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Using a hydrodynamical smoothed particle hydrodynamics (SPH) zoom-in simu lation of a galaxy group, we present a set of tail identification methods, and study the statistical properties of galaxy tails and their correlations with their expected formation mechanisms. We have a sample of 4548 M > 108 M⊙ galaxies across 58 snapshots from z = 0.67 to z = 0. For each galaxy, we apply a series of velocity and density cuts to identify the tail. We observed no significant correlations between galaxy tail mass and ram pressure, though we note some issues with our sampling. Tracking four visually identified jellyfish galaxies over time showed some evidence of increased ram pressure driving ISM mass loss, as well as spikes in tail mass pre ceding spikes in ram pressure with temporal offsets ranging from 500 Myr to 2 Gyr. No correlation was found between ISM mass and tail mass. We track the tail gas of a particularly well defined jellyfish galaxy 3.2 Gyrs back in time. We find that a lower bound of 30% of the tail gas was never in the ISM. Distinguishing between former ISM tail material and never ISM-accreted tail material, we see evidence of temperature mixing with the IGM in the former. Velocity and radial trajectory maps show a sharp impulse of ∆v ≈ 50 km s−1 over 4 snapshots, affecting both the never ISM-accreted tail material and CGM material, with the former showing evidence of momentum mixing onto the former ISM material. Combined with ob servations of CGM stripping, we propose that a significant portion of galaxy tails consists of stripped CGM that got swept up into the stripped ISM / Thesis / Master of Science (MSc)

Most galaxies are either actively forming stars or quenched, but there is a small number of galaxies in transition from one population to the other. These galaxies are "quenching" if they are in the process of becoming quenched or "rejuvenating" if they are returning to the star-forming main sequence after a period of being quenched. Quenching occurs when a galaxy’s limited cold gas supply is heated or removed, halting star formation, while rejuvenation refers to any process that reintroduces cold gas to quenched galaxies, reigniting star formation. Rejuvenating galaxies, which are significantly rarer and less well-studied than quenching galaxies, can offer valuable insights into galaxy evolution processes. This thesis investigates the properties of transitional galaxies, with a focus on their gas content, to explore the mechanisms driving quenching and rejuvenation. We employ a recent classification method using GALEX NUV and Sloan Digital Sky Survey H-alpha measurements to identify transitional galaxies and analyze the derived gas properties of those in the xGASS and xCOLD GASS surveys. We find that rejuvenating and quenching galaxies have intermediate gas fractions compared to actively star-forming and quenched galaxies, and that rejuvenating and quenching galaxies have similar depletion times to star-forming and quenched galaxies, respectively. We also find that the rejuvenating population, particularly at lower stellar mass, is efficient at converting its atomic gas supply to molecular hydrogen, which could be attributed to their high gas-phase metallicities at low stellar mass. / Thesis / Master of Science (MSc)

The environment of a galaxy influences its gas and star formation properties via evolutionary mechanisms, such as ram pressure stripping and tidal stripping. In particular, the molecular to atomic gas ratio and dynamical equilibrium pressure are key parameters for understanding star formation in galaxies. I use 1.2 kpc resolution data for galaxies in the Virgo Cluster from the VERTICO survey and for field galaxies from the HERACLES survey to study the spatially resolved relationship between molecular to atomic gas ratios and star formation properties (eg. star formation rate, molecular gas depletion time) in galaxies as a function of dynamical equilibrium pressure. I find that cluster galaxies have higher molecular to atomic gas ratios at a given dynamical equilibrium pressure than field galaxies do. Within both samples there is strong galaxy to galaxy variation in the relationship driven by the gas content of each galaxy. In order to investigate the role of cluster environmental mechanisms on the properties of cluster galaxies I use atomic gas deficiency as a proxy for these environmental mechanisms. I find that atomic gas deficiency plays a significant role in the gas properties, star formation properties and dynamical equilibrium pressure of cluster galaxies. / Thesis / Master of Science (MSc)

In this thesis I investigate the dynamics and stellar populations of a sample of 28 edge-on early-type (S0--Sb) disk galaxies, 22 of which host a boxy or peanut-shaped bulge. I begin by constructing mass models of the galaxies based on their observed photometry and stellar kinematics. Subject to cosmologically motivated assumptions about the shape of dark haloes, I measure in a purely dynamical way their stellar and dark masses. I make a preliminary comparison between the dynamically determined stellar masses and those predicted by stellar population models. I then compare the Tully-Fisher (luminosity--velocity) relations of the spirals and S0s in the sample. I show that S0s are systematically fainter at a given rotational velocity, but the amount by which they are fainter is less than expected by models in which they are the products of truncation of star formation in spirals. This raises the possibility that S0s are smaller or more concentrated than spirals of the same mass. I then study the vertical structure of the boxy and peanut-shaped bulges of a subset of the sample. Among this sample of five galaxies, I find one example in which the stellar populations show no evidence that the bulge and the disk formed in different processes, and in which the bulge is in perfectly cylindrical rotation, i.e. its line-of-sight velocity does not change with height above the disk. This galaxy is probably a pure disk galaxy. However, even with this small sample, I also show that cylindrical rotation and homogeneous stellar populations are not ubiquitous properties of boxy and peanut-shaped bulges. Finally I analyse central and radial trends in the stellar populations of the bulges of full sample of 28 galaxies. I find that, at a given velocity dispersion, the central stellar populations of these barred early-type disk galaxies are identical to those of elliptical galaxies, which suggests that secular evolution does not dominate the centre of these galaxies. However, the radial metallicity gradients are shallower than those of ellipticals. This is qualitatively consistent with chemodynamical models of bar formation, in which radial inflow and outflow smears out pre-existing gradients.

A unique K-band selected high-redshift spectroscopic dataset (UDSz) is exploited to gain further understanding of galaxy evolution at z > 1. Acquired as part of an ESO Large Programme, this thesis presents the reduction and analysis of a sample of ∼ 450 deep optical spectra of a random 1 in 6 sample of the KAB < 23, z > 1 galaxy population. Based on the final reduced dataset, spectrophotometric modelling of the optical spectra and multi-wavelength photometry available for each galaxy is performed using a combination of single and dual component stellar population models. The stellarmass and age estimates provided by the spectrophotometric modelling are exploited throughout the rest of the thesis to investigate the evolution of massive galaxies at z > 1. Focusing on a K-band bright (K < 21.5) sub-sample in the redshift range 1.3 < z < 1.5 the galaxy size-mass relation has been studied in detailed. In agreement with some previous studies it is found that massive, old, early-type galaxies (ETGs) have characteristic radii a factor ~- 1.5 − 3.0 smaller than their local counterparts at a given stellar-mass. Due to the potential errors in spectrophotometric estimates of the stellarmasses at high redshift velocity dispersion measurements are derived for a sub-sample of massive ETGs at z > 1.3 in order to calculate dynamical mass estimates. To date, only a handful of objects at z > 1.3 have individual velocity dispersion estimates in the literature. Here the largest single sample (13 objects) of velocity dispersion measurements at high redshift is presented. The results for the sub-sample of objects with dynamical mass estimates confirm the results based on stellar mass estimates that high redshift massive systems are more compact than their local counterparts. The fraction of K-band bright objects at high redshift that are passively evolving is calculated with specific star-formation rates from the UV rest-frame continuum, [OII] emission and 24μm data. It is concluded that ∼ 58 ± 10% of the K < 21.5, 1.3 < z < 1.5 galaxy population is passively evolving. Various photometric techniques for separating star-forming and passively evolving galaxies are assessed by exploiting the accurate spectral types derived for the UDSz spectroscopic sample. Popular highredshift selection techniques are shown to fail to effectively select complete samples of passive objects with low levels of contamination. Using detailed information available for the UDSz dataset, various techniques are optimised and then used to estimate the passive fraction from the full UDS photometric catalog. The passive fraction results from the full photometric catalog are found to agree well with the results derived from the UDSz sample. With the Visible and Infrared Survey Telescope for Astronomy (VISTA) now starting to produce data, the opportunity has been taken to develop high-redshift galaxy population dividers based on the VISTA filters. Using the first data release from the VISTA Deep Extragalactic Observations (VIDEO) survey (VVDS D1 field), the passive fractions of K-band limited samples have been estimated to compare with results derived in the UDS. Within the errors the passive fraction estimates in the UDS and VISTA VVDS D1 field are found to agree reasonably well. Finally, composite spectra are used to study the evolution of various different galaxy sub-samples as a function of redshift, age, stellar-mass and specific star-formation rate. This work produces an remarkably clean result, showing that the massive, absolute Kband bright, passively evolving ETGs are always the oldest population, with ages close to the age of the Universe at z ∼ 1.4. In contrast, the late-type, low-mass, star-forming galaxies are always found to be much younger systems. This result strongly supports the downsizing scenario, in which more massive systems complete their stellar-mass assembly before lower-mass counterparts.

The study of dwarf galaxies is important in order to better understand the physics of the young universe and how larger galaxies form and evolve. In this work we focus on Blue Compact Galaxies (BCGs) which havemuch enhanced star formation (starbursts), causing blue colours and strong emission line spectra. Investigating of the inner motions of BCGs provides a means for determining masses and understanding what triggered the current starburst. We have used the Very Large Telescope to perform challenging observations of the stellar motions in several BCGs, as seen in the near-infrared Ca-triplet absorption lines. By comparing these to the kinematics of the ionized interstellar medium, we were able to look into the role of feeback from stellar winds and supernova explosions, as well as further strengthen the notion that the merging of galaxies plays an important role. Spatially resolved spectroscopy can yield information about the 3D-structure of galaxies. We have used a Fabry-Perot interferometer to study the kinematics of the interstellar medium in two samples of galaxies, each containing about twenty objects. We find strong indications for ongoing galaxy mergers that correlate well with the strength of the star-formation activity. Furthermore, by estimating dynamical masses, BCGs are shown to be on average not dynamically supported by rotation. In addition, we have used data from the Sloan Digital Sky Survey to study the frequency of starbursts in the local universe and the connection to their descendants. We selected starbursts by the strength of emission in H-alpha, the first Balmer recombination line, and post-starbursts by the strength of absorption in H-delta. These are indicators of currently ongoing and recent, on the order of 100 Myr, star-formation, respectively. By modelling the stellar populations we derive ages and masses and can establish a link between starbursts and postbursts in a time sequence. We find that starbursts are active on a 100 Myr timescale but are rare objects in the local universe.

Submitted by Alessandra Portugal (alessandradf@ioc.fiocruz.br) on 2013-09-20T18:32:48Z No. of bitstreams: 1 Antonio Claudio Bello Ribeiro_Dissertação.pdf: 10104776 bytes, checksum: 898762236c2195576efe34934817220b (MD5) / Made available in DSpace on 2013-09-20T18:32:48Z (GMT). No. of bitstreams: 1 Antonio Claudio Bello Ribeiro_Dissertação.pdf: 10104776 bytes, checksum: 898762236c2195576efe34934817220b (MD5) Previous issue date: 2012 / Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Vice Direção de Ensino, Informação e Comunicação. Rio de Janeiro, RJ, Brasil. / As tecnologias NGS (Next-Generation Sequencing), desenvolvidas para reduzir o custo e o tempo do processo de sequenciamento, geram uma grande massa de dados, a um custo relativamente baixo e com grande acurácia. No entanto, as leituras curtas, por elas produzidas, dificultam sobremaneira o processo de montagem de genomas, originando novos problemas computacionais. Para tentar suplantar esses desafios, várias ferramentas de software estão disponíveis e continuam a ser desenvolvidas. Cada um desses pacotes possui vantagens e desvantagens e, na maioria das vezes, se apresenta como uma solução individual, não estando integrado a outros. Além disso, tipicamente é exigido um conhecimento mais avançado de informática para a sua correta instalação, configuração e operação; o que, nem sempre, é a realidade do usuário final. Neste contexto, o projeto nomeado LASZLO (Linkage of Assembly Scripts Zero-costed and with License Opened) @ GALAXY propõe combinar diferentes ferramentas de tratamento de dados de NGS de uso livre, na forma de um protótipo básico de serviço de montagem de genomas, buscando facilitar o trabalho do usuário através da disponibilização de uma interface Web, sugestões de parametrização e de fluxos de trabalho para esse tipo de análise. Tomando por base o framework Galaxy, foram agregados fluxos de trabalho para montagens de dados de sequenciamento reais de diferentes organismos e provenientes das tecnologias Illumina, SOLiD™ e 454. O caráter aplicado do projeto originou soluções pontuais para atender a necessidades específicas, as quais foram reunidas sob o módulo NGS: LASZLO's Sandbox, uma "caixa de ferramentas" especialmente designada às abordagens de montagem do tipo de novo e com auxílio de genoma de referência. Durante a pesquisa, o protótipo LASZLO @ GALAXY processou, por exemplo, dados de sequenciamento de Leishmania amazonensis, contribuindo para um primeiro processo de avaliação do genoma do referido organismo. Atualmente, observa-se que a produção de dados não é o mais o "gargalo" em projetos de sequenciamento, mas sim o fluxo de análise subsequente sobre o material obtido. Muitas vezes, tais dados não se traduzem imediatamente em expansão do conhecimento biológico, devido às dificuldades encontradas pelo biólogo experimental em lidar, não somente com a miríade de ferramentas disponíveis, mas também com fatores como a inerente necessidade de integração entre elas e a implementação de infra-estrutura adequada para a sua operação. Os resultados obtidos no projeto indicam que o sistema proposto, vislumbrado como um eventual serviço institucional ou mesmo de menor âmbito, pode se tornar um aliado do usuário final quanto à manipulação dos dados de NGS. / The NGS (Next-Generation Sequencing) technologies, designed to reduce sequencing process costs and time, generate a huge amount of data, at a relatively low cost and with great accuracy. However, the produced short reads strongly difficult the genome assembly process, originating new computational issues. To overcome those challenges, there are several software tools available and continuously being developed. Each of these tools presents advantages and disadvantages and most of them are isolated, not integrated solutions. Moreover, typically it is required a higher level of computer-literacy for their proper installation, configuration and usage, which, not always, is the end-user reality. In this context, the project named LASZLO (Linkage of Assembly Scripts Zero-costed and with License Opened) @ GALAXY suggests to combine different open source tools for NGS data handling, as a basic prototype service for genome assembly, aiming at simplifying the end-user task by providing a Web interface, suggestions of parametrization and workflows for this kind of analysis. Based on the Galaxy framework, some workflows for the assembly of real sequencing data from different organisms and produced by the Illumina, SOLiD™ and 454 technologies were aggregated. Also, due to the applied characteristic of the project, a few punctual solutions were generated to address specific needs. Those solutions were encapsulated in the NGS: LASZLO's Sandbox module, a "toolbox" especially tailored for the de novo and reference-guided assembly approaches. During the research, the LASZLO @ GALAXY prototype processed, for instance, sequencing data of the Leishmania amazonensis organism, contributing for a first evaluating process of its genome. Presently, it's noticed that the data generation is no longer the "bottleneck" of the sequencing projects, but the downstream data analysis. Frequently, the acquired data is not immediately translated into biological knowledge expansion, due to the obstacles met by the experimental biologist when dealing, not only with the myriad of available tools, but also with factors like the inherent need of their integration and the deployment of the adequate infrastructure for their operation. The results achieved during project execution indicate that the proposed system, glimpsed as an eventual institutional service or even as one of smaller scope, might become an end-user's ally in the NGS data manipulation.

Galaxy formation is a continuous process that started only a few hundred million yearsafter the Big Bang. The first galaxies were very volatile, with bursts of star formationand disorganised gas motions. However, even as these galaxies evolved to have orderlyrotating gas discs, the gas within the disc, referred to as the interstellar medium (ISM),still remained highly turbulent. In fact, the ISM is supersonically turbulent, meaning thatthe disorganised gas motion exceeds the speed of sound in the medium. This supersonicturbulence has been connected to several crucial properties related to galaxy evolution; forexample, increasing (and decreasing in some regions) the ISM gas density, star formation,and gas mixing. Many observation have shown that all of the gas phases in the ISM experience su-personic levels of turbulence, with line widths (an observational method to quantify theamount of turbulence) as high as σg ≲ 100 km s−1 in high-redshift (younger) disc galaxies,while local quiescent discs have σg ≲ 40 km s−1 . However, the ISM contains a variety ofgas phases that cover a wide range of temperatures and densities, which exhibit differentlevels of turbulence. For example, the warm ionised gas phase represents the upper limitsquoted above, while colder denser gas only reaches σg ≲ 40 km s−1 and σg ≲ 15 km s−1 inhigh-redshift and local galaxies, respectively. The physical processes driving this turbulence are not fully understood, but a combi-nation of stellar feedback (e.g. supernova) and gravitational instability (e.g. during cloudcollapse) have been suggested to provide a majority of the turbulent energy. In particular,stellar feedback is crucial in the formation of warm ionised gas and may therefore have asignificant contribution on the turbulence within ionised gas. Furthermore, heterogeneousdata of widely different galaxies (in terms of e.g. mass and size) at different resolutions(which causes artificial line broadening) complicates understanding the underlying cause. A commonly used tracer of ionised gas is the Hα emission line and has been usedextensively in high-redshift surveys. However, the contribution of the Hα signal comesfrom two primary sources: the radiatively ionised regions around massive newborn starsembedded in molecular gas (called H II regions) and diffuse ionised gas (DIG) filling theentire galactic disc. Observations have found that