Characterization of how dense molecular cores evolve into stars has historically been made through observational changes in their 2 to 25 μm spectral energy distribution (SED) or bolometric temperature via the Class system. Linking these observational classes to a physical protostellar phase or Stages in a consistent manner remains challenging. In order to provide a uniform indicator of whether an observationally classified embedded protostar candidate is likely to be a physical phase Stage 0 or I protostar, we performed an HCO+(J=3-2) survey of Class 0+I and Flat SED young stellar objects (YSOs) in the Spitzer nearby (D < 500 pc) Gould Belt cloud surveys. We use criteria from van Kempen et al.(2009) to classify sources as Stage 0+I or bona fide protostars and find 84% of our HCO+ detected sources meet that criteria. We recommend 0.54 Myr as an evolutionary timescale for these embedded protostars. We discuss trends in our sample with spatial distribution, molecular cloud extinction, spectral index, and bolometric temperature and luminosity.

We study the asymmetric drift in the Milky Way with the aid of the RAVE data. Then we apply the deduced asymmetric drift correction to the SEGUE data and reconstruct the behaviour of the rotation curve of the Milky Way in the extended solar neighbourhood. The rotation curve appears to be essentially flat. We supplement our data by tangent point measurements of the inner rotation curve and fit it by a density model of the Milky Way.

The Extragalactic Background Light (EBL) at UV, optical and NIR wavelengths consists of the integrated light of all unresolved galaxies along the line of sight plus any contributions by intergalactic matter including hypothetical decaying relic particles. The measurement of the EBL has turned out to be a tedious problem. This is because of the foreground components of the night sky brightness, much larger than the EBL itself: the Zodiacal Light (ZL), Integrated Starlight (ISL), Diffuse Galactic Light (DGL) and, for ground-based observations, the Airglow (AGL) and the tropospheric scattered light. We have been developing a method for the EBL measurement which utilises the screening effect of a dark nebula on the EBL. A differential measurement in the direction of a high-latitude dark nebula and its surrounding area provides a signal that is due to two components only, i.e. the EBL and the diffusely scattered ISL from the cloud. We present a progress report of this method where we are now utilising intermediate resolution spectroscopy with ESO's VLT telescope. We detect and remove the scattered ISL component by using its characteristic Fraunhofer line spectral signature. In contrast to the ISL, in the EBL spectrum all spectral lines are washed out. We present a high quality spectrum representing the difference between an opaque position within our target cloud and several clear OFF positions around the cloud. We derive a preliminary EBL value at 400 nm and an upper limit to the EBL at 520 nm. These values are in the same range as the EBL lower limits derived from galaxy counts.

Unit: We will use in this paper the abbreviation 1 cgs = 10−9erg s−1cm−2sr−1Å−1

We report the detection of a planetary companion around HIP 13044, a metal-poor red horizontal branch star belonging to a stellar halo stream that results from the disruption of an ancient Milky Way satellite galaxy. The detection is based on radial velocity observations with FEROS at the 2.2-m MPG/ESO telescope. The periodic radial velocity variation of P = 16.2 days can be distinguished from the periods of the stellar activity indicators. We computed a minimum planetary mass of 1.25 Mjup and an orbital semimajor axis of 0.116 AU for the planet. This discovery is unique in three aspects: First, it is the first planet detection around a star with a metallicity much lower than few percent of the solar value; second, the planet host star resides in a stellar evolutionary stage that is still unexplored in the exoplanet surveys; third, the planetary system HIP 13044 most likely has an extragalactic origin in a disrupted former satellite of the Milky Way.

In this article I review measurements of deuterium in the Milky Way.

The term “heating” is used loosely to refer to a range of processes that result in an increase in velocity dispersion with age for subgroups of disk stars. We briefly summarise the observational basis for studies of disk heating and show that qualitative differences exist between the evolution of the in-plane and vertical motions. Ways to discriminate between various heating scenarios are discussed; the most recent galaxy merger simulations may in fact suggest that discrimination on purely kinematic grounds might be unfeasible, even with large samples of stars with excellent ages.

A new method to extract information from color-magnitude diagrams (CMDs) is presented. We employ a Richardson-Lucy (RL) algorithm to the analysis of the observational uncertainties. The resulting reconstruction is a cleaned data set with which to perform analyses of the star formation history. For this task, synthetic stellar populations are built and compared with the data CMD. As an application, the star formation rate in the solar vicinity is recovered.

We present a detailed and uniform study of oxygen abundances in a large set of 155 metal-rich dwarfs. EW measurements were carried out for the [OI] 6300 Å line and the OI triplet, while spectral synthesis was performed for several OH lines. NLTE corrections were calculated and applied to the LTE abundance results derived from the triplet. Abundances from [OI], the OI triplet and near-UV OH were obtained in 103, 87 and 77 dwarfs, respectively. A good agreement between [O/H] ratios from forbidden and OH lines is found, while the NLTE triplet shows a systematically lower abundance. Nevertheless, the consistency with other indicators improves if we consider LTE triplet results. In any case, discrepancies between OH, [OI] and the OI triplet hardly exceed 0.2dex. All three indicators show that, on average, [O/Fe] decreases with [Fe/H] in the metallicity range −0.8<[Fe/H]<0.5.