The circumgalactic medium (CGM), loosely defined as the region between a galaxy disk and its virial radius, has long been of interest to astronomers and astrophysicists because it acts as an interface between galaxies and their surroundings. Studying it, therefore, gives us hints of how gas flows between galaxies and the intergalactic medium (IGM), fueling star formation for instance. This thesis addresses some of the current and future observation, analysis and instrumentation challenges that should be tackled for a better understanding of the CGM. Chapter 1 is an overview of science related to the CGM and of instruments that our lab works on: the Circumgalactic Hydrogen-Alpha Spectrograph (CHaS) and the Faint Intergalactic-medium Redshifted Emission Balloon (FIREBall). It sets the ground for a better understanding of the science discussed in subsequent chapters. CHaS is an IFU spectrograph installed on a 2.4 m telescope at the MDM Observatory in Arizona (Melso et al. 2022). It has high sensitivity and high spectral resolution, and it collects individual spectra from points across our targets using a microlens array, allowing us to make detailed spectral maps of observed astronomical objects. FIREBall is a balloon-born UV multi-object spectrograph, allowing us to look at yet another emission line prominent in the CGM. In this thesis, we will focus on what a future FIREBall detector might look like. Chapters 2 and 3 present data collected with CHaS in November 2021 from two very distinct objects: NGC 6946 (the Fireworks galaxy) and M76 (the Little Dumbbell nebula). Both chapters address how we process spectral data from CHaS images and the subsequent making of velocity maps. Using CHaS images, we tackle anomalous gas motion and formations in both targets. We compared the data presented in both chapters to previous literature, showing that CHaS velocity maps were more detailed and complimented previous findings. NGC 6946 is known for being a prolific star forming galaxy and also for having holes in its HI distribution, which have historically been attributed to the expansion and bursting of gas bubbles. In Chapter 2, we find that the motion around these holes is indeed consistent with expanding bubbles and galactic fountains on their edges, with velocities in the -20 km/s to 20 km/s range, consistent with what Boomsma et al. (2008) found, going up to +/-60 km/s, similar to the velocities found by Efremov et al. (2002). We also found that Long et al. (2019)'s supernova remnants candidates catalog had a clear position correlation with the boundaries of different holes in the Boomsma et al. (2008) HI hole catalog, suggesting that these holes might indeed be related to gas bubbles resulting from supernova explosions. The Little Dumbbell nebula, on the other hand, show its own set of anomalies. M76 is a butterfly planetary nebula with a central torus and two polar lobes. We find that these lobes are not completely symmetric. In fact, the wester lobe is more rounded and the eastern one is more stretched and fragmented. From our velocity maps, we propose a couple of explanations for how the ISM might interact with the nebula both in the core star's AGB phase and after the nebula is formed to give M76 its shape. Both explanations vary depending on the assumed direction of motion of the star in it its AGB phase, but both are consistent with models by Villaver, Manchado and García-Segura (2012) and Wareing et al. (2007). Moreover, we compare our data to those of other authors and find similar velocity ranges around an axis going from one lobe to another as spectral maps made by Ramos-Larios et al. (2017) and Bryce et al. (1996). Departing from observational data analysis, Chapter 4 focuses on how we can probe further into the CGM by upgrading existing instruments, turning commonplace condensed matter methods into tools for astrophysics. More specifically, Chapter 4 discusses the possibility of switching FIREBall's current UV sensitive emCCD detectors, which rely on coating to be visible-blind and on cryogenic equipment that is heavy for a balloon flight, for devices made out of hexagonal boron nitride (hBN). hBN's main energy bandgap overlaps with the emission lines that FIREBall is interested in capturing, and it can be combined with graphene (which is isomorphic to hBN) to make high quality, quantum efficient devices. While we weren't able to finish full devices, Chapter 4 discusses their fabrication in detail as well as how our Siesta SISL simulations show that even small device defects might be acceptable for a detector. The chapter ends with considerations about how one might fit individual devices as multi-pixel detectors.

