Mostrando recursos 1 - 20 de 5.358

  1. Multi-band galaxy surveys

    Schoenell, William
    Esta tesis de doctorado abarca el uso de cartografiados astronómicos recientes y de técnicas estadísticas avanzadas para responder a preguntas acerca de la composición de galaxias, siguiendo dos perspectivas diferentes: la instrumentación necesaria para obtener los datos y el desarrollo de una herramienta estadística que permita convertir los datos observados en propiedades físicas de galaxias. Comenzamos contextualizando sobre los cartografiados extragalácticos más grandes hasta la fecha y cómo influyeron en los tres cartografiados estudiados en esta tesis: S-PLUS, ALHAMBRA y J-PAS. En la primera parte de este trabajo nos centramos en S-PLUS, un cartografiado del Universo Local que comenzó a principios...

  2. A multi-frequency study of the star formation histories of galaxies in the integral field area survey CALIFA

    López Fernández, Rafael
    The Calar Alto Legacy Integral Field Area (CALIFA) survey is a large project of the Centro Astron omico Hispano Alem an at the Calar Alto observatory to obtain spatially resolved spectra for 600 local (0.005 < z < 0.03) galaxies by means of Integral Field Spectroscopy (IFS). CALIFA observations started in June 2010 with the Potsdam Multi Aperture Spectrograph (PMAS, Roth et al. 2005), mounted at the 3.5m telescope, employing the PPak wide-fi eld IFU Roth et al. 2005; Kelz et al. 2006. This project provides high quality spectra over a wide, hexagonal field of view of 7200 6400 (331 science fibres with a bre size...

  3. A survey for dwarf galaxy remnants around 14 globular clusters in the outer halo

    Sollima, A.; Martínez Delgado, D.; Muñoz, R. R.; Carballo-Bello, J. A.; Valls-Gabaud, D.; Grebel, E. K.; Santana, F. A.; Côté, P.; Djorgovski, S. G.
    We report the results of a systematic photometric survey of the peripheral regions of a sample of 14 globular clusters in the outer halo of the Milky Way at distances d_(GC) > 25 kpc from the Galactic Centre. The survey is aimed at searching for the remnants of the host satellite galaxies where these clusters could originally have been formed before being accreted on to the Galactic halo. The limiting surface brightness varies within our sample, but reaches μ_(V, lim) = 30–32 mag arcsec^(−2). For only two globular clusters (NGC 7492 and Whiting 1; already suggested to be associated with the Sagittarius galaxy), we...

  4. The Redshift Evolution of Rest-UV Spectroscopic Properties in Lyman-break Galaxies at z ~ 2–4

    Du, Xinnan; Shapley, Alice E.; Reddy, Naveen A.; Jones, Tucker; Stark, Daniel P.; Steidel, Charles C.; Strom, Allison L.; Rudie, Gwen C.; Erb, Dawn K.; Ellis, Richard S.; Pettini, Max
    We present the first comprehensive evolutionary analysis of the rest-frame UV spectroscopic properties of star-forming galaxies at z ~ 2–4. We match samples at different redshifts in UV luminosity and stellar mass, and perform systematic measurements of spectral features and stellar population modeling. By creating composite spectra grouped according to Lyα equivalent width (EW) and various galaxy properties, we study the evolutionary trends among Lyα, low- and high-ionization interstellar (LIS and HIS) absorption features, and integrated galaxy properties. We also examine the redshift evolution of Lyα and LIS absorption kinematics, and fine-structure emission EWs. The connections among the strengths of...

  5. Cosmological simulations of black hole growth II: how (in)significant are merger events for fuelling nuclear activity?

    Steinborn , Lisa; Hirschmann , Michaela; Dolag , Klaus; Shankar , Francesco; Juneau , Stéphanie; Krumpe , Mirko; Remus , Rhea-Silvia; Teklu , Adelheid
    Which mechanism(s) are mainly driving nuclear activity in the centres of galaxies is a major unsettled question. In this study, we investigate the statistical relevance of galaxy mergers for fuelling gas onto the central few kpc of a galaxy, potentially resulting in an active galactic nucleus (AGN). To robustly address that, we employ large-scale cosmological hydrodynamic simulations from the Magneticum Pathfinder set, adopting state-of-the-art models for BH accretion and AGN feedback. Our simulations predict that for luminous AGN ($L_{\rm AGN} > 10^{45}$erg/s) at $z = 2$, more than 50 per cent of their host galaxies have experienced a merger in...

