En esta tesis se explora el estrecho límite que separa las estrellas más masivas que acaban su vida explotando como una supernova y aquellas menos masivas que dan lugar a una nebulosa planetaria. Para ello se ha estudiado, mediante espectroscopía de alta resolución, una muestra de estrellas evolucionadas presentes en cúmulos abiertos jóvenes. Las edades comprendidas se sitúan entre los 30-100 millones de años, muestreando, para estas estrellas, un rango de masas entre 5,5-9,5 masas solares, donde se encuentra el límite de masa anteriormente indicado.

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We examine the globular cluster system (GCS) of the isolated elliptical NGC 720 using the Gemini Multi-Object Spectrograph (GMOS) and have obtained spectra for 241 candidate globular clusters (GCs) extending to a galactocentric radius of 40 kpc. Of the 241 candidates, 120 are confirmed GCs, where 46 are members of the metal-poor, blue, population and 74 are members of the metal-rich, red, population. A (g-i)=0.50 colour split is used to identify the blue and red populations. We measure the full GCS to have a rotational velocity (Vrot) of 50 +/- 7 km/s with a position angle (PA) of 170 +/- 69 degrees. The red population has a Vrot = 97 +/- 14 km/s with PA = 147 +\- 18 degrees and the blue population has a Vrot = 79 +/- 7 km/s with PA = 89 +/- 18 degrees. The full GCS has an average velocity dispersion of 168 +/- 22 km/s, for the red population is 156 +/- 30 km/s and for the blue population is 181 +/- 33 km/s. The velocity dispersion pro file for all populations is constant with increasing radius, suggesting the presence of a dark matter halo. Using a tracer mass estimator, we have measured the mass out to 40 kpc as 1.8(+0.6/-0.1)x10^12 Msun for a potential which traces the dark matter pro file. We also estimate the M/L_V = 30 - 70. This study extends our survey of GCSs to isolated environments. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2011-01-31 11:30:54.389

Cette thèse présente une étude des coeurs denses et massifs de deux régions de formation d'étoiles massives de notre Galaxie. J'utilise pour ce travail des observations Herschel-HOBYS de NGC 6334 et NGC 6357 complémentées par les sondages GLIMPSE, MIPSGAL, ATLASGAL, MALT90 ainsi que des observations SCUBA-2 et SIMBA. La vision multi-longueur d'onde m'a permis d'identifier spatialement les coeurs les plus denses des deux régions et d'extraire leur distribution spectrale d' énergie. J'ai modélisé l'émission des coeurs pour extraire leurs paramètres physiques et j'ai utilisé des données infrarouge, des catalogues de sources masers et radio, ainsi que des raies mol éculaires pour déterminer leur statut évolutif. Mon travail présente l'extraction des coeurs denses et massifs ainsi que l'analyse de leur distribution spatiale et de leurs paramètres physiques dans le contexte évolutif de la formation d'étoiles massives dans les régions NGC 6334 et NGC 6357. / This thesis aims at studying the massive dense cores found inside two regions of high-mass star formation within our Galaxy. I make use of Herschel observations of NGC 6334 and NGC 6357 from the HOBYS project, complemented with the GLIMPSE, MPISGAL, ATLASGAL, MALT90 surveys as well as observations from SCUBA-2 and SIMBA. The multi-wavelength view allows me to spatially identify the densest cores in both regions and extract their spectral energy distribution. I modelled the emission from the cores to extract their physical parameters and I used infrared data, masers and radio catalogues, and molecular lines to assess their evolutionary status. My study present the extraction of massive dense cores in the regions NGC 6334 and NGC 6357 together with the analysis of their spatial distribution and physical parameters in the evolutionnary context of massivestar formation that is occuring in both regions.

