Defining 'Galaxy Groups' As A Unique Objects In The Structural Hierarchy

`Galaxy groups' have hardly been realised as a separate class of objects with specific characteristics in the structural hierarchy. The presumption that the self-similarity of dark matter structures is a valid prescription for the baryonic universe at all scales has rendered smaller structures undetectable by current observational facilities, leading to lesser dedicated studies on them. Some recent reports that indicate a deviation from $\rm{L_x}$-T scaling in groups compared to clusters have motivated us to study their physical properties in depth. In this article, we report the extensive study on physical properties of groups in comparison to the clusters through cosmological hydrodynamic plus N-body simulations using ENZO 2.2 code. As additional physics, radiative cooling, heating due to supernova and star motions, star formation and stellar feedback has been implemented. We have produced a mock sample of 362 objects with mass ranging from $5\times10^{12}\; \rm{M_{\odot}}$ to 2.5$\times 10^{15}\; \rm{M_{\odot}}$. Strikingly, we have found that objects with mass below $\sim$ $8\times 10^{13}\;\rm{M_{\odot}}$ do not follow any of the cluster self-similar laws in hydrostatics, not even in thermal and non-thermal energies. Two distinct scaling laws are observed to be followed with breaks at $\sim$ $8\times 10^{13}\;\rm{M_{\odot}}$ for mass, $\sim$1 keV for temperature and $\sim$1 Mpc for radius. This places groups as a distinct entity in the hierarchical structures, well demarcated from clusters. This study reveals that groups are mostly far away from virialization, suggesting the need for formulating new models for deciphering their physical parameters. They are also shown to have high turbulence and more non-thermal energy stored, indicating better visibility in the non-thermal regime.

We have compared numerical simulations to observations for the nearby (< 40 Mpc) groups of galaxies (Huchra & Geller 1982 and Ramella et al. 2002). The group identi- fication is carried out using a group-finding algorithm developed by Huchra & Geller (1982). Using cosmological N-body simulation code with theCDM cosmology, we show that the dynamical properties of groups of galaxies identified from the simulation data are, in general, in a moderate, within 2σ, agreement with the observational cat- alogues of groups of galaxies. As simulations offer more dynamical information than observations, we used the N-body simulation data to calculate whether the nearby groups of galaxies are gravitationally bound objects by using their virial ratio. We show that in aCDM cosmology about 20 per cent of nearby groups of galaxies, identified by the same algorithm as in the case of observations, are not bound, but merely groups in a visual sense. This is quite significant, specifically because estima- tions of group masses in observations are often based on an assumption that groups of galaxies found by the friends-of-friends algorithm are gravitationally bound objects. Simulations with different resolutions show the same results. We also show how the fraction of gravitationally unbound groups varies when the apparent magnitude limit of the sample and the value of the cosmological constantis changed. In general, a larger value of thegenerates slightly more unbound groups.

Aims. We study the environment in which a galaxy lies (i.e. field or group) and its connection with the morphology of the galaxy. This is done by examining the distribution of parametric and non-parametric statistics across the star-formation rate (SFR) – stellar mass (M⋆) plane and studying how these distributions change with the environment in the local universe (z &lt; 0.15). Methods. We determine the concentration (C), Gini, M20, asymmetry, Gini-M20 bulge statistic (GMB), 50% light radius (r50), total Sérsic index, and bulge Sérsic index (nBulge) for galaxies from the Galaxy and Mass Assembly (GAMA) survey using optical images from the Kilo Degree Survey. We determine the galaxy environment using the GAMA group catalogue and split the galaxies into field or group galaxies. The group galaxies are further divided by the group halo mass (Mh)−11 ≤ log(Mh/M⊙) &lt; 12, 12 ≤ log(Mh/M⊙) &lt; 13, and 13 ≤ log(Mh/M⊙) &lt; 14 – and into central and satellite galaxies. The galaxies in each of these samples are then placed onto the SFR-M⋆ plane, and each parameter is used as a third dimension. We fit the resulting distributions for each parameter in each sample using two two-dimensional Gaussian distributions: one for star-forming galaxies and one for quiescent galaxies. The coefficients of these Gaussian fits are then compared between environments. Results. Using C and r50, we find that galaxies typically become larger as the group mass increases. This change is greater for larger galaxies. There is no indication that galaxies are typically more or less clumpy as the environment changes. Using GMB and nBulge, we see that the star-forming galaxies do not become more bulge or disk dominated as the group mass changes. Asymmetry does not appear to be greatly influenced by environment.

