A new technique for ground based photometric helioseismology has been implemented. The technique is able to detect low amplitude oscillations in the solar irradiance by making simultaneous measurements at continuum wavelengths of 0.507 μm, 0.747 μm, and 1.600 μm. Data is collected from a rectangular region covering approximately 57% of the solar disk, extending ±0.30 R(⊙) about the solar rotational axis, and ±0.38 R(⊙) about the solar equator, using square pixels varying in linear size from 0.032 R(⊙) to 0.053 R(⊙). A differential spatial filter is applied, taking advantage of cancellations of undesired variations and forming a signal which is sensitive to most modes with spherical harmonic index l ≤ 7. Linear combinations are made of the three solar signals and the telescope internal Temperature signal, mitigating the deleterious effects of the terrestrial atmosphere and of local temperature variations. Frequencies of local maxima in the Power Spectrum of the residual signal, in the 400 μHz to 850 μHz range, are found to be consistent with those determined by solar limb profile measurements made in 1979. The measured coincidence levels indicate that the probability that the 1979 and 1999 data sets are random with respect to one another is approximately 5 x 10⁻⁹. Frequency shifts between the 1979 data and the 1999 data, possibly related to the solar activity cycle, are found: δν(n=1;l=4,...,7) = -0.16 ± 0.01 μHz, δν(n=2;l=3,...,7) = -0.04 ± 0.01 μHz, and δν(n=3;l=2,...,4) = -0.11 ± 0.01 μHz.

This dissertation reports on the first "5-minute" solar oscillation observations obtained with the Photometric Telescope, an instrument constructed in the Department of Physics at the University of Arizona. The instrument is designed to simultaneously acquire spatially resolved intensity images of the solar surface at three wavelengths in the solar continuum: 507 nm, 747 nm, and 1600 nm. Images were recorded at an approximate 30 second cadence, weather permitting, for an approximate 3 month duration during the Spring of 1999. A central rectangular region of the solar disk spanning ±0.53 R(⊙) in a direction parallel to the solar equator and ±0.636 R(⊙) in a direction parallel to the solar axis is used in obtaining the "5-minute" results. Differential spatial filters utilizing the natural logarithm are developed. Proper design of these filters allows great reductions in the sensitivity to terrestrial atmospheric fluctuations as well as instrumental noise sources such as image fitter. The processing techniques utilized allow the simultaneous observation of solar oscillations in the 2500 to 3600 μHz region at each of the three instrumental wavelengths. The spatial filters used have high sensitivity to modes in the ℓ = 4 to ℓ = 8 range. One-day power spectra from 40 long observing days are averaged. Concurrent data from the SOHO satellite's Luminosity Oscillation Imager is analyzed in a similar manner showing results in outstanding agreement with the Photometric Telescope spectra. Further comparison of measured power spectra peak locations with theoretically predicted peak locations verifies the Photometric Telescope as a capable helioseismology instrument. New "5-minute" oscillation results are also presented. The amplitudes of the individual "5-minute" oscillations are on the order of 10-100 ppm, in agreement with previous amplitude measurements. While these amplitudes vary greatly depending on the details of the stochastic excitation, the oscillation amplitude ratios and phase differences of solar oscillations for the 507 nm, 747 nm, and 1600 nm wavelengths can be measured with a high degree of accuracy. This dissertation reports the first such measurements. The amplitude ratios (I'/I)₇₄₇/(I'/I)₅₀₇ ∼ 0.6 and (I'/I)₁₆₀₀/(I'/I)₅₀₇) ∼ 0.25 are found to be independent of frequency over the frequency region studied and nearly independent of the angular degree of the mode. By contrast, the relative phase differences (φ₇₄₇ - φ₅₀₇) and (φ₁₆₀₀ - φ₅₀₇) are found to have a significant frequency dependence and to depend somewhat sensitively on the angular degree of the mode. The measured wavelength dependent amplitude and phase relationships provide an invaluable diagnostic tool which can be used in future work to help identify longer period and lower amplitude oscillatory modes.

