Galaxy formation and evolution

Abstract:

We construct mass models of 28 S0-Sb galaxies. The models have an axisymmetric stellar component and a NFW dark halo and are constrained by observed KS-band photometry and stellar kinematics. The median dark halo virial mass is 1012.8 M⊙, and the median dark/total mass fraction is 20% within a sphere of radius r1/2, the intrinsic half-light radius, and 50% within R25. We compare the Tully-Fisher relations of the spirals and S0s in the sample and find that S0s are 0.5 mag fainter than spirals at KS-band and 0.2 dex less massive for a given rotational velocity. We use this result to rule out scenarios in which spirals are transformed into S0s by processes which truncate star formation without affecting galaxy dynamics or structure, and raise the possibility of a break in homology between spirals and S0s. © 2010 American Institute of Physics.

Abstract:

We show that high quality laser guide star (LGS) adaptive optics (AO) observations of nearby early-type galaxies are possible when the tip-tilt correction is done by guiding on nuclei while the focus compensation due to the changing distance to the sodium layer is made 'open loop'. We achieve corrections such that 40% of flux comes from R<0.2 arcsec. To measure a black hole mass (M•) one needs integral field observations of both high spatial resolution and large field of view. With these data it is possible to determine the lower limit to M• even if the spatial resolution of the observations are up to a few times larger than the sphere of influence of the black hole. © 2010 American Institute of Physics.

Abstract:

We summarize the recent results of our survey of the nearest nuclear star clusters. The purpose of the survey is to understand nuclear star cluster formation mechanisms and constrain the presence of black holes using adaptive optics assisted integral field spectroscopy, optical spectroscopy, and HST imaging in 13 galaxies within 5 Mpc. We discuss the formation history of the nuclear star cluster and possible detection of an intermediate mass BH in NGC 404, the nearest S0 galaxy. © 2010 American Institute of Physics.

Abstract:

We study the formation of stellar nuclear clusters (NC) with two types of N-body simulations: mergers of star clusters (SC) at the centre of disk galaxies and the accretion of a SC onto a previous NC. The merging of SCs produces systems consistent with observed scaling relations, they have shapes comparable with those observed and rotation consistent with that observed in the NCs of NGC 4244 and M 33. © 2010 American Institute of Physics.