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Astron. Astrophys. 352, 399-405 (1999)


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The dwarf spheroidal galaxy DDO 44: stellar populations and distance *

I.D. Karachentsev 1, M.E. Sharina 1, E.K. Grebel **  2, A.E. Dolphin 2,3, D. Geisler 4, P. Guhathakurta 5, P.W. Hodge 2, V.E. Karachentseva 6, A. Sarajedini 7 and P. Seitzer 8

1 Special Astrophysical Observatory, Russian Academy of Sciences, N. Arkhyz, KChR, 357147, Russia
2 Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195, USA
3 Kitt Peak National Observatory, National Optical Astronomy Observatories, P.O. Box 26732, Tucson, AZ 85726, USA
4 Departamento de Física, Grupo de Astronomía, Universidad de Concepción, Casilla 160-C, Concepción, Chile
5 UCO/Lick Observatory, University of California at Santa Cruz, Santa Cruz, CA 95064, USA
6 Astronomical Observatory of Kiev University, Observatorna 3, 254053, Kiev, Ukraine
7 Astronomy Department, Wesleyan University, Middletown, CT 06459, USA
8 Department of Astronomy, University of Michigan, 830 Dennison Building, Ann Arbor, MI 48109, USA

Received 8 June 1999 / Accepted 12 October 1999

Abstract

We have ground-based and HST WFPC2 imaging of the nearby low surface brightness dwarf spheroidal galaxy DDO 44. For the first time DDO 44 was resolved into stars. The resulting color-magnitude diagram for about 1290 stars show the red giant branch with a tip at [FORMULA], which yields the distance [FORMULA] Mpc consistent with membership of DDO 44 in the NGC 2403 group. The linear separation of DDO 44 from NGC 2403 is 75 kpc on the sky and [FORMULA] kpc along the line of sight. The relationship between the dwarf galaxy's absolute magnitude, [FORMULA], the central surface brightness, [FORMULA] mag arcsec-2, and the mean metallicity, [Fe/H] = -1.7 dex follow the trend for other nearby dwarf spheroidal galaxies. One globular cluster candidate has also been identified in DDO 44.

Key words: galaxies: dwarf – galaxies: fundamental parameters – galaxies: individual: DDO 44 – galaxies: photometry – galaxies: abundances

* Based on observations made with the BTA telescope at the Special Astrophysical Observatory operated by the Russian Academy of Sciences and with the NASA/ESA Hubble Space Telescope. The Space Telescope Science Institute is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555.
** Hubble Fellow

© European Southern Observatory (ESO) 1999

Online publication: December 2, 1999

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