AAS 201st Meeting, January, 2003
Session 116. Galaxies - Activating
Poster, Thursday, January 9, 2003, 9:20am-4:00pm, Exhibit Hall AB

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[116.09] Star Formation Histories of Three Gas-Rich dIrrs in the Centaurus A Group of Galaxies

B.J. Pritzl (NOAO), P.M. Knezek (WIYN), M. Grossi, M.J. Disney, R.F. Minchin (Cardiff), J.S. Gallagher, III (Univ. of Wisconsin), K.C. Freeman (RSAA, ANU), E. Tolstoy (Kapteyn Inst.), A. Saha (NOAO)

We present HST V&I photometry of three gas-rich dwarf irregular galaxies discovered in the recent HI Parkes All-Sky Survey (HIPASS) and a follow-up deep pointing with the same telescope of the Centaurus A region. All three galaxies have MHI/LB greater than about 2, have surface brightness in B dimmer than 24 mag/arcsec2, and are intrinsically as faint as known dwarfs in the Local Group (MV ~-11). We see that the three dIrrs differ from each other significantly in both their star formation histories, as indicated by their color-magnitude diagrams, and in their spatial distributions of stars. This is consistent with the wide range of star formation histories seen in Local Group dwarfs. We discuss the individual properties of each galaxy and compare them amongst each other, the Centaurus A group as a whole, and Local Group dwarf galaxies.

This reasearch was supported in part by NASA through grant number GO-09115.07 from the Space Telescope Science Institute.

The author(s) of this abstract have provided an email address for comments about the abstract: pritzl@noao.edu

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© 2002. The American Astronomical Soceity.