In this thesis I present an investigation into the presence, nature and origin of the thick disk component in late-type galaxies. I use ground-based wide-field observations to study two edge-on low-mass galaxies in the Local Universe: NGC 4244 and NGC 55. The large field-of-view of the ground-based data enables me to inspect the radial and vertical structure of each galaxy. The vertical profiles are studied up to larger distances fromthemid-plane than in any previous study and the presence of a second disk component beyond the thin disk with a larger scale height is revealed for both galaxies. The high-quality data allows me to carry out stellar population and metallicity studies for stars above and below the plane. Furthermore, direct comparisons with two simulated low-mass galaxies provided by the Preston group at the University of Central Lancashire are carried out. By putting the results for NGC 4244 and NGC 55 into context with the thick disk properties from these simulations and from the literature, the most likely thick disk formation scenarios can be pointed out. The bulgeless low-mass systemNGC 4244 lies at a distance of 4.4 Mpc and is studied using V- and I-band wide-field images taken with Suprime-Cam on the Subaru telescope, Hawaii. The extra-planar regions of NGC 4244 show the presence of a large population of Red Giant Branch (RGB) stars and some Asymptotic Giant Branch (AGB) stars. The best strategy to study the presence and structure of a thick disk component is to use the vertical diffuse light profiles in the crowded central regions and RGB star counts in the sparser and sky background dominated outskirts. The profiles show evidence for the presence of a sparsely populated second structural component beyond ∼ 2 kpc above and below the mid-plane. The profiles are fitted with a twodisk model, where each disk is approximated by an isothermal, self-gravitating sheet. A Bayesian model comparison confirms the need for a second disk component in the profile fit. Furthermore, the AGB profiles are inspected and are found to have a lower scale height than the RGB profiles. Metallicity studies of the RGB population in the thick disk component reveal that the metallicity is much lower than the solar metal-licity. Last, the scale length of the thin disk is quantified from the diffuse light radial profiles. At a distance of 1.9 Mpc the Magellanic type low-mass galaxy NGC 55 is studied using V- and I-band images from the VIsible MultiObject Spectrograph (VIMOS) in imaging mode on the Very Large Telescope (VLT, UT3) on Cerro Paranal, Chile. The very central regions of the galaxy are not covered by the VIMOS pointings so I use additional images from the Curtis-Schmidt telescope on Cerro Tololo. As for NGC 4244, I find that the RGB star count profiles extend to larger scale heights than the AGB profiles. The combined diffuse light + RGB profiles show evidence for a very prominent second disk component beyond ∼ 2 kpc above and below the plane. The metallicity studies of the RGB population show, that there is no trend in themetallicity with height above or below the plane. As for NGC 4244 the metallicity is significantly lower than the solar metallicity. Furthermore, the scale length of the thin and thick disk is derived from the radial profiles. The properties of thick disks in galaxies of all masses is studied by compiling the results fromobserved and simulated galaxies in the literature in addition to the results for NGC 4244, NGC 55 and the two simulated low-mass galaxies provided by the Preston group. By studying the similarities, differences and global trends with mass in the thick disk properties it is possible to confront the thick disk formation models. I find that none of the formation scenarios can be ruled out and even a hybrid scenario is possible.

Neste trabalho, estudamos dois aglomerados globulares, o NGC 6397 com módulo de distância (m- M) = 12,03 ± 0,06 mag e o NGC288 com módulo de distância (m- M) = 14,57 ± 0,08 mag. Para o NGC6397, realizamos um estudo fotométrico em UBV com dados do ESO-VLT, obtendo a função de luminosidade corrigida por completeza. Observamos que próximo à região cent ral do aglomerado, a função de luminosidade apresenta uma maior densidade de estrelas brilhantes do que a região mais externa. Calculamos os modelos projetado e deprojetado cobrindo todo o aglomerado. As formas dos perfis de brilho de superfície e densidade de número mostraram redução de luminosidade, demonstrando assim a segregação de massa. Assumindo a massa média total, estimamos o número de estrelas deste aglomerado. Para as séries temporais obtidas com o ESO-VLT, com rv 11 h de imagens fotométricas ut ilizando o imageador FORS2 distríbuidas ao longo de duas noites consecut ivas, realizamos uma inspeção no aglomerado globular NGC 6397 para determinar a fração de estrelas variáveis. Analisando 9 868 curvas de luz de estrelas mais brilhantes do que magtútude 23 no filtro 