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Title:
New HI Clouds In The M81/M82 Group
Authors:
Chynoweth, Katie M.; Langston, G.
Affiliation:
AA(Vanderbilt Univ), AB(National Radio Astronomy Observatory)
Publication:
American Astronomical Society, AAS Meeting #211, #97.10; Bulletin of the American Astronomical Society, Vol. 39, p.905
Publication Date:
12/2007
Origin:
AAS
Bibliographic Code:
2007AAS...211.9710C

Abstract

We present 5 newly discovered neutral hydrogen clouds in the M81/M82 group of galaxies, detected using the Robert C. Byrd Green Bank Telescope (GBT). All of the objects have properties similar to those of clouds previously found in our galaxy and other nearby galaxies. Based on 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 stabilized relics of ongoing interactions between galaxies in the group. Our results are inconsistent with models of primordial HI clouds falling into the cluster.

Previous studies of HI clouds have focused on the Milky Way and M31. Both galaxies are in a fairly relaxed state, and not currently interacting strongly with other galaxies. The M81/M82 group, in contrast, is highly unrelaxed and obviously interacting. Therefore, the study of HI clouds and other structures in the group is important in order to understand the full lifetime of these structures in relation to galaxy interactions. At 3.63 Mpc, the M81/M82 group is one of the closest groups, and because of its high declination and galactic latitude is an ideal location to search for analogs to local HVCs. We have searched the group in a 2° x 2° area, with a velocity range of greater than ± 500 km/s from any group galaxy, with a velocity resolution of 5.2 km/s. With a 7-sigma detection threshold of 8.4 x 10^5 M_Sun, we detect 5 HI clouds associated with the group, as well as associated filamentary HI structures. The clouds have masses between 10^6 and 10^7 M_Sun. The clouds are found only within small velocity differences from group members, and only at small angular separations.

This work was supported by the NRAO Graduate Summer Student Research Assistantship Program.

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