Dr. Shlosman will develop new methods to study how galaxies like our Milky Way form their disks inside halos of invisible 'dark matter'. He will examine how the density builds up in the central 'cusp' of the dark halo, and how the presence of the disk disturbs and changes that growth. The dark halo does not grow smoothly as the galaxy forms; it is usually lumpy and far from a well-mixed equilibrium. Dr Shlosman will use both gravitational N-body simulations and analytic calculations to follow the growth of disks in asymmetric and lumpy dark halos, and examine how bars are triggered in the stellar disk. The initial conditions for the N-body simulations will be set using the method of Constrained Realizations, an exact algorithm to construct the Gaussian random fields representing the distribution of matter at early times. The effects of interstellar gas, including energy dissipation, star formation, and the feedback of newly-born stars on the surrounding gas, will be taken into account.
A graduate student will be trained by participating in the research. The University of Kentucky at Lexington has recently built an observatory for undergraduate teaching and public outreach. Dr Shlosman will participate in outreach programs at this observatory, illustrating the process of galaxy formation with animations developed from the computations that he will perform.
Understanding the galaxy formation and evolution process is one of the forefront issues of modern astrophysics. In this project, we have attempted to study various aspects of galaxy evolution using observational, theoretical and computational methods, Specifically, we have analyzed formation of basic morphological features of disk galaxies, such as stellar and gaseous bars, disks, bulges, as well as the supermassive black holes at their centers. galaxies are made of gas, stars and dark matter. These components interact and exchange mass, energy and angular momentum. While we do understand that galactic bars facilitate the angular momentum exchange between the disk and the halo, and between the stars and gas, the details of this process remain unclear. The great majority of bars appear to be made of stars with some admixture of gas, but gaseous bars are known to exist as well. They could have an important role in being the dynamical engines of young, gas-rich galaxies. Our results show the intricate details of how stellar bars induce angular momentum trasnfer from galactic disks to dark matter halos. We have focused on a less studied resonanse momentum transfer in pure stellar and mixed gaseous/stellar disks. A number of corolaries have been predicted to be verified by upcoming observations. Furthermore, we analyzed the bar formation as a result of a spontaneous bar instability, and quantified the effect of gas presence on the bar evolution. As a next step, we have compared evolution of dark matter halos with and without gas. An important issue here is to quantify the effect of gas on the shape and dynamics of dark matter. Probabaly the most interesting aspect of this problem is to understand how much dark matter is present in the central region of galaxies. While numerical simulations with the pure dark matter predict formation of central dark matter density cusps, observations tell otherwise. We have been able to demonstrate that clumpy gas, stars and dark matter can destroy these dark matter cusps and replace them with the stellar/gaseous ones. Furthermore, we have focused on morphology of early galaxies, less then 800 million years after the Big Bang. We found that nearly all galaxies more massive than 1% of the Milky Way galaxy are disk galaxies at these early times. As a by-product, we could explain the mass distribution in the earliest (proto)-cluster of galaxies detected so far with the Hubble Space Telescope at reshift of about 8. Finally, we have investigated formation of supermassive black hole seedsat very early times of redhifts larger than 10. Have these objects formed from the remnants of first generation of stars, so-called Population III stars, or via other process. Using high-resolution numerical simulations, we have shown that a direct collapse to very high densities in the galactic centers is plausible alternative to the prevailing paradigm. In the accompanied Figure, we show the face-on projection of such a gravitational collapse at various spatial scales, from ~3 parsec to 400 astronomical units (about few times the size of the Solar System)