The evolution of low- and intermediate-mass stars (1M(⊙) - 8M(⊙)) from the Asymptotic Giant Branch (AGB) to the Planetary Nebula (PN) phase is a poorly understood phase of stellar evolution. We have observed a sample of AGB stars, Proto-Planetary and Planetary Nebulae (PPNe and PNe) at thermal-infrared and millimeter wavelengths. The thermal-infrared emission comes from the warm dust (T(dust) ≈ 100-300 K) circumstellar shells. Images at these wavelengths provide a unique "close-up" look at the morphology of these sources, and therefore allow us to constrain the geometry and/or mass loss rates on short dynamical timescales. The millimeter-wave observations probe the extended circumstellar molecular envelopes; therefore they provide valuable spatial and kinematical information on the larger scales (and over longer dynamical timescales) than the mid-IR images. Our results show that the dust shells of all the planetary and proto-planetary nebulae (PPNe and PNe) in our study are not spherical; those that are well-resolved appear to be bipolar and can be modeled with axially symmetric models. They strongly suggest that the evolution from AGB to PN is often accompanied by higher mass loss rates in the equatorial plane than in the polar regions, as predicted by binary star (common envelope) evolution models, or models involving stellar rotation. At least one bipolar nebula (M 4-18) appears to be a single, low-mass star. From our mid-IR images at feature wavelengths we find that the spatial distribution of the carbonaceous and silicate grains varies over the surface of the nebulae. IC 5117 shows evidence for stratification of carbon- and oxygen-based grains and suggests that some PNe go through temporal changes in circumstellar chemistry (from oxygen-rich to carbon-rich) as they evolve off the AGB. The molecular envelopes of the sources in our study can be modeled with spherically symmetric models though two sources (IRC + 10216 and AFGL 2343) show kinematical and spatial evidence for departures from spherical symmetry. Our millimeter observations of IRC + 10216 also provide confirmation that the interstellar UV photons initiate a variety of photochemical reactions in circumstellar envelopes of AGB stars and PNe.

FASTTRAC (Fast Adaptive Secondary for Tip-Tilt Removal by Automatic Centroiding) is a tip-tilt secondary system which increases the angular resolution of images taken at Steward Observatory's 90" Bok and 61" Bigelow telescopes. K band imagery is gathered with the facility infrared camera and wavefront sensing is done with a small format charge-coupled device (CCD). I examine desirable characteristics of wavefront-sensing CCDs and evaluate the performance of the device used in FASTTRAC according to those criteria. The main drawback of the device is its low quantum efficiency due to frontside illumination. The read noise of the system is adequate, particularly for FASTTRAC which is generally assigned to bright time. The increased angular resolution provided by FASTTRAC is desirable for imaging crowded fields, such as those found in Local Group galaxies. Stellar photometry is a more powerful tool for studying the structure of these galaxies than is surface photometry, in which the light from all types of stars is mixed together. In particular, the distribution of old stars is representative of the underlying mass distribution, so these stars may be used to measure the overdensity in the arms of spiral galaxies. FASTTRAC was used to observe fields in M33, the nearest spiral which is not seen edge-on. These fields were observed in a range of seeing conditions and with guide stars of varying magnitudes and positions relative to the fields of interest. I analyze the performance of FASTTRAC in these varying conditions and offer some advice to future FASTTRAC observers. I also analyze the crowding in the M33 fields and conclude that, to K∼16.5, it does not vary significantly with placement in or outside of a spiral arm. Therefore a coarsely-sampled, wide field survey of the populations of M33 will not be systematically biased by crowding. Therefore a survey covering 35' by 25' was conducted in I and K bands, covering all of M33 out to a deprojected radius of 16'. The resulting star catalogs reach a depth of about I=21.5 and Ks When plotted on a color-magnitude diagram, these stars separate into a young population of red supergiants and an older population of red giants. The giants are old enough to have experienced many orbits and are thus representative of the mass distribution of the galaxy. The fraction of K-band light which is "young" is only 5-10% indicating that surface photometry in general would not be terribly biased, but there are local variations in which the young component is much stronger. Fourier decomposition of the old catalog reveals significant amplitudes (up to 0.5), indicating that the galaxy does indeed contain local overdensities, which supports the basic idea of spiral density wave theory. The strongest component in M33 is one-armed or lopsidedness, with some power in the two-armed component and much less in the higher-order components. The two-armed component may in fact represent a bar in the inner few arcminutes.

The purpose of this study is to understand the space density and properties of active galaxies to z ∼eq 0.8. We have investigated the frequency and nature of unresolved nuclei in galaxies at moderate redshift as indicators of nuclear activity such as Active Galactic Nuclei (AGN) or starbursts. Candidates are selected by fitting imaged galaxies with multi-component models using maximum likelihood estimate techniques to determine the best model fit. We select those galaxies requiring an unresolved, point source component in the galaxy nucleus, in addition to a disk and/or bulge component, to adequately model the galaxy light.

