The Milky Way galaxy, like all spiral galaxies, is surrounded by a roughly spherical distribution of stars called the halo. The halo was largely formed when the galaxy merged with smaller galaxies. The stellar population of the inner halo is dominated by debris from one major such merging event, called the Gaia-Enceladus-Sausage, and the outer halo population is completely built up by several mergers. To properly understand this accretion history, the halo needs to be investigated out to large distances so that as much substructure as possible can be traced. The substructure is expected to leave an imprint in the halo's metallicity structure. In this thesis, we use a catalogue of intrinsically bright stars, giants, to probe the metallicity structure of the halo to large distances. It contains 205,727 stars that all have photometric metallicities from the Pristine survey and distances derived from isochrone fitting, and reaches down to [Fe/H] = -4.0 dex and out to d = 96.16 kpc. Its purity is 90 % and completeness is 67 %. We calculate the distance errors by Monte Carlo simulations and introduce a new cut in colour that is dependent on metallicity to reduce contaminants in the sample. This introduces a metallicity bias in the sample that we can correct for because we coupled metallicity and colour. The correction is done by computing weights for different metallicity bins. The final catalogue allows us to create metallicity distribution functions of the halo as a function of distance. These show us that as heliocentric distance, the distance from the Galactic centre or the Galactic plane increases, the overall metallicity decreases. At the closest distances, the thick disk metallicity peak at -0.7 dex dominates, but as we move further out this smoothly shifts to -1.3 dex and then to -1.6 dex, representing the inner halo, while a peak at -2.2 dex, representing the outer halo, starts to become visible beyond 6 kpc and dominates the metallicity distribution past 26 kpc. These peaks are remnants of merger events in the halo, with the inner halo peak being due to the massive Gaia-Enceladus-Sausage merger and the outer halo peak being due to the many, low-mass and thus low-metallicity galaxies accreted there. We are able to see signals from the Sagittarius stream and Gaia-Enceladus-Sausage's apocentric pile-ups in the metallicity distribution functions, showing that the halo's metallicity changes with not only distance but also sightline. We also detect a diffuse, very metal-poor cloud in the southern footprint that may be an until now unknown structure. This catalogue and its resulting metallicity distribution functions are thus a suitable addition to literature at the metal-poor and distant end, as well as the faint end where e.g. Gaia mission data is unable to provide metallicities and distances. / Vintergatan är, som alla spiralgalaxer, omringad av en ungefärligen sfärisk distribution av stjärnor som kallas halon. Denna halo bildades när galaxen sammansmälte med mindre galaxer. Stjärnpopulationen i den inre halon domineras av stjärnor som kom in med en sådan, väldigt stor, sammanslagning med en annan galax som eter Gaia-Enceladus-Sausage, och den yttre halons stjärnpopulation har helt och hållet byggts upp av sammanslagningar med flera galaxer. För att kunna kartlägga Vintergatans alla sammanslagningar med andra galaxer behöver vi därför undersöka den yttre halon så långt ut som möjligt, för att spåra så mycket substruktur i halon som uppstod till följd av sammanslagningar som möjligt. Sådan substruktur förväntas göra ett avtryck i halons metallicitetsstruktur. I denna masteruppsats används en katalog av intrinsiskt ljusstarka stjärnor, jättar, för att kartlägga halons metallicitetsstruktur till stora avstånd. Katalogen innehåller 205,727 stjärnor som alla har fotometriska metalliciteter från Pristine-undersökningen samt avstånd från isokronanpassning. Den når [Fe/H] = -4.0 dex och d = 96.16 kpc. Mängden jättar i katalogen är 90 % och katalogen behåller 67 % av alla jättar i ursprungskatalogen. Avståndens osäkerhet beräknas med Monte Carlo-simulationer, och det införs ett nytt klipp med färg som är beroende av metallicitet för att undvika kontamination. Detta inför en metallicitetssnedvridning av katalogen som vi kan korrigera eftersom att vi kopplade ihop metallicitet och färg. Korrektionen sker genom att vi beräknar vikter för olika metallicitetsintervall i katalogen. Den slutgiltiga katalogen låter oss skapa metallicitetsdistributioner för halon som beror på avstånd. Dessa distributioner visar oss att när stjärnors avstånd till solen, från galaxens centrum samt från galaxdisken ökar, så minskar den genomsnittliga metalliciteten. Vid väldigt nära avstånd är distributionerna centrerade runt -0.7 dex som motsvarar den tjocka disken, men när avstånden ökar, flyttas denna topp till -1.3 dex och sedan till -1.6 dex, vilket motsvarar den inre halon, samtidigt som en topp vid -2.2 dex, som motsvarar den yttre halon, framträder bortom 6 kpc och dominerar metallicitetsdistributionen för halon bortom 26 kpc. Dessa toppar är kvarlevor efter sammanslagningar mellan Vintergatan och mindre galaxer, där toppen i den inre halon uppstod p.g.a. Gaia-Enceladus-Sausage och toppen i den yttre halon kommer från de många lågmassiva och därmed metallfattiga dvärggalaxer som assimilerats där. Metallicitetsdistributionerna visar signaler från Sagittariusströmmen och Gaia-Enceladus-Sausages apocentriska hopsamlingar, vilket visar att halons metallicitet inte bara beror på avstånd utan även på observationsvinkel. Katalogen visar spår av ett diffust metalfattigt moln i det södra observationsfönstret som potentiellt är en hittills oupptäckt struktur. Denna katalog och dess resulterande metallicitetsdisitributioner är en viktig addering till existerande litteratur i den metallfattiga och avlägsna regimen, samt i den ljussvaga regimen där t.ex. data från Gaiateleskopet inte kan bidra med metallicitets- eller avståndsvärden.

