AAS Meeting #194 - Chicago, Illinois, May/June 1999
Session 72. Shells in the Global ISM
Display, Wednesday, June 2, 1999, 10:00am-6:30pm, Southwest Exhibit Hall

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[72.09] UV Observations of the Powering Source of the Expanding Supergiant Shell in IC2574

S. G. Stewart (USNO), F. Walter (RAIUB)

A multi-band analysis of the region containing the supergiant HI shell in dwarf galaxy IC2574 presents convincing evidence of a causal relationship between central star cluster, HI hole, and secondary star formation sites. Comparisons of the far-UV (1521 Å), H\alpha, X-ray, and HI morphologies suggest that the region is in an auspicious moment of triggered star formation. The derived properties of the HI shell and the star forming region support this scenario. The kinematic age of the HI shell is in agreement with the age of the central stellar cluster, as derived independently using far-UV observations. An estimate for the mechanical energy input from supernovae and stellar winds of the central stellar cluster made from far-UV photometry and the derived cluster age is a few times higher than the kinetic energy of the HI shell. The requisite energy input needed to create the HI shell, derived from the HI observations and the numerical models of Chevalier, is on the order of four times higher than the estimated energy input. Given the overwhelming observational evidence that the central cluster is responsible for the expanding HI shell, this discrepancy suggests that the required energy input, derived from the HI observations using this classical method, is overestimated.

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