Annu. Rev. Astron. Astrophys. 2010. 48: 673-710
Copyright © 2010 by . All rights reserved

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THE HUBBLE CONSTANT

Wendy L. Freedman & Barry F. Madore


Carnegie Observatories, 813 Santa Barbara St., Pasadena, CA 91101, USA


Abstract: Considerable progress has been made in determining the Hubble constant over the past two decades. We discuss the cosmological context and importance of an accurate measurement of the Hubble constant, and focus on six high-precision distance-determination methods: Cepheids, tip of the red giant branch, maser galaxies, surface-brightnes fluctuations, the Tully-Fisher relation and Type Ia supernovae. We discuss in detail known systematic errors in the measurement of galaxy distances and how to minimize them. Our best current estimate of the Hubble constant is 73 ± 2 (random) ± 4 (systematic) km s-1 Mpc-1. The importance of improved accuracy in the Hubble constant will increase over the next decade with new missions and experiments designed to increase the precision in other cosmological parameters. We outline the steps that will be required to deliver a value of the Hubble constant to 2% systematic uncertainty and discuss the constraints on other cosmological parameters that will then be possible with such accuracy.


Key words : Cosmology, Distance Scale, Cepheids, Supernovae, Age of Universe


Table of Contents

INTRODUCTION

EXPANSION OF THE UNIVERSE: THE COSMOLOGICAL CONTEXT

MEASUREMENT OF DISTANCES
Cepheid Distance Scale
Tip of the Red Giant Branch (TRGB) Method
Maser Galaxies
Surface Brightness Fluctuation (SBF) Method
Tully-Fisher Relation
Type Ia Supernovae

THE HUBBLE SPACE TELESCOPE (HST) KEY PROJECT
Systematics on Ho at the End of the Key Project and a Decade Later

OTHER METHODS FOR DETERMINING Ho
Gravitational Lens Time Delays and Ho
The Sunyaev-Zel'dovich (SZ) Effect and Ho
Measurements of Anisotropies in the Cosmic Microwave Background

AGE OF THE UNIVERSE

WHY MEASURE Ho TO HIGHER ACCURACY?
Constraints on Dark Energy
Constraints on the Neutrino Mass
Measuring Ho to ± 2%

FUTURE IMPROVEMENTS

SUMMARY POINTS

DISCLOSURE STATEMENT

REFERENCES

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