L’objectif de ma thèse porte sur les interactions entre les noyaux actifs de galaxies et le milieu interstellaire des galaxies. En particulier, je mets l’accent sur les deux mécanismes possibles responsables de la production des vents par les trous noirs : les jets et les vents produits par le rayonnement de ces trous noirs. Les simulations hydrodynamiques de haute résolution des galaxies comprenant la rétroac- tion d’un jet ont montré que l’activité des noyaux actifs peut conduire à une pression exces- sive sur les régions denses de formation stellaire dans les galaxies, et donc à augmenter la formation d’étoiles, conduisant à un effet positif de rétroaction. Je montre que ces noyaux actifs induits par pression régulée et formation d’étoiles peuvent aussi être une explica- tion possible des taux de formation stellaire élevés observés dans l’Univers à haut décalage spectral. De plus, j’ai également étudié en détails comment le rayonnement émis à partir d’un disque d’accrétion autour du trou noir agit efficacement avec le milieu interstellaire et entraîne un fort vent galactique, en simulant la propagation des photons à partir des équations hydrodynamiques du rayonnement. Les simulations montrent que la grande luminosité d’un quasar est en effet capable de conduire des vents à grande échelle et à grande vitesse. Le rayonnement infrarouge est nécessaire pour transérer efficacement le gaz par multi-diffusion sur la poussière dans les nuages denses. Le nombre typique de multi-diffusion diminue rapidement quand le nuage central de gaz central se dilate et se rompt, ce qui permet au rayonnement de s’échapper à travers les canaux à faible densité. / Supermassive black holes (SMBHs) are known to reside in the centres of most large galaxies. The masses of these SMBHs are known to correlate with large-scale properties of the host galaxy suggesting that the growth of the BHs and large-scale structures are tightly linked. A natural explanation for the observed correlation is to invoke a self-regulated mechanism involving feedback from Active Galactic Nuclei (AGN). The focus of this thesis is on the interactions between AGN outflows and the ISM and how the feedback impacts the host galaxy. In particular, it focuses on the two possible mechanism of outflows, namely, outflows related to AGN jets and outflows produced by AGN radiation. High resolution, galaxy scale hydrodynamical simulations of jet-driven feedback have shown that AGN activity can over-pressurise dense star-formation regions of galaxies and thus enhance star formation, leading to a positive feedback effect. I propose, that such AGN-induced pressure-regulated star formation may also be a possible explanation of the high star formation rates recently found in the high-redshift Universe. In order to study in more detail the effects of over-pressurisation of the galaxy, I have performed a large set of isolated disc simulations with varying gas-richness in the galaxy. I found that even moderate levels of over-pressurisation of the galaxy boosts the global star formation rate by an order of magnitude. Additionally, stable discs turn unstable which leads to significant fragmentation of the gas content of the galaxy, similar to what is observed in high-redshift galaxies. The observed increase in the star formation rate of the galaxy is in line with theoretical predictions. I have also studied in detail how radiation emitted from a thin accretion disc surrounding the BH effectively couples to the surrounding ISM and drives a large scale wind. Quasar activity is typically triggered by extreme episodes of gas accretion onto the SMBH, in particular in high-redshift galaxies. The photons emitted by a quasar eventually couple to the gas and drive large scale winds. In most hydrodynamical simulations, quasar feedback is approximated as a local thermal energy deposit within a few resolution elements, where the efficiency of the coupling between radiation of the gas is represented by a single parameter tuned to match global observations. In reality, this parameter conceals various physical processes that are not yet fully un- derstood as they rely on a number of assumptions about, for instance, the absorption of photons, mean free paths, optical depths, and shielding. To study the coupling between the photons and the gas I simulated the photon propagation using radiation-hydrodynamical equations (RHD), which describe the emission, absorption and propagation of photons with the gas and dust. Such an approach is critical for a better understanding of the coupling between the radiation and gas and how hydrodynamical sub-grid models can be improved in light of these results...