The advent of gravitational wave (GW) astronomy has provided a new window through which to view and understand the Universe. To fully exploit the potential of GW astronomy, an understanding of all the potential electromagnetic counterparts to a gravitational wave detected source will help maximise the science returns. Here I present a study of the electromagnetic emission from relativistic jets that accompany the merger of binary neutron stars or black hole-neutron star systems. These counterparts provide a probe for the structure and dynamics of these relativistic outflows. Binary neutron star, or neutron star-black hole, mergers are thought to be the dominant progenitor of short gamma-ray bursts (GRBs). Here we investigate the possibility that there is a hidden population of low-Lorentz factor jets resulting in failed GRBs, on-axis orphan afterglows, and what kind of counterparts can be expected given a merger-jet population dominated by these failed-GRB jets. I find that for GW detected mergers, ∼ 80% of the population of on-axis events may result in a failed GRB afterglow. The afterglow of a failed GRB is characterised by the lack of any prompt emission; where the γ-rays are emitted within an optically thick region of the low-Lorentz factor (Γ) outflow and significant suppression via pair production and a high opacity results in the photons coupled to the pair plasma. This plasma will undergo adiabatic expansion, and the photons will decouple at the photospheric radius. The energy in the prompt photons, for a sufficiently low-Γ outflow, will have been significantly suppressed. GW detected mergers have a Malmquist bias towards on-axis events (i.e. the rotational axis of the system), where the peak of the probability distribution is an inclination ∼ 30⁰. If the jets from these mergers have an intrinsic structure out to wider angles, then the majority of mergers will be accompanied by electromagnetic counterparts from these various jet structures. By making some simple assumptions about the energetic structure of a jet outside of a bright core region, the various temporal features that result from a given jet structure can be predicted. Where the population of merger jets is dominated by a single structure model, I show the expected fractions of optical counterparts brighter than m_AB = 21. On 17 August 2017, the Light Interferometer Gravitational Wave Observatory (LIGO) in collaboration with Virgo detected the merger of a binary neutron star system. Various electromagnetic counterparts were detected: the GRB 170817A by Fermi/GBM and INTEGRAL; an optical, blue to red, macro/kilo-nova from ∼ 1/2 day post merger to ∼ 5 − 10 days; and a brightening radio, and X-ray counterpart from ∼ 10 days. Optical detection of this counterpart at a magnitude ∼ 26 was made at ∼ 100 days post-merger. Analysis of this counterpart is consistent with the afterglow of a Gaussian structured jet viewed at the system inclination, ∼ 18 ± 8⁰. If all short GRB jets have a similar jet structure, then the rates of orphan afterglows in deep drilling blind surveys e.g. the Large Synoptic Survey Telescope (LSST), will be higher than those expected from a homogeneous, or ‘top-hat’ jet, population. The rates for the various jet structures for orphan afterglows from mergers are discussed, showing that for a population of failed GRBs, or an intrinsic Gaussian structure, an excess in the orphan rate may be apparent. Understanding the dynamics and structure for the jets from black-hole systems born at the merger of a compact binary can help give clues as to the nature of jets from black holes on all scales. As an aside, I show empirically that regardless of black hole mass or system phenomenology, the relativistic jets from such systems share a universal scaling for the jet power and emitted γ-ray luminosity. This scaling could be due to the similar efficiencies of various processes, or alternatively, the scaling may be able to give insights into the emission and physical processes that are responsible for high-energy photons from these outflows. GW astronomy offers a probe of the most extreme relativistic outflows in the Universe, GRBs. The predicted electromagnetic counterparts from these outflows, in association with GW detections, provides a way to probe the Lorentz-factor distribution for merger-jets. Additionally, the phenomenological shape of the afterglows, at various inclinations, gives an indication of the intrinsic structure of these jets. An understanding of these dynamical and structural qualities can be used to constrain the parent population, merger rates, and binary evolution models for compact binary systems.

