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Fine–scale structure of the neutral ISM in M81

Published online by Cambridge University Press:  01 August 2006

Ioannis Bagetakos ,
Elias Brinks ,
Fabian Walter  and
Erwin de Blok
Ioannis Bagetakos
Affiliation:
Centre for Astrophysics Research, University of Hertfordshire, UK
Elias Brinks
Affiliation:
Centre for Astrophysics Research, University of Hertfordshire, UK
Fabian Walter
Affiliation:
Max–Planck–Institut für Astronomie, Heidelberg, Germany
Erwin de Blok
Affiliation:
Mount Stromlo Observatory, Australian National University, Canberra, Australia
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Abstract

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We present an analysis of the fine–scale structure of the neutral ISM as traced via the 21-cm line of atomic hydrogen (HI) in the nearby galaxy M 81. The data show a stunning amount of detail in the form of 330 expanding shells and holes in the neutral ISM of M 81. A comparison with similar structures found in two other spirals and two dwarf galaxies (M 31, M 33, IC 2574 and Holmberg II) reveals that the ISM in M 81 shares a lot of similarities with the two spirals, whereas the structure of its ISM is different to that in dwarf galaxies. The sizes of the HI holes in M 81 range from 80 pc (close to the resolution limit) to 600 pc; the expansion velocities can reach 20 km s−1; estimated ages are 2.5 to 35 Myrs and the energies involved range from 1050 to 3.5 x 1052 ergs. The amount of neutral gas involved is of order 104 to 106 solar masses.

Keywords

galaxies: individual (M 81) — galaxies: ISM — ISM: structure — radio lines: ISM
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 2 , Symposium S237: Triggered Star Formation in a Turbulent ISM , August 2006 , pp. 394
Copyright
Copyright © International Astronomical Union 2007

References

Brinks, E., Walter, F., Ott, J. 2002 Bloated Dwarfs: The Thickness of the HI Disks in Irregular Galaxies (ASP-CS), 275, 57Google Scholar
Walter, F., Brinks, E., de Blok, W. J. G., Thornley, M. D., Kennicutt, R. C. 2005, First Results from THINGS: The HI Nearby Galaxy Survey (ASP-CS), 331, 269Google Scholar