<p>This thesis is a detailed observational study of the accretion processes in T Tauri stars (TTS). The interaction between the central star, the circumstellar disk and the magnetic field gives rise to a wide range of features in the spectra of TTS. The current picture of TTS is based on rather simple models assuming that accretion is a homogeneous and axisymmetric process. Although these models have been successful in explaining some observational signatures of TTS such as the shape of emission lines, the static nature of these models makes them unsuitable for describing the strong variability of the veiling spectrum and emission lines of TTS. An improved understanding of this variability is of key importance to study the dynamic processes related to the accretion flow and the winds.</p><p>This study is based on a set of high-quality spectroscopic observations with the UVES spectrograph at the 8-m VLT in 2000 and 2002. These spectra, with exposure times as short as 10-15 minutes, have high spectral resolution and high signal-to-noise ratios and cover a large part of the optical wavelength range. From this dataset we determine the basic physical parameters of several TTS and model their photospheres. These models then serve as a basis for a detailed investigation of variations of the veiling continuum and line emission. We confirm that the level of veiling correlates with some of the strongest emission lines and that coherent changes in accretion occur on a timescale of a few hours, comparable to the free-fall time from the disk to the star. From the properties of the emission lines formed close to the central star and in the stellar wind we derive restrictions on the geometry of the observed systems.</p><p>Because the intrinsic axial symmetry of a single star makes it almost impossible to disentangle rotational modulation from inhomogeneity and axial asymmetry of the accretion flow, we study a series of spectra of a close spectroscopic binary at different orbital phases and derive the 3D structure of flows between the disk and the star. Finally, we calculate the profiles of hydrogen emission lines by iteratively solving 3D NLTE radiative transfer in a state-of-the-art magnetospheric model.</p>

This thesis is a detailed observational study of the accretion processes in T Tauri stars (TTS). The interaction between the central star, the circumstellar disk and the magnetic field gives rise to a wide range of features in the spectra of TTS. The current picture of TTS is based on rather simple models assuming that accretion is a homogeneous and axisymmetric process. Although these models have been successful in explaining some observational signatures of TTS such as the shape of emission lines, the static nature of these models makes them unsuitable for describing the strong variability of the veiling spectrum and emission lines of TTS. An improved understanding of this variability is of key importance to study the dynamic processes related to the accretion flow and the winds. This study is based on a set of high-quality spectroscopic observations with the UVES spectrograph at the 8-m VLT in 2000 and 2002. These spectra, with exposure times as short as 10-15 minutes, have high spectral resolution and high signal-to-noise ratios and cover a large part of the optical wavelength range. From this dataset we determine the basic physical parameters of several TTS and model their photospheres. These models then serve as a basis for a detailed investigation of variations of the veiling continuum and line emission. We confirm that the level of veiling correlates with some of the strongest emission lines and that coherent changes in accretion occur on a timescale of a few hours, comparable to the free-fall time from the disk to the star. From the properties of the emission lines formed close to the central star and in the stellar wind we derive restrictions on the geometry of the observed systems. Because the intrinsic axial symmetry of a single star makes it almost impossible to disentangle rotational modulation from inhomogeneity and axial asymmetry of the accretion flow, we study a series of spectra of a close spectroscopic binary at different orbital phases and derive the 3D structure of flows between the disk and the star. Finally, we calculate the profiles of hydrogen emission lines by iteratively solving 3D NLTE radiative transfer in a state-of-the-art magnetospheric model.