The most intensely star-forming galaxies lie at z ∼ 2 and are thought to be the progenitors of the most massive galaxies today, yet study of this important population has been hampered by vast quantities of dust, making them almost invisible in the optical and ultraviolet (UV) regimes, and by the low sensitivity and angular resolution of many infrared (IR) facilities. Chapter 2 describes the use of the flux and angular extent boost provided by strong gravitational lensing in the detailed study of individual high-redshift dusty star-forming galaxies (DSFGs). The low number density of such systems has been overcome by recent wide area far-infrared (FIR)–mm surveys, and a sample of candidate systems which are bright enough to study with single-dish FIR telescopes are assembled from these surveys. The chapter further describes spectra of these galaxies obtained using the the Spectral and Photometric Imaging REceiver (SPIRE; Griffin et al. 2010) Fourier transform spectrometer (FTS) on board the Herschel Space Observatory (Pilbratt et al. 2010), exploiting the increased flux densities to search for FIR atomic and ionic spectral lines: important coolants of warm gas surrounding star-formation regions. Chapter 3 describes the first “blind” redshift obtained using Herschel, via the detection of [C ii] 158 μm in one of our spectra. Confirmation of this redshift was provided by detection of CO lines with the Combined Array for Research in Millimeter-wave Astronomy (CARMA) and the Plateau de Bure Interferometer (PdBI), and along with multi-wavelength photometric follow-up, allowed a characterisation of the galaxy, indicating both a merger-driven starburst and an active galactic nucleus (AGN) within the system. Chapter 4 describes the first detection of a massive outflow of molecular gas at high-redshift. Stacking five repeat spectra of the Cosmic Eyelash, one of the best-studied strongly lensed DSFGs, one of the massive star-forming clumps is shown to drive this outflow, albeit likely at a velocity lower than that required to become unbound from the hosting gravitational potential well. Chapter 5 describes line measurements and spectral energy distribution (SED) fitting from the full set of spectra and Herschel PACS mini scan maps. The spectra are stacked to search for faint lines, and compared to a detailed interstellar medium (ISM) model to determine average physical properties of the star-forming gas. Photodissociation region (PDR) properties are found to be similar to those derived using other models, however a cosmic ray ionisation rate of 103 times that of the Milky Way, expected in galaxies of this type cannot reproduce the observed line ratios, in particular the low [O i] 63 μm flux. Chapter 6 finally describes the conclusions drawn from the work presented in this thesis and how these data and analysis add to our knowledge and interpretation of high-redshift DSFGs.

La variété de galaxies dans le Groupe Local rend possible l'étude du milieu interstellaire et de la formation d'étoiles dans des conditions différentes de celles trouvées dans la Voie Lactée, tout en conservant une grande résolution spatiale grâce à leur proximité. Nous avons étudié le milieu interstellaire de deux galaxies du Groupe Local, M33 et NGC6822, dont les métallicités sont inférieures d'un facteur 2 à 3 à celle du soleil et qui sont respectivement dix fois et cent fois moins lumineuses que la Voie Lactée. Nos observations de la transition J=2->1 du monoxyde de carbone, avec une résolution suffisante pour résoudre les nuages moléculaires géants, fournissent la première carte du milieu moléculaire de NGC6822 et la cartographie de M33 avec la meilleure combinaison de résolution et de sensibilité. Nous présentons également une cartographie haute résolution du milieu atomique de M33 à partir d'une mosaïque intérférométrique dans la raie à 21cm de l'ensemble du disque de la galaxie. Combinées avec des données allant de l'ultraviolet à l'infrarouge lointain, ces observations permettent l'étude du milieu interstellaire et de la formation d'étoiles à des échelles allant du nuage individuel à la galaxie dans son ensemble. Ces deux objets, chimiquement jeunes, semblent convertir l'hydrogène moléculaire en étoiles plus rapidement que les grandes galaxies spirales comme la Voie Lactée. Est-ce à rapprocher du taux élevé de formation d'étoiles dans les galaxies de l'univers plus jeune (z~0.5-1), également riches en gaz et bleues comme M33 et NGC6822 ? Un soin particulier a été apporté pour tenter de mesurer la masse de dihydrogène, difficile dans ce type d'objet, à l'échelle de la galaxie ainsi qu'à l'échelle du nuage. Une méthode d'identification automatique et