465-nm, identificamos 412 novas estrelas variáveis com escala de tempos entre 0,004 e 2 dias. Além disso, realizamos uma análise da. já conhecida binária eclipsante V4 no NGC6397, obtendo massas Mp = 0,76 ± 0,02 M0 e Ms = 0,73 ± 0,02 M0 para as componentes primária e secundária e raios de Rp = 1,01± 0,10 R0 and Rp = 0,99 ± 0,10 R0. Analisando curvas de luz de 12 438 estrelas do NGC 288, descobrimos duas novas estrelas variáveis. Pela posição no Diagrama Cor-Magtútude, pelas características de variabilidade, classificamos as novas estrelas como SX Phe. Utilizamos os períodos de seis SX Phe já conhecidas anteriormente e das duas novas descobertas para. estudar a relação período-luminosidade. / In t his work, we studied two globular clusters, NGC 6397 with distance modulus (m-M) = 12.03 ± 0.06 mag and the NGC 288 with distance modulus (m-M) = 14.57 ± 0.08 mag. For NGC6397, we conducted a UBV photometric study with ESO-VLT data, obtaining the luminosity function corrected for completeness. We observe that near the central region of the cluster, the luminosity function has a greater density than the bright stars in the externai region. We estimate the models projected and deprojected covering ali cluster. T he shapes of surface brightness profiles and number density showed reduced luminosity, thus demonstrating the mass segregation. Assuming the average total mass, we estimate the number of stars of this cluster. For the t ime series obtained with the ESO-VLT, with rv 11 h photometric images using imaging FORS2 distributed over two consecut ive nights, we detennined the fraction of variable stars with mass. Analyzing 9 868 light cmves of stars brighter than magnitude 23 in the filter 465-nm, we identified 412 new variable stars with scale t imes between 0.004 and 2days. In addit ion, we analysed of aJready known eclipsing binary V4 in NGC6397, obtaining masses Mp = 0.76 ± 0.02 M0 and Ms = 0.73 ± 0.02!\,10 for the primary and secondary components and radii R,= 1.01± 0. 10~ and R,= 0.99 ± 0. 1 0~. AnaJyzing 12438 light cmves of NGC 288 stru·s , we discovered two new vru·iable stars. The position in the CMD and the chru·acteristics variabilit ies, we classified the new stru·s as SX Phe. We use the redetermined periods of six SX Phe already known and two new discoveries to study the period-lmn inosity relation.

O foco deste trabalho é estudar a influência de buracos negros supermassivos (BNSs) nucleares na dinâmica e na cinemática estelar da região central das galáxias e determinar a massa destes BNSs. Assumindo que a função de distribuição (DF) que descreve a dinâmica da galáxia depende de duas integrais de movimento (f = f(E;Lz), onde E é a energia do sistema e Lz é a componente z do momento angular), construiu-se um modelo dinâmico de Jeans anisotrópico para reproduzir as distribuições de velocidades estelares observadas nas regiões centrais das galáxias ativas NGC4258 e NGC1052. A cinemática estelar das galáxias foi obtida através de observações espectroscópicas na banda-K do infravermelho próximo realizadas com o instrumento NIFS (Near-infrared Integral Field Spectrograph) no telescópio GEMINI Norte, e mostram que a distribuição de velocidades na região nuclear, em particular dentro do raio de influência do BNS, é dominada por uma alta dispersão de velocidades. Esta observação é consistente com a hipótese da presença de BNSs. Foram usadas imagens no infravermelho próximo obtidas com os instrumentos NICMOS (Near-Infrared Camera and Multi-Object Spectrometer) a bordo do HST (Hubble Space Telescope) e do 2MASS (Two Micron All-Sky Survey) para construir modelos de expansão multi-gaussiana (MGE) para parametrizar a distribuição superficial de brilho das galáxias. A partir destes modelos MGE foi possível obter as distribuições de matéria e os potenciais gravitacionais das galáxias. A estes potenciais adicionou-se o potencial de uma fonte pontual representando o BNS central. Estes pares potencial-densidade descritos como funções gaussianas bidimensionais foram então usados para resolver as equações de Jeans semi-isotrópicas com simetria axial e modelar as distribuições de velocidades das galáxias. Comparando a cinemática modelada com as observações concluímos que o BNS no núcleo da galáxia NGC4258 possui uma massa de 4, 8+0,9 -0,8M e que o BNS no núcleo da galáxia NGC1052 possui uma massa de 3,6 108M. / The focus of this work is the study of the in uence of nuclear supermassive black holes (SMBHs) in the dynamics and stellar kinematics of the central region of galaxies and determine the masses of these SMBHs. Assuming that the distribution function (DF) that describes the galaxy dynamics depends of two integrals of motion (f = f(E;Lz), where E is the energy of the system and Lz is the z-component of the angular momentum), we have constructed a Jeans anisotropic dynamical model to t the observed stellar velocity distributions of the central regions of the active galaxies NGC4258 and NGC1052. The stellar