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / Quantitative measurements of line intensities have been made since the beginning of the last century. The quantity and quality of the data available have increased drastically with the advent of electronic detectors. However, the data are widely scattered in the literature. In face of this, we compiled a catalog of emission-lines intensities. It contains data on HII regions in 41 galaxies, all totaling approximately 36 000 line intensities. We have constructed a table with 1 750 emission-lines observed, showing their transition probabilities and configurations or terms. We have standardized the identification of all the emission-lines of the catalog based on this table. The database was used for different studies. We checked the values of the ratios [OIII] λ5007/λ4959 and [NII] λ6583/λ6548 with the emission-line ratios from the HII regions in the catalog. The values found are in agreement with the theoretical ones. With the diagram λ6717/Hβ versus λ6731/Hβ, we verified that most of the objets in the catalog are near the low-density limit. We also present a comparison of different temperature indicators based on observational data from HII regions, HII galaxies and planetary nebulae extracted from the literature. We have found that there is not a unique relation between the temperature indicators of different ionization zones which allows a reliable derivation of one of these from another. We have constructed diagnostic diagrams comparing the emission-lines ratios [OI]/Hα, [OII]/Hβ, [OIII]/Hβ, [NII]/Hα, [SII]/Hα e [OII]/[OIII]. For them, we have distinguished the emission-line ratios of HII regions of different galaxies and, for data from our galaxy, we have distinguished different objects. We described the diagnostic diagrams using theoretical grids varying the ionization parameter and the chemical abundance. These were computed using a photoionization code and different spectral energy distributions. With the diagram [NII]/[OII] versus [OIII]/[OII], we have obtained the best separation between ionization parameter and metallicities. We observed large discrepancies between the chemical abundances of the grids of models and those determined from collisionaly excited lines. / Medidas quantitativas de intensidades de linhas de emissão têm sido feitas desde o in´ıcio do século passado. A quantidade e a qualidade dos dados disponíveis têm crescido drasticamente com o advento dos detectores eletrônicos. Porém, os dados estão amplamente espalhados na literatura. Diante disso, compilamos um catálogo de intensidades de linhas de emissão. Este contém dados de regiões HII de 41 galáxias, totalizando aproximadamente 36 000 intensidades de linhas. Construímos uma tabela com 1 750 linhas de emissão observadas, apresentando suas probabilidades de transição e configurações ou termos. Padronizamos a identificação de todas as linhas de emissão do catálogo com base nessa tabela. O banco de dados foi utilizado para diferentes estudos. Checamos os valores das razões [OIII] λ5007/λ4959 e [NII] λ6583/λ6548 com razões de linhas de emissão de regiões HII do catálogo. Os valores encontrados concordam com os teóricos. Com o diagrama λ6717/Hβ versus λ6731/Hβ, verificamos que a maior parte dos objetos do catálogo estão próximos ao limite de baixa densidade. Apresentamos também uma comparação de diferentes indicadores de temperatura baseada em dados observacionais de regiões HII, de galáxias HII e de nebulosas planetárias extraídos da literatura. Encontramos que não há uma única relação entre indicadores de temperaturas de diferentes zonas de ionização que permita uma derivação confiável de uma destas a partir da outra. Construímos diagramas de diagnóstico comparando as razões de linhas [OI]/Hα, [OII]/Hβ, [OIII]/Hβ, [NII]/Hα, [SII]/Hα e [OII]/[OIII]. Para eles, distinguimos as razões de linhas de emissão de regiões HII de galáxias diferentes e, para os dados de nossa galáxia, distinguimos os diferentes objetos. Descrevemos os diagramas de diagnóstico utilizando grades teóricas variando o parâmetro de ionização e a metalicidade. Estas foram calculadas usando um código de fotoionização e diferentes distribuições espectrais de energia. Com o diagrama [NII]/[OII] versus [OIII]/[OII], obtivemos a melhor separação entre o parâmetro de ionização e a metalicidade. Verificamos grandes discrep ancias entre as abundâncias químicas das grades de modelos e aquelas determinadas de linhas excitadas colisionalmente.

