Neutral Hydrogen Clouds in the M81/M82 Group

TL;DR

This study used the Green Bank Telescope to discover five new neutral hydrogen clouds in the M81/M82 galaxy group, suggesting they are remnants of galaxy interactions.

Contribution

First detection of neutral hydrogen clouds in the M81/M82 group, indicating ongoing galactic interactions and enriching understanding of intergalactic medium.

Findings

Detected 5 new HI clouds associated with the group.

Identified filamentary HI structures indicating interactions.

Cloud velocities suggest they are relics of galaxy interactions.

Abstract

We have observed a 3 degree x 3 degree area centered on the M81/M82 group of galaxies using the Robert C. Byrd Green Bank Telescope (GBT) in a search for analogs to the High Velocity Clouds (HVCs) of neutral hydrogen found around our galaxy. The velocity range from -605 to -85 km/s and 25 to 1970 km/s was searched for HI clouds. Over the inner 2 degrees x 2 degrees the 7-sigma detection threshold was 9.6 x 10^5 M_sun. We detect 5 previously unknown HI clouds associated with the group, as well as numerous associated filamentary HI structures, all lying in the range -105 < V_helio < +280 km/s. From the small angular distance of the clouds to group members, and the small velocity difference between group members and clouds, we conclude that the clouds are most likely relics of ongoing interactions between galaxies in the group.