Nature and Distribution of Dark Matter in Galaxies
Feel the Dark Force of Gravity: Satellites, Streams and Spectacles (GL)
Numerous observations from radio to X-ray imply the presence of "dark"
matter in galaxies and galaxy groups and clusters, much more than the
directly detectable luminous material. What is the nature of this
ubiquitous dark matter (DM)? How is it distributed? These are the two
theme questions addressed in my on-going research. These are important
for understanding structure formation, which is driven by the common
gravitational field of the dark and luminous matter.
Several lines of attack are used here, combining constraints from
galaxy dynamics and gravitational lensing. First microlensing of the
LMC, the SMC and the Galactic Bulge/Bar can be used to constrain the
so-called MACHOs (baryonic DM candidates, say, brown dwarfs in the
Galactic halo, disk and bar).
Second the Milky Way dark matter potential can be mapped out or at
least constrained by studying the motion, orbital decay, and tidal
distortion of its satellites (LMC/SMC, Ursa Minor, etc.) and
satellite remnants (e.g., Sagittarius, omega Centauri etc.).
Another powerful technique of probing the dark halo in distant
galaxies in Gravitational Lensing. Through theretical modeling of the
images and time delays of the lenses (e.g., the quadruple-imaged lens
PG1115+080), I hope to gain more understanding of the dark matter
density, especially the central cusp, in these systems, and check
whether the lenses are consistent with the popular Cold Dark Matter
cosmology.