Malgré des années de travaux théoriques et observationnels intensifs, nous sommes toujours loin d’une complète compréhension de l’univers proche, la Voie Lactée (MW) et ses galaxies voisines. Parmi les satellites de la MW, le Petit et le Grand Nuage de Magellan (LMC) sont particulièrement intéressants puisqu’ils forment le plus proche exemple de galaxies en interaction gravitationnelle et hydrodynamique, et partant, constituent un laboratoire unique pour étudier les effets des marées et l’échange de matière sur l’évolution chimique et l’histoire de la formation stellaire d’une galaxie. Le LMC est une galaxie de petite masse barrée à disque, prototype des galaxies riches en gaz que l’on pense jouer un rôle important dans la construction des grandes galaxies dans le cadre du ΛCDM. De plus, avec sa métallicité actuelle d’environ le tiers de la métallicité solaire, le chemin d’enrichissement chimique suivi par le LMC donne un grand poids aux yields des générations stellaires pauvres en métaux, ce qui fait du LMC un environnement idéal pour étudier la nucléosynthèse aux basses métallicités. Ce travail de doctorat vise à: 1) caractériser chimiquement la population de la barre du LMC, 2) comparer les tendances des éléments de la MW et du LMC et interpréter les différences ou ressemblance en termes d’évolution chimique et/ou de processus nucléosynthétiques (contraintes sur les sites et les processus nucléosynthétiques), 3) comparer l’évolution chimique de la barre et du disque interne du LMC et interpréter les différence ou ressemblance dans le contexte de la formation de la barre. Nos résultats montrent que l’histoire chimique du LMC a connu un forte contribution des supernovae de type I ainsi qu’un fort enrichissement en éléments s par les vents d’étoiles AGB pauvres en métaux. Par rapport à la MW, les étoiles massives ont eu une contribution plus petite à l’enrichissement chimique du LMC. Les différences observées entre la barre et le disque parlent en faveur d’un épisode de formation stellaire accrue il y a quelques Gyr, ayant lieu dans les zones centrales du LMC et conduisant à la formation de la barre. Ceci est en accord avec les histoires de la formation stellaire récemment dérivées. / Despite decades of intensive observational and theoretical work, we are still far from a complete and clear understanding of the nearby universe, the Milky Way (MW) and its neighbours. Among the satellites of the MW, the Small and Large Magellanic Cloud (LMC) are of particular interest since they form the closest example of galaxies in gravitational and hydrodynamical interaction, and therefore constitute a unique laboratory to study the effect of tides and matter exchange on the chemical evolution and star formation history of a galaxy. The LMC is a low-mass barred disc galaxy, prototypical of gas-rich galaxies that are thought to play an important role in the build-up of large galaxies in the ΛCDM framework. Furthermore, with its present day metallicity of only third of solar, the chemical enrichment path followed by the LMC gives a heavy weight to the yields of metal-poor stellar generations, which makes the LMC an ideal environment to study nucleosynthesis at low metallicities. This thesis work aims at: 1) chemically characterizing the LMC bar population, 2) comparing the elemental trends of the MW and the LMC and interpreting the differences or similarities in terms of chemical evolution and/or nucleosynthesis processes (constraints on the nucleosynthetic sites and processes), 3) comparing the chemical evolution of the LMC bar and inner disc and interpreting the differences or similarities between the LMC bar and inner disc in the context of the bar formation. Our results show that the chemical history of the LMC experienced a strong contribution from type Ia supernovae as well as a strong s-process enrichment from metal-poor AGB winds. Massive stars made a smaller contribution to the chemical enrichment compared to the MW. The observed differences between the bar and the disc speak in favour of an episode of enhanced star formation a few Gyr ago, occurring in the central parts of the LMC and leading to the formation of the bar. This is in agreement with recently derived star formation histories.