de mesure des propriétés physiques des nuages moléculaires géants a permis d'obtenir, dans le cas de M33, le plus grand catalogue de nuage moléculaires dans une galaxie extérieure. Il en résulte que les nuages de M33 et de NGC 6822 ont, en moyenne, une largeur de raie plus faible, pour une taille donnée, que les nuages de la Voie Lactée. Dans M33, la fraction de petits nuages augmente significativement avec le rayon galactocentrique. Au moins un sixième des nuages moléculaires géants ne sont pas associés à de la formation stellaire (détectée) mais nous n'avons pas identifié de caractéristiques physiques particulières pour ces nuages. / The variety of galaxies in the Local Group enables the study of the interstellar medium and star formation under conditions different from those found in the Milky Way, while retaining a good spatial resolution due to their proximity. We have studied the interstellar medium of two Local Group galaxies, M33 and NGC6822, that have metallicities 2 to 3 times less than solar and are respectively 10 and 100 times less luminous than the Milky Way. Our large scale observations of the CO(2-1) transition, with a resolution sufficient to resolve giant molecular clouds, provide the the first molecular gas map of NGC6822 and the M33 map with the best combination of resolution and sensitivity. We also present a high resolution map of the atomic gas from an interferometric mosaic of M33's disk through the 21cm hydrogen line. Combining these observations with data ranging from ultraviolet to far infrared, we study the interstellar medium and star formation on scales ranging from individual clouds to the whole galaxy. These two chemically young objects appear to be converting molecular hydrogen into stars at a faster rate than in large spirals like the Milky Way. Can this be linked to the high star formation rate in galaxies of the earlier universe (z~0.5-1) which were bluer and gas rich like M33 and NGC6822 ? We have taken particular care to try and measure the molecular hydrogen mass, a difficult task in such objects, at the scale both of the galaxy and of the clouds. An automated molecular cloud identification and physical property measurement has been applied to the molecular gas data, yielding, in the case of M33, the largest catalog of giant molecular clouds in an external galaxy. From this catalog, it is found that the M33 molecular clouds have, on average, a smaller line-width, for a given size, than their Galactic counterparts. In M33, the fraction of small clouds increases significantly with the galactocentric radius. At least a sixth of the giant molecular clouds are not associated with detected star formation but we have not identified any particular physical characteristics for these clouds.

Ever since the first observations of diffuse ultraviolet radiation by Hayakawa et al. (1969) and Lillie & Witt (1976), there has been an effort to understand its distribution and its origin. Unfortunately, because of the difficulty of the observations and the faintness of the background, many of the early observations were conspicuous more by their disagreements than by the light they shed on the topic. The state of the observations and theories before 1990 have been reviewed by Bowyer (1991) and Henry (1991). There has been significant progress in more recent years, particularly in the far ultraviolet (< 1200˚A) where Murthy et al. (1999) and Murthy & Sahnow (2004) have used spectroscopic data from the Voyager and FUSE (Far Ultraviolet Spectroscopic Explorer) spacecraft, respectively, to trace the radiation field over many different locations in the sky. There have also been a number of observations at longer wavelengths, most recently by the SPEAR instrument (Ryu et al. 2008, and references therein), but no systematic study of the UV background. The Galaxy Evolution Explorer (GALEX) offers us the opportunity to extend coverage of the diffuse background to a significant fraction of the sky with a sensitivity of better than 100 photons cm−2 sr−1 s−1 ˚A−1 . In this work, we will report on one such observation, that of the nebulosity observed near M82 by Sandage (1976). These GALEX observations are the first to probe the diffuse UV background at a spatial resolution comparable to other surveys of dust emission, notably the IR. We obtain a quantitative estimate of the Airglow, the Zodiacal Light and the Extragalactic Background Radiation. We have modelled the data with our monte carlo scattering simulation program, and inferred an estimate of albedo and scattering phase function parameter of the dust in Sandage region. In this thesis the methods and results of these deductions are explained in detail.

