| Abstract | HST F555W and F814W photometry of a portion of the WLM galaxy is presented. The distance modulus is determined via fitting of the entire color-magnitude diagram to be (m-M)0=24.88+/-0.09, which is consistent with the red giant branch tip distance. The galaxy's measurable star formation history appears to have begun no more than 12 Gyr ago, with about half of WLM's total star formation (by mass) formed before 9 Gyr ago. The star formation rate gradually decreased, until a recent increase in activity starting between 1 and 2.5 Gyr ago. This is still continuing to the present time and is concentrated in the bar of the galaxy, as shown by the difference in recent star formation rates in the three WF chips. Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. |
