Search

We investigated the star formation efficiency for all the dust emitting sources in Stephan's Quintet (SQ). We inferred star formation rates using Spitzer MIR/FIR and GALEX FUV data and combined them with gas column density measurements by various authors, in order to position each source in a Kennicutt-Schmidt diagram. Our results show that the bright IGM star formation regions in SQ present star formation efficiencies consistent with those observed within local galaxies. On the other hand, star formation in the intergalactic shock region seems to be rather inhibited., Conference proceedings "Galaxy Mergers in an evolving Universe", 23-28 October 2011, Hualien, Taiwan

In this contribution we review and discuss several aspects of Cosmic Voids, as a background for our void galaxy project (accompanying paper by Stanonik et al.). Voids are a major component of the large scale distribution of matter and galaxies in the Universe. Following a sketch of the general characteristics of void formation and evolution, we describe the influence of the environment on their development and structure and the characteristic hierarchical buildup of the cosmic void population. In order to be able to study the resulting tenuous void substructure and the galaxies populating the interior of voids, we subsequently set out to describe our parameter free tessellation-based watershed void finding technique. It allows us to trace the outline, shape and size of voids in galaxy redshift surveys. The application of this technique enables us to find galaxies in the deepest troughs of the cosmic galaxy distribution, and has formed the basis of our void galaxy program.

The role of the environment on galaxy evolution is still not fully understood. In order to quantify and set limits on the role of nurture one must identify and study a sample of isolated galaxies. The AMIGA project "Analysis of the Interstellar Medium of Isolated GAlaxies" is doing a multi-wavelength study of a large sample of isolated galaxies in order to examine their interstellar medium and star formation activity. We processed data for 950 galaxies from the Catalogue of Isolated Galaxies (CIG, Karachentseva 1973) and evaluated their isolation using an automated star-galaxy classification procedure (down to M_B ~17.5) on large digitised POSS-I fields surrounding each isolated galaxy (within a projected radius of at least 0.5 Mpc). We defined, compared and discussed various criteria to quantify the degree of isolation for these galaxies: e.g. Karachentseva's revised criterion, local surface density computations, estimation of the external tidal force affecting each isolated galaxy. We found galaxies violating Karachentseva's original criterion, and we defined various subsamples of galaxies according to their degree of isolation. Additionally, we sought for the redshifts of the primary and companion galaxies to access the radial dimension. We also applied our pipeline to triplets, compact groups and clusters and interpret the isolated galaxy population in light of these control samples., 4 pages, proceedings of the contributed talk given at the conference "Galaxies in Isolation: Exploring Nature vs. Nurture" held in Granada, May 12-15, 2009

The 4D Eigenvector 1 parameter space was introduced seven years ago as an attempt at multiwavelength spectroscopic representation of quasars. It appears to be the most effective diagnostic space for unifying the diversity of broad line AGN. This progress report shows that the diagnostic power of 4DE1 is confirmed using optical spectra from the SDSS, UV spectra from HST and X-ray spectra from XMM. Our introduction of the population A-B concept continues to provide useful insights into quasar diversity. Largely radio-quiet, high accreting, low BH mass Pop. A sources (FWHM H_beta 4000 km/s) include most radio-loud AGN and show weak FeII emission and little evidence for a soft X-ray excess or a CIV blueshift., 8 pages, 3 figures, 2 tables - review to appear in "The Nuclear Region, Host Galaxy and Environment of Active Galaxies" (RevMexAA - Conference Series)

We attempt to characterize the geometry of Broad Absorption Line (BAL) QSOs by studying a low redshift sample of 12 sources. We find that the majority of these sources are Population A quasars as defined in (broad H-beta FWHM > 4000 kms/s; Sulenticet al 2000). A possible correlation between terminal velocity and absolute V magnitude suggests that the bolometric luminosity to black hole mass ratio \lm is a governing factor with classical BAL sources showing the highest values. CIV 1549 emission in classical BAL sources shows a profile blueshift that supports a disk wind/outflow scenario with a half opening angle of < 50 deg. Observation of ``secondary'' mini-BAL features in the CIV 1549 emission profile motivates us to model BALs with an additional component that may be involved with the BLR outflow and co-axial with the accretion disk., Accepted for publication in Revista Mexicana de Astronomia y Astrofisica