In this thesis I present work done on the subject of star formation through the study of infrared dark clouds. We studied the velocity fields in several IRDCs using spectral line mapping. We also performed observations of a high density tracer and its deuterated counterpart. These observations allow me to assess the kinematics of these clouds and the evolutionary state of the observed targets. The sample observed is an important starting point for the search of early and quiescent high-mass regions. We mapped several IRDCs using the 22m ATNF Mopra Telescope in high-density molecular tracers at 3 mm, HNC (1-0) and N2H+ (1-0). We present integrated intensity emission and velocity field maps of these IRDCs. The molecular emission in the maps matches well with the extinction seen in the mid-IR. For an IRDC-complex we see connecting emission in the whole filament. We calculate kinematic distances and masses of the IRDCs. The IRDCs typically display an ordered velocity field within the clouds. The mean velocity gradient of the sample was 0.4 km/s/pc. We show how this velocity gradient can mean gas flows within the cloud into the central regions in order to feed the central cores. We observed 54 cores in IRDCs using N2H+ (1-0) and (3-2) to determine the kinematics of the densest material, where stars will form. We also observed N2D+ (3-2) towards 29 of the brightest peaks to analyze the level of deuteration which is an excellent probe of the quiescent of the early stages of star formation. There were 13 detections of N2D+ (3-2). This is one of the largest samples of IRDCs yet observed in these species. The deuteration ratio in the sources with detected N2D+ (3-2) has a mean of 0.024 and reaches a maximum value of 0.14. For most of the sources the material traced by N2D+ and N2H+ (3-2) still has significant turbulent motions, however three objects show subthermal N2D+ velocity dispersion. Surprisingly the presence or absence of an embedded 70 micron source shows no correlation with the detection of N2D+ (3-2), nor does it correlate with any change in velocity dispersion or excitation temperature. Comparison with recent models of deuteration suggest evolutionary timescales of these regions of several freefall times or less.

This thesis explores the topic of maximum mass stability of neutron stars. The outer structure is detailed and explores nuclear pasta phases, the neutron drip line, and density transitions of matter in the crust and atmosphere layers. Other discussion points include superfluids in the crust and core, vortex roles in neutron stars, and magnetic field effects on the EOS in neutron stars. The inner core is studied in much more detail due to its significant role in EOS. The variety of stars include pion condensate stars, kaon condensate stars, npeu stars, npeu stars with the inclusion of hyperons, quark-hybrid stars, and strange stars. Included with these is a description of nucleon-nucleon, nucleon-nucleon-nucleon interactions, the appearance factors that affect hyperon species, and the formation process of kaons, pions, quarks, and hyperons. The ending EOS are compared with their maximum mass values to determine which ones are likely to limit the mass of neutron stars.

La formation des étoiles, processus fondamental en astrophysique, résiste toujours à la compréhension. En effet, de nombreux phénomènes interagissent durant les différentes étapes, et ce sur une large gamme d’échelles. Il est donc primordial de comprendre la dynamique du milieu interstellaire, dans lequel les étoiles se forment. En particulier, il est maintenant bien établi que la structure du milieu interstellaire est fortement impactée par des processus de rétroaction de la part des étoiles qui s’y forment. D’une part cette rétroaction limite le taux de formation de nouvelles étoiles, et d’autre part elle est l’un des contributeurs à la morphologie et la dynamique des galaxies : taille du disque, éjection de matière, etc. Ce travail de thèse propose d’étudier numériquement la dynamique du milieu interstellaire, de manière à mettre en évidence l’impact des processus de rétroaction. Le processus principal qui sera étudié est les supernovae, figurant parmi les évènements les plus énergétiques dans le milieu interstellaire. Après l’étude et la modélisation en détail de l’explosion d’une unique supernova dans nuage moléculaire, un modèle numérique incluant formation d’étoiles et rétroaction par supernovae sera présenté et mis en œuvre dans des simulations d’un disque galactique stratifié à l’échelle du kiloparsec. Une extension de ce modèle pour tenir compte du rayonnement ionisant sera proposée. Il est effectivement possible de réguler la formation d’étoiles à l’aide de modèles de rétroaction par les supernovae, mais les résultats précis dépendent de manière significative des détails du schéma mis en œuvre. En utilisant la variante apparaissant comme la plus réaliste, des simulations à haute résolution du milieu interstellaire sont présentées et étudiées. En particulier, il est possible de mettre en évidence des propriétés de la turbulence compressible et magnétisée à l’échelle galactique : variation des spectres de puissance en fonction de l’altitude, alignement spontané de la vitesse et du champ magnétique, effet antagoniste de la rétroaction sur cet alignement et formation de structures. / Star formation, a fundamental process in astrophysics, remains only partially understood. Several processes are known to interact during all the steps over a large range of scales. It is therefore of highest importance to understand the dynamics of the interstellar medium, in which stars form. In particular, it is now well-known that the structure of the interstellar medium is strongly affected by feedback processes emanating from the stars that form in it. On the one hand this feedback limits the rate of formation of new stars, and on the other hand it is one of the main contributors to the shape and dynamics of galaxies: thickness of the disk, matter outflows, etc. This work aims to study numerically the dynamics of the interstellar medium, in order to highlight the impact of stellar feedback processes. The main process that will be studied is supernovae, being among the most energetic events in the interstellar medium. After the study and detailed modeling of the explosion of a single supernova inside a molecular cloud, a numerical model including star formation and supernova feedback will be presented and used in kiloparsec-scale simulations of a stratified galactic disk. An extension of this model will be suggested in order to take into account the ionizing radiation. It is indeed possible to regulate star formation with supernova feedback models, although the precise results strongly depend on the detailed scheme that is implemented. Using the most realistic-looking variant, high-resolution simulations are presented and studied. In particular, it is possible to extract properties of compressible and magnetized turbulence at the galactic scale: variation of the power spectra as a function of altitude, spontaneous alignment between velocity and magnetic field, antagonistic effect of stellar feedback onto this alignment, and structure formation.

