Exploitation of the imaging capabilities of the new generation of ground-based astronomical telescopes relies heavily on Adaptive Optics (AO). Current AO system designs call for sodium guide star lasers capable of producing at least eight Watts of power tuned to the peak of the sodium D₂ line, with a high duty cycle to avoid saturation, and with 0.5-1.0 GHz spectral broadening. This work comprises development and testing of six candidate laser systems and materials which may afford a path to achieving these goals. An end-pumped CW dye laser producing 4.0 Watts of tuned output power was developed and used to obtain the first accurate measurement of sodium layer scattering efficiency. Methods of optimizing the laser output through improving pump overlap efficiency and reducing the number of intracavity scattering surfaces are covered. The 1181 nm fluorescence peak of Mn⁵⁺ ion in Ba₅(PO₄)₃Cl could be tuned and doubled to reach 589 nm. While efforts to grow this crystal were under way, the Mn⁵⁺ ion in natural apatite (Ca₅(PO₄)₃F) was studied as a potential laser material. Fluorescence saturation measurements and transmission saturation are presented, as well as efforts to obtain CW lasing in natural apatite. A Q-switched laser color-center laser in LiF : F⁻₂ was developed and successfully tuned and doubled to the sodium D₂ line. Broad-band lasing of 80 mW and tuned narrow-band lasing of 35 mW at 1178 nm were obtained with 275 mW of input pump power at 1064 nm. The measured thermal properties of this material indicate its potential for scaling to much higher power. A Q-switched intracavity Raman laser was developed in which CaWO₄ was used to shift a Nd:YAG laser, the frequency-doubled output of which was centered at 589.3 nm. To obtain light at 589.0 nm, a compositionally tuned pump laser of Nd : Y₃Ga₁.₁Al₃.₉O₁₂ was produced which generated the desired shift, but was inhomogeneous broadened, limiting the tunable power of the material. Finally, temperature tuning of a Nd:YAG laser was demonstrated in which the laser emitted up to 8.6 Watts at a temperature of -21.5 C, bringing the wavelength into a regime favorable for efficient Raman shifting by CaWO₄.

We conducted a detailed study and comparative analysis of the Voyager UVS and PPS stellar occultations of the Uranian ring system. The primary objective of this study was the determination of the constraints on the sizes of the ring particles. The Voyager UVS and PPS occultations probed the epsilon and delta rings at significantly shorter wavelengths (0.11 μm and 0.27 μm, respectively) and at substantially different viewing geometries than a large number of existing Earth-based occultations. These differences combine to produce a unique mutual sensitivity among the UVS, PPS and Earth-based observations to the particle properties of the rings. Our results yield slight, but significant differences between PPS and UVS optical depths. We interpret these differences as wavelength dependent scattering due to a population of small particles in the mm to cm size range in epsilon and delta rings. The size distribution of particles in epsilon and delta rings were found to be similar, the main difference being the total number of particles. In contrast to studies at longer wavelengths, our results imply a relatively steep particle size distribution characterized by a power law of index 3 or greater.

