Browsing by Author "Toledo, Ignacio"

Now showing 1 - 5 of 5
  • Thumbnail Image
    Item
    Discovery of new companions to high proper motion stars from the VVV Survey
    (2013) Ivanov, Valentín D.; Minniti, D.; Hempel, Maren; Kurtev, Radostín; Toledo, Ignacio; Saito, Roberto K.; García, Javier Alonso; Beamin, Juan Carlos; Borissova, Jura; Catelan, Márcio; Chene, André Nicolas; Emerson, Jin; González, Óscar A.; Lucas, Phillip W.; Martín, Eduardo L.; Rejkuba, Marina; Gromadzki, Mariusz
  • Thumbnail Image
    Item
    Galaxy Evolution in a Pilot Survey up to z = 1 and CDM Halos
    (2011) Giraud, E.; Quintana Godoy, Hernán; Toledo, Ignacio; Zelaya García, Paula Andrea
  • No Thumbnail Available
    Item
    Low-ionization galaxies and evolution in a pilot survey up to z = 1
    (2011) Giraud, Edmond; Gu, Qiu-Sheng; Melnick, Jorge; Quintana, Hernan; Selman, Fernando; Toledo, Ignacio; Zelaya, Paula
    We present galactic spectroscopic data from a pencil beam of 10.75' x 7.5' centered on the X-ray cluster RXJ0054.0-2823 at z = 0.29. We study the spectral evolution of galaxies from z = 1 down to the cluster redshift in a magnitude-limited sample at R <= 23, for which the statistical properties of the sample are well understood. We divide emission-line galaxies into star-forming galaxies, Low Ionization Nuclear Emission line Regions (LINERs), and Seyferts by using emission-line ratios of [OII], H beta, and [OIII], and derive stellar fractions from population synthesis models. We focus our analysis on absorption and low-ionization galaxies. For absorption-line galaxies, we recover the well-known result that these galaxies have had no detectable evolution since z similar to 0.6 - 0.7, but we also find that in the range z = 0.65 - 1, at least 50% of the stars in bright absorption systems are younger than 2.5 Gyr. Faint absorption-line galaxies in the cluster at z = 0.29 also had significant star formation during the previous 2 - 3 Gyr, but their brighter counterparts seem to be only composed of old stars. At z similar to 0.8, our dynamically young cluster had a truncated red-sequence. This result seems to be consistent with a scenario where the final assembly of E/S0 took place at z < 1. In the volume-limited range 0.35 <= z <= 0.65, we find that 23% of the early-type galaxies have LINER-like spectra with H beta in absorption and have a significant component of A stars. The vast majority of LINERs in our sample have significant populations of young and intermediate-aged stars and are thus not related to AGNs, but to the population of 'retired galaxies' recently identified by Cid Fernandes et al. in the Sloan Digital Sky Survey (SDSS). Early-type LINERs with various fractions of A stars and E+A galaxies appear to play an important role in the formation of the red sequence.
  • Thumbnail Image
    Item
    Low-ionization galaxies and evolution in a pilot survey up to z = 1
    (2011) Giraud, E.; Quintana Godoy, Hernán; Toledo, Ignacio; Zelaya García, Paula Andrea
  • Thumbnail Image
    Item
    The long bar as seen by the VVV survey I. Colour-magnitude diagrams
    (2012) Gonzalez, C.; Minniti, D.; Toledo, Ignacio