We determine the radial abundance gradient of Cl in the Milky Way from H II regions spectra. For the first time, the Cl/H ratios are computed by simply adding ionic abundances and not using an ionization correction factor (ICF). We use a collection of published very deep spectra of Galactic H II regions. We have recalculated the physical conditions

Recent determinations of the radial distributions of mono-metallicity populations (MMPs, i.e., stars in narrow bins in [Fe/H] within wider [α/Fe] ranges) by the SDSS-III/APOGEE DR12 survey cast doubts on the classical thin- and thick-disk dichotomy. The analysis of these observations led to the non-[α /Fe] enhanced populations splitting into MMPs

We have analyzed ACS/WFC and WFPC2 images from HST, as well as ground-based data to study the radial distribution of the double sub-giant branch (SGB) recently discovered in the Galactic globular cluster NGC 1851. We found that the SGB split can be followed all the way from the cluster center out to at least 8´ from the center. Beyond this distance

Context. NRAO 150 is one of the brightest radio and mm AGN sources in the northern sky, and is an interesting source to study extreme relativistic jet phenomena. However, its cosmological distance has not yet been calibrated, because of its optical faintness due to strong Galactic extinction. Aims: We measure the redshift of NRAO 150, to enable us

The redshift distribution of flat-spectrum radio sources with 5 GHz flux densities S5>~5 mJy is a key component in using current radio lens surveys to probe the cosmological model. We have constructed the first flat-spectrum radio sample in the flux density range 3-20 mJy. Our new sample has 33 sources; we have determined the redshifts of 14 of

Active galactic nuclei (AGNs), particularly the most luminous AGNs, are commonly assumed to be triggered through major mergers; however, observational evidence for this scenario is mixed. To investigate any influence of galaxy mergers on AGN triggering and luminosities through cosmic time, we present a sample of 106 luminous X-ray-selected type 1