Publications of the MPIfR
Optical & Infrared
Interferometry Group
J.-M. Deharveng, R. Albrecht, C.
Barbieri, J.C. Blades, A. Boksenberg, P. Crane, M.J. Disney, P.
Jakobsen, T.M. Kamperman, I.R. King, F. Macchetto, C.D. Mackay, F.
Paresce, G. Weigelt, D. Baxter, P. Greenfield, R. Jedrzejewski, A.
Nota, W.B. Sparks
The Massive Star Content of the Blue Dwarf
Galaxy IZw 36 from Faint Object Camera Observations
Astronomy and Astrophysics, v.288, p.413-424 (1994)
Abstract
We have observed the blue dwarf galaxy IZw 36 with the f/96 relay of
the
Faint Object Camera and have for the first time resolved massive stars,
using the broad band filters F175W, F342W, F430W and F480LP. We have
measured the fluxes of 143 of these objects and studied their
characteristics in color-magnitude diagrams. A few stars may be red
supergiants but their contribution to the integrated light is less than
5% in the F430W filter. The F175W-F430W color of the integrated stellar
population is redder than expected from the current burst of star
formation, suggesting therefore the presence of an older and unresolved
underlying population. The ultraviolet measurements combined with
synthetic photometry calculations allow us to place the massive stars
in
a bolometric magnitude vs. temperature diagram. In this diagram, the
stars are compared to evolutionary tracks for different stellar masses.
The current burst probably has an age less than 12 Myr. We infer an
Initial Mass Function, with a power-law slope in the range -1.7 to -2.6
for masses M>20Msun_. This is consistent with most of the
values reported for sites of star formation in the Galaxy and the
Magellanic Clouds and does not support the view of an IMF flattening at
low metallicity.
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