Other
Scientific paper
Jan 1999
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999iaus..192..402h&link_type=abstract
The stellar content of Local Group galaxies, Proceedings of the 192nd symposium of the International Astronomical Union held in
Other
Scientific paper
We investigate dark matter (DM) content in the Local Group dwarf spheroidal galaxies (dSphs), examining the correlation among their physical quantities. To emphasize the possibility of DM content in dSphs, we compare two extreme models for their internal kinematics: (1) tidal model (mass of a dSph is estimated with luminous mass, since the large velocity dispersions of the dSphs are attributed to tidal force by the Galaxy), and (2) DM model (mass of a dSph is estimated with virial mass, since the velocity dispersion is considered to reflect the DM potential). In the context of tidal model, there is a correlation between surface brightness of dSphs and tidal force exerted by the Galaxy. This is pointed out by some previous researches. On the other hand, in the DM model, we barely find correlation between the above two quantities. Indeed, we cannot find clear correlation between them when the mass of dSphs is estimated from the virial theorem. Therefore, we never judge which of the two models is more promising for the dSphs. Performing the more precise examination of tidal disruption, we find that tidal force disrupts the dSphs only by near passage of perigalactic distance (˜20 kpc), and that the timescale for tidally perturbed stars to escape is much shorter than orbital periods of the dSphs. Especially, the latter point does not imply that tidally perturbed dSphs exist as an assembly. Thus, we insist that gravitational field of DM is necessary to bind the dSphs with large velocity dispersion.
Hirashita Hiroyuki
Kamaya Hideyuki
Takeuchi Tadashi
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