What we know about IC10... and what we want to know

IC10 is an irregular galaxy, which means it does not fit into Hubble's classification of spiral or elliptical galaxies. It is in the Local Group. There have been varying estimates of its distance in recent years, but I have used 820 kpc, as calculated by Saha et. al. (1996)[6]. It is moving toward us with a systemic velocity of -345 km/s (Wilcots & Miller 1998)[12].

It is a starburst galaxy, which means that it has a high rate of star formation compared to other galaxies with similar HI masses. IC10's star formation rate is ~0.15 solar masses per year, as measured by Thronson et. al. (1996)[9].

Previous studies of IC10 have noted a number of holes and expanding shells in the HI, and it is suspected that they are caused by outflows of energy from stars, either from supernovae or stellar winds. This is a plausible claim, since studies of other galaxies suggest that the energy output from star formation has a significant impact on the dynamics of the ISM, leading to further star formation and galactic evolution. However, due to interactions between structures in the ISM, the energy put out by stars seems to be partially dissipated rather than being transferred fully to the gas. (See Dopita et. al. 1985[1] ; Scalo & Chappell 1999[7].)

We can test this idea with data from the VLA on HI distribution. If we can locate expanding shells of gas, we can estimate their mass and velocity and thereby determine their kinetic energy. We can then compare this energy with the energy associated with known regions of star formation within the shells.

In addition, we can study the peculiar kinematics of the galaxy. From previous observations, IC10 appears to be surrounded by a very large envelope of HI with an unusual rotation curve - its outer disk appears to be counter-rotating (Wilcots & Miller 1998)[12].



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