optically dark HI features in the Leo Cloud, highlighting complex interactions and the importance of wide-field surveys for understanding galaxy evolution.

Contribution

It provides new detailed HI maps of the Leo Cloud, revealing large-scale dark HI features and emphasizing the need for future wide-field surveys in galaxy group studies.

Findings

Detection of HI tails exceeding 600 kpc in extent.

Optically dark HI features contain significant portions of group HI mass.

Complex morphology of HI emission suggests dynamic interactions.

Abstract

We present ALFALFA HI observations of a well studied region of the Leo Cloud, which includes the NGC 3227 group and the NGC 3190 group. We detect optically dark HI tails and plumes with extents potentially exceeding 600 kpc, well beyond the field of view of previous observations. These HI features contain approximately 40% of the total HI mass in the NGC~3227 group and 10% in the NGC~3190 group. We also present WSRT maps which show the complex morphology of the extended emission in the NGC~3227 group. We comment on previously proposed models of the interactions in these groups and the implications for the scale of group processing through interactions. Motivated by the extent of the HI plumes, we place the HI observations in the context of the larger loose group, demonstrating the need for future sensitive, wide field HI surveys to understand the role of group processing in galaxy evolution.