M.S.

The GMT-Consortium Large Earth Finder (G-CLEF) will be a cross-dispersed, optical band echelle spectrograph to be delivered as the first light scientific instrument for the Giant Magellan Telescope (GMT) in 2022. G-CLEF is vacuumenclosed and fiber-fed to enable precision radial velocity (PRV) measurements, especially for the detection and characterization of low-mass exoplanets orbiting solar-type stars. The passband of G-CLEF is broad, extending from 3500 angstrom to . This passband provides good sensitivity at blue wavelengths for stellar abundance studies and deep red response for observations of high-redshift phenomena. The design of G-CLEF incorporates several novel technical innovations. We give an overview of the innovative features of the current design. G-CLEF will be the first PRV spectrograph to have a composite optical bench so as to exploit that material's extremely low coefficient of thermal expansion, high in-plane thermal conductivity and high stiffness-to-mass ratio. The spectrograph camera subsystem is divided into a red and a blue channel, split by a dichroic, so there are two independent refractive spectrograph cameras. The control system software is being developed in model-driven software context that has been adopted globally by the GMT. G-CLEF has been conceived and designed within a strict systems engineering framework. As a part of this process, we have developed a analytical toolset to assess the predicted performance of G-CLEF as it has evolved through design phases.

A hipernasalidade de fala é um distúrbio da ressonância nasal, freqüentemente encontrada em portadores de fissura palatina com disfunção velofaríngea. Constitui-se de uma nasalidade imprópria e excessiva dos sons exclusivamente orais, que pode ser analisada pela espectrografia, que decompõe o sinal de fala em três dimensões de análise: freqüência, tempo e intensidade, gerando um gráfico, o espectrograma. Assim, o objetivo do presente estudo é investigar as características espectrográficas da hipernasalidade de fala de mulheres portadoras de fissura palatina e comparar os achados com os resultados da nasometria e da avaliação perceptivo -auditiva de suas emissões de fala. Contou-se com a colaboração de 30 mulheres sem comprometimentos de fala e do trato vocal, 5 portadoras de fissura palatina não operada e 21 portadoras de fissura palatina operada, na faixa etária de 18 a 40 anos de idade. Emitiram as vogais [a] e nasal sustentadas, separadamente e dentro de uma frase-veículo diante do nasômetro e de um gravador digital. Estas amostras de fala foram avaliadas perceptivo-auditivamente, determinadas suas nasalâncias e características formânticas. Foram encontradas as seguintes características espectrográficas: inserção de formantes nasais e antiformantes dentre os formantes orais nas emissões nasalizadas/hipernasalizadas. Não houve correspondência direta desses achados com a nasometria nem com a avaliação perceptivo- auditiva e nem destas entre si / Speech hypernasality is a nasal resonance’s disorder, come across often in cleft palate persons with velopharingeal disfuction. It is an inappropriate and excessive nasality just oral sounds, that can be analyzed for spectrograph (decompose speech signal in three dimensions: frequency, time and intensity, generating the spectrogram). Hence, this dissertation has the objective of investigating speech hipernasality spectrographic cues of the cleft palate women and to compare the findings with the nasometry results and auditory perceptual evaluation of the speech issues. Thirty women without speech and of the vocal tract problems, 5 cleft palate women no operated and 21 operated (18 to 40 years old) issues [a] and nasal, isolated and within of the carrier phrase in front of the nasometer and digital record. After auditory perceptual evaluation, nasalances and formants cues it was possible to verify nasal formants and antiformants among oral formants in the nasalized/hipernasalyzed issues and don´t have correspondency this findings with the nasometry neither with the auditory perceptual evaluation neither themselves

