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The main sequence offers a method for the systematization of quasar spectral proper- ties. Extreme FeII emitters (or Extreme Population A,xA) are believed to be sources accreting matter at very high rates. Along the quasar main sequence, they are eas- ily identifiable in large spectroscopic surveys over a broad redshift range. The very high accretion rate makes it possible that massive black holes hosted in xA quasars radiate at a stable, extreme luminosity-to-mass ratio. After reviewing basic trends associated with the main sequence, we show that the analysis of of optical and UV xA quasar spectra supports the possibility of identifying a virial broadening esti- mators from low-ionization line widths, and provide evidence of the the conceptual validity of redshift-independent luminosities based on virial broadening for a known luminosity-to-mass ratio., Slides on the contributed talk presented on Oct. 8, 2019 at the IAU Symp. No 356 held in Addis Ababa.

Broad emission lines in quasars enable us to "resolve" structure and kinematics of the broad line emitting region (BLR) thought to in- volve an accretion disk feeding a supermassive black hole. Interpretation of broad line measures within the 4DE1 formalism simplifies the apparent confusion among such data by contrasting and unifying properties of so-called high and low accreting Population A and B sources. H�� serves as an estimator of black hole mass, Eddington ratio and source rest frame, the latter a valuable input for Civ��1549 studies which allow us to isolate the blueshifted wind component. Optical and HST-UV spectra yield H�� and Civ��1549 spectra for low-luminosity sources while VLT-ISAAC and FORS and TNG-LRS provide spectra for high Luminosity sources. New high S/N data for Civ in high-luminosity quasars are presented here for comparison with the other previously published data. Comparison of H�� and Civ��1549 profile widths/shifts indicates that much of the emission from the two lines arise in regions with different structure and kinematics. Covering a wide range of luminosity and redshift shows evidence for a correlation between Civ��1549 blueshift and source Eddington ratio, with a weaker trend with source luminosity (similar amplitude outflows are seen over 4 of the 5 dex luminosity range in our combined samples). At low luminosity (z < 0.7) only Population A sources show evidence for a significant outflow while at high luminosity the outflow signature begins to appear in Population B quasars as well., 18 pages, 11 figures

The 4D eigenvector 1 parameter space defined by Sulentic et al. may be seen as a surrogate H-R diagram for quasars. As in the stellar H-R diagram, a source sequence can be easily identified. In the case of quasars, the main sequence appears to be mainly driven by Eddington ratio. A transition Eddington ratio may in part explain the striking observational differences between quasars at opposite ends of the main sequence. The eigenvector-1 approach opens the door towards properly contextualized models of quasar physics, geometry and kinematics. We review some of the progress that has been made over the past 15 years, and point out still unsolved issues.

Outflows from quasars may be almost ubiquitous, but there are significant differences on a source- by-source basis. These differences can be organized along the 4D Eigenvector 1 sequence: at low z, only the Population A sources radiating at relatively high Eddington ratio show evidences of prominent high- velocity outflows from the Civλ1549 line profiles. Here we discuss, starting from recent observations of high-luminosity sample of Hamburg-ESO quasars, the Civλ1549 emission line profiles and how they are affected by outflow motion as a function of the quasar luminosity. Our high-luminosity sample has the notable advantage that the rest frame has been set by previous Hβ observations in the J, H, and K band, therefore making measurements of inter-line shift accurate and free of systemic biases. As the redshift increases and the luminosity of the brightest quasars grows, powerful, high-velocity outflows may become more frequent. We then discuss the outflow contextualisation following the 4DE1 approach as a tool for unveiling the nature of the so-called Weak Lined Quasars (WLQs) that have emerged in recent years as a new, poorly understood class of quasars. We estimate the kinetic power associated with the Civλ1549 emitting gas in outflow, and we suggest that the host galaxies of the most luminous sources may experience a significant feedback effect.

While quasar outflows may be quasi-ubiquitous, there are significant differences on a source-by- source basis. These differences can be organized along the 4D Eigenvector 1 sequence: at least at low z, with only Population A sources radiating at relatively high Eddington ratio and showing prominent high-velocity outflows in Civ ��1549 line profiles. We discuss in this paper VLT-FORS observations of Civ ��1549 emission line profiles for a high-luminosity sample of Hamburg- ESO quasars and how they are affected by outflow motion as a function of quasar luminosity. Our high- luminosity sample has the notable advantage that the rest frame has been accurately determined from previous VLT-ISAAC observations of H�� in the J, H, and K bands. This makes measures of inter-line velocity shifts accurate and free of systemic biases. As the redshift increases and the luminosity of the brightest quasars increases, powerful, high-velocity outflows become more frequent. We discuss the outflow contextualisation, fol- lowing the 4DE1 formalism, as a tool for understanding the nature of the so-called weak lined quasars (WLQ) discovered in recent years as a new, poorly understood class of quasars. We estimate the kinetic power associ- ated with Civ ��1549 outflows and suggest that the host galaxies in the most luminous sources likely experience significant feedback., Accepted for publication in Astrophysics and Space Science

