Invited review in "The New Cosmology", eds. R. E. Allen, D. V. Nanopoulos, and C. N. Pope, in press.
astro-ph/0411244

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CONSTRAINTS ON FIELD GALAXY HALOS FROM WEAK LENSING AND SATELLITE DYNAMICS

Tereasa G. Brainerd


Boston University, Institute for Astrophysical Research, 725 Commonwealth Ave., Boston, MA 02215


Abstract. Here I summarize constraints on the nature of the dark matter halos of field galaxies that have been obtained from the most recent investigations of (i) weak galaxy-galaxy lensing and (ii) the dynamics of satellite galaxies in orbit about large host galaxies. Both of these techniques are statistical in their nature (i.e., large samples of galaxies are required to obtain a "signal"), but since they have inherently different selection biases and systematic errors, they are quite complementary to each other. Results of work over the last several years on weak lensing and satellite dynamics is revealing a remarkably consistent picture regarding the dark matter halos of bright field galaxies (L gtapprox L*). The halos extend to large physical radii (gtapprox 150 h-1 kpc) and are flattened in projection on the sky, there is a marked difference in the depths of the potential wells of early-type galaxies and late-type galaxies, and the velocity dispersion profiles of the halos, sigmav(rp), decrease at large projected radii. All of these are expected to hold true in a cold dark matter universe and, while neither technique can address the possible small-scale (ltapprox 5 h-1 kpc) conflicts between cold dark matter and observed galaxies, on scales gtapprox 50 h-1 kpc both techniques yield results that are consistent with each other, and with the predictions of cold dark matter.


Table of Contents

INTRODUCTION

THE SURVEYS
COMBO-17: Galaxy-Galaxy Lensing
RCS: Galaxy-Galaxy Lensing
SDSS: Galaxy-Galaxy Lensing & Satellite Dynamics
2dFGRS: Satellite Dynamics

PROBING HALO POTENTIALS WITH WEAK LENSING

PROBING HALO POTENTIALS WITH SATELLITE GALAXIES

THEORY: "UNIVERSAL" (NFW) HALOS VS. ISOTHERMAL HALOS

OBSERVED VELOCITY DISPERSION PROFILES

HALO MASSES AND GALAXY MASS-TO-LIGHT RATIOS
M and M/L from Galaxy-Galaxy Lensing
M and M/L from Satellite Dynamics

NON-SPHERICAL HALOS
Evidence for Flattened Halos from Galaxy-Galaxy Lensing
Evidence for Flattened Halos from Satellite Galaxies

SUMMARY

REFERENCES

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