The relationship first pointed out by Tully and Fisher between the luminosity of spiral galaxies and their maximum rotation velocity, as measured by the 21 cm line-width, continues to be one of the best methods available to measure relative distances. At infrared wavelengths, the observational scatter about this relation is typically 0.35 to 0.50 magnitudes, permitting relative distance estimates with an accuracy of about 20 percent. The Malmquist bias in a magnitude-limited sample is 1.38σ ², and while the solution to the general problem is complex, it is clear that reducing the scatter about the Tully-Fisher relation by even a factor of two would make a large difference in our ability to determine the local velocity field from distances and velocities of individual galaxies. In this dissertation we discuss the scatter in the Tully-Fisher relation at infrared wavelengths, and look for ways to reduce that dispersion through the inclusion of additional observational parameters. The data for this study are derived from a CCD survey of 244 spiral galaxies in twenty clusters falling in the redshift range 3,000 to 11,000 km s⁻¹. From surface brightness profiles and elliptical aperture photometry, we obtained isophotal and total magnitudes at B, R, and I, isophotal diameters, mean and nuclear surface brightnesses, and a concentration parameter indicative of the bulge-to-disk ratio. These quantities were then combined with colors and HI-content measures taken from the literature in a search for correlations with Tully-Fisher residuals. None of the trial second-parameters resulted in a substantial decrease in the scatter about the fiducial Tully-Fisher relation. An examination of the properties of the cluster samples shows that many of the clusters exhibit considerable substructure. While it is possible that the implied depth effects are important to the scatter about the magnitude/line-width relation, calculated lower limits to the dispersion in depth turn out to be rather small.

The sporadic accretion following the tidal disruption of a star by a super-massive black hole (TDE) leads to a bright. UV and soft X-ray flare in the galactic nucleus. The gas and dust surrounding the black hole responses to such a flare with an echo in emission lines and infrared emission. In this paper, we report the detection of long fading mid-IR emission lasting up to 14 years after the flare in four TDE candidates with transient coronal lines using the WISE public data release. We estimate that the reprocessed mid-IR luminosities are in the range between 4 x 10(42) and 2 x 10(43) erg s(-1) and dust temperature in the range of 570-800 K when WISE first detected these sources three to five years after the flare. Both luminosity and dust temperature decrease with time. We interpret the mid-IR emission as the infrared echo of the tidal disruption flare. We estimate the UV luminosity at the peak flare to be 1 to 30 times 10(44) erg s(-1) and that for. warm dust masses to be. in the range of 0.05-1.3 M-circle dot within a few parsecs. Our results suggest that the. mid-infrared echo is a general signature of TDE in the gas-rich environment.

Data on the UBV system are presented for 14 quasistellar radio sources, 8 N galaxies,39 radio galaxies and 19 radioquiet galaxies south of +20° declination. Their positions in the two - color diagram show that the integrated colors of the radio galaxies are similar to those of the radioquiet galaxies of the same morphological type. In an absolute radio magnitude - radio index diagram a linear relation exists between M158 and ím158 Boo for radio galaxies of all classes. The QSO:s, however, do not follow this relation, and possible explanations are considered. The brightness and color distributions in the larger galaxies are described in detail. Our results are combined with other data for a discussion of the compositions of these systems. It is suggested that a fairly high amount of reddening occurs in the central regions of several galaxies, as for instance, in NGC 1068 and NGC 1316.

We use simulated galaxy surveys to study: (i) how galaxy membership in redMaPPer clusters maps to the underlying halo population, and (ii) the accuracy of a mean dynamical cluster mass, M-sigma(lambda), derived from stacked pairwise spectroscopy of clusters with richness lambda. Using similar to 130 000 galaxy pairs patterned after the Sloan Digital Sky Survey (SDSS) redMaPPer cluster sample study of Rozo et al., we show that the pairwise velocity probability density function of central-satellite pairs with m(i) < 19 in the simulation matches the form seen in Rozo et al. Through joint membership matching, we deconstruct the main Gaussian velocity component into its halo contributions, finding that the top-ranked halo contributes similar to 60 per cent of the stacked signal. The halo mass scale inferred by applying the virial scaling of Evrard et al. to the velocity normalization matches, to within a few per cent, the log-mean halo mass derived through galaxy membership matching. We apply this approach, along with miscentring and galaxy velocity bias corrections, to estimate the log-mean matched halo mass at z = 0.2 of SDSS redMaPPer clusters. Employing the velocity bias constraints of Guo et al., we find aEuroln (M-200c)|lambda aEuro parts per thousand = ln (< M-30) + alpha(m) ln (lambda/30) with M-30 = 1.56 +/- 0.35 x 10(14) M-aS (TM) and alpha(m) = 1.31 +/- 0.06(stat) +/- 0.13(sys). Systematic uncertainty in the velocity bias of satellite galaxies overwhelmingly dominates the error budget.