We present preliminary results from a pencil-beam spectroscopic survey of low-luminosity quasars at z ~ 2.2-2.5. Our goal is to compare these sources with low redshift analogues of similar luminosity. High s/n and moderate resolution spectra were obtained for 15 sources using the faint object spectrograph Osiris on the 10m Gran Telescopio Canarias. The new data make possible an almost unprecedented comparison between sources with the same (moderate) luminosity at widely different cosmic epochs. Preliminary analysis of our spectra confirms the presence of a relatively evolved population of quasars radiating at modest Eddington ratios. A notable difference between the low and high z quasars may involve the presence of lower metallicity quasars at high redshift., Accepted for publication in Advances in Space Research. Contributed talk presented at the 9th Serbian Conference on Spectral Line Shapes in Astrophysics (SCSLSA) held in Banja Koviliaca, on May 13-17, 2013. Minor corrections from previous version

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

The empirical basis of quasar astronomy can be overawing especially in the twenty-first century. A first source of intricacy involves the nomenclature that has evolved to label the multifold phenomenological manifestations now united under the umbrella of active galactic nuclei (AGNs). A further complication involves observations of the many subclasses with the observations now spanning the electromagnetic spectrum.

Most of the questions in this chapter deal with sources that do not show the “classical” broad emission-line spectrum that characterizes the majority of known AGNs at high and low redshift. If that majority represents a “parent population” of AGNs, is the apparent absence of broad lines a result of obscuration, orientation, or different physical conditions? Can all of the subclasses be unified under the AGN umbrella? With the unification scheme set in place and assumed to be fundamentally correct, there are at least four overarching questions: do all type-2 AGNs possess an obscured broad-line region? Or how can we distinguishing type-2 AGNs without a broad-line region if they exist? Where is the low end of quasar activity? The least luminous AGNs are the so-called low-ionization nuclear emission-line regions (LINERs), but it is legitimate to ask if they are all true AGNs.

We test the recent claim by Hu et al. (2008) that FeII emission in Type 1 AGN shows a systematic redshift relative to the local source rest frame and broad-line Hbeta. We compile high s/n median composites using SDSS spectra from both the Hu et al. sample and our own sample of the 469 brightest DR5 spectra. Our composites are generated in bins of FWHM Hbeta and FeII strength as defined in our 4D Eigenvector 1 (4DE1) formalism. We find no evidence for a systematic FeII redshift and consistency with previous assumptions that FeII shift and width (FWHM) follow Hbeta shift and FWHM in virtually all sources. This result is consistent with the hypothesis that FeII emission (quasi-ubiquitous in type 1 sources) arises from a broad-line region with geometry and kinematics the same as that producing the Balmer lines., Comment: 12 pages, 1 table, 1 figure - accepted for publication in ApJ Letters

We have completed a pilot survey imaging 15 SDSS selected void galaxies

To understand the processes that build up galaxies we investigate the stellar structure and gas kinematics of spiral and irregular galaxies out to redshift 1. We target 92 galaxies in four cluster ( z = 0.3 & 0.5 ) fields to study the environmental influence. Their stellar masses derived from multiband VLT/FORS photometry are distributed around but mostly below the characteristic Schechter-fit mass. From HST/ACS images we determine morphologies and structural parameters like disk length, position angle and ellipticity. Combining the spectra of three slit positions per galaxy using the MXU mode of VLT/FORS2 we construct the two-dimensional velocity field from gas emission lines for 16 cluster members and 33 field galaxies. The kinematic position angle and flatness are derived by a Fourier expansion of elliptical velocity profiles. To trace possible interaction processes, we define three irregularity indicators based on an identical analysis of local galaxies from the SINGS project. Our distant sample displays a higher fraction of disturbed velocity fields with varying percentages (10%, 30% and 70%) because they trace different features. While we find far fewer candidates for major mergers than the SINS sample at z ˜ 2, our data are sensitive enough to trace less violent processes. Most irregular signatures are related to star formation events and less massive disks are affected more than Milky-Way type objects. We detect similarly high fractions of irregular objects both for the distant field and cluster galaxies with similar distributions. We conclude that we may witness the building-up of disk galaxies still at redshifts z ˜ 0.5 via minor mergers and gas accretion, while some cluster members may additionally experience stripping, evaporation or harassment interactions.