Les Antennes sont une des fusions de galaxies les plus connues dans l’Univers proche. Sa proximité nous permet d’observer et d’étudier ses gaz à l’échelle de la formation des amas stellaires. C’est une source idéale pour comprendre comment la dynamique dans les fusions de galaxies déclenche la formation d’étoiles. La plupart des étoiles dans les Antennes sont formées dans des amas stellaires compacts et massifs, surnommés super-star clusters (SSC). Les SSC les plus massifs (>106 M⊙) et les plus jeunes (<6 Myr) sont situés dans la région de collision entre les deux galaxies et sont associés aux complexes moléculaires massifs (~108 M⊙) et super-géants (des centaines de pc) (super-giant molecular clouds, SGMCs). La formation de SSC doit impliquer une intéraction complexe entre la dynamique des gaz et une turbulence entraînée par la fusion des galaxies, et la dissipation de l’énergie cinétique des gaz. Dans les SGMC, une hiérarchie de structures doit être produite, incluant des concentrations denses et compactes de gaz moléculaires qui sont suffisamment massifs pour former un SSC, des nuages pre-cluster clouds (PCC). La formation des étoiles se produira si l’énergie mécanique des PCC est émise dans le lointain, permettant à l’auto-gravité de gagner localement les pressions thermique et turbulente du gaz. Des diagnostics spécifiques de dissipation turbulente sont donc des éléments essentiels pour tester la validité de ce scénario.J’étudie la région d’intéraction des Antennes. J’utilise des observations avec le spectro- imageur SINFONI sur le VLT (raies rovibrationnelles de H2) et ALMA (raie CO(3–2) et l’émission du continuum de la poussière). Les données ont des résolutions angulaires pour résoudre les échelles de la formation des SSC et des résolutions spectrales pour résoudre les mouvements à l’intérieur du SGMC. La combinaison des raies CO et H2 est essentielle dans mon travail. J’utilise le CO comme traceur de la distribution et de la cinématique du gaz moléculaire, et H2 comme traceur du taux de dissipation d’énergie mécanique de gaz.Ma thèse se concentre sur des sources traçant des différentes étapes de la formation d’étoiles : le rassemblement des gaz pour former des SGMCs, la formation des PCC dans les SGMCs et la destruction des nuages moléculaires par les SSC. Je montre que la turbulence joue un rôle essentiel à chaque étape. J’ai trouvé que l’énergie cinétique de rencontre des deux galaxies n’est pas thermalisée dans les chocs aux échelles où elle est injectée. Elle entraîne une turbulence dans l’ISM moléculaire à un niveau beaucoup plus élevé que celui observé dans la Voie Lactée. Sauf dans les SSC encore intégrés dans les nuages moléculaires, la raie de H2 est produite par des chocs et trace la dissipation de l’énergie cinétique turbulente du gaz. J’associe l’émission de H2 à la perte d’énergie cinétique nécessaire pour former des nuages gravitationnellement liés. Cette interprétation est étayée par la découverte d’une source lumineuse et compacte en H2, qui n’est associée à aucun SSC connu, située là où les données montrent le plus grand gradient de vitesse. À notre connaissance, c’est la première fois qu’une source extragalactique avec ces caractéristiques est identifiée. Nous observons la formation d’un nuage suffisamment massif pour former un SSC. Les données montrent également la destruction d’un nuage moléculaire par un SSC récemment formé. Sa matière est faiblement liée. Sa gravité serait soutenue par la turbulence, ce qui rend plus facile pour les mécanismes de rétroaction de perturber le nuage parent.Enfin, je présente deux projets. Je propose d’établir d’autres traceurs de dissipation d’énergie observables avec ALMA, proposition du Cycle 1 acceptée en première priorité. Je propose également d’étendre mon travail pour étudier la formation des étoiles entraînées par la turbulence dans différentes sources extragalactiques en combinant les observations dans le proche infrarouge et submillimétrique. / The Antennae (22 Mpc) is one of the most well-known mergers in the nearby Universe. Its distance allow us to observe and study the gas at the scales of stellar cluster formation. It is an ideal source to understand how the galaxy dynamics in mergers trigger the formation of stars. Most of the stars in the Antennae are formed in compact and massive stellar clusters, dubbed super-star clusters (SSCs). The most massive (>106 M⊙) and youngest (<6 Myr) SSCs are located in the overlap region, where the two galaxies collide, and are associated with massive (several 108 M⊙) and super-giant (few hundred of pc) molecular complexes (SGMCs). The formation of SSCs must involve a complex interplay of merger-driven gas dynamics, turbulence fed by the galaxy interaction, and dissipation of the kinetic energy of the gas. Within SGMCs, a hierarchy of structures must be produced, including dense and compact concentrations of molecular gas massive enough to form SSCs, pre-cluster clouds (PCCs). For star formation to occur, the mechanical energy of PCCs