275 research outputs found
Faint Fuzzy Star Clusters in NGC1023 as Remnants of Merged Star Cluster Complexes
In the lenticular galaxy NGC1023 a third population of globular clusters
(GCs), called faint fuzzies (FFs), was discovered next to the blue and red GC
populations by Larsen & Brodie. While these FFs have colors comparable to the
red population, the new population is fainter, larger (R_eff > 7 pc) and, most
importantly, shows clear signs of co-rotation with the galactic disk of
NGC1023. We present N-body simulations verifying the hypothesis that these
disk-associated FFs are related to the young massive cluster complexes (CCs)
observed by Bastian et. al in M51, who discovered a mass-radius relation for
these CCs. Our models have an initial configuration based on the observations
from M51 and are placed on various orbits in a galactic potential derived for
NGC1023. All computations end up with a stable object containing 10 to 60% of
the initial CC mass after an integration time of 5 Gyr. A conversion to visual
magnitudes demonstrates that the resulting objects cover exactly the observed
range for FFs. Moreover, the simulated objects show projected half-mass radii
between 3.6 and 13.4 pc, in good agreement with the observed FF sizes. We
conclude that objects like the young massive CCs in M51 are likely progenitors
of the FFs observed in NGC1023.Comment: Accepted for publication in Ap
Star clusters as building blocks for dSph galaxies formation
We study numerically the formation of dSph galaxies. Intense star bursts,
e.g. in gas-rich environments, typically produce a few to a few hundred young
star clusters, within a region of just a few hundred pc. The dynamical
evolution of these star clusters may explain the formation of the luminous
component of dwarf spheroidal galaxies (dSph). Here we perform a numerical
experiment to show that the evolution of star clusters complexes in dark matter
haloes can explain the formation of the luminous components of dSph galaxies.Comment: 4 pages, 4 figures, Proceedings of IAU symposium 266 'Star Clusters -
Basic Building Blocks
Star Cluster collisions - a formation scenario for the Extended Globular Cluster Scl-dE1 GC1
Recent observations of the dwarf elliptical galaxy Scl-dE1 (Sc22) in the
Sculptor group of galaxies revealed an extended globular cluster (Scl-dE1 GC1),
which exhibits an extremely large core radius of about 21.2 pc. The authors of
the discovery paper speculated on whether this object could reside in its own
dark matter halo and/or if it might have formed through the merging of two or
more star clusters. In this paper, we present N-body simulations to explore
thoroughly this particular formation scenario. We follow the merger of two star
clusters within dark matter haloes of a range of masses (as well as in the
absence of a dark matter halo). In order to obtain a remnant which resembles
the observed extended star cluster, we find that the star formation efficiency
has to be quite high (around 33 per cent) and the dark matter halo, if present
at all, has to be of very low mass, i.e. raising the mass to light ratio of the
object within the body of the stellar distribution by at most a factor of a
few. We also find that expansion of a single star cluster following mass loss
provides another viable formation path. Finally, we show that future
measurements of the velocity dispersion of this system may be able to
distinguish between the various scenarios we have explored.Comment: accepted by MNRAS, 9 pages, 2 figures, 9 table
Star Cluster Survival in Star Cluster Complexes under Extreme Residual Gas Expulsion
After the stars of a new, embedded star cluster have formed they blow the
remaining gas out of the cluster. Especially winds of massive stars and
definitely the on-set of the first supernovae can remove the residual gas from
a cluster. This leads to a very violent mass-loss and leaves the cluster out of
dynamical equilibrium. Standard models predict that within the cluster volume
the star formation efficiency (SFE) has to be about 33 per cent for sudden
(within one crossing-time of the cluster) gas expulsion to retain some of the
stars in a bound cluster. If the efficiency is lower the stars of the cluster
disperse mostly. Recent observations reveal that in strong star bursts star
clusters do not form in isolation but in complexes containing dozens and up to
several hundred star clusters, i.e. in super-clusters. By carrying out
numerical experiments for such objects placed at distances >= 10 kpc from the
centre of the galaxy we demonstrate that under these conditions (i.e. the
deeper potential of the star cluster complex and the merging process of the
star clusters within these super-clusters) the SFEs can be as low as 20 per
cent and still leave a gravitationally bound stellar population. Such an object
resembles the outer Milky Way globular clusters and the faint fuzzy star
clusters recently discovered in NGC 1023.Comment: 21 pages, 8 figures, accepted by Ap
- …