34 research outputs found
Dynamical friction in multi-component evolving globular clusters
We use the Chandrasekhar formalism and direct N-body simulations to study the
effect of dynamical friction on a test object only slightly more massive than
the field stars, orbiting a spherically symmetric background of particles with
a mass spectrum. The main goal is to verify whether the dynamical friction time
(t_DF) develops a non-monotonic radial-dependence that could explain the
bimodality of the Blue Straggler radial distributions observed in globular
clusters. In these systems, in fact, relaxation effects lead to a mass and
velocity radial segregation of the different mass components, so that
mass-spectrum effects on t_DF are expected to be dependent on radius. We find
that, in spite of the presence of different masses, t_DF is always a monotonic
function of radius, at all evolutionary times and independently of the initial
concentration of the simulated cluster. This because the radial dependence of
t_DF is largely dominated by the total mass density profile of the background
stars (which is monotonically decreasing with radius). Hence, a progressive
temporal erosion of the BSS population at larger and larger distances from the
cluster center remains the simplest and the most likely explanation of the
shape of the observed BSS radial distributions, as suggested in previous works.
We also confirm the theoretical expectation that approximating a multi-mass
globular cluster as made of (averaged) equal-mass stars can lead to significant
overestimates of t_DF within the half-mass radius.Comment: In press on Ap
Investigating mass segregation process in globular clusters with Blue Straggler Stars: the impact of dark remnants
We present the results of a set of N-body simulations aimed at exploring how
the process of mass segregation (as traced by the spatial distribution of blue
straggler stars, BSSs) is affected by the presence of a population of heavy
dark remnants (as neutron stars and black holes). To this end, clusters
characterized by different initial concentrations and different fractions of
dark remnants have been modeled. We find that an increasing fraction of
stellar-mass black holes significantly delays the mass segregation of BSSs and
the visible stellar component. In order to trace the evolution of BSS
segregation, we introduce a new parameter () that can be easily measured
when the cumulative radial distribution of these stars and a reference
population are available. Our simulations show that might also be used as
an approximate indicator of the time remaining to the core collapse of the
visible component.Comment: ApJ accepte
Astrocomp: a web service for the use of high performance computers in Astrophysics
Astrocomp is a joint project, developed by the INAF-Astrophysical Observatory
of Catania, University of Roma La Sapienza and Enea. The project has the goal
of providing the scientific community of a web-based user-friendly interface
which allows running parallel codes on a set of high-performance computing
(HPC) resources, without any need for specific knowledge about parallel
programming and Operating Systems commands. Astrocomp provides, also, computing
time on a set of parallel computing systems, available to the authorized user.
At present, the portal makes a few codes available, among which: FLY, a
cosmological code for studying three-dimensional collisionless self-gravitating
systems with periodic boundary conditions; ATD, a parallel tree-code for the
simulation of the dynamics of boundary-free collisional and collisionless
self-gravitating systems and MARA, a code for stellar light curves analysis.
Other codes are going to be added to the portal.Comment: LaTeX with elsart.cls and harvard.sty (included). 7 pages. To be
submitted to a specific journa
Tidal tails around globular clusters
We present the results of detailed N-body simulations of clusters moving in a realistic Milky Way potential. The strong interaction with the bulge and the disk of the Galaxy leads to the formation of tidal tails, emanating from opposite sides of the cluster. Their orientation and morphology may be interpreted easily in terms of a comoving frame of coordinates
Dynamical evolution of globular clusters and its influence on the galactic nucleic activity
Dottorato di ricerca in fisica. 12. ciclo. A. a. 1997-98. Relatore Roberto Capuzzo-Dolcetta. Coordinatore Marzio CassandroConsiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7, Rome; Biblioteca Nazionale Centrale - P.za Cavalleggeri, 1, Florence / CNR - Consiglio Nazionale delle RichercheSIGLEITItal