<p> Stellar velocity dispersion is a key measurable quantity in galactic astronomy, yet its variation during galaxy mergers is not well-understood theoretically. Thus, while it is fairly common to measure velocity dispersion in galaxies that are in the process of merging, it is unclear how these measurements should be interpreted. In this dissertation, I provide a theoretical analysis of the evolution of stellar velocity dispersion during galaxy mergers. This is done using a set of numerical simulations. The temporal and directional evolution of velocity dispersion are examined in detail for a variety of merger simulations. I also examine the effects that dust attenuation and star formation have on measurements of velocity dispersion by creating detailed, Doppler broadened galaxy spectra. Velocity dispersions are measured from the synthetic spectra using the same technique that is employed for observations of real galaxies. </p><p> I find that velocity dispersion increases rapidly and significantly as two galaxies pass through one another. As galaxies recede from a collision, their velocity dispersions rapidly decrease and nearly return to their pre-collision values. Velocity dispersion increases in all directions during collisions, however the enhancement is most significant along the collision axis. After the nuclei of the progenitor system coalesce, the velocity dispersion oscillates slightly of the coalesced system oscillated around its final equilibrium value for up to several dynamical timescales. </p><p> I also find that the mean velocity dispersion of young stars tends to be lower than the velocity dispersion of the galaxy as a whole. The young stars become dynamically heated with time. In most cases, the youngest stars are found in dusty environments. Thus, dust preferen- tially obscures young stars, partially removing them from the flux-weighted velocity dispersion measurement. This causes flux-weighted velocity dispersion measurements to be elevated with respect to mass-weighted measurements because the young stars are dynamically cooler. On the other hand, since young stellar populations are brighter, per unit mass, than older stellar populations, the low dispersion of young stars tends to weight measurements of velocity dis- persion downward when the young stars are not more significantly obscured by dust than the older populations.</p>

<p>Kuiper Belt Objects (KBOs) are primordial icy objects in the outer solar system. Compositional information for KBOs helps us understand the original environment of the solar system as well as identify objects that are compositionally anomalous. Due to the faint nature of KBOs, very few spectroscopic observations have been made of them. Instead, photometric observations at infrared wavelengths are made to partially construct their spectra. I calculate near infrared reflectances for 12 objects using photometric observations from the Gemini North telescope. I combine these near infrared reflectances with data from the Spitzer Space Telescope. This combination of Gemini and Spitzer photometry along with compositional model analysis allows us to find the surface composition (organics, <i> H</i>₂<i>O</i>, <i>CO</i>₂, <i> CH</i>₄, and other hydrated silicates) for these 12 objects. I found that my objects fit into one of four taxonomic classes found in the Kuiper Belt. We have found using the color analysis, that Haumea has water on its surface and Eris is most likely to have methane on its surface. By analyzing this data we measure the compositional mixing in the outer solar system. </p>

<p>In my thesis I investigate the luminous <i>z</i> &sim; 3 Lyman break galaxies in deep wide field surveys.</p><p> In the first part of the thesis, I use the LBT/LUCIFER to observe a lensed high-redshift star-forming galaxy (J0900+2234) at <i>z</i> = 2.03. With the high S/N near-IR spectroscopic observations, I reveal the detailed physical properties of this high-redshift galaxy, including SFR, metallicity, dust extinction, dynamical mass, and electron number density.</p><p> In the second part of the thesis, I select a large sample of LBGs at <i> z</i> &sim; 3 from our new LBT Bo&ouml;tes field survey, and study the bright end luminosity function (LF), stellar mass function (SMF) and clustering properties of bright LBGs (1<i>L</i>_&lowast; &lt; <i> L</i> &lt; 2.5<i>L</i>_&lowast;). Together with other LF and SMF measurements, the evolution of LF and SMF can be well described by continuously rising star formation history model. Using the clustering measurements in this work and other works, a tight relation between the average host galaxy halo mass and the galaxy star formation rate is found, which can be interpreted as arising from cold flow accretion. The relation also suggests that the cosmic star formation efficiency is about 5%-20% of the total cold flow mass. This cosmic star formation efficiency does not evolve with redshift (from <i>z</i> &sim; 5 to <i>z</i> &sim; 3), hosting dark matter halo mass (10¹¹ &ndash; 10¹³ [special characters omitted]), or galaxy luminosity (from 0.3<i>L*</i> to 3<i>L* </i>).</p><p> In the third and fourth parts, with the spectroscopic follow-up observations of the bright LBGs, I establish a sample of spectroscopically-confirmed ultraluminous LBGs (ULBGs) in NOAO Boo&Dot;tes field. With this new ULBG sample, the rest-frame UV LF of LBG at M_1700&angst; = &minus;23.0 was measured for the first time. I find that the ULBGs have larger outflow velocity, broader Ly&alpha; emission and ISM absorption line profiles, and more prominent C <p style="font-variant: small-caps">IV </p> P-Cygni profile. This profile may imply a top-heavy IMF in these ULBGs. The ULBGs have larger stellar mass and SFR, but smaller dust extinction than the typical <i>L*</i> LBGs at <i>z</i> &sim; 2 &ndash; 3. We proposed two evolutionary scenarios, pre-burst and post-burst. The properties of the ULBGs, especially the morphologies, prefer the pre-starburst scenario. Further high spatial resolution HST imaging and IFU spectroscopic observations will allow us to distinguish these two scenarios.</p>