The benefits of the continued progress in integrated circuit manufacturing have been numerous, most notably in the explosion of computing power in devices ranging from cell phones to cars. Key to this success has been strategies to identify, manage, and mitigate yield loss. One such strategy is the use of test structures to identify sources of yield loss early in the development of a new manufacturing process. However, the aggressive scaling of feature dimensions, the integration of new materials, and the increase in structural complexity in modern technologies has challenged the capabilities of conventional test structures. To help address these challenges, a new logic test chip, called the Carnegie Mellon Logic Characterization Vehicle (CM-LCV), has been developed. The CM-LCV utilizes a two- dimensional array of functional unit blocks (FUBs) that each implement an innovative functionality. Properties including fault coverage, logical and physical design features, and fault distinguishability are shown to be composable within the FUB array; that is, they exist regardless of the size and composition of the FUB array. A synthesis ow that leverages this composability to adapt the FUB array to a wide range of test chip design requirements is presented. The connection between the innovative FUB functionality and orthogonal Latin squares is identified and used to analyze the universe of possible FUB functions. Two additional variants to the FUB array are also developed: heterogenous FUB arrays utilize multiple FUB functions to improve the synthesis ow performance, while pipelined FUB arrays incorporate sequential circuit elements (e.g., ip- ops and latches) that are absent from the original combinational FUB array. In addition to the design of the CM-LCV, methods for testing it are presented. Techniques to create minimal sets of test patterns that exhaustively exercise each FUB within the FUB array are developed. Additional constraints are described for the heterogenous and pipelined FUB arrays that allow these techniques to be applied for both variant FUB arrays. Furthermore, a simple built-in self test (BIST) scheme is described and applied to a reference design, resulting in a 88.0% reduction in the number of test cycles required without loss in fault coverage. A hierarchical FUB array diagnosis methodology (HFAD) is also presented for the CM- LCV that leverages its unique properties to improve performance for multiple defects. Experiments demonstrate that this HFAD methodology is capable of perfect accuracy in 93.1% of simulations with two injected faults, an improvement on the state-of-the-art commercial diagnosis. Additionally, silicon fail data was collected from a CM-LCV manufactured using a 14nm process by an industry partner. A comparison of the diagnosis results for the 1,375 fail logs examined shows that the HFAD methodology discovers additional defects during multiple defect diagnosis that the commercial tool misses for 40 of the diagnosed fail logs. Examination of these cases shows that the additional defects found by the HFAD methodology can result in improved diagnosis confidence and more precise descriptions of the defect behavior(s). The contributions of this dissertation can thus be summarized as the description of the design, test, and diagnosis of a new logic test chip for use in yield learning during process development. This CM-LCV can be adapted to meet a wide range of test chip requirements, can be efficiently and rigorously tested, and exhibits properties that can be used to improve diagnosis outcomes. All of these claims are validated through both simulated experiments and silicon data.

N-Body Simulations and Galactic Habitability

The formation of elliptical galaxies by merging galaxies has been investigated adopting three different paths. First, we confirm that the frequency of major merger events predicted by hierarchical models is in fair agreement with observations. Second, the generally assumed initial conditions used in numerical simulations of merging galaxies were tested. Orbital parameters of the merging galaxies are derived self-consistently from large scale N-body simulations, showing that the commonly used parameters are in agreement, but resemble just a small fraction of the possible parameter space. Most of the mergers are taking place on parabolic orbits with pericenter distances larger than generally assumed in simulations. Using semi-analytical modeling techniques, the morphology of progenitors is found to be dependent on the luminosity of the present-day elliptical. One can distinguish three different regions: ellipticals with M_B -18 are the product of disk galaxies merging, as usually assumed in merger simulations. The third path is to implement results of detailed numerical simulations into a semi-analytic models of galaxy formation model and to compare global predictions for ellipticals with observations. The dependence of the isophotal shape of an elliptical on the mass ratio of the last major merger, as suggested by dissipationless simulations, fails in reproducing the observed correlation between isophotal shape and mass of an elliptical. Only the assumption that all major mergers between elliptical galaxies lead to boxy ellipticals allows to recover the observed trend. Including the effects of binary black hole merging in the centers of the remnants, it is possible to recover the observed core mass deficit-black hole mass relation.