kinematics of the galaxies was obtained from near-infrared spectroscopic observations in the K-band performed with the instrument NIFS (Near-infrared Integral Field Spectrograph) of the GEMINI North telescope. The observations show that the velocity distributions in the nuclear regions, particularly inside the black hole sphere of in uence, of the galaxies is dominated by high velocity dispersions. These observations are consistent with the hypothesis of the presence of SMBHs at the nucleus. We have used near-infrared K-band and H-band images obtained with the NICMOS instrument (Near-Infrared Camera and Multi-Object Spectrometer) aboard the HST (Hubble Space Telescope) and from 2MASS (Two Micron All-Sky Survey) to build multi-gaussian expansion models (MGE) to parametrise the surface brightness distributions of the galaxies. From these MGE models it was possible to obtain the mass distributions and the gravitational potentials of the galaxies. To these potentials we added the potential of a point source representing the SMBH. These densitypotential pairs described as two-dimensional gaussian functions were then used to obtain the solutions of the semi-isotropic axisymmetric Jeans equations and to model the velocity distributions of the galaxies. By comparing the modelled kinematics with the observed one we concluded that the SMBH in the nucleus of the galaxy NGC4258 has a mass of 4, 8+0,9 -0,8M and that the SMBH in the nucleus of the galaxy NGC1052 has a mass of 3,6 108M.

Neste trabalho, estudamos dois aglomerados globulares, o NGC 6397 com módulo de distância (m- M) = 12,03 ± 0,06 mag e o NGC288 com módulo de distância (m- M) = 14,57 ± 0,08 mag. Para o NGC6397, realizamos um estudo fotométrico em UBV com dados do ESO-VLT, obtendo a função de luminosidade corrigida por completeza. Observamos que próximo à região cent ral do aglomerado, a função de luminosidade apresenta uma maior densidade de estrelas brilhantes do que a região mais externa. Calculamos os modelos projetado e deprojetado cobrindo todo o aglomerado. As formas dos perfis de brilho de superfície e densidade de número mostraram redução de luminosidade, demonstrando assim a segregação de massa. Assumindo a massa média total, estimamos o número de estrelas deste aglomerado. Para as séries temporais obtidas com o ESO-VLT, com rv 11 h de imagens fotométricas ut ilizando o imageador FORS2 distríbuidas ao longo de duas noites consecut ivas, realizamos uma inspeção no aglomerado globular NGC 6397 para determinar a fração de estrelas variáveis. Analisando 9 868 curvas de luz de estrelas mais brilhantes do que magtútude 23 no filtro 465-nm, identificamos 412 novas estrelas variáveis com escala de tempos entre 0,004 e 2 dias. Além disso, realizamos uma análise da. já conhecida binária eclipsante V4 no NGC6397, obtendo massas Mp = 0,76 ± 0,02 M0 e Ms = 0,73 ± 0,02 M0 para as componentes primária e secundária e raios de Rp = 1,01± 0,10 R0 and Rp = 0,99 ± 0,10 R0. Analisando curvas de luz de 12 438 estrelas do NGC 288, descobrimos duas novas estrelas variáveis. Pela posição no Diagrama Cor-Magtútude, pelas características de variabilidade, classificamos as novas estrelas como SX Phe. Utilizamos os períodos de seis SX Phe já conhecidas anteriormente e das duas novas descobertas para. estudar a relação período-luminosidade. / In t his work, we studied two globular clusters, NGC 6397 with distance modulus (m-M) = 12.03 ± 0.06 mag and the NGC 288 with distance modulus (m-M) = 14.57 ± 0.08 mag. For NGC6397, we conducted a UBV photometric study with ESO-VLT data, obtaining the luminosity function corrected for completeness. We observe that near the central region of the cluster, the luminosity function has a greater density than the bright stars in the externai region. We estimate the models projected and deprojected covering ali cluster. T he shapes of surface brightness profiles and number density showed reduced luminosity, thus demonstrating the mass segregation. Assuming the average total mass, we estimate the number of stars of this cluster. For the t ime series obtained with the ESO-VLT, with rv 11 h photometric images using imaging FORS2 distributed over two consecut ive nights, we detennined the fraction of variable stars with mass. Analyzing 9 868 light cmves of stars brighter than magnitude 23 in the filter 465-nm, we identified 412 new variable stars with scale t imes between 0.004 and 2days. In addit ion, we analysed of aJready known eclipsing binary V4 in NGC6397, obtaining masses Mp = 0.76 ± 0.02 M0 and Ms = 0.73 ± 0.02!\,10 for the primary and secondary components and radii R,= 1.01± 0. 10~ and R,= 0.99 ± 0. 1 0~. AnaJyzing 12438 light cmves of NGC 288 stru·s , we discovered two new vru·iable stars. The position in the CMD and the chru·acteristics variabilit ies, we classified the new stru·s as SX Phe. We use the redetermined periods of six SX Phe already known and two new discoveries to study the period-lmn inosity relation.