The primary goal of the recently formed Absorption Cross Sections of Ozone (ACSO) Commission is to establish an international standard for the ozone cross section used in the retrieval of atmospheric ozone number density profiles. The Canadian instrument OSIRIS onboard the Swedish spacecraft Odin has produced high quality ozone profiles since 2002, and as such the OSIRIS research team has been asked to contribute to the ACSO Commission by evaluating the impact of implementing different ozone cross sections into SASKTRAN, the radiative transfer model used in the retrieval of OSIRIS ozone profiles. Preliminary analysis revealed that the current state of the OSIRIS spectral point spread function, an array of values describing the dispersion of light within OSIRIS, would make such an evaluation difficult. Specifically, the current spectral point spread function is time-independent and therefore unable to account for any changes in the optics introduced by changes in the operational environment of the instrument. Such a situation introduces systematic errors when modelling the atmosphere as seen by OSIRIS, errors that impact the quality of the ozone number density profiles retrieved from OSIRIS measurements and make it difficult to accurately evaluate the impact of using different ozone cross sections within the SASKTRAN model. To eliminate these errors a method is developed to calculate, for the 310-350 nm wavelength range, a unique spectral point spread function for every scan in the OSIRIS mission history, the end result of which is a time-dependent spectral point spread function. The development of a modelling equation is then presented, which allows for any noise present in the time-dependent spectral point spread function to be reduced and relates the spectral point spread function to measured satellite parameters. Implementing this modelled time-dependent spectral point spread function into OSIRIS ozone retrieval algorithms is shown to improve all OSIRIS ozone profiles by 1-2% for tangent altitudes of 35-48 km. Analysis is also presented that reveals a previously unaccounted for temperature-dependent altitude shift in OSIRIS measurements. In conjunction with the use of the time-dependent spectral point spread function, accounting for this altitude shift is shown to result in an almost complete elimination of the temperature-induced systematic errors seen in OSIRIS ozone profiles. Such improvements lead to improved ozone number density profiles for all times of the OSIRIS mission and make it possible to evaluate the use of different ozone cross sections as requested by the ACSO Commission.

This thesis reports the design, construction, and the initial results obtained from a digital spectrograph for observations of radio burst emission from the Sun. One of the distinct advantages of radio spectral studies of the Sun during events such as solar flares, coronal mass ejections (CMEs), etc. is that it gives a straight forward estimate of the speed of the outflowing material into the outer atmosphere of the Sun and subsequently the interplanetary medium. It is well known that in the solar atmosphere, the electron density and consequently the plasma frequency gradually decreases with increasing distance from the center. Therefore in a time-frequency plane, the intensity of the associated radio emission should generally drift from high to low frequencies with time. From this, and from a knowledge of the height of the successive plasma levels in the solar atmosphere, one can deduce the speed of the outward moving disturbance. In this respect, a study of the radio bursts at decameter wavelengths is important since such radiation originates from the corona at heights ≥1.3 R⊙ (1 R⊙ = 6.96 x 10° km = radius of the Sun) from the center of the Sun, which are otherwise accessible only through the use of white light coronagraphs atop high altitude mountains and onboard space vehicles. The primary units of the instrument are (i) zero-crossing detector (ZCD), (ii) sampler and (iii) correlator. The function of the ZCD is to digitize the input signal waveform. In the present case, we use a one-bit quantizer, i.e., its output is either a '1' or '0' depending on whether the input is above or below the zero level, respectively. The digitized signals are then sampled at the Nyquist rate using the sampler. The output of the sampler is then passed through a set of shift registers, and finally fed to the correlator. The latter measures the correlation between the signals at its input as a function of the delay (introduced by the shift registers) between them. After successful completion of several static/dynamic tests in the laboratory, the system was moved to the Gauribidanur radio observatory (Latitude: 13°36’12”; Longitude:77°27’07”), and is presently used along with the existing radiohe-liograph to derive both the spectral and spatial information of the various radio emitting transient sources on the Sun, respectively. The R..F. signal (40-150 MHz) from one of the antenna groups of the ra-dioheliograph forms the input to the spectrograph. The signal from the field goes through a series of amplification and mixing operations to bring it down to an I.F. of 10 MHz with a bandwidth of 1 MHz, and then fed to the spectrograph. The present frequency range of the spectrograph is 40 MHz, and the data corresponding to the above band is obtained in steps of 1 MHz by switching the local oscillator through a GPIB interface, after each integration period. Each 1 MHz data is then Fourier tranformed to get its corresponding power spectrum. Successive data sets are then arranged in order according to the frequency of the local oscillator signal to get the spectrum corresponding to the entire 40 MHz band. The initial results obtained with our instrument are also presented.

