21 cm cosmology opens an observational window to previously unexplored cosmological epochs such as the Epoch of Reionization (EoR), the Cosmic Dawn and the Dark Ages using powerful radio interferometers such as the planned Square Kilometer Array (SKA). Among all the other applications which can potentially improve the understanding of standard cosmology, we study the promising opportunity given by measuring the weak gravitational lensing sourced by 21 cm radiation. We performed this study in two different cosmological epochs, at a typical EoR redshift and successively at a post-EoR redshift. We will show how the lensing signal can be reconstructed using a three dimensional optimal quadratic lensing estimator in Fourier space, using single frequency band or combining multiple frequency band measurements. To this purpose, we implemented a simulation pipeline capable of dealing with issues that can not be treated analytically. Considering the current SKA plans, we studied the performance of the quadratic estimator at typical EoR redshifts, for different survey strategies and comparing two thermal noise models for the SKA-Low array. The simulation we performed takes into account the beam of the telescope and the discreteness of visibility measurements. We found that an SKA-Low interferometer should obtain high-fidelity images of the underlying mass distribution in its phase 1 only if several bands are stacked together, covering a redshift range that goes from z=7 to z=11.5. The SKA-Low phase 2, modeled in order to improve the sensitivity of the instrument by almost an order of magnitude, should be capable of providing images with good quality even when the signal is detected within a single frequency band. Considering also the serious effect that foregrounds could have on this detections, we discussed the limits of these results and also the possibility provided by these models of measuring an accurate lensing power spectrum.

In this thesis work we will explore and discuss the properties of the gamma-ray sources included in the first Fermi-LAT catalog of sources above 10 GeV (1FHL), by considering both blazars and the non negligible fraction of still unassociated gamma-ray sources (UGS, 13%). We perform a statistical analysis of a complete sample of hard gamma-ray sources, included in the 1FHL catalog, mostly composed of HSP blazars, and we present new VLBI observations of the faintest members of the sample. The new VLBI data, complemented by an extensive search of the archives for brighter sources, are essential to gather a sample as large as possible for the assessment of the significance of the correlation between radio and very high energy (E>100 GeV) emission bands. After the characterization of the statistical properties of HSP blazars and UGS, we use a complementary approach, by focusing on an intensive multi-frequency observing VLBI and gamma-ray campaign carried out for one of the most remarkable and closest HSP blazar Markarian 421.

We have used high-resolution spectra, acquired with UVES@ESO-VLT, to determine the chemical abundances of different samples of AGB and RGB stars in 4 Galactic globular clusters, namely 47Tuc, NGC3201, M22 and M62. For almost all the analyzed AGB stars we found a clear discrepancy between the iron abundance measured from neutral lines and that obtained from single ionized lines, while this discrepancy is not obtained for the RGB samples observed in the same clusters and analyzed with the same procedure. Such a behavior exactly corresponds to what expected in the case of Non-Local Thermodynamical Equilibrium (NLTE) in the star atmosphere. These results have a huge impact on the proper determination of GC chemistry. In fact, one of the most intriguing consequences is that, at odds with previous claims, no iron spread is found in NGC3201 and M22 if the iron abundance is obtained from ionized lines only.