must be radiated away to allow their self-gravity to locally win over their turbulent gas pressure. Specific tracers of turbulent dissipation are therefore key inputs to test the validity of this theoretical scenario. In my thesis, I studied the Antennae overlap region. My work is based on observations with the SINFONI spectro-imager at the VLT, which includes H2 rovibrational and Brγ line emission, and with ALMA, which includes the CO(3-2) line and dust continuum emission. Both data-sets have the needed sub-arcsecond angular resolution to resolve the scales of SSC formation. The spectral resolutions are enough to resolve motions within SGMCs. Combining CO and H2 line emission is key in my PhD work. I use CO as a tracer of the distribution and kinematics of the molecular gas, and H2 as a tracer of the rate at which the gas mechanical energy is dissipated.My thesis focuses on diverse sources in the Antennae overlap region which trace different stages of star formation: the gathering of mass necessary to form SGMCs, the formation of PCCs within SGMCs and the disruption of a parent cloud by a newly formed SSC. I show that at each stage turbulence plays a key role. I found that the kinetic energy of the galaxies is not thermalized in large scale shocks, it drives the turbulence in the molecular ISM at a much higher level than what is observed in the Milky Way. Near-IR spectral diagnostics show that, outside of SSCs embedded in their parent clouds, the H2 line emission is powered by shocks and traces the dissipation of the gas turbulent kinetic energy. I relate the H2 emission to the loss of kinetic energy required to form gravitationally bound clouds. This interpretation is supported by the discovery of a compact, bright H2 source not associated with any known SSC. It has the largest H2/CO emission ratio and is located where the data show the largest velocity gradient in the interaction region. To our knowledge, this is the first time that an extragalactic source with such characteristics is identified. We would be witnessing the formation of a cloud massive enough to form a SSC. The data also allow us to study the disruption of a parent molecular cloud by an embedded SSC. Its matter is loosely bound and its gravity would be supported by turbulence, which makes it easier for feedback to disrupt the parent cloud. I end my manuscript presenting two projects. I propose to establish additional energy dissipation tracers observable with ALMA, which gives us the high spatial and spectral resolution needed to isolate scales at which clusters form. This is a Cycle 1 proposal accepted in first priority. I also plan to expand my work to other nearby extragalactic sources by investigating the turbulence-driven formation of stars in different extragalactic sources by combining near-IR and submillimeter observations.

New radio telescopes under development, will significantly enhance the capabilities of radio astronomy in the Southern Hemisphere. South Africa, in particular, is actively involved in the development of a new array (MeerKAT) as well as in the expansion of existing very long baseline interferometer arrays in the south. Participation in these new developments demands a thorough understanding of radio astronomy techniques, and data analysis, and this thesis focusses on two projects with the aim of gaining such experience. The Southern Hemisphere very long baselines array is not well served with calibrator sources and there are significant gaps in the present calibrator distribution on the sky. An adequately dense, well distributed, set of strong, compact calibrator or reference sources is needed. With this in mind, observations using the Southern Hemisphere long baseline array were conducted to investigate a sample of candidate calibrator sources. The compactness of the sources was investigated and new potential calibrators have been identified. Single antenna radio spectroscopy of OH masers has identified sources of 1720 MHz emission associated with supernova remnants at the shock interface between the expanding supernova remnant and a molecular cloud. Models indicate that these masers are shock excited and can only be produced under tight physical constraints. Out ows from newly-formed stars create nebulous regions known as Herbig-Haro objects when they interact with the surrounding medium, and these regions are potentially similar to those seen in supernova remnants. If conditions behind the shock fronts of Herbig-Haro objects are able to support 1720-MHz OH masers they could be a useful diagnostic tool for star formation. A survey toward Herbig-Haro objects using a single-dish radio telescope did detect 1720-MHz OH lines in emission, but neither their spectral signature nor follow-up observations with the Very Large Array showed evidence of maser emission. / Mathematical Sciences / Ph.D. (Astronomy)