My dissertation focuses on a relatively new field of study: the region immediately around galaxies known as the circumgalactic medium (CGM). The CGM holds vast quantities of mass and metals, yet its connection to galaxies is not well understood. My work uses cosmological hydrodynamic simulations and comparisons to data from Hubble's Cosmic Origins Spectrograph (COS) to understand the CGM's connection to galaxy evolution, gas accretion, outflows, star formation, and baryon cycling. This includes studies of the CGM's extent and physical conditions; the cause and nature of outflows; gas dynamics, including the first comprehensive study of tracers of inflowing and outflowing gas at low redshift (z=0.25); and direct comparison of theoretical results to observational data. Chapter 1 introduces my research and show its connection to galaxy evolution. Chapter 2 investigates hydrogen and metal line absorption around low-redshift galaxies in cosmological hydrodynamic simulations. This chapter studies different models for stellar outflows, physical conditions, and dependencies on halo mass. Chapter 3 examines the flow of gas into, out of, and around galaxies using a novel particle tracking technique. This chapter examines the baryon cycle in detail for our preferred model of stellar outflows. Chapter 4 compares our model results, including two separate prescriptions for outflows, with data from COS. We contrast these wind models, showing how they cycle baryons differently, and show degeneracies in observational diagnostics. In Chapter 5, I summarize and discuss plans for future research in this field, and how it can be more fully leveraged to understand galaxy evolution.

The James Web Space telescope will replace the aging Hubble in 2012. One instrument onboard will be the Near Infrared Spectroscope which will require a reconfigurable slit mask to control light incident upon it. One design for this device is called the Mechanically Actuated Reconfigurable Slit mask (MARS). The MARS uses several electromagnetic clamps to move shutters though the focal plane. The goal of this thesis is to develop a system to characterise these clamps at cryogenic temperatures. FEA simulations predicted clamp performance and aided in the development of a test apparatus. An apparatus which utilises the Lorentz force to force the clamp jaws open was developed, built and tested. The device was built inside a cryostat which operated at 30 K. It was found that the test apparatus performed as intended. The clamps themselves proved to be problematic. Small perturbations or misalignments caused significant inconsistencies in experimental results.

