Eva K. Grebel

Ring Nebula and Bipolar Outflows Associated with the B1.5 Supergiant Sher 25 in NGC 3603

We have identified a ring-shaped emission-line nebula and a possible bipolar outflow centered on the B1.5 supergiant Sher 25 in the Galactic giant H II region NGC 3603 (distance 6 kpc). The clumpy ring around Sher 25 appears to be tilted by 64° against the plane of the sky. Its semimajor axis (position angle ≈ 165°) is 69 long, which corresponds to a ring diameter of 0.4 pc. The bipolar outflow filaments, presumably located above and below the ring plane on either side of Sher 25, show a separation of ≈ 0.5 pc from the central star. High-resolution spectra show that the ring has a systemic velocity of VLSR = +19 km s-1 and a deprojected expansion velocity of 20 km s-1, and that one of the bipolar filaments has an outflow speed of ~83 km s-1. The spectra also show a high [N II]/Hα ratio, suggestive of strong N enrichment. Sher 25 must be an evolved blue supergiant (BSG) past the red supergiant (RSG) stage. We find that the ratio of equatorial to polar mass-loss rate during the RSG phase was ≈ 16. We discuss the results in the framework of RSG-BSG wind evolutionary models. We compare Sher 25 to the progenitor of SN 1987A, which it resembles in many aspects.

Local disc model in view of Gaia DR1 and RAVE data

We test the performance of the semi-analytic self-consistent Just-Jahreis disc model (JJ model) with the astrometric data from the Tycho-Gaia Astrometric Solution (TGAS) sub-catalogue of the first Gaia data release (Gaia DR1), as well as the radial velocities from the fifth data release of the Radial Velocity Experiment survey (RAVE DR5). We use a sample of 19,746 thin disc stars from the TGAS

Further Evidence of a Merger Origin for the Thick Disk: Galactic Stars along Lines of Sight to Dwarf Spheroidal Galaxies

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NAOS-CONICA performance in a crowded field – the Arches cluster

RAVE cross-match selected in the local solar cylinder of 300 pc radius and 1 kpc height below the Galactic plane and simulate this sample via the forward modelling technique. First, we convert the predicted vertical density laws of the thin disc populations into a mock sample. Then the obtained mock populations are reddened with a 3D dust map and are subjected to the selection criteria corresponding to the RAVE and TGAS observational limitations as well as to additional cuts applied to the data sample. We calculate the quantities of interest separately at different heights above the Galactic plane taking into account the distance error effects separately in horizontal and vertical directions. We investigate the simulated sample in terms of the vertical number density profiles, Hess diagrams and velocity distribution functions. Basing on a good agreement of our simulations with the data, we conclude that our fiducial disc model confidently reproduces the vertical trends in the thin disc stellar population properties. Thus, it can serve as a starting point for the future extension of the JJ model to other Galactocentric distances.