Beta Lyrae is a complex binary star system with a 13-day orbital period containing two massive stars that are in the process of mass reversal accretion. The primary star is the higher mass star which is gaining mass from the secondary star. This reversal mass accretion causes gas to build and form a disk around the primary star. The disk is geometrically and optically thick. Previous interferometric studies in Optical and Infrared wavelengths have shown that a bipolar jet exists in the system and suggest that the jet contributes to the H-alpha emission. Meanwhile, other studies have suggested that the disk contributes to the H-alpha emission. We have taken into account various factors to model the emission of H-alpha from Beta Lyrae. The observed profile is double-peaked and varies with orbital phase. We found that the jet produces a single-peak for H-alpha emission. Meanwhile, the disk produces a double-peak for H-alpha emission if it is based on Keplerian motion. We use our model to interpret the observed H-alpha emission variations in the line shape with orbital phase.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第21565号 / 理博第4472号 / 新制||理||1642(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)准教授 細川 隆史, 教授 田中 貴浩, 教授 井岡 邦仁 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

Observing the dynamic interaction between stars and their close stellar neighbors is key to establishing the stars’ orbits, masses, and other properties. Our ability to visually discriminate nearby stars is limited by the power of our telescopes, posing a challenge to astronomers at small observatories that contribute to binary star surveys. Masks placed at the telescope aperture promise to augment the resolving power of telescopes of all sizes, but many of these masks must be manually and repetitively reoriented about the optical axis to achieve their full benefits. This paper introduces a design concept for a mask rotation mechanism that can be adapted to telescopes of different types and proportions, focusing on an implementation for a Celestron C11 Schmidt–Cassegrain optical tube assembly. Mask concepts were first evaluated using diffraction simulation programs, later manufactured, and finally tested on close double stars using a C11. An electronic rotation mechanism was designed, produced, and evaluated. Results show that applying a properly shaped and oriented mask to a C11 enhances contrast in images of double star systems relative to images captured with the unmasked telescope, and they show that the rotation mechanism accurately and repeatably places masks at target orientations with minimal manual effort. Detail drawings of the mask rotation mechanism and code for the software interface are included.

