The Local Halo Density

Abstract

For almost 20 years models of the Galaxy have included a dark halo responsible for supporting a substantial fraction of the local rotation velocity and a flat rotation curve at large distances. Estimates of the local halo density range from 2 X 10-25g cm-3to 10 X 10-25g cm-3. By careful modeling of the Galaxy, taking account of the evidence that dark halos are flattened and recent microlensing data, we arrive at a more quantitative estimate, 9.2ff X 10-25g cm-3. Microlensing toward the LMC indicates that only a small fraction, less than -30%, can be in the form of MACHOs, which is consistent with the idea that most of the halo consists of cold dark matter particles. © 1995 The American Astronomical Society.