We report 75 milli-arcsec resolution, near-IR imaging spectroscopy within the central 30 light days of the Galactic Center, taken with the new adaptive optics assisted, integral field spectrometer SINFONI on the ESO-VLT. To a limiting magnitude of K~16, 9 of 10 1 based on observations obtained at the Very Large Telescope (VLT) of the European Southern Observatory, Chile 1 stars in the central 0.4", and 13 of 17 stars out to 0.7" from the central black hole have spectral properties of B0-B9, main sequence stars. Based on the 2.1127µm HeI line width all brighter early type stars have normal rotation velocities, similar to solar neighborhood stars.We combine the new radial velocities with SHARP/NACO astrometry to derive improved 3 d stellar orbits for six of these 'S'-stars in the central 0.5". Their orientations in space appear random. Their orbital planes are not co-aligned with those of the two disks of massive young stars 1-10" from SgrA*. We can thus exclude the hypothesis that the S-stars as a group inhabit the inner regions of these disks. They also cannot have been located/formed in these disks and then migrated inwards within their planes. From the combination of their normal rotation and random orbital orientations we conclude that the S-stars were most likely brought into the central light month by strong individual scattering events.The updated estimate of distance to the Galactic center from the S2 orbit fit is R o = 7.62 ± 0.32 kpc, resulting in a central mass value of 3.61 ± 0.32 x 10 6 M ⊙ .We happened to catch two smaller flaring events from SgrA* during our spectral observations. The 1.7-2.45µm spectral energy distributions of these flares are fit by a featureless, 'red' power law of spectral index α'=-4±1 (S ν~ν α' ). The observed spectral slope is in good agreement with synchrotron models in which the infrared emission 2 comes from accelerated non-thermal, high energy electrons in a radiative inefficient accretion flow in the central R~10 R s region.

Context. The internal dynamics of ultra-compact dwarf galaxies (UCDs) has attracted increasing attention, with most of the UCDs studied to date located in the Virgo cluster. Aims. Our aim is to perform a comprehensive census of the internal dynamics of UCDs in the Fornax cluster, and to shed light on the nature of the interface between star clusters and galaxies. Methods. We obtained high-resolution spectra of 23 Fornax UCDs with -10.4 > M V > −13.5 mag (10 6 < M/M < 10 8 ), using FLAMES/Giraffe at the VLT. This is the largest homogeneous data set of UCD internal dynamics assembled to date. We derive dynamical M/L ratios for 15 UCDs covered by HST imaging. Results. In the M V -σ plane, UCDs with M V < −12 mag are consistent with the extrapolated Faber-Jackson relation for luminous elliptical galaxies, while most of the fainter UCDs are closer to the extrapolated globular cluster (GC) relation. At a given metallicity, Fornax UCDs have, on average, M/L ratios lower by 30-40% than Virgo UCDs, suggesting possible differences in age or dark matter content between Fornax and Virgo UCDs. For our sample of Fornax UCDs we find no significant correlation between M/L ratio and mass. We combine our data with available M/L ratio measurements of compact stellar systems with 10 4 < M/M < 10 8 M, and normalise all M/L estimates to solar metallicity. We find that UCDs (M 2 × 10 6 M ) have M/L ratios twice as large as GCs (M 2 × 10 6 M ). We argue that dynamical evolution has probably had only a small effect on the current M/L ratios of objects in the combined sample, implying that stellar population models tend to under-predict dynamical M/L ratios of UCDs and over-predict those of GCs. Considering the scaling relations of stellar spheroids, we find that UCDs align well along the "Fundamental Manifold". UCDs can be considered the small-scale end of the galaxy sequence in this context. The alignment for UCDs is especially clear for r e 7 pc, which corresponds to dynamical relaxation times that exceed a Hubble time. In contrast, globular clusters exhibit a broader scatter and do not appear to align along the manifold. Conclusions. We argue that UCDs are the smallest dynamically un-relaxed stellar systems, with M 2×10 6 M and 7 r e /pc 100. Future studies should aim at explaining the elevated M/L ratios of UCDs and the environmental dependence of their properties.

Abstract. Radial velocities of 94 galaxies brighter than about V tot = 20 mag in the direction of the central Fornax cluster have been measured1 . Except for 8 Fornax members, all galaxies lie in the background. Among the 8 members, there are 5 nucleated dwarf ellipticals that are already listed in the FCC (Ferguson 1989). Two of the 3 "new" members are very compact and have surface brightnesses comparable to globular clusters, however their luminosities are in the range of dwarf elliptical nuclei.The measured line indices (especially Mg2, Hβ, and iron) of the brighter of the compact objects suggest a solar metallicity, whereas the fainter compact object as well as the dE, Ns have line indices that are similar to those of old metal-poor globular clusters (GCs). However, with these data it is not possible to clearly classify the compact objects either as very bright globular clusters, isolated nuclei of dE, Ns, or even compact ellipticals.A background galaxy cluster at z = 0.11 has been found just behind the center of the Fornax cluster. This explains the excess population of galaxies reported in Paper I. The brightest galaxy of the background cluster lies only 1. 1 south of NGC 1399 and is comparable in absolute luminosity with the central Fornax galaxy itself.Key words: galaxies: clusters: Fornax clustergalaxies: distances and redshifts -galaxies: abundances -galaxies: dwarf Send offprint requests to: M. Hilker 1 Table 2 containing the position, magnitude and velocity of all galaxies is also available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html