The way mass is distributed in galaxies plays a major role in shaping their evolution across cosmic time. The galaxy's total mass is usually determined by tracing the motion of stars in its potential, which can be probed observationally by measuring stellar spectra at different distances from the galactic centre, whose kinematics is used to constrain dynamical models. A class of such models, commonly used to accurately determine the distribution of luminous and dark matter in galaxies, is that of equilibrium models. In this Thesis, a novel approach to the design of equilibrium dynamical models, in which the distribution function is an analytic function of the action integrals, is presented. Axisymmetric and rotating models are used to explain observations of a sample of nearby early-type galaxies in the Calar Alto Legacy Integral Field Area survey. Photometric and spectroscopic data for round and flattened galaxies are well fitted by the models, which are then used to get the galaxies' total mass distribution and orbital anisotropy. The time evolution of massive early-type galaxies is also investigated with numerical models. Their structural properties (mass, size, velocity dispersion) are observed to evolve, on average, with redshift. In particular, they appear to be significantly more compact at higher redshift, at fixed stellar mass, so it is interesting to investigate what drives such evolution. This Thesis focuses on the role played by dark-matter haloes: their mass-size and mass-velocity dispersion correlations evolve similarly to the analogous correlations of ellipticals; at fixed halo mass, the haloes are more compact at higher redshift, similarly to massive galaxies; a simple model, in which all the galaxy's size and velocity-dispersion evolution is due to the cosmological evolution of the underlying halo population, reproduces the observed size and velocity-dispersion of massive compact early-type galaxies up to redshift of about 2.

The kinematics is a fundamental tool to infer the dynamical structure of galaxies and to understand their formation and evolution. Spectroscopic observations of gas emission lines are often used to derive rotation curves and velocity dispersions. It is however difficult to disentangle these two quantities in low spatial-resolution data because of beam smearing. In this thesis, we present 3D-Barolo, a new software to derive the gas kinematics of disk galaxies from emission-line data-cubes. The code builds tilted-ring models in the 3D observational space and compares them with the actual data-cubes. 3D-Barolo works with data at a wide range of spatial resolutions without being affected by instrumental biases. We use 3D-Barolo to derive rotation curves and velocity dispersions of several galaxies in both the local and the high-redshift Universe. We run our code on HI observations of nearby galaxies and we compare our results with 2D traditional approaches. We show that a 3D approach to the derivation of the gas kinematics has to be preferred to a 2D approach whenever a galaxy is resolved with less than about 20 elements across the disk. We moreover analyze a sample of galaxies at z~1, observed in the H-alpha line with the KMOS/VLT spectrograph. Our 3D modeling reveals that the kinematics of these high-z systems is comparable to that of local disk galaxies, with steeply-rising rotation curves followed by a flat part and H-alpha velocity dispersions of 15-40 km/s over the whole disks. This evidence suggests that disk galaxies were already fully settled about 7-8 billion years ago. In summary, 3D-Barolo is a powerful and robust tool to separate physical and instrumental effects and to derive a reliable kinematics. The analysis of large samples of galaxies at different redshifts with 3D-Barolo will provide new insights on how galaxies assemble and evolve throughout cosmic time.

The study of supermassive black hole (SMBH) accretion during their phase of activity (hence becoming active galactic nuclei, AGN), and its relation to the host-galaxy growth, requires large datasets of AGN, including a significant fraction of obscured sources. X-ray data are strategic in AGN selection, because at X-ray energies the contamination from non-active galaxies is far less significant than in optical/infrared surveys, and the selection of obscured AGN, including also a fraction of heavily obscured AGN, is much more effective. In this thesis, I present the results of the Chandra COSMOS Legacy survey, a 4.6 Ms X-ray survey covering the equatorial COSMOS area. The COSMOS Legacy depth (flux limit f=2x10^(-16) erg/s/cm^(-2) in the 0.5-2 keV band) is significantly better than that of other X-ray surveys on similar area, and represents the path for surveys with future facilities, like Athena and X-ray Surveyor. The final Chandra COSMOS Legacy catalog contains 4016 point-like sources, 97% of which with redshift. 65% of the sources are optically obscured and potentially caught in the phase of main BH growth. We used the sample of 174 Chandra COSMOS Legacy at z>3 to place constraints on the BH formation scenario. We found a significant disagreement between our space density and the predictions of a physical model of AGN activation through major-merger. This suggests that in our luminosity range the BH triggering through secular accretion is likely preferred to a major-merger triggering scenario. Thanks to its large statistics, the Chandra COSMOS Legacy dataset, combined with the other multiwavelength COSMOS catalogs, will be used to answer questions related to a large number of astrophysical topics, with particular focus on the SMBH accretion in different luminosity and redshift regimes.

