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Date and Time of the Query: 2019-05-24 T00:17:19 PDT
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For refcode 1996AstL...22...71Z:
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Copyright by American Institute of Physics. 1996AstL...22...71Z An Estimate of the Hubble Constant Using a Criterion for Gravitational Stability of Gaseous Disks A. V. Zasov and D. V. Bizyaev Sternberg Astronomical Institute, Universitetskii pr 13, Moscow 119899 Russia Receive May 26,1995; in final form, August 10,1995 Abstract-A semi-empirical method for determination of the Hubble constant H_0_ using a criterion for the gravitational stability of the gaseous disks of galaxies, proposed earlier by Zasov, is developed. The premise is considered that at the distance R_H_ from the center of a galaxy at which the azimuthally averaged surface densities of atomic ({sigma}_HI_) and molecular ({sigma}_H_2__) hydrogen are equal, the total surface density of gas ({sigma}_c_) is equal to or proportional to the critical density ({sigma}_c_) for gravitational stability of the gaseous disk. Since the estimate of {sigma}_c_ depends on the adopted distance to the galaxy, this condition allows one to estimate the distance based on a experimental determination of R_H_ and the shape of the rotation curve. For five nearby spiral galaxies for which the distances are considered to be known, the coefficient of proportionality {sigma}_g_/{sigma}_c_ at R = R_H_ is found to be 1.)c_g_/10 km s^-1^, where c_g_ is the dispersion velocity for the clouds of gas. Estimates of the distances to 11 Sb-Scd field galaxies lead to the value H_0_ = 76 +/- 8 km s^-1^ Mpc^-1^ (with allowance for motion toward Virgo). The mean distance to five galaxies located at the periphery of the Virgo cluster is found to be 14.8 +/- 3 Mpc. The close correlation between R_H_ and the radius at which {sigma}_g_ = {sigma}_c_ is evidence of the defining role of gravitational instability in the formation of molecular gas in the disks of late-type spiral galaxies.
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