\documentstyle{preprint}
\begin{document}

\title{GLOBULAR CLUSTERS AS DISTANCE INDICATORS}

\author{Bradley C.\ Whitmore\\
\\
Space Telescope Science Institute\\
\\
3700 San Martin Drive\\
\\
Baltimore, MD, 21218\\
\\
whitmore@stsci.edu}

\pub{{\em the proceedings of}\\
~\\
The Extragalactic Distance Scale,\\
~\\
{\em held May 1996 in Baltimore, MD}}

\maketitle

\begin{abstract}
The globular cluster luminosity function (GCLF) for bright elliptical
galaxies can be approximately represented as a Gaussian distribution,
with a mean value \mv\ = --7.21 $\pm$ 0.26 mag and a width $\sigma$ =
1.35 $\pm$ 0.05 mag.  Most of the uncertainty in \mv\ is due to the
Cepheid distance scale to the Virgo cluster used to determine the
zeropoint.  The intrinsic dispersion in \mv\ is $\approx$ 0.12 mag for
bright ellipticals, making it competitive with the best distance
indicators.  The value of \mv\ appears to be nearly universal, with
only a weak second-order dependence on luminosity clearly demonstrated
and other second-order dependencies possible at about the 0.1--0.2
mag level (e.g., Hubble type, color, and environment).  The Hubble
Space Telescope provides a significant improvement in our ability to
measure \mv, with limiting magnitudes for one orbit observations more
than two magnitudes beyond the turnover in the GCLF for galaxies in
the Virgo cluster.  Historical estimates of the Hubble constant based
on the GCLF have been surprisingly stable for nearly 30 years, with a
mean H$_0$ = 72 km s$^{-1}$ Mpc$^{-1}$. At present the best estimate
can probably be determined using seven galaxies in the Fornax cluster,
yielding a value of H$_0$ = 82 $\pm$ 13 km s$^{-1}$
Mpc$^{-1}$. Several hundred high quality GCLF's should be published in
the next few years, making globular clusters one
of the most important distance indicators during the next decade.

\end{abstract}