HST/NICMOS Observations of M82 |
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| Authors: | Almudena Alonso-Herrero Marcia J Rieke George H Rieke Douglas M Kelly |
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| Institution: | (1) Steward Observatory, the, University of Arizona, Tucson, AZ 85721, USA |
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| Abstract: | The irregular galaxy M82 is known as the archetypal starburst galaxy. Its proximity (3.5 Mpc) makes this galaxy an ideal laboratory
for studying the properties of its starburst. The detailed morphology of the FeII] 1.644 μm and emission Paα (at 1.87 μm) is revealed by the NICMOS images. The peak of the 2.2 μm continuum brightness(evolved population) lies very
close to the dynamical centre. Most of the Paα emission (which traces the young population) is distributed in a ring of star formation (with a `hole' lacking line emission
at the centre of the galaxy). These observations support the scenario in which the starburst in M82 is propagating outwards.
It has long been suggested that the FeII] emission in starburst galaxies can be used as a measure of supernova (SN) activity.
M82 shows a large number of radio supernova remnants (SNRs), approximately 50, lying in the plane of the galaxy. The comparison
of the positions of the bright compact FeII] emitting regions with the location of the radio SNRs shows that there is no one-to-one spatial correspondence between
the two emissions, suggesting that the radio and FeII] emissions trace two populations of SNRs with different ages. Young
(a few hundred years) SNRs are best traced by their radio emission, whereas the FeII] stage lasts for at least a few 104 yr. The compact FeII] sources contribute only some 20 % of the total FeII] emission observed in M82. However, much of the remaining unresolved
FeII] emission in the plane of the galaxy may arise from SNRs that expanded and merged into a general interstellar medium
within a few 104 yr. Presumably, as much as 70% of the total extinction-corrected FeII]1.644 μm in M82 is associated with SNRs. The extended
and diffuse FeII] component in M82 seems to be related with the superwind above and below the disc of the galaxy.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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