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DETERMINATION OF THE HUBBLE CONSTANT FROM THE GRAVITATIONAL STABILITY
CRITERION OF THE GASEOUS DISKS, by A.V.Zasov, D.V.Bizyaev.


Semi-empirical method of estimation of the Hubble constant
develops which was proposed earlier by one of the authors (A.Zasov).
Following proposition has been put forward: a total surface density of
gas at radius $R_H$, where the mean densities of atomic ($\sigma_{HI}$)
and molecular ($\sigma_{H_2}$) hydrogen are equal, corresponds (or
proportional to) the critical gas density $\sigma_c$ for gravitational
stability of gaseous disk. As far as $\sigma_c$ depends on the
adopted distance to galaxy, this assumption allows to estimate the
distance if the $R_H$ and the rotation curve are known from
observations. For five nearby spiral galaxies with known distances the
proportionality factor $k \,=\sigma_g/\sigma_c$ is estimated to be $1.0
\cdot c_g / 10 km/s$, where $c_g$ is the velocity dispersion of gas.
Distances found by this method for 11 field galaxies give $H_o \,=
76\, \pm 8\, km/s/Mpc$ (Virgocentric flow is taken into account).
Mean distance to six galaxies in the outer parts of Virgo cluster is
found to be $14.8 \pm 3$ Mpc. Tight correlation between $R_H$ and the radius
where $\sigma_g = \sigma_c$ shows that the gravitational instability
plays key role in the origin of molecular gas in the disks of
late-type spiral galaxies.