Copyright © 1997 by Annual Reviews. All rights reserved
|
| Annu. Rev. Astron. Astrophys. 1997. 35:
101-136 Copyright © 1997 by Annual Reviews. All rights reserved |
In this section I gather together some of the most recent results and ideas concerning the Malmquist biases of the first and second kind.
8.1. Sosies Galaxies and Partial Incompleteness
Witasse & Paturel
(1997)
have discussed the effect of partial incompleteness on the derivation of
the Hubble constant, when Kapteyn's Equation 1 is used to make the bias (of
the second kind) correction at each redshift. They inspected the
completeness of their sample of sosies galaxies ["look-alike"; the
distance indicator introduced by
Paturel (1984)]
and concluded that there is partial incompleteness starting at B
= 12.0 mag, relative to the assumed 100.6m law. (Another
possibility, which
Witasse & Paturel
(1997)
mention for the first time in this kind of work, is that the apparent
incompleteness may actually reflect a fractal distribution of galaxies.)
Inserting the empirical
selection probability into Kapteyn's formula, they could reduce the Hubble
constant by about 15%, as compared with the assumption of a complete sample
and obtained Ho
60 from 181 sosies
galaxies. In comparison,
Sandage (1996b)
applied Paturel's look-alike idea to the sosies galaxies of M31 and M101
and derived by the Spaenhauer method Ho
50.