Internal color gradients in galaxies probe a variation in stellar populations as a function of radius. Galaxies that have formed through monolithic collapse, should have a steep metallicity gradient (Carlberg 1984), whereas galaxy merging is expected to wash out gradients (White 1980). Studies of elliptical galaxies (Peletier et al. 1990) have found primarily negative gradients that have been interpreted as mainly due to metallicity (Faber 1977).We are extending these studies to dwarf galaxies in one of the richest environments of the local Universe, using high resolution and high sensitivity data from the Coma ACS Survey (Carter et al. 2008). Our goal is to test galaxy formation schemes for dwarf galaxies and quantify the influence of the environment on their evolution.We use galphot (Jorgensen, Franx and Kjærgaard 1992) to measure the azimuthally averaged surface brightness in the to a common resolution convolved F814W and F475W filter bands for a sample of likely Coma members (Trentham et al. 2009). The dwarf galaxies in our sample show primarily blue nuclei, whereas the central colors of ellipticals are reddened because of dust. After excluding the central parts of these galaxies, we find surprisingly weak but slightly negative logarithmic color gradients independent of host galaxy magnitude.

[Abridged] We compare broad emission line profiles and estimate line ratios for all major emission lines between Ly-alpha and H-beta in a sample of six quasars. The sources were chosen with two criteria in mind: the existence of high quality optical and UV spectra as well as the possibility to sample the spectroscopic diversity in the 4D Eigenvector 1 context . In the latter sense each source occupies a region (bin) in the FWHM(H-beta) vs. optical FeII strength plane that is significantly different from the others. High S/N H-beta emission line profiles are used as templates for modeling the other lines (Ly-alpha, CIV 1549, HeII 1640, Al III 1860, Si III] 1892, and Mg II 2800). We can adequately model all broad lines assuming the existence of three components distinguished by blueshifted, unshifted and redshifted centroids (indicated as blue, broad and very broad component respectively). The broad component (high electron density, low ionization parameter; high column density) is present in almost all type-1 quasars and therefore corresponds most closely to the classical broad line emitting region (the reverberating component). The blue component emission (lower electron density; high ionization; low column density) arises in less optically thick gas; it is often thought to arise in an accretion disk wind. The least understood component involves the very broad component (high ionization and large column density). It is perhaps the most distinguishing characteristic of quasars with FWHM H-beta > 4000 km/s that belong to the so-called Population B of our 4DE1 space. Population A quasars (FWHM H-beta < 4000 km/s) are dominated by broad component emission in H-beta and blue component emission in CIV 1549 and other high ionization lines. 4DE1 appears to be the most useful current context for revealing and unifying spectral diversity in type-1 quasars., 7 Tables, 5 Figures; accepted for publication in Monthly Notices of the Royal Astronomical Society

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

International conference “Galaxies in Isolation: Exploring Nature vs. Nurture” held in Granada (Spain), May 12–15, 2009., The project AMIGA (Analysis of the interstellar Medium of Isolated GAlaxies) provides a statistically significant sample of the most isolated galaxies in the northern sky. Such a control sample is necessary to understand the role of the environment in evolution and galaxy properties like the interstellar medium (ISM), star formation and nuclear activity. The data is publicly released under a VO interface at this http URL One of our main goals is the study of nuclear activity in non-interacting galaxies using different methods. We focus on the well known radiocontinuum-far infrared (FIR) correlation in order to findradio-excess galaxies which are candidates to host an active galactic nucleus (AGN) and FIR colours to find obscured AGN candidates. We looked for the existing information on nuclear activity in the V\'eron-Cetty catalogue and in the NASA Extragalactic Database (NED). We also used the nuclear spectra from the Sloan Digital Sky Survey which allow us to determine the possible presence of an AGN and to study the properties of the underlying stellar populations. We produced a final catalogue of AGN-candidate galaxies which will provide a baseline for the study of the nuclear activity depending on the environment. We find that the fraction of FIR selected AGN-candidates ranges between 7% and 20%. There are no radio-excess galaxies in our sample above a factor 5 of radio excess which is the lowest rate found in comparison with other samples in denser environments. Finally, we obtained a fraction of about 22% of AGN using the optical spectra, a significant fraction for a sample of isolated galaxies. We conclude that the environment plays a crucial and direct role in triggering radio nuclear activity and not only via the density-morphology or the density-luminosity relations., The authors are partially supported by DGI Grant AYA2008-06181-C02 and Junta de Adalucía (Spain) TIC-114 and P08-FQM-4205-PEX.