A hipernasalidade de fala é um distúrbio da ressonância nasal, freqüentemente encontrada em portadores de fissura palatina com disfunção velofaríngea. Constitui-se de uma nasalidade imprópria e excessiva dos sons exclusivamente orais, que pode ser analisada pela espectrografia, que decompõe o sinal de fala em três dimensões de análise: freqüência, tempo e intensidade, gerando um gráfico, o espectrograma. Assim, o objetivo do presente estudo é investigar as características espectrográficas da hipernasalidade de fala de mulheres portadoras de fissura palatina e comparar os achados com os resultados da nasometria e da avaliação perceptivo -auditiva de suas emissões de fala. Contou-se com a colaboração de 30 mulheres sem comprometimentos de fala e do trato vocal, 5 portadoras de fissura palatina não operada e 21 portadoras de fissura palatina operada, na faixa etária de 18 a 40 anos de idade. Emitiram as vogais [a] e nasal sustentadas, separadamente e dentro de uma frase-veículo diante do nasômetro e de um gravador digital. Estas amostras de fala foram avaliadas perceptivo-auditivamente, determinadas suas nasalâncias e características formânticas. Foram encontradas as seguintes características espectrográficas: inserção de formantes nasais e antiformantes dentre os formantes orais nas emissões nasalizadas/hipernasalizadas. Não houve correspondência direta desses achados com a nasometria nem com a avaliação perceptivo- auditiva e nem destas entre si / Speech hypernasality is a nasal resonance’s disorder, come across often in cleft palate persons with velopharingeal disfuction. It is an inappropriate and excessive nasality just oral sounds, that can be analyzed for spectrograph (decompose speech signal in three dimensions: frequency, time and intensity, generating the spectrogram). Hence, this dissertation has the objective of investigating speech hipernasality spectrographic cues of the cleft palate women and to compare the findings with the nasometry results and auditory perceptual evaluation of the speech issues. Thirty women without speech and of the vocal tract problems, 5 cleft palate women no operated and 21 operated (18 to 40 years old) issues [a] and nasal, isolated and within of the carrier phrase in front of the nasometer and digital record. After auditory perceptual evaluation, nasalances and formants cues it was possible to verify nasal formants and antiformants among oral formants in the nasalized/hipernasalyzed issues and don´t have correspondency this findings with the nasometry neither with the auditory perceptual evaluation neither themselves

The Large Ultraviolet/Optical/Infrared Surveyor (LUVOIR) is one of four large mission concepts currently undergoing community study for consideration by the 2020 Astronomy and Astrophysics Decadal Survey. LUVOIR is being designed to pursue an ambitious program of exoplanetary discovery and characterization, cosmic origins astrophysics, and planetary science. The LUVOIR study team is investigating two large telescope apertures (9- and 15-meter primary mirror diameters) and a host of science instruments to carry out the primary mission goals. Many of the exoplanet, cosmic origins, and planetary science goals of LUVOIR require high-throughput, imaging spectroscopy at ultraviolet (100 - 400 nm) wavelengths. The LUVOIR Ultraviolet Multi-Object Spectrograph, LUMOS, is being designed to support all of the UV science requirements of LUVOIR, from exoplanet host star characterization to tomography of circumgalactic halos to water plumes on outer solar system satellites. LUMOS offers point source and multi-object spectroscopy across the UV bandpass, with multiple resolution modes to support different science goals. The instrument will provide low (R = 8,000 - 18,000) and medium (R = 30,000 - 65,000) resolution modes across the far-ultraviolet (FUV: 100 - 200 nm) and near-ultraviolet (NUV: 200 - 400 nm) windows, and a very low resolution mode (R = 500) for spectroscopic investigations of extremely faint objects in the FUV. Imaging spectroscopy will be accomplished over a 3 x 1.6 arcminute field-of-view by employing holographically-ruled diffraction gratings to control optical aberrations, microshutter arrays (MSA) built on the heritage of the Near Infrared Spectrograph (NIRSpec) on the James Webb Space Telescope (JWST), advanced optical coatings for high-throughput in the FUV, and next generation large-format photon-counting detectors. The spectroscopic capabilities of LUMOS are augmented by an FUV imaging channel (100 - 200nm, 13 milliarcsecond angular resolution, 2 x 2 arcminute field-of-view) that will employ a complement of narrow-and medium-band filters. The instrument definition, design, and development are being carried out by an instrument study team led by the University of Colorado, Goddard Space Flight Center, and the LUVOIR Science and Technology Definition Team. LUMOS has recently completed a preliminary design in Goddard's Instrument Design Laboratory and is being incorporated into the working LUVOIR mission concept. In this proceeding, we describe the instrument requirements for LUMOS, the instrument design, and technology development recommendations to support the hardware required for LUMOS. We present an overview of LUMOS' observing modes and estimated performance curves for effective area, spectral resolution, and imaging performance. Example "LUMOS 100-hour Highlights" observing programs are presented to demonstrate the potential power of LUVOIR's ultraviolet spectroscopic capabilities.