AGN spiral galaxies in groups: effects of bars

We explore properties of barred active spiral galaxies in groups selected from the SDSS-DR7, with the aim of assessing the effects of bars on AGN and the role of the high density environment. We identified barred active galaxies that reside in groups from SDSS-DR7 group catalog. To provide a suitable quantification of the effects of bars, a reliable control sample of unbarred active galaxies in high density environments with similar redshift, magnitude, morphology, and bulge size distributions was constructed. We found that the fraction of barred AGN galaxies in groups (~ 38 %) is higher than those in the total barred AGN sample ( ~ 28 %), indicating that AGN spiral galaxies in groups are more likely to be barred than those in the field. We also found that barred AGN galaxies are more concentrated towards the group centers than the other unbarred AGN group members. In addition, barred AGN host galaxies show an excess of population dominated by red colors suggesting that bars produce an importanteffect on galaxy colors of AGN hosts. The host groups of the barred AGN exhibit a larger fraction of red colors than the host groups of the corresponding unbarred active galaxies. Color-magnitude relations of both host groups of AGN differ significantly: the host group colors of barred active galaxies display distributions spreading toward red populations, with respect to the host groups of the unbarred AGN objects. Barred active galaxies show an excess of nuclear activity compared to galaxies without bars. We found that barred active galaxies located farther from the group-center have stronger Lum[OIII]. Our findings suggest that the efficiency of bars to transport material towards the more central regions of the AGN galaxies in high density environments reveals an important dependence on the localization of objects within the group and on the host group colors.Comment: 10 pages, 10 figures. Accepted for Astronomy & Astrophysic

Galaxy triplets in Sloan Digital Sky Survey Data Release 7 - III. Analysis of Configuration and Dynamics

We analyse the spatial configuration and the dynamical properties of a sample of 92 galaxy triplets obtained from the SDSS-DR7 (SDSS-triplets) restricted to have members with spectroscopic redshifts in the range $0.01\le z \le 0.14$ and absolute r-band luminosities brighter than $M_r=-20.5$. The configuration analysis was performed through Agekyan & Anosova map (AA-map). We estimated dynamical parameters, namely the radius of the system, the velocity dispersion, a dimensionless crossing-time and the virial mass. We compared our results with those obtained for a sample of triplets from the catalogue "Isolated Triplets of Galaxies" (K-triplets) and a sample of Compact Groups. We have also studied a mock catalogue in order to compare real and projected configurations, and to estimate the three dimensional dynamical parameters of the triple systems. We found that the SDSS-triplets prefer alignment configurations while K-triplets present an uniform distribution in the AA-map. From the dynamical analysis we conclude that the SDSS-triplets, K-triplets and Compact Groups present a similar behaviour comprising compact systems with low crossing-time values, with velocity dispersions and virial masses similar to those of low mass loose groups. Moreover, we found that observed and simulated triplets present similar dynamical parameters. We also performed an analysis of the dark matter content of galaxy triplets finding that member galaxies of mock triplets belong to the same dark matter halo, showing a dynamical co-evolution of the system. These results suggest that the configuration and dynamics of triple systems favour galaxy interactions and mergers.Comment: Accepted for publication in MNRAS. 9 pages, 8 figure

An improved method for the identification of galaxy systems: Measuring the gravitational redshift by Dark Matter Haloes

We introduce a new method for the identification of galaxy systems in redshift surveys based on the halo model. This method is a modified version of the K-means identification algorithm developed by Yang et al (2005). We have calibrated and tested our algorithms using mock catalogs generated using the Millennium simulations (Springel et al. 2005) and applied them to the NYU-DR7 galaxy catalog (based on the SDSS datasets). Using this local sample of groups and clusters of galaxies we have measured the effect of gravitational redshift produced by their host dark matter haloes. Our results shows radial velocity decrements consistent with general relativity predictions and previous measurements by Wojtak et al (2011) in clusters of galaxies.Comment: Accepted for Publication in MNRAS Letters, 2 figures. arXiv admin note: text overlap with arXiv:astro-ph/0405234, arXiv:astro-ph/0406593 by other author