Piezocomposites are attracting widespread interest since they can offer greater flexibility and better performances in specific applications with respect to traditional piezoelectric wafers. Design of piezocomposites requires accurate homogenisation models for the prediction of the equivalent electro-mechanical properties. In macro-scale models of structures with piezocomposite transducers, these properties are adopted in order to avoid the complexity of the piezocomposite microstructure. In the case of smart structures the accurate modelling of the actuation and the response of the structure is of primary importance. If classical structural finite elements are not sufficiently accurate, higher order or solid elements should be adopted. Thanks to adaptation or mixed-dimensional methods, it is possible to adopt computationally expensive higher order or solid elements only in some sub-domains of the structure. In this work, the modelling of smart structures equipped with thin piezoelectric transducers is considered in a multi-scale framework. Micromechanical homogenisation models are developed and employed for the prediction of the equivalent properties of piezocomposites. A micromechanical model based on the concept of inclusion is proposed to investigate the influence of the shape of the inclusions, of the constituent materials and of the polarisation on the equivalent properties. It has been found that fibre-shaped inclusions should be considered in order to obtain piezocomposites with strong piezoelectric effect and to have at the same time high direction-dependence. The equivalent properties of Macro Fiber Composites are determined via the Asymptotic Homogenisation Method (AHM) with an analytical solution and with a numerical solution via FEM which takes into account the effect of the electrodes. AHM analytical solution is adopted to investigate the effect of the material properties of the matrix on the overall piezocomposite. Results indicate that low values of the Young's modulus and of the Poisson's ratio yield high directional dependence in the piezoelectric properties. A laminated design with anisotropic layers and a piezocomposite layer is investigated via UFM. A configuration with maximum directional dependence in terms of equivalent piezoelectric strain constants is proposed, whereas maximum directional dependence in terms of piezoelectric stress constants is proved to be not achievable with such a design. Hierarchical finite elements for structural analyses based on a Unified Formulation (UF) by Carrera are developed and coupled via the Arlequin method proposed by Ben Dhia. Solid, plate and beam finite elements for mechanical and for piezoelectric problems are presented. Via UF, higher order and piezoelectric elements can be formulated straightforwardly. These elements are combined in variable kinematic solutions in the Arlequin framework. Higher-order elements are adopted locally where the stress field is three-dimensional, whereas the remaining parts of the structure are modelled with computationally cheap lower-order elements. Two electro-mechanical coupling operator for the Arlequin method in the context of piezoelectric analyses are proposed. Results are validated towards monomodel solutions and three-dimensional analytical and numerical reference solutions. Accurate solutions are obtained reducing the computational costs

Collection of Solved Nonlinear Problems for Remote Shaping and Patterning of Liquid Structures on Flat and Curved Substrates by Electric and Thermal Fields