Este trabalho consiste no estudo de cubos de dados das regiões centrais de quatro galáxias com mesmo tipo morfológico da Via Láctea: NGC 1566, NGC 6744, NGC 613 e NGC 134. As observações foram feitas no período de 2013 a 2015 com o Integral Field Unit do Gemini Multi-Object Spectrograph do telescópio Gemini Sul. Foram utilizadas técnicas de análise de dados como Tomografia PCA, síntese espectral e Penalized Pixel Fitting. Além disso, para todos objetos, foram calculadas razões de linhas de emissão dos espectros das regiões centrais, imagens da emissão de [SII] 6716, 6731 das nuvens de alta e baixa densidades foram feitas e, em dois casos (NGC 1566 e NGC 613), analisaram-se imagens do Hubble Space Telescope para melhor entendimento do ambiente circumnuclear. Foram encontrados 6 espectros com emissão compatível com a de AGNs na amostra, sendo que, em duas galáxias, existe a possibilidade de AGNs duplos: NGC 6744 e NGC 613. No geral, todas as galáxias apresentaram populações estelares de idades variadas em suas regiões centrais, porém, predominantemente, com metalicidades altas (0.02 e 0.05). Todas as galáxias apresentaram cinemática estelar compatível com discos de rotação em torno do núcleo e, em duas galáxias (NGC 1566 e NGC 6744), foi observado um decréscimo da dispersão de velocidades estelar em direção ao núcleo, possivelmente devido à presença de estrelas jovens massivas. A emissão do featureless continuum do núcleo da galáxia de Seyfert NGC 1566 foi, pela primeira vez, isolada e estudada, sendo que foi encontrado um índice espectral igual 1.7. Uma amostra de quatro galáxias não é estatisticamente conclusiva e será necessário ampliar a amostra para um melhor entendimento global dos núcleos de galáxias de mesmo tipo morfológico da Via Láctea. / This work involved the analysis of data cubes of four nuclear regions of galaxies that have the same morphological type of the Milky Way: NGC 1566, NGC 6744, NGC 613 and NGC 134. The observations were taken in the period of 2013 to 2015 with the Integral Field Unit of Gemini Multi-object Spectrograph on the Gemini South telescope. The data were analyzed using techniques like PCA Tomography, spectral synthesis and the Penalized Pixel Fitting process. Besides that, for all the objects, emission-line ratios of the central regions were calculated, images of the emission-lines [SII]6716, 6731 of clouds of high and low densities were made and, in two cases (NGC 1566 and NGC 6744), their Hubble Space Telescope images were analyzed for better understanding of their circumnuclear regions. 6 spectra of the sample had emission compatible with that of AGNs, in two galaxies, there is a possibility of double AGN: NGC 613 and NGC 6744. In general, all the galaxies presented stellar populations with varying ages in their central regions, however mainly with high metallicities (0.02 and 0.05). All the galaxies presented stellar kinematics compatible with rotation disks around the central source and, in two galaxies (NGC 1566 and NGC 6744), there was a stellar dispersion velocity decrease toward the nuclei, possibly due to the presence of massive young stars. The featureless continuum emission of the Seyfert galaxy NGC 1566 was, for the rst time, isolated and studied. It was found that its spectral index is equal to 1.7. A sample of four galaxies is not conclusive and it is necessary to enlarge this sample to a better global understanding of the nuclei of galaxies with the same morphological type of the Milky Way.

Submitted by Luis Ricardo Andrade da Silva (lrasilva@uefs.br) on 2017-11-28T22:15:22Z No. of bitstreams: 1 AILINE-corrigida e completa-enviada pgca.pdf: 18819458 bytes, checksum: 1356b2bb4c6c8fbf60dec709646715da (MD5) / Made available in DSpace on 2017-11-28T22:15:22Z (GMT). No. of bitstreams: 1 AILINE-corrigida e completa-enviada pgca.pdf: 18819458 bytes, checksum: 1356b2bb4c6c8fbf60dec709646715da (MD5) Previous issue date: 2017-08-24 / Advances in the acquisition technology of astronomical spectra resulted in an enormous amount of data. Not being more feasible to analyze them using classical approaches, the need for automatic methods arises. Then, in this research is presented, an Intelligent Algorithm for Identifying Spectral Lines, the AILINE (in Portuguese), which utilizes an artificial neural network to identify the emission lines in the optical spectra of galaxies. This method that in the tests carried out has achieved a accuracy higher than 95% is evaluated and faced with other automatic approaches and other machine learning algorithms. / Os avan?os na tecnologia de aquisi??o de espectros astron?micos resultaram em uma enorme quantidade de dados. N?o sendo mais vi?vel analis?-los usando abordagens cl?ssicas, surge a necessidade de m?todos autom?ticos. Ent?o, nesta pesquisa ? apresentado um Algoritmo Inteligente para Identifica??o de Linhas Espectrais, o AILINE, que utiliza uma Rede Neural Artificial para identificar as linhas em emiss?o nos espectros ?pticos de gal?xias. Este m?todo que nos testes realizados alcan?ou uma acur?cia superior a 95%, ? avaliado e confrontado com outras abordagens autom?ticas e outros algoritmos de aprendizado de m?quina.