Orientador: Abraham Hirsz Zimerman / Doutor

Orientador: Tadashi Yokoyama / Banca: Roberto Vieira Martins / Banca: Sandro da Silva Fernandes / Resumo: Phobos e Triton são dois satélites que estão decaindo devido efeitos da maré. Ambos passarão por várias \ressonâncias seculares " sendo que Triton, cruzará também ressonâncias orbitais envolvendo os satélites mais internos de Netuno. Este problema foi inicialmente estudado por Yokoyama (2002) considerando várias hipóteses simplicado- ras. Aqui fazemos importantes generalizacões incluindo a elipticidade da órbita de Marte, perturbações planetárias, precessão do equador e integracões por tempos muito mais significativos. Os resultados mostram interessantes capturas e escapes, os quais são altamente sensíveis æas condicões iniciais. Na dupla ressonância (Marte-Phobos) , observa-se uma variação da inclinaçao muito mais significativa do que aquela apontada em Yokoyama (2002). Nas ressonâncias orbitais para o problema de Netuno-Triton, verifica-se a não ocorrência de capturas nas comensurabilidades retrógradas. O efeito da perturbação do achatamento é muito importante. Por outro lado, mesmo para valores relativamente próximos dos semi-eixos (satélite e Triton) que ocorrer~ao no futuro, algumas experi^encias mostraram que o satélite interno pode permanecer estável por tempo relativamente longo, que os planos de suas órbitas estarão ainda mais separados devido o efeito da maré que aumentará o sin(IT ). / Abstract: Under the action of the tides, the orbits of Phobos and Triton are spiralling in towards their host planets. The main purpose of this work is to analyze some interesting features that will occur while these orbits are contracting, i. e., these satellites will pass through some secular and orbital resonances. Here we revisit a previous work of Yokoyama (2002) taking a more complete model for the motion of the planet. The integrations are extended to much longer time. Then it is shown that the escapes are very sensitive to the initial con- ditions. The possibility of the existence of an \universal inclination " is brie°y discussed. Phobos will face an interesting case of \double resonance " which plays an important role , because a new resonance will be subsequently encountered. For Neptune-Triton system, it is shown that the e®ect of some orbital retrograde resonances can be very weak if the oblateness of the planet is neglected. No capture in these resonances seems to be possible. Due to the high inclination of Triton's orbit, in some cases an inner satellite can survive for some moderate time even when it's semi major axis is rather close to Triton's semi major axis. / Mestre

Este trabalho relata as atividades desenvolvidas em duas turmas de 8ª série da E. E. de Educação Básica Estado de Goiás de Santa Cruz do Sul, RS, tendo como tema, Astronomia: motivação para o ensino de Física na 8ª série. Através de um levantamento bibliográfico sobre a história dos programas de ensino de Ciências do Rio Grande do Sul, conseguimos compreender o motivo do uso do livro didático de Ciências como fonte quase exclusiva de apoio à sala de aula. O embasamento teórico do trabalho acontece em cima de abordagens construtivistas, destacando Piaget e os períodos gerais de desenvolvimento cognitivo; Vigotsky e a interação social e as teorias de aprendizagem significativas de Ausubel e de Novak. Avaliação prévia do conhecimento dos alunos, a Física e o Universo, comparação entre o tamanho dos planetas e o Sol, atividades em grupo, uso da informática, visita ao planetário e práticas realizadas no laboratório de Física estão entre as atividades que relatamos neste trabalho. Percebemos pela empolgação dos alunos, pelos relatos por eles escritos, pela avaliação das aulas e do professor por parte dos alunos, pelos comentários positivos dos pais e direção da escola, que o tema tratado se mostrou pertinente para introduzir os estudos de Física na 8ª série e também pelo leque de conteúdos que podem ser trabalhados a partir da Astronomia, como a luz, calor, e até os movimentos, que na maioria dos livros-texto de ciências aparece como assunto introdutório à Física.