The resolution of the cosmic far-infrared background at long wavelengths has uncovered a population of high-redshift, highly infrared-luminous galaxies that indicate that a significant amount of highly obscured star formation occurred in the early history of the Universe, which has not been taken into account in studies of the cosmic star formation and mass assembly histories. Since such studies are important tests of hierarchical galaxy formation models in a cold dark matter- dominated universe, it is vital that the contribution of these luminous submillimeter-selected galaxies to the buildup of stellar mass in the Universe be understood and included when testing galaxy formation models. Progress in understanding the nature of submillimeter-selected galaxies has been slow, however, due to the faintness of the population outside of the submillimeter bands and the coarse resolution of the single-dish submillimeter surveys in which the galaxies were discovered. The slow progress has at least two important consequences: (1) there is still much that is unknown about submillimeterselected galaxies at all wavelengths, so the properties of and evolutionary predictions for the population are often inferred by making analogies to local galaxies of similar luminosity and assuming the high-redshift galaxies represent a uniform population of galaxies; and (2) the relationships of the submillimeter-selected galaxies to other high-redshift galaxy populations selected at other wavelengths remain poorly understood. In this work we capitalize on recently-available observing resources of the Spitzer Space Telescope, at near- and mid-infrared wavelengths, and the Green Bank Telescope, at 1 cm, to improve the characterization of the largest representative sample of submillimeter-selected galaxies with spectroscopic redshifts. We combine our new data with data from the literature at a variety of wavelengths to place new constraints on the fundamental properties of gas mass, stellar mass, infrared luminosity, and spectral energy distribution, and use our new constraints to test a variety of assumptions which have been used in the past to predict and infer characteristics of submillimeter-selected galaxies. We also use our new data to compare different populations of high-redshift galaxies selected at different wavelengths in an effort to understand the relationships between the different types of galaxies. First, we use observations of CO rotational line emission with the Green Bank Telescope to constrain the cold gas mass and gas conditions in several submillimeter-selected galaxies. We obtain the first detection of CO(1→0) emission from a submillimeter-selected galaxy, finding that the CO(4→3)/CO(1→0) brightness temperature ratio of ~ 0.26 suggests n(H₂) > 3 − 10 × 10² cm⁻³ and the presence of sub-thermally excited gas. The integrated line flux implies a cold molecular gas mass 4 times larger than the mass predicted from the CO(4→3) line, assuming a brightness temperature ratio of 1.0, suggesting that extrapolating molecular gas masses from J upper ≥ 3 transitions of CO, which is the primary method of estimating molecular gas masses of high-z galaxies in the literature, leads to considerable uncertainties. Next, we use deep imaging with the Multiband Imaging Photometer for Spitzer (MIPS) on the Spitzer Space Telescope of the spectroscopic sample of radio-detected submillimeter-selected galaxies of Chapman et al. (2005) to derive new estimates of the infrared luminosity for these objects. Our Spitzer data constrain the Wien side of the infrared spectral energy distribution peak of high-redshift submillimeter-selected galaxies, and thus are extremely important to determine the contribution of hot dust emission to the total infrared luminosity. We find that most submillimeter-selected galaxies do not have dominant contributions from hot dust at rest-frame mid-infrared wavelengths. We also find that the spectral energy distribution of the nearest ultraluminous infrared galaxy, Arp 220, is significantly different on average from most high-z submillimeter-selected galaxies and is thus a poor template with which to predict properties of submillimeter-selected galaxies even though it has been often used in the past. Using our new infrared luminosity estimates constrained by multiple infrared and submillimeter data points, we show that submillimeter-selected galaxies display a relatively tight, almost linear correlation between total infrared luminosity and radio luminosity, which is not largely different from the far-infrared–radio correlation of local galaxies selected by the Infrared Astronomical Satellite (IRAS). We examine the rest-frame ultraviolet through near-infrared spectral energy distributions of the same sample of radio-detected submillimeter-selected galaxies with spectroscopic redshifts, obtained using measurements from imaging with the Infrared Array Camera (IRAC) on Spitzer in combination with observed-frame optical and near-infrared data from the literature. We find from these spectral energy distributions, which trace the stellar light from a galaxy in the absence of an active nucleus, that submillimeter-selected galaxies suffer significant extinction at rest-frame optical wavelengths, and that both stars and dust emission contribute to the near-infrared luminosity in many z > 2 submillimeter-selected galaxies. We estimate stellar masses for the individual galaxies in the sample using restframe H-band luminosities interpolated from the observed spectral energy distributions, obtaining a median stellar mass for the sample of 6 − 7 × 10¹⁰ Msun. By comparing our stellar mass estimates to molecular gas and dynamical mass estimates for 13 individual submillimeter-selected galaxies in our sample observed in CO emission lines, we determine that the molecular gas fraction in submillimeter-selected galaxies declines with increasing stellar mass, which is suggestive of an evolutionary trend. If the molecular gas masses for the 13 galaxies for which gas mass estimates are available are typical of the entire radiodetected submillimeter-selected galaxy population, then a typical lower limit to the total baryonic mass of submillimeter-selected galaxies is ~ 10¹¹ Msun, and these galaxies are unlikely to significantly increase their stellar mass in the current epoch of activity which is the source of their enormous infrared luminosity. Lastly, we compare the IRAC and MIPS properties of submillimeter-selected galaxies and their stellar masses to those of high-redshift ultraviolet- and optically-selected galaxies, 24 μm-selected galaxies, and powerful radio galaxies. In the IRAC bands, submillimeter-selected galaxies are brighter and redder than ultraviolet-selected galaxies, suggesting they have higher dust content, higher stellar mass, a higher contribution from an active nucleus, or some combination of these factors. The near-infrared colors of submillimeterselected galaxies are most similar to those of high-z radio galaxies, objects which are known to contain powerful, obscured active nuclei. However, submillimeter-selected galaxies are fainter in the MIPS 24 μm band than high-z radio galaxies, suggesting that the dust in the submillimeter-selected galaxies is not heated to such high temperatures as in the radio sources. We find that the typical stellar mass of submillimeter-selected galaxies is larger by a factor of 3–4 than that of high-redshift ultraviolet-selected galaxies, roughly similar to the typical stellar mass of optically-selected high-z galaxies, and lower than the typical stellar mass of powerful high-z radio galaxies. These comparisons suggest that submillimeter-selected galaxies are among the more massive galaxies of their epoch, but not necessarily the most massive, as has been suggested in the literature. However, systematic errors in the stellar masses of any of the high-redshift galaxy samples of a factor of a few, which are certainly possible, can alter this conclusion.

