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For refcode 1998ApJ...504L..83H:
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Copyright by American Astronomical Society. Reproduced by permission
1998ApJ...504L..83H Physical Interpretation of the Mass-Luminosity Relation of Dwarf Spheroidal Galaxies HIROYUKI HIRASHITA, TSUTOMU T. TAKEUCHI, AND NAOYUKI TAMURA Department of Astronomy, Faculty of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan; hirasita@kusastro.kyoto-u.ac.jp Received 1998 May 26; accepted 1998 June 29; published 1998 August 19 ABSTRACT We discuss a physical interpretation of the relation between M_vir_/L and M_vir_ of dwarf spheroidal galaxies (dSphs), where M_vir_ and L are the virial mass and the total luminosity of a dSph, respectively. We used 11 dSphs in the Local Group as the sample. We find two distinct sequences on the M_vir_/L-M_vir_ plane: M_vir_/L is proportional to M_vir_^2.0^ for dSphs with M_vir_ < 10^8^ M_sun_, whereas M_vir/L is approximately constant for M_vir_ > 10^8^ M_sun_. A "discontinuity" is seen at M_vir_ ~ 10^8^ M_sun_. We interpret the discontinuity as the threshold for the gas in dSphs to be blown away by successive supernovae. If a dSph has virial mass (most of which is dark mass) less than 10^8^ M_sun_, the gas is blown away, while in a dSph of larger mass, the deep potential well prevents the blow- away mechanism from working effectively. Thus, a large mass ratio of dark matter to baryonic matter (i.e., large M_vir_/L) is realized in a low-mass (M_vir_ < 10^8^ M_sun_) dSph through gas depletion, whereas M_vir_/L becomes lower in high-mass (M_vir_ > 10^8^ M_sun_) dSphs. We further make an attempt to explain the above relation for the low-mass dSphs, M_vir_/L is proportional to M_vir_^2.0^, based on an estimate of cooling time, using the scaling laws of virial temperature, virial mass, and radius of a dSph and assuming that the heating by OB star radiation terminates the star formation activity. We succeed in deriving the above relation for the mass-to-light ratio and luminosity. Subject headings: galaxies: evolution-galaxies: fundamental parameters- Local Group
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