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas, Programa de Pós-Graduação em Física, Florianópolis, 2017. / Made available in DSpace on 2017-06-27T04:22:58Z (GMT). No. of bitstreams: 1 346422.pdf: 15487171 bytes, checksum: 0b999851c6227d67d100d0ac9a177b74 (MD5) Previous issue date: 2017 / O paradigma da classificação espectral de galáxias, largamente utilizado atualmente com o avanço das técnicas de síntese espectral, dos modelos de populações estelares e dos grandes levantamentos de dados, proporcionou a obtenção de uma quantidade sem precedentes de informações físicas acerca da evolução das galáxias no Universo. Neste contexto, utilizamos dados públicos de três grandes levantamentos de galáxias, cobrindo desde o ultravioleta (Galaxy Evolution Explorer ; GALEX), passando pelo óptico (Sloan Digital Sky Survey; SDSS), até o infravermelho médio (Wide-field Infrared Survey Explorer ; WISE), com o objetivo de investigar as propriedades de galáxias early-type classificadas com base nas linhas de emissão presentes ou ausentes em seus espectros.Investigamos as propriedades físicas no WISE da classe de galáxias hospedeiras de região de emissão nuclear de baixa ionização (LINER), definidas por meio de diagramas de diagnóstico de linhas de emissão. Neste processo, utilizamos as classes espectrais definidas através do método que leva em consideração a largura equivalente de Ha e a razão [N ii]/Ha, obtendo uma linha divisória ?ideal? que separa as galáxias do Universo Local entre as que são puramente star forming daquelas que já estão ?aposentadas? da tarefa de formar estrelas. Utilizando os indicadores morfológicos disponibilizados pelo Galaxy Zoo, percebemos que ~ 30% das galáxias classificadas como aposentadas são objetos espirais, com disco extenso dominado por regiões de formação estelar. Nestes objetos, a fibra utilizada na obtenção do espectro utilizado na classificação espectral observou apenas a região do bojo dominada por populações estelares velhas. Com estes apontamentos, selecionamos uma amostra de LINERs utilizando diferentes marcadores, de forma a testar se de fato possuem núcleo ativo (AGN) quando considerado um combinado de linhas de emissão com a cor no infravermelho. Encontramos que a maior parte destas galáxias não hospedam de fato um AGN, com suas linhas de emissão sendo providas pelas populações de estrelas evoluídas de baixa massa (HOLMES).Excluída a contribuição de AGN, investigamos as propriedades das galáxias ?aposentadas?, cuja característica é a ausência de formação estelar recente quantificada pela largura equivalente de Ha, WHa. Estes objetos pararam de formar estrelas há muito tempo e seus espectros mostram somente contribuições de estrelas velhas. São divididas em duas classes: (1) galáxias que possuem linhas de emissão fracas, com 0,5 < WHa < 3 Å (ELR); e (2) galáxias sem linhas, com WHa < 0,5 Å (LLR). Utilizando os fluxos no infravermelho médio do WISE, observamos que as ELR são mais brilhantes na banda centrada em torno de 12 µm, associada com emissão oriunda de poeira morna. Em uma comparação com os dados obtidos coma síntese espectral com o código Starlight, percebemos que estas duas classes de galáxias aposentadas também têm atenuação (AV ) diferente, com características similares às da emissão em 12 µm. Isto indica que a luz emitida pelas estrelas velhas é reprocessada por um meio difuso. Comparando galáxias similares das duas classes, não encontramos evidências de outras diferenças significativas nas propriedades de suas populações estelares, especialmente nas idades médias. Porém, análises comparativas envolvendo emissão no ultravioleta e indicadores de idade e metalicidade mostram que a metalicidade das duas classes tem uma diferença sensível, enquanto que a idade das populações estelares é sistematicamente diferente, com as ELR sendo um pouco mais jovens. Desta forma, isto implica na coexistência dos dois fenômenos: presença de gás difuso e populações estelares com idades diferentes. Neste sentido, sugerimos um cenário em que alguma formação estelar (SFR < 0,3 Msol yr -1 ) tenha ocorrido em um tempo entre 1 e 5 Gyr nas ELR através da adição de material frio do meio externo. Nas galáxias LLR, este fenômeno parou em um tempo muito maior (t > 5 Gyr), de forma que apenas são observadas as populações estelares velhas. Neste caso, nas ELRs é observada uma mistura de propriedades físicas, compostas pela parte oriunda das propriedades das estrelas velhas e pela contribuição das mais jovens. Neste cenário, a presença de um meio interestelar difuso também é compatível, uma vez que o material adquirido ainda não dissipou completamente, estando espalhado nas partes externas da galáxia.