Context. Very low-metallicity massive stars are key to understanding the reionization epoch. Radiation-driven winds, chief agents in the evolution of massive stars, are consequently an important ingredient in our models of the early-Universe. Recent findings hint that the winds of massive stars with poorer metallicity than the SMC may be stronger

Aims: We present the spectroscopic characterization of the unusual high-amplitude very low mass pre-main-sequence periodic variable CHS 7797. Methods: This study is based on optical medium-resolution (R = 2200) spectroscopy in the 6450 - 8600 Å range, carried out with GMOS-GEMINI -S in March 2011. Observations of CHS 7797 have been carried out at

NGC 6388 and NGC 6441 are two massive Galactic bulge globular clusters that share many properties, including the presence of an extended horizontal branch (HB), quite unexpected because of their high metal content. In this paper we use Hubble Space Telescope's WFPC2, ACS, and WFC3 images and present a broad multicolor study of their stellar content

We use numerical simulations to investigate how the statistical properties of dark matter (DM) haloes are affected by the baryonic processes associated with galaxy formation. We focus on how these processes influence the spin and shape of a large number of DM haloes covering a wide range of mass scales, from galaxies to clusters at z = 0, 1

Using the OSIRIS tunable narrowband imager on the 10.4 m GTC (La Palma), we have mapped the SAB(rs)cd galaxy NGC 6946 over a ~7.3 × 7.5 arcmin2 field in the emission lines of the [S II] λλ6717, 6731 doublet, and in Hα. From these maps we have produced catalogs of the Hα luminosities and effective radii of 557 H II regions across the disk, and