Neste trabalho, estudamos dois aglomerados globulares, o NGC 6397 com módulo de distância (m- M) = 12,03 ± 0,06 mag e o NGC288 com módulo de distância (m- M) = 14,57 ± 0,08 mag. Para o NGC6397, realizamos um estudo fotométrico em UBV com dados do ESO-VLT, obtendo a função de luminosidade corrigida por completeza. Observamos que próximo à região cent ral do aglomerado, a função de luminosidade apresenta uma maior densidade de estrelas brilhantes do que a região mais externa. Calculamos os modelos projetado e deprojetado cobrindo todo o aglomerado. As formas dos perfis de brilho de superfície e densidade de número mostraram redução de luminosidade, demonstrando assim a segregação de massa. Assumindo a massa média total, estimamos o número de estrelas deste aglomerado. Para as séries temporais obtidas com o ESO-VLT, com rv 11 h de imagens fotométricas ut ilizando o imageador FORS2 distríbuidas ao longo de duas noites consecut ivas, realizamos uma inspeção no aglomerado globular NGC 6397 para determinar a fração de estrelas variáveis. Analisando 9 868 curvas de luz de estrelas mais brilhantes do que magtútude 23 no filtro 465-nm, identificamos 412 novas estrelas variáveis com escala de tempos entre 0,004 e 2 dias. Além disso, realizamos uma análise da. já conhecida binária eclipsante V4 no NGC6397, obtendo massas Mp = 0,76 ± 0,02 M0 e Ms = 0,73 ± 0,02 M0 para as componentes primária e secundária e raios de Rp = 1,01± 0,10 R0 and Rp = 0,99 ± 0,10 R0. Analisando curvas de luz de 12 438 estrelas do NGC 288, descobrimos duas novas estrelas variáveis. Pela posição no Diagrama Cor-Magtútude, pelas características de variabilidade, classificamos as novas estrelas como SX Phe. Utilizamos os períodos de seis SX Phe já conhecidas anteriormente e das duas novas descobertas para. estudar a relação período-luminosidade. / In t his work, we studied two globular clusters, NGC 6397 with distance modulus (m-M) = 12.03 ± 0.06 mag and the NGC 288 with distance modulus (m-M) = 14.57 ± 0.08 mag. For NGC6397, we conducted a UBV photometric study with ESO-VLT data, obtaining the luminosity function corrected for completeness. We observe that near the central region of the cluster, the luminosity function has a greater density than the bright stars in the externai region. We estimate the models projected and deprojected covering ali cluster. T he shapes of surface brightness profiles and number density showed reduced luminosity, thus demonstrating the mass segregation. Assuming the average total mass, we estimate the number of stars of this cluster. For the t ime series obtained with the ESO-VLT, with rv 11 h photometric images using imaging FORS2 distributed over two consecut ive nights, we detennined the fraction of variable stars with mass. Analyzing 9 868 light cmves of stars brighter than magnitude 23 in the filter 465-nm, we identified 412 new variable stars with scale t imes between 0.004 and 2days. In addit ion, we analysed of aJready known eclipsing binary V4 in NGC6397, obtaining masses Mp = 0.76 ± 0.02 M0 and Ms = 0.73 ± 0.02!\,10 for the primary and secondary components and radii R,= 1.01± 0. 10~ and R,= 0.99 ± 0. 1 0~. AnaJyzing 12438 light cmves of NGC 288 stru·s , we discovered two new vru·iable stars. The position in the CMD and the chru·acteristics variabilit ies, we classified the new stru·s as SX Phe. We use the redetermined periods of six SX Phe already known and two new discoveries to study the period-lmn inosity relation.