In this dissertation the results of a ten-year spectrophotometric survey of comets are presented. By measuring in a systematic way the production rates of C₂ NH₂, CN, and H₂O released from the nucleus, we sought to explore comet-to-comet variations that may yield clues to conditions in the early solar nebula. We classify our observed comets into four taxonomic classes (Type I, II, III, IV). The two classes which comprise the great majority of our sample (Type I and II) were also discerned in the recent survey by A'Hearn et al. (1996) and in general can be thought of as "normal" and "C₂ depleted" comets. It is argued that the "normal" comets in general originate in the inner comet forming regions at the distances of Uranus and Neptune whereas the "C₂ depleted" may originate in the inner edge of the Kuiper disk. Evolved from our interest in extinct cometary candidates, we present the results of out near-Earth asteroid spectroscopy survey. Though taken at a wavelength range that makes firm classification difficult (0.5-1.0μm) we find that in general our sample is much closer spectroscopically to the ordinary chondrites and basaltic achondrites than to the spectra of main-belt asteroids, firming the link between near-Earth asteroids and meteorites.

This thesis examines the properties of star forming regions in galaxies across the Hubble sequence. It focuses on the stellar populations of giant extragalactic H scII regions and OB associations, addressing in particular the question of Initial Mass Function (IMF) variations with metallicity and/or galaxy morphology. This work is composed of three main sections: (a) 3650-10,000 Å spectroscopy of nearly 100 H scII regions in 20 spiral galaxies (Sa through Sm). Two indicators of the ionizing cluster effective temperature (T ͙) are analyzed: the intensity of the He I λ5876 line, and the 'radiation softness' parameter η = (O⁺O⁺⁺)/(S⁺S⁺⁺). The interpretation of the data relies on CLOUDY photoionization models. A positive T ͙ gradient of 7000-8000 K is found between 2 Z(⊙) and 0.2 Z(⊙). The diagnostic diagrams and the T ͙ - metallicity relation are consistent with an upper mass limit of the IMF of ∼100 M(⊙) and an age of ∼1 Myr, irrespective of chemical abundance or Hubble type. (b) An investigation of extragalactic OB associations, based on Hubble Space Telescope images. The size distribution of the associations (found with an automated search algorithm) is similar in all galaxies examined, with a mean size around 80 pc. An indication is found that the average number of bright blue stars depends on the parent galaxy Hubble type. The upper stellar V luminosity function is comparable among galaxies, with slope d log N/dMᵥ=0.61±0.03. A few star cluster candidates are identified. (c) UBVR and Hα photometry of 266 H II regions in 10 spiral galaxies (Sa through Sd). The Hα equivalent width is independent of Hubble type. The continuum and Hα luminosity functions show similar trends, namely a steeper slope and a smaller characteristic luminosity for early-type galaxies. These results lead to the conclusion that changes in the properties of H II regions and associations along the Hubble sequence are most likely due to variations in the number of stars per star forming region and in the number of regions per unit area, rather than the mass function.

A multi-pronged study aimed at disentangling the kinematical signatures of the earliest stages of star formation is presented. Radiative transfer calculations of millimeter and submillimeter molecular line emission from fully three-dimensional models of protostars are reported. These models are compared with detailed submillimeter molecular line observations of dynamical motions towards seven Class 0 protostellar objects. The radiative transfer calculations are performed for two classes of protostellar collapse solutions: (1) "self-consistent", nonspherical, hydrodynamic, collapsing, rotating protostellar systems (Boss 1993); (2) parameterized, semi-analytic, rotating collapse solutions of Terebey, Shu and Cassen (1984) The morphology of the gas and dust emission is found to be a strong function of collapse time and angular resolution. From model centroid velocity maps, a distinctive new infall signature called the "blue-bulge" infall signature is derived. The blue-bulge infall signature can be observed in the centroid velocity maps of protostellar objects when infall dominates over rotation. This infall signature can be detected under a wide variety of source conditions, and should be easily observable using single-dish submillimeter telescopes. At high angular resolutions, models with moderate to high rotational rates exhibit the "polar blue-bulge" - a centroid velocity signature of underlying Keplerian rotation in an embedded cloud core. Submillimeter transitions of HCO+ and CS are found to be better than millimeter transitions in detecting infall, especially at early collapse times. Using new submillimeter observations in CS and HCO+ towards IRAS 16293-2422, the first detection of the "blue-bulge" signature towards a protostellar object is presented. The mass accretion rate through the infall region appears consistent with an inside-out collapse model for the source. Using new submillimeter HCO+ and CO observations, a detailed study was performed of six other nearby Class 0 objects. The blue-bulge signature of infall is detected in five sources. Among these, SMM4 and B335 are known infall candidates. VLA 1623, L483 and L1262 are new sources for which evidence for infall is derived in this work. SM1N, which does not exhibit a blue-bulge appears to be a pre-protostellar object. A low luminosity bipolar outflow was detected toward SM1N, suggesting that it may be in an extremely early stage of collapse. Of the six sources, only three, SMM4, B335 and L1262 exhibited the classic blue asymmetric line profile signature of infall, suggesting that the blue-bulge signature is more robust in detecting infall than traditional line profile techniques. Evolutionary trends are seen between observationally obtainable source parameters and model derived timescales for the Class 0 sources presented in this work. Such a study when extended to a larger sample of YSOs will help in the understanding of the evolution of YSOs from the embedded protostellar stage to revealed pre-main-sequence objects.