We review constraints on models of the broad line region that are imposed by observations of the emission lines in Active Galactic Nuclei. Comparison of high and low ionization lines in sources with FWHM Hbeta < 4000 km/s points toward low ionization line emission produced in a flattened geometry (the accretion disk?) with an associated high ionization wind. It remains unclear whether these results can be extended to all radio quiet AGN and particularly to radio loud AGN., 8 pages, 2 figures. Invited talk to be published in Astrophysical Plasmas: Codes, Models and Observations, proceedings of a meeting held on October 25--29, 1999 at Mexico City, Rev. Mexicana de Astron. y Astrof., Serie de Conferencias

We present an introduction to the Eigenvector 1 parameter space, which is an attempt to find a spectroscopic unification for broad-line emitting AGN. It is a 4D parameter space that uses optical, UV and X{ray measures to discriminate between different classes of AGN. Differences in parameter space occupation suggest that radio- loud sources are fundamentally different from the radio-quiet majority. This is a derivative of our suggestion that two distinct populations of broad-line emitting AGN may exist. We suggest that exploration of Eigenvector 1 space at higher redshift and source luminosities would be a valuable program for the proposed new telescopes at San Pedro Mártir

The evolutionary history of galaxies is thought to be strongly conditioned by the environment. In order to quantify and set limits on the role of nurture one must identify and study an isolated sample of galaxies. But it is not enough to identify a small number of the "most isolated" galaxies. We begin with 950 galaxies from the Catalogue of Isolated Galaxies (Karachentseva 1973) and reevaluate isolation using an automated star-galaxy classification procedure on large digitised POSS-I fields. We define, compare and discuss various criteria to quantify the degree of isolation for these galaxies: Karachentseva's revised criterion, local surface density computations and an estimation of the external tidal force affecting each isolated galaxy. Comparison of multi-wavelength ISM properties, in particular the H$\alpha$ emission line, will allow us to separate the influence of the environment from the one due to the initial conditions at formation., Comment: 2 pages, no figure, to be published in SF2A-2005, EdP Sciences, F. Casoli, T. Contini, J.M. Hameury and L. Pagani, editors

International conference “Galaxies in Isolation: Exploring Nature vs. Nurture” held in Granada (Spain), May 12–15, 2009., Studying the atomic gas (HI) properties of the most isolated galaxies is essential to quantify the effect that the environment exerts on this sensitive component of the interstellar medium. We observed and compiled HI data for a well defined sample of ~ 800 galaxies in the Catalog of Isolated Galaxies, as part of the AMIGA project (Analysis of the ISM in Isolated GAlaxies, this http URL), which enlarges considerably previous samples used to quantify the HI deficiency in galaxies located in denser environments. By studying the shape of 182 HI profiles, we revisited the usually accepted result that, independently of the environment, more than half of the galaxies present a perturbed HI disk. In isolated galaxies this would certainly be a striking result if these are supposed to be the most relaxed systems, and has implications in the relaxation time scales of HI disks and the nature of the most frequent perturbing mechanisms in galaxies. Our sample likely exhibits the lowest HI asymmetry level in the local Universe. We found that other field samples present an excess of ~ 20% more asymmetric HI profiles than that in CIG. Still a small percentage of galaxies in our sample present large asymmetries. Follow-up high resolution VLA maps give insight into the origin of such asymmetries., This work has been partially supported by Spanish DGI grant AYA2008-06181-C02, as well as Junta de Andalucia (Spain) grants P08-FQM-4205-PEX and TIC-114 16-C02-01. DE is supported by the Marie Curie International fellowship MOIF-CT-2006-40298.

"Sulentic et al. (2007) defined the 4DE1, which is a four dimensions parameter space that uses optical, UV and X-ray measures to discriminate between different classes of AGN. Using new X-ray data from the satellite XMM-Newton, we present a way to visualize all the parameters in one 3D graph made by the open source software TOP CAT. The different correlations have been framed in the context of an evolutionary scheme and we make an interpretation of the underlying physics."