  6. The science case for POLLUX, a high-resolution UV spectropolarimeter onboard LUVOIR

    Bouret , Jean-Claude; Neiner , Coralie; Gómez de Castro , Ana ,; Evans , Chris; Gaensicke , Boris; Shore , Steve; Fossati , Luca; Gry , Cécile; Charlot , Stéphane; Marin , Frédéric; Noterdaeme , Pasquier; Chaufray , Jean-Yves
    POLLUX is a high-resolution, UV spectropolarimeter proposed for the 15-meter primary mirror option of LUVOIR. The instrument Phase 0 study is supported by the French Space Agency (CNES) and performed by a consortium of European scientists. POLLUX has been designed to deliver high-resolution spectroscopy (R> 120,000) over a broad spectral range (90-390 nm). Its unique spectropolarimetric capabilities will open-up a vast new parameter space, in particular in the unexplored UV domain and in a regime where high-resolution observations with current facilities in the visible domain are severely photon starved. POLLUX will address a range of questions at the core of...

  7. XENON1T Takes a Razor to a Dark $E_6$-Inspired Model

    Camargo , Daniel; Mambrini , Yann; Queiroz , Farinaldo
    Motivated by the recent result of XENON1T collaboration with full exposure, 279 life days, that sets the most stringent limit on the spin-independent dark matter-nucleon scattering cross section we discuss a dark $E_6$-inspired model that features the presence of a $U(1)_{d-u}$ gauge symmetry. The dark matter candidate is a dirac fermion that interacts with Standard Model fermions via a massive $Z^\prime$ that preserves the quantum number assignments of this symmetry. We compute the spin-independent scattering cross section off xenon nucleus and compare with the XENON1T limit; find the LHC bound on the $Z^\prime$ mass as well as the projection sensitivity...

  8. Modeling optical and UV polarization of AGNs. V. Dilution by interstellar polarization and the host galaxy

    Marin , F.
    One of the main challenges for polarimetric observations of active galactic nuclei (AGN) is to properly estimate the amount of parasitic light that contaminates the polarization signal. Removing this unpolarized flux is a complex task that has only been achieved in a couple of objects. In this fifth paper of the series, we present a new version of the Monte Carlo code STOKES that accounts for dilution by interstellar polarization and host starlight in radiative transfer modeling. We upgrade our code by including spectral energy distribution (SED) templates for a set of representative host galaxies. The unpolarized light emitted by...

  9. A moda na Filosofia: O incapturável tempo em galáxias de crochê

    Preciosa, Rosane
    Para o filósofo Gilles Deleuze, é por necessidade que criamos, nunca pelo capricho de um ego ávido em contar suas historinhas, no mais das vezes irrelevantes e sem sabor. O que me interessa aqui é sublinhar essa ideia de criação artística menos afeita ao regozijo de um eu que deseja manifestar-se, comunicar-se, e muito mais uma outra, em que um sujeito pensa sobre si mesmo e sobre a existência como “uma sinuca de bico vital”, como diz, de maneira exemplar, o poeta Waly Salomão. A criação seria então um modo de escapar dessa sinuca de bico. (...)

  10. Star Wars: perspectivas espaciales en una galaxia muy, muy lejana

    Arévalo, Miller
    Abstract The text analyzes the filmic space of the Star Wars saga, identifying how some key concepts regarding geography are applied and, at the same time, are relevant in relation to its multi-faceted analysis, as is the case in regards to the idea of territory. Similarly, the article seeks to classify the aspects that make this galaxy a utopian or dystopian setting. It concludes that, despite its fictional nature, the filmic space of the saga has a complexity that does not allow a categorization of the galaxy as a utopia or dystopia, since this varies according to the scale and...

  11. Bifurcation in the tidal streams of Sagittarius: Numerical Simulations

    Camargo, Yeimi; Casas, Rigoberto
    N-body simulations of the interaction between the Sagittarius dwarf galaxy and the Milky Way are performed to study whether it is possible to reproduce both the bifurcations in the tidal streams and the physical properties of Sagittarius. Both galaxies are simulated as sets of particles (live potentials). The initial structures are formed using GALIC and the gravitational interaction between these galaxies is simulated with gadget-2. Sagittarius initially is simulated as a rotating disk-type galaxy with two components: dark matter halo and stellar disk and the Milky Way is a disk galaxy with three components: dark matter halo, stellar disk and...