Many asteroids show absorption features diagnostic of hydrated minerals in the 3-μm spectral region. Reflectance studies in this region can determine the hydration state of surface minerals, and by inference, the thermal histories of bodies. Observations of M-class asteroids from 1.25-3.5 μm show that many of these asteroids have water of hydration, and those that do cannot be interpreted as the cores of differentiated parent bodies. Because of this, it is suggested that the hydrated M asteroids should be split off into their own class--the W class. Simple spectral mixing models of these asteroids show they are consistent with enstatite chondritic material mixed with talc, suggesting the W asteroids may be the result of aqueous alteration of enstatite chondrites, though other models may also hold merit. The E asteroids are also found to have hydrated members, inconsistent with their interpretation as purely igneous bodies. A trend for large E and M asteroids to be hydrated is found. A compilation of S-class asteroid data at 3 μm has been performed, supporting the finding that some S asteroids have spectra consistent with a mixture of ordinary chondrite and metal. There is some evidence for a trend altering the spectra of near-Earth asteroids to look like main-belt asteroids, but no simple trend can also include the ordinary chondrite meteorites. Variation in asteroids at 3 mu m was studied, and while no clear evidence of rotational variation is found, there is circumstantial evidence for latitudinal variation on several asteroids, perhaps as interior layers of an aqueously altered body are excavated. Finally, high-resolution studies of C-class asteroids were performed. A finding that 1 Ceres' spectrum matches that of an ammoniated phyllosilicate is supported over an extended wavelength range. Observations of other CBG-class asteroids find no ammoniated minerals. The CBG-class asteroids, other than Ceres, all share very similar spectra, suggesting similar hydrated minerals on their surfaces.

I present the data for an optical/near-infrared study of radio-loud quasar environments from z = 0.6-2.0, and the analysis of the data from z = 1.0-2.0. I thoroughly discuss the sample selection, observing, data reduction, and object cataloging. Even accounting for possible systematic offsets, I find a significant excess of K ≳ 19 galaxies in the fields of z = 1-2 RLQs, on two spatial scales. One component is at θ <40'' from the quasars and is significant compared to the galaxy surface density at θ >40'' in the same fields. The other component appears roughly uniform across the fields (to θ∼100'') and is significant compared to the galaxy surface density seen in random-field surveys in the literature. The r-K color distributions of the excess galaxy populations are indistinguishable, and are significantly redder than the color distribution of the field population. The excess galaxy population is thus consistent with being predominantly early-type galaxies at the quasar redshifts. The average excess within 0.5h⁻¹₇₅ Mpc $(∼65'') of the quasars corresponds to Abell richness class ∼0 compared to the galaxy surface density at >0.5h⁻¹₇₅ Mpc from the quasars, and to Abell richness class ∼1 compared to that from the literature. I estimate -0.65⁺⁰·⁴¹₋₀.₅₅ magnitudes of evolution in M*(K) to z̄ = 1.67 by assuming the excess galaxies are at the quasar redshifts. I discuss the spectral energy distributions (SEDs) of galaxies in fields with data in several passbands. Most candidate quasar-associated galaxies are consistent with being 2-3 Gyr old early-types at the quasar redshifts of z∼1.5. However, some objects have SEDs similar to extremely late-type stars; others have SEDs consistent with being 4-5 Gyr old at z∼1.5 and others are consistent with old but dust-reddened galaxies at the quasar redshifts. These potentially different galaxy types suggest there may be considerable dispersion in the properties of early-type cluster galaxies at z∼1.5. There is also a population of galaxies whose SEDs are best modelled by background galaxies at z≳2.5, Many of these are dusty or have composite stellar populations, or both, and some may be ≳2 Gyr old at z≳ 2.5. Confirmation of old galaxies at high redshift would constrain the cosmology by requiring a relatively old universe at large lookback times.