view Abstract Citations (38) References (24) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS N-body simulations of galaxy clustering. II. Groups of galaxies. Turner, E. L. ; Aarseth, S. J. ; Gott, J. R., III ; Blanchard, N. T. ; Mathieu, R. D. Abstract Two of the previously presented N-body simulations of galaxy clustering are analyzed in terms of the detailed dynamical and morphological properties of their binaries, groups, and clusters. The analysis is closely analogous to the studies of groups among bright Zwicky-catalog galaxies by Turner and Gott (1976, 1977). The simulated groups, particularly those in the Omegazero = 0.1 and n = -1 model, resemble the observed groups. The models provide complete (position, velocity, mass) information on group and field 'galaxies' identified using the Turner and Gott surface-density enhancement procedure. These data are used to assess the validity of the membership assignments, the influence of non-Hubble motions on descriptions of the clustering, the accuracy and stability of various M/L estimators, the significance of field galaxies, and the statistical properties of binary systems. Publication: The Astrophysical Journal Pub Date: March 1979 DOI: 10.1086/156893 Bibcode: 1979ApJ...228..684T Keywords: Computerized Simulation; Cosmology; Galactic Clusters; Many Body Problem; Stellar Motions; Astronomical Catalogs; Astronomical Models; Error Analysis; Estimating; Red Shift; Astrophysics; Galaxy Clustering:Universe; Groups of Galaxies:Formation; Groups of Galaxies:N-Body Problem full text sources ADS |

During soil formation, the interaction of different biota (plants, soil fauna, microbes) with weathered mineral material shape unique structures depending on the parental material and the site specific climatic conditions. We here explore soil structure formation on a chronosequence in Rheinisch lignite mining area. In this area loess material from a depth of 4-10 m is used for reclamation in a standardized procedure since 24 years. Thus, it is an ideal site for studying soil structure formation as a function of time. Changes in soil pore system are characterised by parameters such as tortuosity, connectivity and pore size distribution. To derive these, undisturbed soil columns with a diameter of 10 cm were taken from two different depths (0-20 cm and 40-60 cm) with sites ranging in age from 0 to 24 years. X-ray CT is used for scanning the original columns as well as undisturbed subsamples of 3 and 1 cm diameter. This hierarchical sampling scheme was developed to overcome the trade-off between sample size and resolution – starting with an effective resolution of 57 µm for 10 cm cores via 19 µm for 3 cm columns to 6 µm for the smallest samples size of 1 cm. Subsamples therefore reveal information on micropores and small roots. The importance of roots for soil structure / pore system development in not only investigated in the CT images but also by destructive analyses and determination of root length with WinRHIZO The dataset is complemented by HYPROP measurements of water retention curves and unsaturated hydraulic conductivities; both functions of the pore system. In cooperation with project partners, VisNIR images from different slices of the soil columns will be taken to combine information about the local distribution of chemical features (iron oxides and organic compounds) with structural information of pores and roots. The current study is part of the DFG-Project Soil Structure (AOBJ: 628683).