The Milky Way's halo is an approximately spherical distribution of stars surrounding the Galaxy that carries the history of the Milky Way. The outer halo is a Galactic region with long dynamical timescales largely built up by accreted material. Probing its stellar constituents has been historically difficult due to the distances of outer halo stars, making them appear faint. To characterise the distant halo and unravel the history of our galaxy, we thus need to use stars that are intrinsically bright, i.e. giant stars. To draw useful conclusions about the distant halo, these target giants should have metallicity and kinematics information. Therefore a catalogue of distant halo giants with Pristine survey metallicities, Gaia mission data and distances has been created in this work. The cuts used to create this catalogue are made to remove as many dwarf stars as possible and have been tested on a training sample containing spectroscopic metallicities and surface gravities as well as Gaia mission data. Defining giants as being all stars with log(g) < 3.5 dex, we can calculate the purity and completeness of the sample after the cuts have been applied to test which cuts optimise the catalogue. The methods used to cut away the dwarfs are to first plot all stars with positive Gaia parallaxes and fractional parallax uncertainties smaller than 50% in a colour-absolute magnitude diagram and remove all stars from the sample that in this plot populate the main sequence. We then colour-code the colour-apparent magnitude diagram by purity and completeness after this parallax cut has been performed, and select a region in this diagram in which both purity and completeness are maximised, with the final region being (GBP,0 - GRP,0) > 0.8 and G0 < 17.6. The distances to the stars in this region are then computed by comparing their apparent magnitudes to the absolute ones of isochrones. These cuts are then applied to a sample of 6,884,547 stars with Pristine survey and Gaia mission data. The final catalogue is kinematically unbiased and contains 345,303 halo giants. It contains 78% giants and only 4% of giants are erroneously deselected.  With the final sample we are able to probe as deep as 103 kpc into the halo and have created preliminary metallicity distribution functions of different regions of the halo. This sample will be used to further investigate the distant halo metallicity structure and its substructure that was created through merger events.

According to the paradigm of lambda-CDM cosmology, the stellar halo ofour Galaxy has been built-up over time through the accretion of other galaxiesand star clusters. The remnants of some of these are still observable today asstellar streams, but are typically very faint and difficult to resolve amidst the farmore numerous foreground Milky Way stars. The VelHel-4 stream, discoveredby Helmi et al. [2017], consists of seven members selected based on their energiesand angular momenta. Further studies of these stars has shown evidence ofglobular cluster (GC) abundance patterns, suggesting that the stream originatedfrom a GC progenitor, but a larger sample is needed to verify this signature. Theobjective of this thesis is to find new candidate members of the VelHel-4 stellarstream in order to better characterize its properties and to confirm a possibleGC origin.The preliminary selection of stars was done kinematically, by computing theorbital actions and energies using astrometric data and radial velocities for abright subset of the Gaia DR3 database, and then analyzing the clustering ofstream members in different combinations of action space. The selected samplewas then cleaned by analyzing the positions of these stars in a colour-magnitudediagram. In total, 34 stars were included in the final selection. Follow-up high-resolution spectroscopy of these candidates is needed to study their stellar abun-dances and confirm the possible GC origin of this stream.

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.

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.

