We report the discovery of 28 candidate high-velocity stars (HVSs) at heliocentric distances of less than 3 kpc, based on the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) Data Release 1. All candidates have velocities, with respect to the Galactic rest frame, in excess of 300 km s−1; 12 objects move faster than 400 km s−1. Our sample of HVS candidates covers a much broader color range than the equivalent ranges discussed in previous studies and comprises the first and largest sample of HVSs in the solar neighborhood. The observed as well as the derived parameters for all candidates are sufficiently accurate to allow us to ascertain their nature as genuine HVSs, of which a subset of 12 objects represents the most promising candidates. Our results also highlight the great potential of discovering statistically large numbers of HVSs of different spectral types in LAMOST survey data. The results reported here also highlight the great potential of discovering statistically large numbers of HVSs of different spectral types in LAMOST survey data. We will continue to perform further systematic HVS searches based on the LAMOST data; the resulting stellar samples will eventually enable us to better understand the nature of the HVSs themselves and ultimately constrain the structure of the Galaxy. As a consequence, it is of great importance for investigating the various HVS ejection mechanisms, which may be more complex than previously thought.

We present the dependence of the amount of nuclear star formation on the non-axisymmetry of a bulge of disk galaxies. For this, we use a volume-limited sample of spiral galaxies at 0.02 < = z < 0.055 from the SDSS DR7. Among 3173 final sample galaxies with an axis ratio b/a > 0.6 and a bulge fraction ranged in B/T <= 0.41, nuclear starburst galaxies are 10%. We find that a fraction of the nuclear starburst galaxies become higher when ellipticity of a bulge increases in early type galaxies. Also, the fraction increases clearly when early type galaxies are isolated and in low density region. Our results indicate that the non-axisymmetry of bulges assists gas to fall inside and affects the nuclear starburst process in disk galaxies.

The Magellanic System represents one of the best places to study the formation and evolution of galaxies. Photometric surveys of various depths, areas and wavelengths have had a significant impact on our understanding of the system; however, a complete picture is still lacking. VMC (the VISTA near-infrared YJKs survey of the Magellanic System) will provide new data to derive the spatially resolved star formation history and to construct a three-dimensional map of the system. These data combined with those from other ongoing and planned surveys will give us an absolutely unique view of the system opening up the doors to truly new science!

The stellar initial mass function (IMF) is a very important question in modern astrophysics. Globular clusters (GCs) are good samples for studying the IMF, but the Galactic GCs can provide only one time-scale evolutionary stage. The Large Magellanic Cloud (LMC) is an ideal environment for studying the IMF because it contains compact clusters at different evolutionary stages. By studying the IMF at different evolutionary stages, we can see how the mass function evolves with time.

We derived proper motions and membership probabilities of stars in the regions of two very young (~ 2–4 Myr-old) open clusters NGC 2244 and NGC 6530. Both clusters show clear evidence of mass segregation, which provides strong support for the suggestion that the observed mass segregation is – at least partially – due to the way in which star formation has proceeded in these complex star-forming regions (“primordial” mass segregation).

We review our work on Galactic open clusters in recent years, and introduce our proposed large program for the LOCS (LAMOST Open Cluster Survey). First, based on the most complete open clusters sample with metallicity, age and distance data as well as kinematic information, some preliminary statistical analysis regarding the spatial and metallicity distributions is presented. In particular, a radial abundance gradient of −0.058±0.006 dex kpc−1 is derived. By dividing clusters into the age groups we show that the disk abundance gradient was steeper in the past. Secondly, proper motions, membership probabilities, and velocity dispersions of stars in the regions of two very young open clusters are derived. Both clusters show clear evidence of mass segregation, which provides support for the “primordial” mass segregation scenario. Based on the advantages of the forthcoming LAMOST facility, we have proposed a detailed open cluster survey with LAMOST (the LOCS). The aim, feasibility, and the present development of the LOCS are briefly summarized.

The total mass of a distant star cluster is often derived from the virial theorem, using line-of-sight velocity dispersion measurements and half-light radii, under the implicit assumption that all stars are single (although it is known that most stars form part of binary systems). The components of binary stars exhibit orbital motion, which increases the measured velocity dispersion, resulting in a dynamical mass overestimation. In these proceedings we quantify the effect of neglecting the binary population on the derivation of the dynamical mass of a star cluster. We find that the presence of binaries plays an important role for clusters with total mass Mcl ≤ 105 M⊙; the dynamical mass can be significantly overestimated (by a factor of two or more). For the more massive clusters, with Mcl ≥ 105 M⊙, binaries do not affect the dynamical mass estimation significantly, provided that the cluster is significantly compact (half-mass radius ≤qslant 5 pc).

We report on recent progress in the modelling of the near-IR spectra of young stellar populations, i.e. populations in which red supergiants (RSGs) are dominant. First, we discuss the determination of fundamental parameters of RSGs from Phoenix model fits to their near-IR spectra; RSG-specific surface abundances are accounted for and effects of the microturbulence parameter are explored. New population synthesis predictions are then described and, as an example, it is shown that the spectra of young star clusters in M 82 can be reproduced very well from 0.5 to 2.4 μm. We warn of remaining uncertainties in cluster ages.

Based on new spectra spanning wavelengths from 0.8 to 2.4μm, we study the properties of bright near-IR clusters in M82. We focus on age and extinction, which are critical parameters when one uses dynamical masses to constrain the stellar IMF. The modelling of red supergiant evolution by various authors leads to very significant differences in synthetic cluster spectra. Near-IR fluxes alone therefore do not rule out a normal IMF for cluster F, previously found to be deficient in low mass stars. Combined optical and near-IR studies are being undertaken.

W Hydrae is a prototype AGB star with a dusty circumstellar shell. The shell is marginally resolved at ground-based sub-arcsecond resolution; the unresolved dust condensation radius is expected to be of order 30-50 mas. Since the dusty circumstellar shell is brightest in the mid-IR, the high spatial resolution required at mid-infrared wavelengths can currently only be achieved by using MIDI on the VLTI. We therefore outline a possible observing programme for the VLTI, using MIDI at 10 μm. In a single night of short-baseline VLTI observations with two Auxiliary Telescopes, we can achieve sufficient (u,v) plane coverage to resolve the shell geometry of W Hya, which will provide strong constraints on the mass loss processes in late-type stars. We expect to either obtain an estimate of the dust condensation temperature, or evidence for interrupted mass loss.

Using new HST imaging, we identify a large, evolved system of super star clusters in a disk region just outside the starburst core in the prototypical starburst galaxy M82, “M82 B.” This region has been suspected to be a fossil starburst site in which an intense episode of star formation occurred over 100 Myr ago, which is now confirmed by our derived age distribution. It suggests steady, continuing cluster formation at a modest rate at early times (> 2 Gyr ago), followed by a concentrated formation episode ∼ 600 Myr ago and more recent suppression of cluster formation. The peak episode coincides with independent dynamical estimates for the last tidal encounter with M81.

We have fitted exponential, isothermal (“sech2”) and intermediate (“sech”) model distributions to the observed vertical light profiles in edge-on galaxies.