Mayrita Vitvitska
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| Research Assistant |
| Entered: | 1999 |
| Office: | 101 Astronomy |
| Phone: | (575)646-4438 |
| Fax: | (575)646-1602 |
| |
| E-mail: | mvitvit |
| (append "@nmsu.edu") |
| |
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| M.S. | St. Petersburg State University, | 1995 |
| B.S. | St. Petersburg State University, | 1994 |
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Research
I am studying the origin of angular momentum in dark matter halos. With Dr.
Klypin and Dr. Andrey Kratsov (University of Chicago), I have proposed a new
explanation for the origin of angular momentum in galaxies and their dark
halos, in which the halos obtain their spin through the cumulative
acquisition of angular momentum from satellite accretion.
In our model, the build-up of angular momentum is a random walk process
associated with the mass assembly history of the halo's major progenitor. We
assume no correlation between the angular momenta of accreted objects. The
main role of tidal torques in this approach is to produce the random
tangential velocities of merging satellites. Using the extended
Press-Schechter approximation, we have calculated the growth of mass,
angular momentum, and spin parameter for many halos. Our random walk
model reproduces the key features of the angular momentum of halos found in
lambda-CDM N-body simulations: a lognormal distribution in the spin
parameter with an average value of 0.045 with a 0.56 dispersion, independent
of mass and redshift.
The evolution of the spin parameter in individual halos in this model is
quite different from the steady increase with time of angular momentum in
the tidal torque picture. We find both in N-body simulations and in our
random walk model that the value changes significantly with time for
a halo's major progenitor. (It typically has a sharp increase due to major
mergers and a steady decline during periods of gradual accretion of small
satellites). The model predicts that, on average, the spin parameter should
be substantially larger for 1012 solar mass halos that
had major mergers after redshift z = 3 than for those that did not.
Perhaps surprisingly, this suggests that halos that host later forming
elliptical galaxies should rotate faster than halos of spiral galaxies.
Future Work
I completed an M.S. degree at NMSU in 2003.