To elucidate the intrinsic broadband infrared (IR) emission properties of active galactic nuclei (AGNs), we analyze the spectral energy distributions (SEDs) of 87 z less than or similar to 0.5 Palomar-Green (PG) quasars. While the Elvis AGN template with a moderate far-IR correction can reasonably match the SEDs of the AGN components in similar to 60% of the sample (and is superior to alternatives such as that by Assef), it fails on two quasar populations: (1) hot-dustdeficient (HDD) quasars that show very weak emission thoroughly from the near-IR to the far-IR, and (2) warm-dust- deficient (WDD) quasars that have similar hot dust emission as normal quasars but are relatively faint in the mid-and far-IR. After building composite AGN templates for these dust-deficient quasars, we successfully fit the 0.3-500 mu m SEDs of the PG sample with the appropriate AGN template, an infrared template of a star-forming galaxy, and a host galaxy stellar template. 20 HDD and 12 WDD quasars are identified from the SED decomposition, including seven ambiguous cases. Compared with normal quasars, the HDD quasars have AGNs with relatively low Eddington ratios and the fraction of WDD quasars increases with AGN luminosity. Moreover, both the HDD and WDD quasar populations show relatively stronger mid-IR silicate emission. Virtually identical SED properties are also found in some quasars from z = 0.5 to 6. We propose a conceptual model to demonstrate that the observed dust deficiency of quasars can result from a change of structures of the circumnuclear tori that can occur at any cosmic epoch.

The range of currently proposed active galactic nucleus (AGN) far-infrared templates results in uncertainties in retrieving host galaxy information from infrared observations and also undermines constraints on the outer part of the AGN torus. We discuss how to test and reconcile these templates. Physically, the fraction of the intrinsic AGN IR-processed luminosity compared with that from the central engine should be consistent with the dust-covering factor. In addition, besides reproducing the composite spectral energy distributions (SEDs) of quasars, a correct AGN IR template combined with an accurate library of star-forming galaxy templates should be able to reproduce the IR properties of the host galaxies, such as the luminosity-dependent SED shapes and aromatic feature strengths. We develop tests based on these expected behaviors and find that the shape of the AGN intrinsic far-IR emission drops off rapidly starting at similar to 20 mu m and can be matched by an Elvis et al.-like template with a. minor modification. Despite the variations in the near- to mid-IR bands, AGNs in quasars and Seyfert galaxies have remarkably similar intrinsic far-IR SEDs at lambda similar to 20-100 mu m, suggesting a similar emission character of the outermost region of the circumnuclear torus. The variations of the intrinsic AGN IR SEDs among the type-1 quasar population can be explained by the changing relative strengths of four major dust components with similar characteristic temperatures, and there is evidence for compact AGN-heated dusty structures at sub-kiloparsec scales in the far-IR.