Observatorio Cordón Macón

Resumen: Se describen brevemente los proyectos ABRAS, ISON y TOROS que se desarrollan en el nuevo observatorio del Cerro Macón, en la Provincia de Salta, Argentina.Abstract: We provide a brief summary of the ABRAS; ISON and TOROS projects being under development in the new observatory at Cerro Macon in Salta Province; Argentina.http://adsabs.harvard.edu/abs/2013BAAA...56..433GpublishedVersionFil: García Lambas, Diego. Conicet, Instituto de Astronomía Teórica y Experimental; Argentina.Fil: Recabarren, Pablo. Ministerio de Ciencia, Tecnología e Innovación de la Nación. Conicet; Argentina.Óptica (incluida Óptica Láser y Óptica Cuántica), Acústic

Dependencia de la longitud de correlación de galaxias con el tipo morfológico y la velocidad circular

Utilizando el catálogo de velocidades radiales CfA investigamos la dependencia entre la longitud de correlación r. de galaxias con el tipo morfológico t y la velocidad circular Vc. Adoptando una ley de potencia para la función de correlación bipuntual x(r) =(r/r₀) con g = 1.8 y r₀ = 6 h Mpc (valor medio), se determina una relación entre r₀ y t que resulta: r₀ = (6.7 - 0.3 t) h Mpc. Encontramos una dependencia significativa entre el número medio de vecinos y la velocidad circular de las galaxias. Objetos con Vc mayor que 250 km/s presentan un exceso en el número medio de vecinos dentro de esferas de radio R, R < 6 h Mpc. Este exceso implica un incremento del 20% en el valor de r. respecto a su valor medio. Por otra parte no se encuentra evidencia estadística de una dependencia similar para objetos con velocidades Vc < 250 km/s.Asociación Argentina de Astronomí

Photometric observations of Southern Abell Cluster Redshifts Survey Clusters: Structure of galaxies in the inner region of clusters of galaxies

We analyze photometric properties of 1384 cluster galaxies as a function of the normalized distance to cluster center. These galaxies were selected in the central region ($r/r_{200} \leq$ 0.8) of 14 southern Abell clusters chosen from the Southern Abell Cluster Redshifts Survey (SARS). For 507 of these galaxies we also obtained their luminosity profiles. We have studied the morphology-clustercentric distance relation on the basis of the shape parameter $n$ of the S\'ersic's law. We also have analyzed the presence of a possible segregation in magnitude for both, the galaxy total luminosity and that of their components (i.e. the bulge and the disk). Results show a marginal ($2\sigma$ level) decrease of the total luminosity as a function of normalized radius. However, when bulges are analyzed separately, a significant luminosity segregation is found ($3\sigma$ and $2\sigma$ for galaxies in projection and member galaxies respectively). The fraction of bulges brighter than $M_B \leq -22$ is three times larger in the core of clusters than in the outer region. Our analysis of the disk component suggests that disks are, on average, less luminous in the cluster core than at $r/r_{200} \sim 0.8$. In addition, we found that the magnitude-size relation as a function of $r/r_{200}$ indicates (at $2\sigma$ level) that disks are smaller and centrally brighter in the core of clusters. However, the Kormendy relation (the bulge magnitude-size relation) appears to be independent of environment.Comment: To appear in the A

Chemical Enrichment at High Redshifts: Understanding the Nature of Damped Lyα Systems in Hierarchical Models

We use cosmological hydrodynamical simulations including star formation and metal enrichment to study the evolution of the chemical properties of galaxy-like objects at high redshift in the range 0.25 < z < 2.35 in a hierarchical clustering scenario. We find that as the galactic objects are assembled, their gaseous components exhibit neutral hydrogen column densities with abundances and scatter comparable to those observed in damped Lyα systems (DLAs). The unweighted mean of abundance ratios and least-square linear regressions through the simulated DLAs yield intrinsic metallicity evolution for [Zn/H] and [Fe/H] consistent with results obtained from similar analyses of available observations. Our model statistically reproduces the mild evolution detected in the metallicity of the neutral hydrogen content of the universe, given by mass-weighted means, if observational constraints are considered (as suggested in 1998 by Boissée and co-workers). For the α-elements in the simulated DLAs, we find neither enhancement nor dependence on metallicity. Our results support the hypotheses that DLAs trace a variety of galactic objects with different formation histories and that both Type I and Type II supernovae are contributing to the chemical enrichment of the gas component, at least since z ≈ 2. This study indicates that DLAs could be understood as the building blocks that merged to form current normal galaxies within a hierarchical clustering scenario.Facultad de Ciencias Astronómicas y Geofísica