Este trabalho consiste no estudo de cubos de dados das regiões centrais de quatro galáxias com mesmo tipo morfológico da Via Láctea: NGC 1566, NGC 6744, NGC 613 e NGC 134. As observações foram feitas no período de 2013 a 2015 com o Integral Field Unit do Gemini Multi-Object Spectrograph do telescópio Gemini Sul. Foram utilizadas técnicas de análise de dados como Tomografia PCA, síntese espectral e Penalized Pixel Fitting. Além disso, para todos objetos, foram calculadas razões de linhas de emissão dos espectros das regiões centrais, imagens da emissão de [SII] 6716, 6731 das nuvens de alta e baixa densidades foram feitas e, em dois casos (NGC 1566 e NGC 613), analisaram-se imagens do Hubble Space Telescope para melhor entendimento do ambiente circumnuclear. Foram encontrados 6 espectros com emissão compatível com a de AGNs na amostra, sendo que, em duas galáxias, existe a possibilidade de AGNs duplos: NGC 6744 e NGC 613. No geral, todas as galáxias apresentaram populações estelares de idades variadas em suas regiões centrais, porém, predominantemente, com metalicidades altas (0.02 e 0.05). Todas as galáxias apresentaram cinemática estelar compatível com discos de rotação em torno do núcleo e, em duas galáxias (NGC 1566 e NGC 6744), foi observado um decréscimo da dispersão de velocidades estelar em direção ao núcleo, possivelmente devido à presença de estrelas jovens massivas. A emissão do featureless continuum do núcleo da galáxia de Seyfert NGC 1566 foi, pela primeira vez, isolada e estudada, sendo que foi encontrado um índice espectral igual 1.7. Uma amostra de quatro galáxias não é estatisticamente conclusiva e será necessário ampliar a amostra para um melhor entendimento global dos núcleos de galáxias de mesmo tipo morfológico da Via Láctea. / This work involved the analysis of data cubes of four nuclear regions of galaxies that have the same morphological type of the Milky Way: NGC 1566, NGC 6744, NGC 613 and NGC 134. The observations were taken in the period of 2013 to 2015 with the Integral Field Unit of Gemini Multi-object Spectrograph on the Gemini South telescope. The data were analyzed using techniques like PCA Tomography, spectral synthesis and the Penalized Pixel Fitting process. Besides that, for all the objects, emission-line ratios of the central regions were calculated, images of the emission-lines [SII]6716, 6731 of clouds of high and low densities were made and, in two cases (NGC 1566 and NGC 6744), their Hubble Space Telescope images were analyzed for better understanding of their circumnuclear regions. 6 spectra of the sample had emission compatible with that of AGNs, in two galaxies, there is a possibility of double AGN: NGC 613 and NGC 6744. In general, all the galaxies presented stellar populations with varying ages in their central regions, however mainly with high metallicities (0.02 and 0.05). All the galaxies presented stellar kinematics compatible with rotation disks around the central source and, in two galaxies (NGC 1566 and NGC 6744), there was a stellar dispersion velocity decrease toward the nuclei, possibly due to the presence of massive young stars. The featureless continuum emission of the Seyfert galaxy NGC 1566 was, for the rst time, isolated and studied. It was found that its spectral index is equal to 1.7. A sample of four galaxies is not conclusive and it is necessary to enlarge this sample to a better global understanding of the nuclei of galaxies with the same morphological type of the Milky Way.