High resolution spectra have been analyzed for two and three stars respectively in the candidate extragalactic globular clusters, NGC 5024 and NGC 5466, with the High-Resolution Spectrograph on the 9.2 m Hobby-Eberly Telescope. The goal of this investigation is to evaluate the proposed extragalactic origins of these two globular clusters. Evidence of a tidal tail in NGC 5466 (Belokurov et al., 2006) and the association of NGC 5024 with the Sagittarius stream (Martinez-Delgado et al., 2004) targeted the clusters as likely remnants of recent accretion events and thus potentially of extragalactic origin. Determination of their chemical abundance patterns could provide unique evidence to either support or dispute these claims. NGC 5024 has been associated with a proposed wrap in the Sagittarius stream which could be supported if the chemistry of NGC 5024 is similar to other clusters associated with the stream. NGC 5466 has the longest tidal tail known, which hints at an origin in a now dispersed dwarf spheroidal galaxy. Additional evidence for these clusters' capture origins has been compiled by Yoon & Lee (2002), demonstrating that these two low metallicity clusters, along with five others, are aligned in a single highly inclined plane in the outer halo. Confirmation that these clusters are remnants of dwarf galaxies would support a Galactic history which includes recent accretion events. Such evidence may bolster the cold dark matter hierarchical clustering scenario, which postulates the presence of a significant amount of substructure in the Milky Way. Unfortunately, at the metallicity of the target clusters ([Fe/H] = -1.9), the chemical distinction between Galactic stars and known dSph stars is not significant. The low [alpha/Fe] of dSph stars seen at higher metallicity is not apparent at [Fe/H] = -1.9 in either Galactic or dSph stars. Aside from a few mild discrepancies, NGC 5024 and NGC 5466 appear chemically similar to the Galactic field stars and globular clusters compiled by Pritzl et al. (2005). A moderate enhancement in the [Ba/Y] ratios relative to the halo field stars is the only positively detected chemical signature that is typically observed in dSph stars. Comparisons with Galactic GCs of similar age, metallicity and horizontal branch morphology (NGC 2298, NGC 6397 and NGC 5897) reveal a few other differences, but these could be attributed to systematic effects in the different analysis techniques. Although NGC 5024 has a similar metallicity to the GC Arp 2 that was stripped from the merging Sagittarius dwarf, neither Arp 2 (Mottini et al., 2008) nor the clusters in this study show any particularly unusual chemical abundance patterns. Thus, no conclusive evidence in support of or in opposition to the target clusters' proposed extragalactic origins has been discovered.

The physical explanation for the existence of the galactic warp is one of the major research areas in Astronomy. People have proposed various theories but nobody has yet given a convincing explanation. Most of the spiral galaxies are observed to be warped which reveals that the galactic warp is a stable characteristic. In the theory of kinematic bending wave, warp is considered as a wave that is propagated through the galactic disk with a speed called pattern speed. If the pattern initially had straight line of nodes, according to bending wave theory, the warp would tend to wind up rapidly in the gravitational field of galactic disk. But still we observe warped galaxies in the sky. In the literature, it has been claimed that the winding problem of galactic warp may be solved by incorporating the effect of gravitational field of the dark matter halo in which the galactic disk is embedded. Recently some works on the dynamics of galactic disk claim that the shape of the dark matter halo is pro late spheroid. In this thesis, the effect of the gravitational field of a prolate spheroidal dark matter halo with varying eccentricity to the galactic warp is calculated and discussed. Chapter1 gives the general introduction of the topics discussed in the following chapters. The structure of the spiral galaxy, their classifications, and the disk dynamics are discussed in the first few sections. One of the revolutionary concepts that emerged in the previous century was the existence of the dark matter. Presently tracing the mass distribution and the constituent particles of dark matter is one of the major research areas in theoretical and experimental physics. In this thesis, the effect of a particular type of mass distribution in dark matter halo on the warp is discussed in detail. In the next few sections, the following topics are discussed namely; how the concept of dark matter came into astrophysics, how to measure the total mass inside a given radius and what are the different distributions used for various purposes. A new theory called Modified Newtonian Mechanism was also proposed in the previous century as an alternative to the dark matter concept which is also discussed briefly. Kinematic bending wave theory and the winding problem of the galactic warp is also discussed in detail. In the last section a relation between the pattern speed of the warp and the shape of the dark matter halo is obtained. The calculation of the potential of a prolate spheroidal mass distribution with varying eccentricity is not done in any literature as we know. The calculation of the potential and the patten speed of prolate spheroidal mass distributions and of the galactic disk are described in chapter 2. The calculations of oblate spheroidal mass distribution are also discussed in this chapter but that is out of main theme. In chapter 3 we apply the equations obtained in the Chapter 2 to one simple toy model and to the Galaxy. The rotation curve and the pattern speed of a warp in the gravitational field of prolate spheroidal mass distribution of varying eccentricity are described. Usually the Milky Way disk is treated as an in infinitesimally thin disk but for our calculations the three dimensional but thin disk is used. The usually people use some approximation to calculate the potential due to galactic infinitesimal thin disk. The difference of the work from earlier works done by different people(with the approximation mentioned in above line) is also discussed in this Chapter. Chapter 4 discusses the summary of the entire work.

