Volume 375, Number 2, August IV 2001
|Page(s)||359 - 365|
|Section||Cosmology (including clusters of galaxies)|
|Published online||15 August 2001|
WFPC2 observations of two dwarf spheroidal galaxies in the M 81 group*
Special Astrophysical Observatory, Russian Academy of Sciences, N. Arkhyz, KChR, 369167, Russia
2 Isaac Newton Institute, SAO Branch Chile
3 Kitt Peak National Observatory, National Optical Astronomy Observatories, PO Box 26732, Tucson, AZ 85726, USA
4 Departamento de Fisica, Grupo de Astronomia, Universidad de Concepcion, Casilla 160-C, Concepcion, Chile
5 Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
6 Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195, USA
7 UCO/Lick Observatory, University of California at Santa Cruz, Santa Cruz, CA 95064, USA
8 Astronomical Observatory of Kiev University, 04053, Observatorna 3, Kiev, Ukraine
9 Astronomy Department, Wesleyan University, Middletown, CT 06459, USA
10 Department of Astronomy, University of Michigan, 830 Dennison Building, Ann Arbor, MI 48109, USA
Corresponding author: I. D. Karachentsev, firstname.lastname@example.org
Accepted: 17 May 2001
We have obtained HST WFPC2 and ground-based images of two low surface brightness dwarf spheroidal galaxies in the M 81 group, FM1 and KKH57. Their colour-magnitude diagrams show red giant branches with tips at and , respectively. The derived true distance moduli, and , agree well with the mean distance modulus of the M 81 group, . Absolute V magnitudes of the galaxies (-11.46 and -10.85), their colours ( and 0.80), and central surface brightnesses ( = 24.8 and 24.4 mag/) are in the range of other dSph companions of M 81, M 31, and Milky Way. With two new objects the maximum projected radius of the dwarf spheroidal subsystem around M 81 is 380 kpc.
Key words: galaxies: dwarf / galaxies: stellar content / galaxies: distances and redshifts / galaxies: individual: M 81 group: FM1 and KKH57
Based on observations made 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. Based in part on observations obtained with the Apache Point Observatory 3.5-meter telescope, which is owned and operated by the Astrophysical Research Consortium.
© ESO, 2001
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