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Modeling Asymmetry in the Rotation of Disk Galaxies
No full textGalaxy rotation has been studied for over a century, using spectroscopic measurements to construct rotational models that describe the motions of their gas and stars. However, only a small subset of this work has recognized that galaxies are not entirely radially symmetrical, but are instead often disrupted in ways that simple velocity field models cannot capture. In this dissertation, I describe my work modelling nonaxisymmetric galaxy rotation and the astrophysical insights gained from these models.Gravitational lensing distorts a galaxy's velocity field in a manner distinct from the distortions of its photometric shape, an effect called kinematic weak lensing. This allows for the construction of a model that uses this difference to extract lensing information about the system. I detail the properties and strengths of such a model, finding that for mock observations of source galaxies at moderate redshifts, the signal-to-noise of the lensing measurements improves by up to a factor of six over previous works, enabling the possibility of future lensing studies independent of current weak lensing systematic constraints.I also describe the development of Nirvana, a Bayesian nonparametric velocity field fitting code designed to describe the bisymmetric motions present in barred galaxies. Using a sample of barred galaxies from the MaNGA survey, I construct the Nirvana-MaNGA sample, which is comprised of velocity field models of >1000 local barred galaxies, as well as a matched control sample of unbarred galaxies. Nirvana determines bar strength and location independent of imaging, providing an independent and direct test of dynamical models of higher-order noncircular motions in bars, agreeing with visual bar classifications on bar angle. I also find direct evidence of flattening in stellar population gradients along bar kinematic axes as compared to surrounding disk regions at the same radii, verifying results reliant on visual classifications and affirming the dynamic connection between the presence of bars and radial mixing of stellar populations
Observational Disk Dynamics of Late-Type Galaxies
No full text(Abridged) The primary concern of this thesis is the measurement of the stellar velocity ellipsoid (SVE) in galaxy disks. While a few attempts exist in the literature, we know of no study providing as detailed a discussion of the empirical procedure nor of the associated errors in SVE measurements as that presented herein. This is despite the relevance of the SVE to galaxy-disk dynamics as it quantifies, in gross terms, the stellar phase-space distribution function, but largely due to the observational expense of the measurement. We address the observational obstacles by using the WIYN SparsePak integral-field unit, which is well-suited to measuring line-of-sight kinematics in the low-surface-brightness, low-velocity-dispersion regime presented by galaxy disks. Thus, we obtain ionized gas and stellar kinematics for seven galaxies and characterize the SVE using a set of six decomposition methods resulting from consideration of four dynamical relations pulled from the literature and theories of galactic dynamics. These analyses have resulted in the following conclusions: (1) We find general agreement with the results of previous SVE studies; however, we do not confirm a cold-to-hot progression of "disk temperature'' from late- to early-type (Sa) galaxies due to the dominance of different secular processes. The mean vertical-to-radial axial ratio is 0.66 for our sample. (2) