Thesis (Ph.D.)--Ohio University, March, 2004. / Title from PDF t.p. Includes bibliographical references (p. 95-101)

This thesis considers various topics and open questions in galaxy formation during the epoch of reionization and presents multiple new computational techniques developed specifically to study this era. This work naturally divides into two main sections: 1) The formation of the first massive black holes and 2) Interpreting ALMA observations of galaxy formation during the epoch of reionization. The first topic addresses the existence of super massive black holes (SMBHs) with $M_{\rm BH} > 10^9$M$_{\odot}$ at $z > 6$. It is well established that stellar mass black holes are very unlikely to be able to accrete matter efficiently enough to grow to this mass at this redshift. For this reason, many alternative channels have been proposed for black hole formation that produce objects with significantly larger initial masses. In this thesis, I consider a mechanism whereby runaway stellar collisions in dense primordial star clusters form a very massive star that is likely to collapse to an intermediate mass black hole (IMBH) with $M_{\rm BH} > 10^3$M$_{\odot}$. In order to test this scenario, I added 12 species non-equilibrium chemistry to the massively parallel adaptive mesh refinement code RAMSES, and simulated, at sub-pc resolution, the collapse of the first metal-enriched halo which is likely to host a Population II star cluster. The properties of the central gas cloud in the collapsing halo were then extracted from the simulation and used to create initial conditions for the direct N-body integrator, NBODY6. These star clusters were simulated for 3.5Myr (until the first supernova is expected to occur) and it was determined that the properties of the gas clouds that form in cosmological simulations were indeed suitable to form a very massive star by collisional runaway. This suggests that this mechanism is a promising channel for forming the seeds of SMBHs at high redshift. The second topic of this thesis aims to help interpret the plethora of recent and upcoming ALMA observations of star forming galaxies during the epoch of reionization. These observations target far-infrared lines such as [CII] and [OIII] which directly probe the interstellar medium (ISM) of these $z > 6$ galaxies. In order to study this epoch, I employ the RAMSES-RT code, which allows for the computation of multifrequency radiative transfer on-the-fly. I modified this code in a number of ways so that it can handle radiation-coupled H$_2$ non-equilibrium chemistry (including Lyman-Werner band radiation) and I developed the variable speed of light approximation which changes the speed of light in the simulation depending on the density of gas so that ionisation fronts propagate at the correct speed in all gas phases. Cosmological boxes were initialised to include galaxies with masses comparable to the observations of Maiolino et al. (2015) and run at various resolutions to test convergence properties. One of the major goals of this study was to identify the physical mechanism responsible for the spatial offset observed between [CII] and UV/Lyα in many high-redshift galaxies.

NASCIMENTO, Débora Macêdo do. Caracterização tecnológica de um ultramilonito da região de Marco-CE. 2014. 95 f. Dissertação (Mestrado em geologia)- Universidade Federal do Ceará, Fortaleza-CE, 2014. / Submitted by Elineudson Ribeiro (elineudsonr@gmail.com) on 2016-06-03T19:59:04Z No. of bitstreams: 1 2014_dis_dmnascimento.pdf: 3341925 bytes, checksum: 92fb99e6bb15bb7a4405ee73095aabf4 (MD5) / Approved for entry into archive by José Jairo Viana de Sousa (jairo@ufc.br) on 2016-07-21T19:12:34Z (GMT) No. of bitstreams: 1 2014_dis_dmnascimento.pdf: 3341925 bytes, checksum: 92fb99e6bb15bb7a4405ee73095aabf4 (MD5) / Made available in DSpace on 2016-07-21T19:12:34Z (GMT). No. of bitstreams: 1 2014_dis_dmnascimento.pdf: 3341925 bytes, checksum: 92fb99e6bb15bb7a4405ee73095aabf4 (MD5) Previous issue date: 2014 / This dissertation presents the mineralogical and technological characteristics of the Granite Tucunduba, commercially known as Green Galaxy, located in the municipality of Marco - CE. Technological tests of physical indexes (bulk density, apparent porosity and water absorption apparent d'), uniaxial compression, bending in three and four points, AMSLER abrasive wear, impact and hard freezing and thawing body and speed of wave propagation were performed ultrasonic, based ABNT. To complement the data also quantified the rate of exhalation of radon. Radiometric measurement was performed by applying the active detection method exhalation gas for monitoring the amount of 222Rn. With the choice of the tests described, aimed to evaluate the quality of rock for use as ornamental stone. Was added to the main objectives of this work focused on the recognition of the mineralogical composition and textural features and the degree of microcracking of the material petrographic analysis. The petrographic analysis allowed to classify the rock as Ultramilonito feldspathic quartz. Macroscopically we can describe it as a rock of predominantly green. Their degree of microcracking settles around 1.8 / mm ². The results of technological tests showed that the rock has good quality for ornamental use and coating even in places with large temperature ranges. The radon exhalation rate was within the limits of the United States Environmental Protection Agency. Within this context, the Ultramilonito feldspathic quartz proved to be very tough for use as coating materials. / A presente dissertação apresenta as características mineralógicas e tecnológicas do Granito Tucunduba, conhecido comercialmente como Green Galaxy, localizado no município de Marco – CE. Foram realizados ensaios tecnológicos de índices físicos (massa específica aparente, porosidade aparente e absorção d’água aparente), compressão uniaxial, flexão em três e quatro pontos, desgaste abrasivo AMSLER, impacto em corpo duro e congelamento e degelo e velocidade de propagação de ondas ultrassônicas, baseados em normas da ABNT. Para as análises Radiométricas, escolheu-se quantificar a taxa de exalação do gás radônio, devido a importância do emprego deste ensaio voltado para rochas ornamentais. A medição radiométrica foi realizada através da aplicação do método de detecção ativa de exalação do gás para o monitoramento da quantidade de 222Rn. Com a escolha dos ensaios descritos, objetivou-se avaliar a qualidade da rocha para aplicação como rocha ornamental. Foi adicionado aos principais objetivos deste trabalho a análise petrográficas voltada ao reconhecimento da composição mineralógica e feições texturais e o grau de microfissuramento do material. A análise petrográfica permitiu classificar a rocha como Ultramilonito Quartzo Feldspático. Macroscopicamente podemos descrevê-la como uma rocha de coloração predominantemente verde. Seu grau de microfissuramento se estabelece em torno de 1,8/mm². Os resultados dos ensaios tecnológicos mostraram que a rocha apresenta boa qualidade para uso ornamental e revestimento até mesmo em locais de grande amplitudes térmicas. A taxa de exalação de radônio ficou dentro dos limites da Agência de Proteção Ambiental dos Estados unidos. Dentro deste contexto, o Ultramilonito Quartzo Feldspático mostrou-se bastante resistente para uso como materiais de revestimentos.

In this thesis we construct a B-band catalogue of the local universe which we call the Millennium Galaxy Catalogue (MGC). The MGC is photometrically and astrometrically accurate to +/-0.03 mags and +/-0.08" respectively and covers an area of~ 36 sq deg in the NGP. Colour and redshift information are available from overlapping regions of the two-degree Field Galaxy Redshift Survey (2dFGRS) and the Sloan Digital Sky Survey Early Data Release (SDSS-EDR). With an exposure time of 750s and an isophotal surface brightness limit of 26 mags/sq arcsecs, the MGC is the largest and deepest photometric survey of the local universe to-date. As well as containing photometric information, by making use of a newly developed software package-Galaxy Image 2D (GIM2D), and assuming a standard de Vaucouleurs and exponential galaxy profile, the MGC also contains structural parameters (half light radius and (B/T) etc) to all galaxies in the magnitude range 16 < BMGC < 20. By making use of the information in the MGC we are able to classify our galaxies into three morphological types (E/SO, Sabc and Sd/Irr) using (B/T) cuts. In doing this we find that 30.52% of the galaxies form a "new" galaxy population identified by having a (B/T) of exactly 0. After visual inspection this population is found to be a mixture of early and late type star-forming Spirals and Irregular galaxies, all of which have a disk component that is flatter than an exponential. After visually redistributing these galaxies we find that the local galaxy population consists of 28.1% E/SO, 39.64% Sabc and 31.37% Sd/Irr. From the redshift information contained within the MGC we are able to look at the galaxy distribution in terms of physical parameters. We find that the galaxies are distributed in absolute magnitude, surface brightness and half light radii in a manner that is consistent with the hierarchical formation scenario. We derive total and morphological galaxy number counts and, after combining them via a step wise maximum likelihood (SWML) technique, we arrive at morphological LFs. From examining the galaxy counts we find that there is no steep rise in the bright end, eradicating the need for strong local evolution. Also one does not need to renormalise the morphological or total galaxy counts in order for them to be consistent with faitner counts. The Sabc and Sd/Irr LFs are surprisingly similar with both showing a mild faint end slope. We look at the properties of bulges and disks of galaxies. We find that as galaxies become more diskey there bulges move away from the Kormendy law for Elliptical galaxies. Due to the similarity of the Spiral and Irregular population LFs, as well as apparent and intrinsic parameter distributions, we are forced to conclude that one can only reliably distinguish between the Ellipticals and the general galaxy population, and that investigating the bulge and disk components of a galaxy may be more useful than Hubble types.

When we look throughout the Universe, we can see the stages of galaxy evolution across cosmic time; however there are still many unanswered questions about the details of galaxy evolution. How did galaxies like our Milky Way assemble? Do the first galaxies look different than our own? What makes galaxies stop forming stars? Many of these questions can be addressed by studying the detailed chemistry of gas located in and around galaxies. Absorption lines imprinted on quasar spectra probe this hard-to-see gas within and surrounding galaxies, giving an luminosity-unbiased census of gas from z~0 to the epoch of the most distant quasars. In this thesis, I present two samples of high resolution spectra of quasars obtained from both ground- and space-based observatories to study the evolution of galaxies through their gas-phase absorption lines. The first of the two samples presented in this thesis consists of the 100 quasar sightlines from the XQ-100 legacy survey completed with the X-Shooter spectrograph on the Very Large Telescope in Chile. The XQ-100 survey provides a blind sample of over 350 HI absorption line systems associated with galaxies with column densities 18.8<=logN(HI)<=21.5. Using this sample, I investigated the evolution of neutral gas reservoirs from z~4.5 to z~2.0. I demonstrate that the lower column density sub-damped Lyman alpha systems (with column densities 19.0<=logN(HI)<20.3) contribute ~20% of the HI observed in galaxy gas reservoirs compared to the rarer but high column density damped Lyman alpha systems (DLAs; logN(HI)>=20.3). Furthermore, I show that using the presence of metal lines (particularly MgII absorption) to identify and select absorbing systems can potentially bias the properties of the sample; absorbers selected to contain strong metal line absorbers tend to exclude low metallicity and low HI column density systems. I demonstrate that the systems missed by metal-selected searches can have a significant impact on the study of the cosmic evolution of neutral gas reservoirs. In addition to the HI content, the metal abundances for 13 elements in the 41 DLAs of the XQ-100 sample are presented. In concert with my literature compilation of 280 DLA metal abundance measurements, I studied the dust-corrected [Zn/Fe]. This work emphasizes that near-IR coverage of X-Shooter provides unprecedented access to MgII, CaII and TiII lines (at redshifts 3-4) to provide additional evidence for subsolar [Zn/Fe] ratio in DLAs, a chemical signature that DLAs can be high-redshift dwarf galaxy analogues. Furthermore, the XQ-100 DLA sample consists of several unique systems that probe the effects of environment on the chemical evolution of the Universe, as well as the chemical makeup of the first generations of stars. I demonstrate that DLAs close to their background quasar (within 5000 km/s) with logN(HI)<21.0 show lower [S/H] and [Fe/H] (relative to intervening systems with similar redshift and N(HI)), whilst higher [S/H] and [Si/H] are seen in these proximate systems with logN(HI)>21.0. Contrary to previous studies, DLAs within 10,000 km/s of another DLA show no difference in [alpha/Fe] relative to single DLAs matched in metallicity and redshift. In addition, I present follow-up high-resolution data of J0034+1639, a sightline containing three DLAs, including a metal-poor DLA with [Fe/H]=-2.82 (the third lowest [Fe/H] in DLAs identified to date) at z=4.25. In the latter part of this thesis, I study the circumgalactic medium (CGM) of galaxies that host an active galactic nucleus (AGN). AGN are thought to play a critical role in shaping galaxies, but their effect on the gaseous reservoirs surrounding galaxies is not well studied. I present results from the COS-AGN survey: 19 quasar sightlines that probe the gas surrounding 20 optically-selected AGN host galaxies observed over 65 hours with the Hubble Space Telescope. Absorption lines from a variety of species are measured and compared to a stellar mass and impact parameter matched sample of sightlines through non-AGN galaxies. Amongst the observed species in the COS-AGN sample (HI, CII, SiII, SiIII, CIV, SiIV, NV), only HI shows a high covering fraction whilst many of the metal ions are not detected in individual sightlines. A sightline-by-sightline comparison between COS-AGN and the control sample yields no significant difference in equivalent width distribution. However, stacked spectra of the COS-AGN and control samples show significant enhancements in the equivalent width of both Lya and SiIII at high impact parameters (>164 kpc) by a factor of +0.45+/-0.05 dex and >+0.75 dex respectively. The lack of detections of both high-ionization species near the AGN and strong kinematic offsets between the absorption systemic galaxy redshifts indicates that neither the AGN's ionization nor its outflows are the origin of these differences. Instead, I suggest the observed differences could result from either AGN hosts residing in haloes with intrinsically distinct gas properties, or that their CGM has been affected by a previous event, such as a starburst, which may also have fuelled the nuclear activity. / Graduate

>Magister Scientiae - MSc / We have used the Spitzer Survey of Stellar Structure in Galaxies (S⁴G) as a representative sample of the local universe (total of 2352 galaxies in S⁴G) to make a catalog of offset disk barred galaxies. Using the combined variation of the position angle and the ellipticity (provided by ellipse fit) and also through visual inspection, we have been able to identify all offset structures in S⁴G. While primary bars are present in 2=3 of the disk galaxies in the visible universe, offset bars have a much lower fraction. Of the ̴ 1500 (3.6µm images) disk galaxies available in S⁴G, we classified only 49 as offset barred disk galaxies. We have determined basic properties (bar to total luminosity ratio, bar length, disk scale-length and bars of offset bars shape) using GALFIT, a widely used galaxy decomposition software package. Our main conclusion is that all the offset bars are boxy, independent of their offset from the galaxy center, or the mass of the host galaxy. Additionally we find that, the early type offset bars seem to be more boxy than the late types. The comparison of our offset sample with two other samples, respectively, low mass and high mass normal barred galaxies ("normal" for bars located at the photometric center of the host galaxy), reveals them to be at an intermediate position between the two normal samples. The bar length, disk scale-length and bar to total luminosity ratio are on average larger than the low mass normal and smaller than high mass normal barred galaxies. We have found, overall, a tighter correlation between the disk and bar properties for offset bars in comparison to the two normal samples. Our explanation is that, although the offset has no visible impact on the global shape of the bars, the process responsible for these disturbances seems to affect the star formation rate such that their disk and bars are on average more active than the normal barred galaxies in the same mass range, but not enough to surpass normal barred galaxies with much higher mass.