these two sources contribute, on average,roughly the same amount to the Hα signal (although with a large spread), but the levelsof turbulence is starkly different; with the DIG being roughly 2-3 times more turbulethan the gas in H II regions. Numerical simulations have come a long way and are now able to simulate entire discgalaxies at parsec-scale resolution (in regions of interest). Furthermore, galaxy simulationshave been able to reproduce the level of turbulence observed in local and high-redshiftgalaxies. Direct comparisons between numerical and observational studies are crucial tounderstand the relevant physics driving observed correlations. However, numerical andobservational work have different data available and the reduction/analysis varies betweenauthors, and so diligence is required to perform qualitative comparisons. In this work, I perform numerical simulations to investigate ISM turbulence in differentgas phases. My simulations model a Milky Way-like galaxy at two different redshifts(using gas fraction as a proxy for redshift) and with/without stellar feedback physics, toevaluate its impact. I perform mock observations to explore the relation between the starformation rate and turbulence, and investigate what is driving this relation. Additionally, Ianalyse the Hα emission line and compare the contribution in intensity and line broadening(turbulence) from H II regions and DIG. / Galaxbildning är en kontinuerlig process som började bara några hundra miljoner år efterBig Bang. De första galaxerna var mycket volatila, med utbrott av stjärnbildning ochoorganiserade gasrörelser. Men även efter att dessa galaxer utvecklade ordnade roterandegasskivor, förblev gasen inom skivan, kallat det interstellära mediet (ISM), fortfarandehögt turbulent. Faktum är att ISM är supersoniskt turbulent, vilket innebär att de oorgan-iserade gasrörelserna överstiger ljudets hastighet i mediet. Denna supersoniska turbulenshar kopplats till flera avgörande egenskaper relaterade till galaxutveckling; till exempel,öka (och i vissa regioner minska) ISM:ets gas densitet, stjärnbildning och gasblandning. Många observationer har visat att alla gasfaser i ISM upplever supersoniska nivåer avturbulens, med linjebredder (en observationsmetod för att kvantifiera mängden turbulens)så höga som σg ≲ 100 km s−1 i hög-rödförskjutnings (dvs. yngre) skivgalaxer, medanlokala lugna skivor har σg ≲ 40 km s−1. Emellertid innehåller ISM olika gasfaser somtäcker ett brett spektrum av temperaturer och densiteter, vilka uppvisar olika nivåer avturbulens. Till exempel representerar den varma joniserade gasfasen de övre gränsernasom nämns ovan, medan kallare, tätare gas endast når σg ≲ 40 km s−1 och σg ≲ 15 km s−1i hög-rödförskjutnings och lokala galaxer, respektive. De fysikaliska processer som driver denna turbulens är inte fullt förstådda, men enkombination av stellär feedback (t.ex. supernova) och gravitationsinstabilitet (t.ex. undermolnkollaps) har föreslagits ge en majoritet av den turbulenta energin. I synnerhet ärstellär feedback avgörande för bildandet av varm joniserad gas och kan därför ha ettbetydande bidrag till turbulensen inom joniserad gas. Dessutom komplicerar heterogenadata från mycket olika galaxer (i termer av t.ex. massa och storlek) vid olika upplösningar(vilket orsakar konstgjord linjebreddning) förståelsen av den underliggande orsaken. En vanligt använd spårare av joniserad gas är Hα-emissionslinjen och har använts om-fattande i undersökningar vid hög rödförskjutning. Emellertid kommer bidraget från Hα-signalen från två primära källor: de strålningsjoniserade regionerna runt massiva nyföddastjärnor inbäddade i molekylär gas (kallade H II -regioner) och diffus joniserad gas (DIG) som fyller hela den galaktiska skivan. Observationer har funnit att dessa två källor bidrar,i genomsnitt, ungefär lika mycket till Hα-signalen (dock med en stor spridning), mennivåerna av turbulens är markant olika; med DIG ungefär 2-3 gånger mer turbulent ängasen i H II-regioner. Numeriska simuleringar har kommit långt och kan nu simulera hela skivgalaxer medparsec-skala upplösning (i områden av intresse). Dessutom har galaxsimuleringar kunnatåterskapa den nivå av turbulens som observerats i lokala och hög-rödförskjutningsgalaxer. Men numeriska och observationsbaserade arbeten har olika tillgängliga data och reduk-tion/analys varierar mellan författare, och därför krävs noggrannhet för att göra kvalita-tiva jämförelser. I detta arbete utför jag numeriska simuleringar för att undersöka ISM-turbulens i olikagasfaser. Mina simuleringar modellerar jag en Vintergatan-liknande galax vid två olikarödförskutningar (användande gasfraktion som en proxy för rödförskutning) och med/utanfysik för stellär feedback, för att utvärdera dess påverkan. Jag utforskar förhållandetmellan stjärnbildningshastigheten och turbulensen, och undersöker vad som driver dettaförhållande. Dessutom analyserar jag Hα-emissionslinjen och jämför bidraget i intensitetoch linjebreddning (turbulens) från H II-regioner och DIG.

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