Annu. Rev. Astron. Astrophys. 1997. 35: 101-136
Copyright © 1997 by . All rights reserved

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OBSERVATIONAL SELECTION BIAS AFFECTING THE DETERMINATION OF THE EXTRAGALACTIC DISTANCE SCALE

P. Teerikorpi


Tuorla Observatory, Turku University, Piikkiö, FIN-21500 Finland; e-mail: pekkatee@sara.cc.utu.fi


Abstract. The influence of Malmquist bias on the studies of extragalactic distances is reviewed, with brief glimpses of the history from Kapteyn to Scott. Special attention is paid to two kinds of biases, for which the names Malmquist biases of the first and second kind are proposed. The essence of these biases and the situations where they occur are discussed.

The bias of the first kind is related to the classical Malmquist bias (involving the "volume effect"), while the bias of the second kind appears when standard candles are observed at different (true) distances, whereby magnitude limit cuts away a part of the luminosity function. In particular, study of the latter bias in distance indicators such as Tully Fisher, available for large fundamental samples of galaxies, allows construction of an unbiased absolute distance scale in the local galaxy universe where approximate kinematic relative distances can be derived. Such investigations, using the method of normalized distances or of the Spaenhauer diagram, support the linearity of the Hubble law and make it possible to derive an unbiased value of the Hubble constant.


Key Words: galaxies, Tully-Fisher relation, Malmquist bias, distance scale, cosmology


Table of Contents

INTRODUCTORY REMARKS
Stars and Galaxies are Gathered from the Sky and not from Space
Distances and Hubble Law
Aim of the Present Review

SOME HISTORY FROM KAPTEYN TO SCOTT
Kapteyn's Problem I and Problem II
The Classical Malmquist Bias
The Scott Effect

TWO KINDS OF MALMQUIST BIAS
Biases of the First and Second Kind
Situations Where the First or General Malmquist Bias Appears
Situations Where the Second Malmquist Bias Is Important

ATTEMPTS TO OVERCOME THE SECOND KIND OF BIAS
The Bias-Free Redshift Range
The Method of Normalized Distances for Field Galaxies
Spaenhauer Diagrams and the Triple-Entry Correction by Sandage
The Cluster Incompleteness Bias
Normalization: Other Applications

THE INVERSE TULLY-FISHER RELATION AND THE SECOND KIND OF BIAS
The Ideal Case of the Inverse Relation
Problems in the Use of the Inverse Relation

THE BIAS OF THE FIRST KIND IN DIRECT AND INVERSE TF DISTANCE MODULI

MALMQUIST BIAS AND THE GREAT ATTRACTOR

SOME RECENT DEVELOPMENTS
Sosies Galaxies and Partial Incompleteness
About the Unbiased Plateau in the MND
Gould's Effect
Simulation Approach

CONCLUDING REMARKS

REFERENCES

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