The Milky Way has undergone several mergers with other galaxies during its lifetime. The mergers have been identified via stellar debris in the Halo of the Milky Way. The practice of mapping these mergers is called galactic archaeology. To perform this archaeologic inspection, three stellar features must be mapped: chemistry, kinematics and age. Historically, the latter has been difficult to determine, but can today to high degree be determined through asteroseismology. Red giants are well fit for these analyses. In this thesis, the red giant HE1405-0822 is completely characterized, using spectroscopy, asteroseismology and orbit integration, to map its origin. HE1405-0822 is a CEMP-r/s enhanced star in a binary system. Spectroscopy and asteroseismology are used in concert, iteratively to get precise stellar parameters, abundances and age. Its kinematics are analyzed, e.g. in action and velocity space, to see if it belongs to any known kinematical substructures in the Halo. It is shown that the mass accretion that HE1405-0822 has undergone has given it a seemingly younger age than probable. The binary probably transfered C- and s-process rich matter, but how it gained its r-process enhancement is still unknown. It also does not seem like the star comes from a known merger event based on its kinematics, and could possibly be a heated thick disk star. / Vintergatan har genomgått flera sammanslagningar med andra galaxer under sin livstid. Dessa sammanslagningar har identifierats genom rester av stjärnor i Vintergatans Halo. Arbetssättet för att kartlägga dessa sammanslagningar kallas galaktisk arkeologi. För att kunna göra en arkeologisk undersökning krävs tre egenskaper hos de undersökta stjärnorna: kemi, kinematik och ålder. Historiskt sett har den sistnämnda varit svår att bestämma, men kan idag bestämmas med hög precision m.h.a. asteroseismologi. Röda jättar lämpar sig väl för dessa analyser. I denna uppsats undersöks den röda jätten HE1405-0822. Den kartläggs helt m.h.a. spektroskopi, asteroseismologi och bananalys. HE1405-0822 är en CEMP-r/s-förhöjd stjärna i ett binärt system. Spektroskopi och asteroseismologi används tillsammans, iterativt, för att få precisa stjärnparametrar, kemiskt innehåll och ålder. Dess kinematik analyseras, t.ex. i verkan- och hastighetsrummet, för att se om den tillhör någon känd kinematisk substruktur i Halon. Det visas att massöverföringen som HE1405-0822 genomgått har gett den en skenbart yngre ålder än vad som är troligt. Denna binära kompanjon har troligtvis övertfört C- och s-process-rikt material, men hur den fick sin mängd r-processämnen är fortfarande okänt. Det verkar inte som att stjärnan kommer från någon tidigare kartlagd sammanslagning baserat på dess kinematik, och skulle kunna vara en stjärna med upphettad kinematik från Vintergatans tjocka disk.

No description available.

Detailed chemical abundances of globular clusters in the Milky Way and M31 (the Andromeda Galaxy) are presented based on analyses of high resolution spectra. The unusual Milky Way cluster Palomar 1 (Pal 1) is studied through spectra of individual red giant branch stars; these abundances show that Pal 1 is not a classical globular cluster, and may have been accreted from a dwarf satellite of the Milky Way. The Milky Way globular clusters 47 Tuc, M3, M13, NGC 7006, and M15 are studied through their integrated light (i.e. a single spectrum is obtained for each cluster) in order to test high resolution integrated light analyses. The integrated abundances from these clusters reproduce the average abundances from individual stellar analyses for elements that do not vary within a cluster (e.g. Fe, Ca, and Ni). For elements that do vary within the clusters (e.g. Na and Mg) the integrated abundances fall within the observed ranges from individual stars. Certain abundance ratios are found to be extremely sensitive to uncertainties in the underlying stellar populations, such as input models, empirical relations to determine atmospheric parameters, interloping field stars, etc., while others (such as [Ca I/Fe I]) are largely insensitive to these effects. With these constraints on the accuracy and precision of high resolution integrated light analyses, detailed abundances are obtained for seven clusters in the outer halo of M31 that were recently discovered in the Pan-Andromeda Archaeological Survey (PAndAS) and are likely to have originated in dwarf galaxy satellites. Three clusters are relatively metal rich ([Fe/H] > −1.5) for their locations in the outer halo; their chemical abundances suggest that they likely originated in one or more fairly massive dwarf satellities. The other four are more metal-poor, and may have originated in less massive dwarf satellites. These results indicate that the Milky Way and M31 have both experienced some amount of accretion from dwarf satellites, though M31 may have had a more active accretion history. / Graduate