O foco deste trabalho é estudar a influência de buracos negros supermassivos (BNSs) nucleares na dinâmica e na cinemática estelar da região central das galáxias e determinar a massa destes BNSs. Assumindo que a função de distribuição (DF) que descreve a dinâmica da galáxia depende de duas integrais de movimento (f = f(E;Lz), onde E é a energia do sistema e Lz é a componente z do momento angular), construiu-se um modelo dinâmico de Jeans anisotrópico para reproduzir as distribuições de velocidades estelares observadas nas regiões centrais das galáxias ativas NGC4258 e NGC1052. A cinemática estelar das galáxias foi obtida através de observações espectroscópicas na banda-K do infravermelho próximo realizadas com o instrumento NIFS (Near-infrared Integral Field Spectrograph) no telescópio GEMINI Norte, e mostram que a distribuição de velocidades na região nuclear, em particular dentro do raio de influência do BNS, é dominada por uma alta dispersão de velocidades. Esta observação é consistente com a hipótese da presença de BNSs. Foram usadas imagens no infravermelho próximo obtidas com os instrumentos NICMOS (Near-Infrared Camera and Multi-Object Spectrometer) a bordo do HST (Hubble Space Telescope) e do 2MASS (Two Micron All-Sky Survey) para construir modelos de expansão multi-gaussiana (MGE) para parametrizar a distribuição superficial de brilho das galáxias. A partir destes modelos MGE foi possível obter as distribuições de matéria e os potenciais gravitacionais das galáxias. A estes potenciais adicionou-se o potencial de uma fonte pontual representando o BNS central. Estes pares potencial-densidade descritos como funções gaussianas bidimensionais foram então usados para resolver as equações de Jeans semi-isotrópicas com simetria axial e modelar as distribuições de velocidades das galáxias. Comparando a cinemática modelada com as observações concluímos que o BNS no núcleo da galáxia NGC4258 possui uma massa de 4, 8+0,9 -0,8M e que o BNS no núcleo da galáxia NGC1052 possui uma massa de 3,6 108M. / The focus of this work is the study of the in uence of nuclear supermassive black holes (SMBHs) in the dynamics and stellar kinematics of the central region of galaxies and determine the masses of these SMBHs. Assuming that the distribution function (DF) that describes the galaxy dynamics depends of two integrals of motion (f = f(E;Lz), where E is the energy of the system and Lz is the z-component of the angular momentum), we have constructed a Jeans anisotropic dynamical model to t the observed stellar velocity distributions of the central regions of the active galaxies NGC4258 and NGC1052. The stellar kinematics of the galaxies was obtained from near-infrared spectroscopic observations in the K-band performed with the instrument NIFS (Near-infrared Integral Field Spectrograph) of the GEMINI North telescope. The observations show that the velocity distributions in the nuclear regions, particularly inside the black hole sphere of in uence, of the galaxies is dominated by high velocity dispersions. These observations are consistent with the hypothesis of the presence of SMBHs at the nucleus. We have used near-infrared K-band and H-band images obtained with the NICMOS instrument (Near-Infrared Camera and Multi-Object Spectrometer) aboard the HST (Hubble Space Telescope) and from 2MASS (Two Micron All-Sky Survey) to build multi-gaussian expansion models (MGE) to parametrise the surface brightness distributions of the galaxies. From these MGE models it was possible to obtain the mass distributions and the gravitational potentials of the galaxies. To these potentials we added the potential of a point source representing the SMBH. These densitypotential pairs described as two-dimensional gaussian functions were then used to obtain the solutions of the semi-isotropic axisymmetric Jeans equations and to model the velocity distributions of the galaxies. By comparing the modelled kinematics with the observed one we concluded that the SMBH in the nucleus of the galaxy NGC4258 has a mass of 4, 8+0,9 -0,8M and that the SMBH in the nucleus of the galaxy NGC1052 has a mass of 3,6 108M.