The last decade saw long-awaited improvements in our understanding of active galactic nuclei (AGN) spectral properties. This contribution reviews some important observational results obtained from optical and UV data as well as constraints on physical parameters that control the structure and dynamics of the Broad Line Region., 5 pages, invited talk to appear in "The Nuclear Region, Host Galaxy and Environment of Active Galaxies" (RevMexAA - Conference Series)

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 present a comprehensive study of the local environments of four E+S galaxy pairs with the main goal to investigate their formation/evolution histories. New XMM-Newton data were obtained for two pairs (RR 143 and RR 242) that complements existing ROSAT data for the other two (RR 210 and RR 216). The new observations reveal diffuse X-ray emission in both pairs. The emission is asymmetric in both cases and extends out to 120 kpc and 160 kpc in RR 143 and RR 242 respectively. The nucleus of RR 242 hosts a low luminosity mildly absorbed AGN. We find that the early-type components of pairs with diffuse hot gas appear to be relaxed objects while those in RR 210 and RR 216, where no diffuse emission has been found, display unambiguous signatures of ongoing interaction. Wide-field V and R-band data are used to study the photometric properties of the early-type components and to search for a candidate faint galaxy populations around each of the pairs. While no diffuse optical light is found for any of the pairs, all of the early-type members show very extended and concentric luminous envelopes. We identify a faint galaxy sample in each field and we consider whether they could be physically associated with the luminous pairs based upon (V-R) colors and photometric properties. We find that the distribution of r_e and M_R for the candidates are similar in three of the fields (RR 143, 216 and 242). The same selection criteria applied to the field of RR 210 suggest a fainter and more compact population possibly suggesting a larger background fraction than in the other fields., Comment: 47 pages, 18 figures, Astron. J. in press

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 examine the properties of the Fe emission lines that arise near 6.4 keV in the ASCA spectra of AGN. Our emphasis is on the Seyfert 1 galaxies where broad and apparently complex Fe K alpha emission is observed. We consider various origins for the line but focus on the pros and cons for line emitting accretion disk models. We develop a simple model of an illuminated disk capable of producing both X-ray and optical lines from a disk. The model is able to reproduce the observed Fe K alpha FWHM ratio as well as the radii of maximum emissivity implied by the profile redshifts. The overall profile shapes however do not fit well the predictions of our disk illumination model nor do we derive always consistent disk inclinations for the two lines. We conclude that the evidence for and against an accretion disk origin for the Fe K alpha emission is equal at best. The bulk of the data requires a very disparate set of line fits which shed little light on a coherent physical model. We briefly consider alternatives to disk emission models and show that a simple bicone model can reproduce the FE line profiles equally well., 29 pages, 6 tables, 6 figures. Submitted for publication in the Astrophysical Journal part I

UGC 3995 is a close pair of spiral galaxies whose eastern component hosts a Seyfert 2 nucleus. We present a detailed analysis of this system using long slit spectroscopy and narrow (\ha + \nii) as well as broad band (B, R) imaging and an archive WFPC2 image. The component galaxies reveal surprisingly small signs of interaction considering their spatial proximity and almost identical recession velocities, as the bright filament is probably an optical illusion due to the superposition of the bar of the Seyfert galaxy and of the spiral arms of the companion. The broad band morphology, a B--R color map, and a continuum-subtracted \ha + \nii image demonstrate that the western component UGC 3995B is in front of the Seyfert-hosting component UGC 3995A, partly obscuring its western side. The small radial velocity difference leaves the relative motion of the two galaxies largely unconstrained. The observed lack of major tidal deformations, along with some morphological peculiarities, suggests that the galaxies are proximate in space but may have recently approached each other on the plane of the sky. The geometry of the system and the radial velocity curve at P. A. = 106 suggest that the encounter may be retrograde or, alternatively, prograde before perigalacticon. The partial overlap of the two galaxies allows us to estimate the optical thickness of the disk of component B. We derive an extinction = 0.18 visual magnitudes in the infra-arms parts of the foreground galaxy disk, and >= 1-1.5 visual magnitudes in correspondence of the spiral arms., Accepted for publication in the Astronomical Journal (June 1999 issue)

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.

We review the evidence for AGN optical and X-ray broad line emission from an accretion disk. We argue that there is little, if any, statistical evidence to support this assertion. The inconsistency is strongest for the rare class of Balmer profiles that show double peaks. The line profiles predicted by a simple illuminated disk model are often incompatible with the observations. We suggest that the Fe Kalpha line in Seyfert 1 galaxies, where a broad line is most often and most strongly detected, is actually a composite of two lines both with Gaussian profiles; one narrow/unshifted and the other broad/redshifted., 11 pages, 3 figures, to be published in Structure and Kinematics of Quasars Broad Line Regions, Proceedings of a meeting held in Lincoln, March 23-36, 1998, ASP Conference Series, in press