<p> The Arecibo Legacy Fast ALFA (ALFALFA) survey is a blind, extragalactic survey in the 21cm emission line of atomic hydrogen (HI). Presently, sources have been cataloged over &ap;4,000 deg² of sky (~60% of its final area), resulting in the largest HI-selected sample to date. We use the rich ALFALFA dataset to measure the statistical properties of HI-bearing galaxies, such as their mass distribution and clustering characteristics. These statistical distributions are determined by the properties of darkmatter on galactic scales, and by the complex baryonic processes through which galaxies form over cosmic time. As a result, detailed studies of these distributions can lead to important insights in galaxy formation &amp; evolution and near-field cosmology.</p><p> In particular, we measure the space density of HI-bearing galaxies as a function of the width of their HI profile (i.e. the velocity width function of galaxies), and find substantial disagreement with the distribution expected in a lambda cold dark matter (&Lambda;CDM) universe. In particular, the number of galaxies with maximum rotational velocities &upsi;<i>_rot</i> &ap; 35 kms^&ndash;1 (as judged by their HI velocity width) is about an order of magnitude lower than what predicted based on populating &Lambda;CDM halos with modeled galaxies. We identify two possible solutions to the discrepancy: First, an alternative dark matter scenario in which the formation of low-mass halos is heavily suppressed (e.g. a warm dark matter universe with keV-scale dark matter particles). Secondly, we consider the possibility that rotational velocitites of dwarf galaxies derived from HI velocity widths may systematically underestimate the true mass of the host halo, due to the shape of their rotation curves. In this latter scenario, quantitative predictions for the internal kinematics of dwarf galaxies can be made, which can be checked in the future to probe the nature of dark matter.</p><p> Furthermore, we take advantage of the overlap of ALFALFA with the Sloan Digital Sky Survey (SDSS), to measure the number density of galaxies as a function of their &ldquo;baryonic&rdquo; mass (stars + atomic gas). In the context of a &Lambda;CDM cosmological model, the measured distribution reveals that low-mass halos are heavily &ldquo;baryon depleted&rdquo;, i.e. their baryonic-to-dark mass ratio is much lower than the cosmological value. These baryon deficits are usually attributed to stellar feedback (e.g. supernova-driven gas outflows), but the efficiency implied by our measurement is extremely high. Whether such efficient feedback can be accommodated in a consistent picture of galaxy formation is an open question, and remains one of the principle scientific drivers for hydrodynamic simulations of galaxy formation.</p><p> Lastly, we measure the clustering properties of HI-selected samples, through the two-point correlation function of ALFALFA galaxies. We find no compelling evidence for a dependence of clustering on HI mass, suggesting that the relationship between galactic gas mass and host halo mass is not tight. We furthermore find that HI galaxies cluster more weakly than optically selected ones, when no color selection is applied. However, SDSS galaxies with blue colors have very similar clustering characteristics with ALFALFA galaxies, both in real as well as in redshift space. On the other hand, HI galaxies cluster much more weakly than optical galaxies with red colors, and in fact &ldquo;avoid&rdquo; being located within &ap;3 Mpc from the latter. By considering the clustering properties of &Lambda;CDM halos, we confirm our previous intuition for an <i>M_HI-M_h</i> relation with large scatter, and find that spin parameter may be a key halo property related to the gas content of present-day galaxies.</p>

