Massive present-day early-type (elliptical and lenticular) galaxies probably gained the bulk of their stellar mass and heavy elements through intense, dust-enshrouded starbursts--that is, increased rates of star formation--in the most massive dark-matter haloes at early epochs. However, it remains unknown how soon after the Big Bang massive

Asimismo, investigamos las características fotométricas de los 351 miembros de Toro ya conocidos. En total se aplicaron 40 criterios de selección. Para confirmar la pertenencia a una de las regiones de todas las fuentes selecionadas, los candidatos se observaron mediante espectroscopia óptica de baja resolución. En estos rangos de longitud de onda

Luminosity functions are one of the most important observational clues when studying galaxy evolution over cosmic time. In this paper we present the X-ray luminosity functions for X-ray detected AGN in the SXDS and GWS fields. The limiting fluxes of our samples are 9.0 ×10-15 and 4.8 ×10-16 erg cm-2 s-1 in the 0.5-7.0 keV band in the two fields

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