Les étoiles sont de très mauvaises voisines: elles perturbent souvent leur environnement. Parfois, elles se déplacent à grande vitesse dans le milieu interstellaire (MIS). Souvent, elles subissent des soubresauts violents qui laissent une empreinte dans leur voisinage (jets, vents, supernovae). Ces flots supersoniques génèrent des chocs à la fois dans le matériau éjecté par l'étoile et dans l'environnement stellaire. L'étude de ces chocs constituent le sujet de cette thèse, et nous les modélisons avec le code de chocs stationnaires plan parallèle Paris-Durham, qui incorpore une riche panoplie de processus microphysiques et chimiques adaptés au MIS magnétisé.Tout d'abord, nous utilisons ce code pour modéliser des chocs magnétisés 3D pour des formes arbitraires à symétrie axiale, grâce à un formalisme qui lie mathématiquement la forme des chocs à une fonction de distribution de chocs 1D équivalente. Pour la première fois, nous examinons systématiquement l'effet de la géométrie, de l'âge, et de quelques autres paramètres sur le diagramme d'excitation de H2 résultant et la forme des profils raies d'émission de H2. Par exemple, nous dévoilons un effet géométrique qui montre que l'ajustement par des modèles 1D de l'émission de H2 observée sur un choc 3D est sujette à un biais vers les basses vitesses. Nous appliquons aussi nos modèles à l'observation de H2 spatialement intégrée de chocs d'étrave dans Orion BN-KL et BHR71 où nous obtenons un bien meilleur ajustement des observations avec un nombre à peine plus grand de paramètres comparé aux modèles précédents. Nous illustrons sur l'objet de Herbig-Haro HH54 la grande richesse d'information dynamique que renferme le profil des raies d'émission résolues de H2. Ensuite, nous incluons dans le code de Paris-Durham un ensemble minimal de processus nécessaires pour décrire les modèles de vents d'étoiles de la branche asymptotique des géantes (AGB): la dilution géométrique, l'éclairage UV externe, la pression de radiation sur les grains, la gravité, le chauffage dû au pompage radiatif par l'étoile, les réactions à trois corps et le passage du point sonique. Avec cet outil, nous commençons à examiner la cinétique chimique de l'hydrogène dans les vents d'étoiles AGB chaudes et froides. Nous suggérons que la faible abondance de HI déduite des observations s'explique par la forme principalement moléculaire que prend l'hydrogène. Nous générons le choc terminal dans le vent et nous essayons avec nos modèles de reproduire les observations de la raie HI dans une AGB chaude (Y CVn).Bien que nous ayons principalement concentré notre attention sur l'hydrogène (atomique ou bien moléculaire) dans cette étude, l'extension de ce travail à des transitions optiquement minces d'autres molécules est assez directe. Ces modèles simplifiés pour modéliser la chimie dans des géométries et dynamiques néanmoins complexes se révèlent très utiles au moment où de nouveaux instruments comme ALMA dévoilent une grande richesse spectrale et spatiale pour une multitude de traceurs chimiques. Ceci alors que le JWST est sur le point d'apporter dans l'infra-rouge de l'information complémentaire sur les raies de H2 et les raies ioniques avec une résolution et une sensibilité inégalées. / Stars are bad neighbors: they often disturb their surroundings. They sometimes travel very fast through the interstellar medium (ISM). They frequently undergo violent ejection events which leave an imprint on their neighborhood (jets, winds, supernovae). These supersonic flows generate shocks both in the ejected material and in the stellar environment. The study of these shocks constitute the subject of this thesis, and we model them with the Paris-Durham planar shock code, which incorporates a wealth of micro-physics and chemical processes relevant to the magnetized ISM.First, we use this code to model 3D magnetized axisymmetric shocks with arbitrary shapes, thanks to a formalism which links mathematically the shape of shocks to an equivalent statistical distribution of 1D shocks. For the first time, we examine systematically the effect of the geometry, age, and various other parameters on the H2 excitation diagram and emission line profiles. For example, we unveil a geometrical effect which shows that 1D planar shocks emission fits to 3D bow shocks are biased towards small velocities. We also apply our models to spatially integrated H2 observations of bow-shocks in Orion BN-KL and BHR71 where a much better match is obtained with only a limited number of additional parameters compared to former planar models. We illustrate on the Herbig-Haro object HH54 how spectrally resolved H2 line emission profiles can be used to extract a wealth of dynamical information.Second, we include in the Paris-Durham shock code a minimum set of processes necessary to describe asymptotic giant branch (AGB) wind models: geometrical dilution, external UV radiation, radiative pressure on grains, gravity, heating from stellar radiation pumping, three-body reactions, and sonic-point crossing. With this tool, we started to examine the time-dependent chemistry of hydrogen in winds of hot and cool AGB stars. We suggest that the low abundance of HI inferred from observations is due to hydrogen locked in its molecular form, and we use our model to try and reproduce HI line observations lines in a hot AGB (Y CVn).Although we have mainly focused on atomic or molecular hydrogen in this study it would be straightforward to extend it to other molecules with optically thin transitions. These simplified tools to model chemistry for complex geometries and dynamics are proving very useful at a time when new instruments such as ALMA discover a wealth of spectral and spatial information for a multitude of chemical tracers, and also when the JWST will soon provide complementary data in the infrared H$_2$ and ionic lines with unprecedented resolution and sensitivity.