<br> / Abstract : The galaxy spectral classification paradigm, largely used nowadays with the advance of the spectral synthesis techniques, the stellar population models and the large galaxy surveys, have allowed us the acquisition of a huge amount of physical properties of galaxies in the Universe. In this way, we use the data of three public surveys, covering from the ultraviolet (Galaxy Evolution Explorer; GALEX), passing through the optic (The Sloan Digital Sky Survey; SDSS), and reaching the mid-infrared (Wide-field Infrared Survey; WISE), with the aim to investigate the properties of early-type galaxies classified based on the presence or absence of emission lines in their spectra.Initially, we investigate the mid-infrared properties of galaxies hosting a low ionization nuclear emission region (LINER), defined by emission line diagnostic diagrams. We use the spectral classes defined by the method that take into account the equivalent width of Ha and the [N ii]/Ha ratio, obtaining an optimal divisor line which separate star forming galaxies from galaxies that are retired from their duty of forming stars. Selecting these galaxies using the morphological information from the Galaxy Zoo project, we realize that many of the retired galaxies have spiral morphology, with only the old bulge being observed by the SDSS fiber. We then select a sample of LINERs using different definitions to test if they are in fact hosting an active nuclei (AGN) when considering a combination of emission lines and infrared colors. We find that most of these objects are not truly AGN, but their emission lines are powered by their hot low-mass stellar populations (HOLMES).Excluded the AGN contribution, we investigate the properties of retired galaxies, characterized by the absence of recent star formation as quantified by the equivalent width of Ha, WHa. These objects stopped forming stars long ago and their spectra show only the contribution of old stellar populations. These galaxies are divided into two classes: (1) galaxies with weak emission lines, with 0.5 < WHa < 3 Å (ELR); and (2) galaxies without lines, with WHa < 0.5 Å (LLR). Using the mid-infrared fluxes from the WISE survey, we observe that ELR galaxies have brighter fluxes on the band centered at 12 µm, associated with the warm dust emission. In a comparison with the data obtained from the spectral synthesis code Starlight, we realize that these two classes of galaxies also have different attenuation parameter (A V ), which resembles the dust emission at 12 µm. This indicates that the light provided by the old stars are reprocessed by a diffuse medium. Comparing similar galaxies of both retired classes, we do not find any significant evidence of other differences in their stellar population properties, specially on the mean stellar age. However, comparative analysis involving the ultraviolet emission and the age and metallicity indicators based on the Lick indices, shows that the metallicity and the age of their stellar populations are different. In this sense, we suggest that the most probable scenario to explain this findings is that star formation have occurred in a look-back time of 1 to 5 Gyr for the ELR, which was triggered by external cold gas accretion. For the LLR galaxies, this phenomena occurred in a longer look-back time, since we only observe the emission coming from their old stellar populations. In this case, for ELR galaxies we observe a mix of physical properties, composed by the properties of their old and intermediate age stellar populations. In this scenario, the presence of a diffuse interstellar medium is also compatible, since the extra material acquired does not have completely vanished yet,being scattered in the galaxy.