  12. Cosmología hoy: una revisión

    Cervantes-Cota, Jorge L.; Amigo, Santiago De Lope
    Se presenta un resumen del modelo estándar de cosmología, des­de su origen hasta hoy. Se discuten primero los resultados observacionales recientes, entre los cuales están las diversas mediciones de la RCF, de super-novas tipo Ia y catálogos de galaxias; se mencionan resultados importantes de las simulaciones cosmológicas de N-cuerpos. A continuación se presenta una parte teórica que analiza los modelos de FRW, y enseguida se discuten los problemas de la constante cosmológica, de inflación y de oscilaciones acústicas. Finalmente se presentan las ideas generales de quintaesencia. 

  13. Analysis of Anisotropy in the Hubble Flow

    Torres, Sergio; Cuervo, Juan Carlos
    An analysis of variations in the Hubble parameter (H0) with line-of-sight direction has been done in order to investigate anisotropy in the motion of the galaxies. Depending on the distance range available in the galaxy sample analyzed, H0 measurements can be used as a probe of intrinsic anisotropies at cosmological scales. At shorter scales, deviations from a smooth Hubble expansion flow are expected when galaxies participate in bulk flow motions towards great attractors. Using a galaxy catalogue that spans the distance range between 45 and 500 Mpc, a statistically robust detection of spatial anisotropy of 6.4 ± 1.4 km s-1...

  14. Jorge Luis Borges: Un ensayo autobiográfico, prólogo y traducción de Aníbal González, epílogo de María Kodama, Barcelona: Galaxia Gutenberg y Círculo de Lectores, 1999

    Martinón Cejas, Miguel

  15. Juan Ramón Jiménez: Lírica de una Atlántida, edición de Alfonso Alegre Heitzmann, Barcelona: Círculo de Lectores / Galaxia Gutenberg, 1999, 496 páginas

    Martinón Cejas, Miguel

  16. La Galaxia Internet: reflexiones sobre Internet, empresa y sociedad

    Alcalá, Miryam

  17. GARCÍA DELGADO, J. L. (edit.) (2017) Rey de la democracia, Barcelona, Galaxia Gutenberg,

    Rodero Franganillo, Adolfo

  18. A produção editorial de revistas científicas on-line: uma análise de publicações brasileiras da área da Comunicação

    Castedo, Raquel da Silva; Gruszynski, Ana Cláudia
    The article presents results of research that has as objective the identification of tendencies in the editorial production of Brazilian online scientific journals in the area of Communication, considering especially the publications design. The following journals have been studied: Comunicação, Mídia e Consumo; E-Compós; Eptic On Line, Galáxia; Intercom – Revista Brasileira de Ciências da Comunicação; Intexto; Revista FAMECOS; Revista Fronteiras; and Studium. The analysis was focused on the publications edition flow, from planning to circulation, which reflects in the final product available to readers. It was detected that although some changes indicate de influence of information technology in the...

  19. El papel de la supercomputación en la investigación: astrofísica de núcleos galácticos y agujeros negros

    Fiestas Iquira, José Antonio
    This article is based on the application of supercomputing techniques through an example in the investigation of the astronomical phenomena of evolution of galactic nuclei and black holes within the time period of the Universe’s existence. Numerical models of stellar dynamics simulations on supercomputers are essential in this area of research. This work was done in various research centers around the world, and the software employed uses N-body techniques in C ++, CUDA (Compute Unifi ed Device Architecture) and parallelized by using a MPI (Message Passing Interface). The scalability of the problem allows one to access accurate numerical models regarding...

  20. A MegaCam Survey of Outer Halo Satellites. III. Photometric and Structural Parameters

    Muñoz, Ricardo R.; Côté, Patrick; Santana, Felipe A.; Geha, Marla; Simon, Joshua D.; Oyarzún, Grecco A.; Stetson, Peter B.; Djorgovski, S. G.
    We present structural parameters from a wide-field homogeneous imaging survey of Milky Way satellites carried out with the MegaCam imagers on the 3.6 m Canada–France–Hawaii Telescope and 6.5 m Magellan-Clay telescope. Our survey targets an unbiased sample of "outer halo" satellites (i.e., substructures having galactocentric distances greater than 25 kpc) and includes classical dSph galaxies, ultra-faint dwarfs, and remote globular clusters. We combine deep, panoramic gr imaging for 44 satellites and archival gr imaging for 14 additional objects (primarily obtained with the DECam instrument as part of the Dark Energy Survey) to measure photometric and structural parameters for 58 outer...

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