This thesis refers to windshear recovery systems, designed to increase the survival capability of an aircraft. It is known that optimal trajectories in take-off are difficult to implement because of the lack of global information on the wind flow field and the lack of enough time and computing capability onboard. Consequently, one is forced to employ local/prior information on the windshear and the downdraft. An investigation of the gamma guidance scheme is presented with reference to the take-off problem. Attention is focused on the feedback control form of the gamma guidance law. This law is modified so that not only the aircraft can react to unfavorable shears, but can take advantage of favorable shears. Indeed, every unfavorable shear (central core of the downburst) is both preceded and followed by favorable shears. Therefore, a systematic investigation of the effect of parameters on survival capability is presented for two windshear models. The results indicate that, through a proper choice of the parameters, the windshear efficiency of the gamma guidance law is within 5% of that of an optimal trajectory. (Abstract shortened with permission of author.)

This thesis studies the Bowen resonance fluorescence mechanism of OIII in three planetary nebulae: NGC 6210, 7027, and 7662. It utilizes the best spectra to date of this phenomena in the wavelength range of 3100 A-3850 A. The data are presented in the form of flux ratios relative to the strong 3444.1 A line and compared to expectations based on current theory. Harrington's theoretical predictions which take into account the additional enhancement of some of the Bowen resonance fluorescence lines due to pumping of next higher energy level, OIII 2p3d $\sp3$P$\sbsp{1}{0}$, show agreement with NGC 7027 and 7662; however, predictions by Neufeld agree poorly for all three planetary nebulae studied. Enhancement by charge exchange reactions is quite evident in NGC 6210. Finally, the HeII 3203 A line is used to determine efficiencies of 0.57 and 0.48 for NGC 7027 and 7662 respectively, only slightly higher than Kallman and McCray's prediction of 0.42; while NGC 6210 yielded an impossible value of 1.37.

The common defining factor of coronae is a distinct annulus of tectonic origin. Current coronae classification is based on an intensive study of coronae primarily with maximum widths in excess of 100 km. Topographically coronae with maximum widths in excess of 250 km tend to exhibit raised interiors with exterior rim and moat structures, which may or may not correspond to coronae annuli. These coronae are believed to be the result of gravitational relaxation of a diapir or hot-spot generated uplift. This mode of formation however, does not account for small coronae, coronae with diameters less than 200 km, that tend to exhibit depressed interiors with down-dropped or topographically level annuli. These small coronae represent caldera-like activity on Venus.

Results of spectral analysis and time series analysis of the transient source x-ray nova Velorum 1993 (GRS 1009-45) and x-ray nova Ophicuhus 1993 (GRS 1716-249) are presented. These data were accumulated using the OSSE (Oriented Scintillation Spectrometer Experiment) low-energy gamma ray telescope on the Compton Gamma Ray Observatory. Spectral observations of the two x-ray novae showed the presence of gamma ray emission to greater than 100 keV, which is thought to be a signature of a binary system with an accreting black hole. Observations of GRS 1009-45 shows that it was in a gamma-ray soft state during the one-day OSSE observation, which occurred during the exponential decay phase of the outburst. The spectrum of GRS 2716-249 acquired during the plateau stage of outburst indicated a hard state, while spectra acquired during the sawtooth outbursts suggest that a hard to soft transition occurs as the decay progresses. The 40-200 keV pre-outburst luminosity of GRS 1716-249 is shown to be two orders of magnitude less than that estimated during the plateau-stage observation. The only significant power density spectrum was that acquired for GRS 1716-249 during the plateau stage of outburst. It is consistent with the sum of two QPO peaks at 0.128 and 0.32 Hz and a red noise ($\nu\sp{-1}$) component. This power spectrum is consistent with other black hole candidate power spectra for which the source is in the low state. Power spectra for GRS 1009-45 and GRS 1716-249 during the peak of a sawtooth outburst are also presented. They are consistent with band-limited white noise. Corresponding autocorrelations are shown for all observations.