Open Access. Powered by Scholars. Published by Universities.®
Physical Sciences and Mathematics Commons™
Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 5 of 5
Full-Text Articles in Physical Sciences and Mathematics
The Effect Of The Galactic Spheroid On Globular Cluster Evolution, C Murali, Md Weinberg
The Effect Of The Galactic Spheroid On Globular Cluster Evolution, C Murali, Md Weinberg
Astronomy Department Faculty Publication Series
We study the combined effects of relaxation, tidal heating and binary heating on globular cluster evolution, exploring the physical consequences of external effects and examining evolutionary trends in the MilkyWay population. Our analysis demonstrates that heating on circular and low-eccentricity orbits can dominate cluster evolution. The results also predict rapid evolution on eccentric orbits either due to strong relaxation caused by the high densities needed for tidal limitation or due to efficient bulge shocking of low density clusters. The combination of effects leads to strong evolution of the population as a whole. For example, within the solar circle, tidally-limited 105M⊙ …
Globular Cluster Evolution In M87 And Fundamental Plane Ellipticals, C Murali, Md Weinberg
Globular Cluster Evolution In M87 And Fundamental Plane Ellipticals, C Murali, Md Weinberg
Astronomy Department Faculty Publication Series
The globular cluster population in M87 has decreased measurably through dynamical evolution caused by relaxation, binary heating and time-dependent tidal perturbation. For fundamental plane ellipticals in general, cluster populations evolve more rapidly in smaller galaxies because of the higher mass density. A simple evolutionary model reproduces the observed trend in specific frequency with luminosity for an initially constant relationship. Fits of theoretically evolved populations to M87 cluster data from McLaughlin et al. (1994) show the following: 1) dynamical effects drive evolution in the initial mass and space distributions and can account for the large core in the spatial profile as …
Intergalactic Helium Absorption In Cold Dark Matter Models, Rac Croft, Dh Weinberg, N Katz, L Hernquist
Intergalactic Helium Absorption In Cold Dark Matter Models, Rac Croft, Dh Weinberg, N Katz, L Hernquist
Astronomy Department Faculty Publication Series
Observations from the Hopkins Ultraviolet Telescope and the Hubble Space Telescope have recently detected He II absorption along the lines of sight to two high-redshift quasars. We use cosmological simulations with gas dynamics to investigate He II absorption in the cold dark matter (CDM) theory of structure formation. We consider two Ω = 1 CDM models with different normalizations and one open universe (Ω0 = 0.4) CDM model. The simulations incorporate the photoionizing UV background spectrum computed by Haardt & Madau, which is based on the output of observed quasars and reprocessing by the Lyα forest. The simulated …
Evolution Of The Galactic Globular Cluster System, C Murali, Md Weinberg
Evolution Of The Galactic Globular Cluster System, C Murali, Md Weinberg
Astronomy Department Faculty Publication Series
We study the dynamical evolution of disk and halo globular clusters in the Milky Way using a series of Fokker-Planck calculations combined with parametric statistical models. Our sample of 113 clusters with velocity data is predicted to descend from an initial population of 250 clusters, implying more than a factor of two decrease in population size due to evolution. Approximately 200 of these clusters are in a halo component and 50 in a disk component. The estimated initial halo population follows a coreless R−3.38 density profile in good agreement with current estimates for the distribution of halo field stars. The …
Testing Cosmological Models Against The Abundance Of Damped Lyman-Alpha Absorbers, Jp Gardner, N Katz, Dh Weinberg, L Hernquist
Testing Cosmological Models Against The Abundance Of Damped Lyman-Alpha Absorbers, Jp Gardner, N Katz, Dh Weinberg, L Hernquist
Astronomy Department Faculty Publication Series
We calculate the number of damped Lyα absorbers expected in various popular cosmological models as a function of redshift and compare our predictions with observed abundances. The Press-Schechter formalism is used to obtain the distribution of halos with circular velocity in different cosmologies, and we calibrate the relation between circular velocity and absorption cross section using detailed gasdynamical simulations of a standard cold dark matter (CDM) model. Because of this calibration, our approach makes more realistic assumptions about the absorption properties of collapsed objects than previous, analytic calculations of the damped Lyα abundance. CDM models with Ω0 = 1, …