New radio telescopes under development, will significantly enhance the capabilities of radio astronomy in the Southern Hemisphere. South Africa, in particular, is actively involved in the development of a new array (MeerKAT) as well as in the expansion of existing very long baseline interferometer arrays in the south. Participation in these new developments demands a thorough understanding of radio astronomy techniques, and data analysis, and this thesis focusses on two projects with the aim of gaining such experience. The Southern Hemisphere very long baselines array is not well served with calibrator sources and there are significant gaps in the present calibrator distribution on the sky. An adequately dense, well distributed, set of strong, compact calibrator or reference sources is needed. With this in mind, observations using the Southern Hemisphere long baseline array were conducted to investigate a sample of candidate calibrator sources. The compactness of the sources was investigated and new potential calibrators have been identified. Single antenna radio spectroscopy of OH masers has identified sources of 1720 MHz emission associated with supernova remnants at the shock interface between the expanding supernova remnant and a molecular cloud. Models indicate that these masers are shock excited and can only be produced under tight physical constraints. Out ows from newly-formed stars create nebulous regions known as Herbig-Haro objects when they interact with the surrounding medium, and these regions are potentially similar to those seen in supernova remnants. If conditions behind the shock fronts of Herbig-Haro objects are able to support 1720-MHz OH masers they could be a useful diagnostic tool for star formation. A survey toward Herbig-Haro objects using a single-dish radio telescope did detect 1720-MHz OH lines in emission, but neither their spectral signature nor follow-up observations with the Very Large Array showed evidence of maser emission. / Mathematical Sciences / Ph.D. (Astronomy)

Au cours des dernières décennies, l’astronomie infrarouge a changé notre point de vue au sujet de l’évolution des galaxies, en particulier à de grandes distances. Nous avons accès à une grande variété d’informations physiques grâce au domaine spectral infrarouge. Toutefois, les limites de diffraction des instruments infrarouges et l’existence d’un grand nombre de sources font de l’identification individuelle des galaxies une tâché difficile. La première partie de cette thèse est consacrée à Résoudre le fond extragalactique infrarouge avec l’observatoire spatial Herschel, à, l’aide de simulations réalistes, correspondant aux images les plus profondes jusqu’ici obtenues en infrarouge lointain. Nous avons étudié l’origine du bruit de confusion dans les images GOODS-Herschel et résolu une partie de fond cosmique infrarouge en galaxies individuelles. De nouvelles techniques ont été développées pour prédire les flux en infrarouge lointain à partir de la connaissance préalable des positions, décalages spectraux et densités de flux des sources dans l’infrarouge moyen. Les images simulées ont été construites en utilisant les flux prédits afin d’évaluer le rôle du bruit local de confusion et d’identifier des sources individuelles. La deuxième partie de la thèse concerne l’étude de la Destruction de grains de poussières par des jets vus en radio. Nous avons étudié les effets des noyaux actifs de galaxies dans le milieu interstellaire, en particulier le mécanisme qui donne lieu à la région des raies étroites dans les galaxies de type Seyfert. Des spectres en infrarouge proche à fente longue a ont été enregistrés sur un ensemble de galaxies Seyfert de type 2 afin de mesurer les raies d’émission de ([Fe II], [P II] et Paβ) qui révèlent la destruction de poussières par les ondes de choc produites par les jets radio. Nous avons constaté que le mécanisme dominant l’ionisation près du noyau des galaxies Seyfert est le champ de rayonnement produit par l’activité du trou noir. Dans la partie extérieure de la région des raies étroites, des ondes de choc induites par des jets de radio contribuent également au budget énergétique du milieu interstellaire et à la destruction des grains de poussière. Cette thèse s’est déroulée en co-encadrement au Service d’Astrophysique du CEA-Saclay et au Département d’Astronomie de l’Université de Concepción, au Chili. / During the last decades, infrared astronomy has changed our view about the evolution of galaxies, especially at large distances. We have access to large variety of physical information in the