Estudamos neste trabalho as propriedades globais dos superaglomerados de galáxias com uma amostra de galáxias observadas espectroscopicamente pelo Sloan Digital Sky Survey (SDSS). Nossa amostra limitada em volume possui 121.002 galáxias com $M_r<-21$ dentro do intervalo de redshift $0,02<z<0,155$. Identificamos os superaglomerados utilizando os métodos de campo de densidades e \\textit{friends-of-friends}. Escolhemos um parãmetro de suavização $\\sigma=8h^{-1}Mpc$ e amostramos o campo de densidades numa grade de largura $l_{cel}=4h^{-1}Mpc$. Com o intuito de avaliar o efeito do limiar de densidade na identificação dos superaglomerados, escolhemos dois valores: um correspondente ao número máximo de estruturas em grande escala e um com o maior superaglomerado com dimensão de aproximadamente $120h^{-1}Mpc$. Para cada valor obtivemos a riqueza e a luminosidade total dos objetos. Para uma análise morfológica, os Funcionais de Minkowski foram calculados e os superaglomerados foram classificados como filamentos, fitas e panquecas. Analisando possíveis correlações entre as características dos superaglomerados, encontramos que filamentos tendem a ser mais ricos e consequentemente mais luminosos e com uma maior dispersão de velocidades. Usando a distribuição cumulativa de luminosidade de superaglomerados, encontramos que as distribuições de filamentos e fitas são distintas entre si. Num apêndice apresentamos um estudo das populações estelares de galáxias em superaglomerados. Calculamos a densidade local para cada galáxia e estudamos um análogo da relação morfologia-densidade através da relação entre densidade local e os parâmetros espectrais. Nenhuma diferença significativa foi notada entre filamentos, fitas e panquecas. Em outras palavras, comportamentos similares foram identificados para todos os parâmetros espectrais e morfologias dos superaglomerados, em todos os limiares. Resultado semelhante foi obtido para a distribuição cumulativa dos parâmetros espectrais. Finalmente, estudamos a influência dos aglomerados no ambiente interno dos superaglomerados. Valores médios dos parâmetros espectrais foram calculados dentro de esferas centradas nas BCGs (\\textit{Brightest Cluster Galaxies}) e verificamos todos os perfis dos parâmetros espectrais apresentam tendências a populações mais jovens à medida que a distância da BCG aumenta. O perfil mediano apresentou valores assintóticos para distâncias maiores que aproximadamente $8h^{-1}Mpc$. Esse valor é da mesma ordem que o parâmetro de suavização o que usamos, o que pode explicar porque não encontramos relações entre a morfologia dos superaglomerados e os valores médios dos parâmetros espectrais das populações estelares das galáxias que os constituem. / We have studied the global properties of galaxy superclusters with a sample of galaxies observed spectroscopically by the Sloan Digital Sky Survey (SDSS). Our volume limited sample has 121,002 galaxies with $M_r<-21$ and the in redshift range $0.02<z<0.155$. We have identified superclusters using the density field and friends-of-friends methods. We have adopted a smoothing parameter $\\sigma=8h^{-1}Mpc$ and sampled the density field in a grid of size $l_{cel}=4h^{-1}Mpc$. In order to evaluate the effect of the threshold density value on supercluster identification, we have choosen two values: the threshold which corresponds to the highest number of superclusters and the threshold where the largest supercluster is about $120h^{-1}Mpc$ long. For each value, we have obtained the richness and the total luminosity of the objects. For the morphological analisys the Minkowski Functionals were calculated and the superclusters were classified as filaments, ribbons and pancakes. Analyzing possible correlations among superclusters features, we have found that filaments tend to be richer and consequently more luminous and have a higher velocity dispersion. Using the cumulative distribution of supercluster luminosities, we have found that the distributions of filaments-like and pancakes-like objects are probably distinct. In an appendix we present a study of stellar populations of galaxies. We have calculated the local density for each galaxy, obtaining an analogous of the morphology-density relation through the relation between local density and spectral parameters. No significative difference in this relation has been noticed among filaments, ribbons and pancakes. In other words, similar behaviors have been identified for all spectral parameters and superclusters morphologies, in all threshold densities. A similar result was obtained for the cumulative distributions of spectral parameters. Finally, we have studied the influence of clusters on the inner environment of superclusters. Average values of spectral parameters were calculated inside spheres centered at each BCG(\\textit{Brightest Cluster Galaxy}) and all spectral parameter profiles have shown trends towards younger populations as the distance from BCG increases. The median profile presented asymptotic values for distances greater than roughly $8h^{-1}Mpc$. Since this is of the same order of magnitude of the smoothing parameter, this might explain why we did not find any relation between the supercluster morphology and the mean value of spectral parameters of the galaxies.

Thesis (Ph. D.)--Texas Christian University, 2007. / Title from dissertation title page (viewed Dec. 10, 2007). Includes abstract. Includes bibliographical references.