THE ASTRONOMICAL JOURNAL    VOLUME 114, NUMBER 4, PAGE 1458       OCTOBER 1997

           WFPC2 OBSERVATIONS OF THE CARINA DWARF SPHEROIDAL GALAXY

                              KENNETH J. MIGHELL

   Kitt Peak National Observatory, National Optical Astronomy Observatories,
                  P.O. Box 26732, Tucson, Arizona 85726-6732
                       Electronic mail: mighell@noao.edu


                                   ABSTRACT

     We present our analysis of Hubble Space Telescope Wide Field Planetary
     Camera 2 observations in F555W (~V) and F814W (~I) of the Carina dwarf
     spheroidal galaxy. The resulting V vs V-I color-magnitude diagrams
     reach V ~ 27.1 mag. The reddening of Carina is estimated to be E(V-I)
     = 0.08 +/- 0.02 mag. A new estimate of the distance modulus of Carina,
     (m-M)0 = 19.87 +/- 0.11 mag, has been derived primarily from existing
     photometry in the literature. The apparent distance moduli in V and I
     were determined to be (m-M)V = 20.05 +/- 0.11 mag and (m-M)I = 19.98
     +/- 0.12 mag, respectively. These determinations assumed that Carina
     has a metallicity of [Fe/H] = -1.9 +/- 0.2 dex. This space-based
     observation, when combined with previous ground-based observations, is
     consistent with (but does not necessarily prove) the following star
     formation scenario. The Carina dwarf spheroidal galaxy formed its old
     stellar population in a short burst (~< 3 Gyr) at about the same time
     the Milky Way formed its globular clusters. The dominant burst of
     intermediate-age star formation then began in the central region of
     the galaxy where stars formed for several billion years before the
     process of star formation became efficient enough in the outer regions
     of the galaxy to allow for the formation of large numbers of
     stars. There has been negligible star formation during the last few
     billion years. This observation provides evidence that at least some
     dwarf galaxies can have complex global star formation histories with
     local variations of the rate of star formation as a function of time
     and position within the galaxy. (c) 1997 American Astronomical
     Society.