infrared bands. However, diffraction limits of the infrared instruments and the existence of a large number of sources makes individualization of galaxies a difficult task. The first part of this thesis is entitled Resolving the Cosmic Infrared Background with the Herschel Space Observatory where, by the use of far-infrared realistic simulations of the deepest infrared images of the Universe, we have studied the origin of the confusion noise in the GOODS-Herschel images and resolved a substantive part of the Cosmic Infrared Background into individual galaxies. New techniques were developed to predict the fluxes in the far-infrared from prior knowledge in the mid-infrared. Mock images were built using those predicted fluxes to evaluate the role of local confusion noise and identify individual sources. The second part of the thesis concerns the study of the Destruction of dust grains by radio jets. We study the effects of active galactic nuclei in the insterstellar medium, in particular in the mechanism that gives rise to the narrow-line region in Seyfert galaxies. Long-slit near-Infrared spectra of a set of type-2 Seyfert galaxies were taken to measure diagnostic emission lines ([Fe II], [P II] and Paβ) that reveal the destruction of dust grains due to the shock waves produced by the radio jets. We found that the dominant mechanism of ionization close to the nuclei of the Seyfert galaxies is the radiation field produced by the back hole activity. In the outer part of the narrow-line region, shock waves induced by the radio jets also contribute to the energy budget of the interstellar medium and sputter the dust grains. This was a co-advising thesis performed in the Service d’Astrophysique CEA-Saclay and the Astronomy Department of the University of Concepción, Chile. / Durante las últimas décadas, la astronomía infrarroja ha cambiado nuestra visión sobre la evolución de galaxias, en especial revelando que a grandes distancias (z >1) las galaxias individuales son típicamente Galaxias Infrarrojas Ultraluminosas (cuyas siglas en inglés son ULIRGs por Ultraluminous Infrared Galaxies, 1012 < Lbol < 1013 L⊙). Actualmente tenemos acceso a una gran variedad de información física basada en la emisión en bandas espectrales infrarrojas (IR), radiación que en el caso de las galaxias es producida en su mayoría por granos de polvo. Sin embargo, el límite de difracción de los instrumentos infrarrojos junto con el gran número de fuentes de emisión hace de la individualización de galaxias una tarea difícil. La primera parte de esta tesis se titula Resolviendo el Fondo Cósmico Infrarrojo con el Observatorio Espacial Herschel donde, con el uso de simulaciones realistas de las imágenes más profundas del Universo, hemos estudiado el origen del ruido de confusión en las imágenes GOODS-Herschel y resuelto en galaxias individuales una parte sustantiva del Fondo Cósmico Infrarrojo. Nuevas técnicas fueron desarrolladas para predecir los flujos en el infrarrojo lejano a partir del conocimiento a priori en el infrarrojo medio. Las imágenes simuladas fueron construidas usando esos flujos predichos y con ellos evaluar el rol del ruido de confusión local así como identificar fuentes individuales. La segunda parte de la tesis trata del estudio sobre la Destrucción de granos de polvo por chorros en ondas de radio. Este proyecto que se concentró en la observación de galaxias Seyfert y ULIRGS y apunta a entender mejor el ciclo de vida del polvo al estudiar la destrucción de granos en galaxias con nucleos activos y los efectos de la actividad de estas últimas en el medio interestelar, en particular en el mecanismo que da origen a la región de líneas de emisión angostas en las galaxias Seyfert. Se obtuvo espectros infrarrojos de rendija larga de galaxias Seyfert del tipo 2 para medir líneas de emisión ([Fe II], [P II] y Paβ) las cuales revelan la destrucción de granos de polvo debido a las perturbaciones de las ondas de choque producidas por chorros detectados en ondas de radio. Hemos encontrado que el mecanismo dominante de la ionización cerca de los núcleos de las galaxias Seyfers es el campo de radiación producido por la actividad del agujero negro central. En la parte externa de la región de líneas de angostas, las ondas de choque inducidas por los chorros en radio también contribuyen al balance energético del medio interestelar y desintegran los granos de polvo. Esta fue una tesis de co-tutela llevada a cabo en el Departamento de Astronomía de la Universidad de Concepción y en el Service d’Astrophysique del Commissariat á l’Énergie Atomique (CEA), Francia