The population of galaxies we see today is the result of billions of years of gas inflows, outflows, mergers, and feedback. To develop any holistic picture of the origin and evolution of galaxies, we thus need to understand their environments. The circumgalactic and intergalactic media (CGM and IGM) - the gas around and between galaxies, respectively - represent a large part of this environment. However, this gas is extremely faint and thus difficult to observe, and only recently have we been able to image it directly. This thesis presents instrumental and observational work focused on revealing galaxy environments in the early universe. Chapter 1 presents a brief history of our understanding of galaxies and an overview of our current picture of galaxy formation, including the role played by galaxy environments. In particular, it focuses on presenting the evolution of baryonic structures within a cosmological density field dominated by dark matter. Chapter 2 presents instrumental work on the Keck Cosmic Web Imager (KCWI, Morrissey et al. 2018), a new integral field spectrograph (IFS) for the Keck-2 10m telescope designed to study faint, extended emission. As an introduction, I discuss the advantages and disadvantages of integral field spectroscopy for the application of studying galaxy environments, as well as an overview of the prototype instrument - the Palomar Cosmic Web Imager (PCWI, Matuszewski et al. 2010). This chapter focuses primarily on engineering work during the development and testing of KCWI, though I conclude with a brief comparison of PCWI and KCWI performance in measuring the CGM around a high-redshift QSO. Chapter 3 presents the development of a software package designed to extract and analyze faint, extended emission in PCWI and KCWI data: CWITools. Although software is often an afterthought in astronomical and observational work, it is likely to become a primary barrier to conducting large IFS surveys of the CGM and IGM. This semi-automated analysis pipeline is presented and released publicly to empower future PCWI and KCWI studies. Chapter 4 presents the FLASHES (Fluorescent Lyman-α Structures in High-z Environments) pilot survey, published as O'Sullivan et al. 2020. The FLASHES pilot survey is an IFS study of extended HI Lyman-α emission in the environments of 48 z = 2.3 - 3.0 QSOs. The FLASHES Survey is the core project of this thesis, enabled by the instrumentation in Chapter 2 and the analysis pipeline developed in Chapter 3. The pilot survey represents the first statistically significant (N ≳ 30) sample of direct CGM observations in its redshift range. As such, it provides the first direct constraints on the 2D morphology, surface brightness profiles, and spatially resolved kinematics of the CGM during this period. Chapter 5 presents the first FLASHES follow-up study; deep IFS observations targeting extended Lyα 1216A, NV 1240A, CIV 1549A, and HeII 1640A emission from a subset of FLASHES pilot targets (O'Sullivan et al., in prep). Emission from metals in the CGM is expected to be an order of magnitude or more fainter than its Lyα, yet is a crucial ingredient in understanding the composition of the gas. Detecting this emission still requires multiple hours on 10m class telescopes. As such, large surveys of the multi-phase CGM remain extremely difficult to conduct. In this chapter, I present detections and upper limits of CGM metal emission around 8 FLASHES targets. Chapter 6 presents engineering work on FIREBall-2 (the Faint Intergalactic Redshifted Emission Balloon, second generation), a high-altitude UV telescope and IFS targeting CGM emission in the low-redshift universe (z ≃ 0.7). FIREBall-2 is an ambitious project deploying a novel, electron-multiplying CCD designed to achieve ≳ 50% quantum efficiency in the UV. This technology represents an order of magnitude increase in sensitivity from the microchannel plates used in the GALEX space telescope. FIREBall-2 serves as both an observational project in its own right, studying the low-z CGM, and a pathfinder mission for future UV space missions. Finally, Chapter 7 summarizes the contributions from this thesis and present a brief outlook on a few topics related to observations of galaxy environments.

Reliable and efficient vibroacoustic loads prediction is often critical in structural design, yet it remains a challenging task for many applications. Spacecraft structures are characterised by extensive use of composite materials, complex connections between components and various non-trivial geometrical features. Accurate treatment necessitates the construction of highly detailed numerical models, traditionally employing deterministic representations. Simultaneously, the broadband acoustic excitation due to the diffuse sound field experienced during launch requires modelling the fluid domain and solving the resulting elasto-acoustic interaction at = multiple frequencies. To alleviate the computational demand implications for large problem sizes, substructuring and reduction techniques for the structural domain are commonplace, component mode synthesis (CMS) being a framework widely adopted in the aerospace industry. Nevertheless, despite ongoing research, the topic still presents a range of difficulties when a universal, robust method of accounting for model uncertainties is sought. In this study, two CMS based approaches are proposed and evaluated. Firstly, the Craig-Bampton stochastic method (CBSM) is improved via a set of modifications enhancing its efficiency, and subsequently adapted for use in a vibroacoustic setting. Optimal perturbation levels and scope of validity of the technique are established against a probabilistic structural analysis (PSA) simulation for a spacecraft structure. Secondly, a novel stochastic finite element method (FEM) is presented. The underlying mathematical foundation is derived so that uncertainty can naturally be controlled at the subsystem level, in partitions of the corresponding condensed mass and stiffness matrices. This decomposition based approach ensures that realisations of the random matrices have key properties such as positive (semi)definiteness strictly preserved, guaranteeing complete robustness. The method is validated with a spacecraft test case, comparing its predictions against PSA, the improved CBSM and experimental data. A coupling scheme with a hierarchical matrix accelerated boundary element method is formulated, resulting in the construction of a complete stochastic vibroacoustic solver.

Protein adsorption at oil-water interfaces interfacial structure and function of proteins in emulsions