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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[116.14] The Recent Evolution Of The Dwarf Starburst Galaxy NGC 625 From Hubble Space Telescope Imaging

J.M. Cannon (University of Minnesota), R.C. Dohm-Palmer (University of Minnesota & Macalester College), E.D. Skillman (University of Minnesota), D.J. Bomans (Ruhr-Univ. Bochum, Astronomy Institute), S. Cote (HIA/NRCC), B.W. Miller (Gemini Observatory)

We present new HST/WFPC2 imaging of the nearby dwarf starburst galaxy NGC 625. Deep images in V and I reach limiting magnitudes of ~ 26.5 and 26, respectively. Narrow band images in H Alpha and H Beta allow us to address the internal extinction within the starburst regions. We derive a tip of the red giant branch (TRGB) distance of 3.89 +/- 0.22 Mpc, in excellent agreement with the value derived from the empirical distance-velocity relation within the Sculptor Group. We find an older stellar population that is relatively smoothly distributed throughout the galaxy, and we also detect a very red, extended AGB branch, similar to that found in the Local Group dIrr NGC 6822. From the young stars, we derive the recent star formation history of NGC 625; it is found that the recent level of star formation has been significantly elevated compared to the average value over much of the galaxy's history. We speculate on the possible causes of the present burst of star formation in this apparently isolated galaxy.

This research was supported, in part, by NASA through grants GO-8708, NAG5-9221 and NGT 5-50345.

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