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Date and Time of the Query: 2019-05-19 T09:58:10 PDT
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For refcode 2000PASP..112..529V:
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Copyright by Astronomical Society of the Pacific. Reproduced by permission
2000PASP..112..529V Updated Information on the Local Group SIDNEY VAN DEN BERGH Dominion Astrophysical Observatory, National Research Council, 5071 West Saanich Road, Victoria, BC V8X 4M6, Canada; Sidney.vandenbergh@hia.nrc.ca Received 1999 November 22; accepted 1999 December 22 ABSTRACT - The present note updates the information published in my recent monograph on The Galaxies of the Local Group. Highlights include (1) the addition of the newly discovered Cetus dwarf spheroidal as a certain member of the Local Group; (2) an improved distance for the Sagittarius dwarf irregular galaxy (SagDIG), which now places this object very close to the edge of the Local Group zero-velocity surface; (3) more information on the evolutionary histories of some individual Local Group members; and (4) improved distance determinations to, and luminosities for, a number of Local Group members. These data increase the number of certain (or probable) Local Group members to 36. The spatial distribution of these galaxies supports Hubble's claim that the Local Group "is isolated in the general field." Currently available evidence suggests that star formation continued much longer in many dwarf spheroidals than it did in the main body of the Galactic halo. It is suggested that "young" globular clusters, such as Ruprecht 106, might have formed in now defunct dwarf spheroidals. Assuming SagDIG, which is the most remote Local Group galaxy, to lie on, or just inside, the zero-velocity surface of the Local Group yields a dynamical age > 17.9 +/- 2.7 Gyr. However, this value is meaningful only if the outer regions of the local Group are in virial equilibrium.
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