We use the deep CANDELS observations in the GOODS North and South fields to revisit the correlations between stellar mass (M-*), star formation rate (SFR) and morphology, and to introduce a fourth dimension, the mass-weighted stellar age, in galaxies at 1.2 < z < 4. We do this by making new measures of M-*, SFR, and stellar age thanks to an improved SED fitting procedure that allows various star formation history for each galaxy. Like others, we find that the slope of the main sequence (MS) of star formation in the (M-*; SFR) plane bends at high mass. We observe clear morphological differences among galaxies across the MS, which also correlate with stellar age. At all redshifts, galaxies that are quenching or quenched, and thus old, have high Sigma(1) (the projected density within the central 1 kpc), while younger, star-forming galaxies span a much broader range of Sigma(1), which includes the high values observed for quenched galaxies, but also extends to much lower values. As galaxies age and quench, the stellar age and the dispersion of Sigma(1) for fixed values of M* shows two different regimes: one at the low-mass end, where quenching might be driven by causes external to the galaxies; the other at the high-mass end, where quenching is driven by internal causes, very likely the mass given the low scatter of Sigma(1) (mass quenching). We suggest that the monotonic increase of central density as galaxies grow is one manifestation of a more general phenomenon of structural transformation that galaxies undergo as they evolve.

In this second installment of the series, we look at the internal kinematics of the multiple stellar populations of the globular cluster omega Centauri in one of the parallel Hubble Space Telescope (HST) fields, located at about 3.5 hal-flight radii from the center of the cluster. Thanks to the over 15 yr long baseline and the exquisite astrometric precision of the HST cameras, well-measured stars in our proper-motion catalog have errors as low as similar to 10 mu as yr(-1), and the catalog itself extends to near the hydrogen-burning limit of the cluster. We show that second-generation (2G) stars are significantly more radially anisotropic than first-generation (1G) stars. The latter are instead consistent with an isotropic velocity distribution. In addition, 1G stars have excess systemic rotation in the plane of the sky with respect to 2G stars. We show that the six populations below the main-sequence (MS) knee identified in our first paper are associated with the five main population groups recently isolated on the upper MS in the core of cluster. Furthermore, we find both 1G and 2G stars in the field to be far from being in energy equipartition, with eta(1G) = -0.007 +/- 0.026 for the former and eta(2G) = 0.074 +/- 0.029 for the latter, where eta is defined so that the velocity dispersion sigma(mu) scales with stellar mass as sigma(mu) proportional to m(-eta). The kinematical differences reported here can help constrain the formation mechanisms for the multiple stellar populations in omega Centauri and other globular clusters. We make our astro-photometric catalog publicly available.

No description available.

We report the peculiar chemical abundance patterns of 11 atypical Milky Way (MW) field red giant stars observed by the Apache Point Observatory Galactic Evolution Experiment (APOGEE). These atypical giants exhibit strong Al and N enhancements accompanied by C and Mg depletions, strikingly similar to those observed in the so-called second-generation (SG) stars of globular clusters (GCs). Remarkably, we find low Mg abundances ([Mg/Fe]. < 0.0) together with strong Al and N overabundances in the majority (5/7) of the metal-rich ([Fe/H] greater than or similar to-1.0) sample stars, which is at odds with actual observations of SG stars in Galactic GCs of similar metallicities. This chemical pattern is unique and unprecedented among MW stars, posing urgent questions about its origin. These atypical stars could be former SG stars of dissolved GCs formed with intrinsically lower abundances of Mg and enriched Al (subsequently self-polluted by massive AGB stars) or the result of exotic binary systems. We speculate that the stars Mg-deficiency as well as the orbital properties suggest that they could have an extragalactic origin. This discovery should guide future dedicated spectroscopic searches of atypical stellar chemical patterns in our Galaxy, a fundamental step forward to understanding the Galactic formation and evolution.