| Annu. Rev. Astron. Astrophys. 1997. 35:
101-136 Copyright © 1997 by . All rights reserved |
4.5. Normalization: Other Applications
Normalization is not restricted to kinematic distances of field galaxies or to TF parameters of cluster members. It is a useful approach to try when a range of values exists for some parameter on which the bias depends. The aim is to reveal the bias from the observed trend and to recognize the unbiased plateau. Teerikorpi (1986) inspected how selection affects the inner rings in galaxies as a distance indicator by constructing a normalized parameter from the quantity k, which indicates the dependence of the inner ring size on de Vaucouleurs's morphological galaxy class, as calibrated by Buta & de Vaucouleurs (1983). The analysis dropped Buta & de Vaucouleurs's Ho = 93 ± 4 to 75 ± 3 [or to 58 for the Sandage & Tammann (1975a) primary calibration], which is close to what happens with the TF indicator. There are two factors at work: 1. A relation between ring size and galaxy luminosity makes the former larger when the latter is larger. 2. At large distances, small rings cannot be measured. These are akin to a problem inherent in HII region size as a distance indicator, which is also clearly seen by normalization (Teerikorpi 1985). The possibilities of the inner ring method of Buta & de Vaucouleurs (1983) do not yet seem to be fully exploited.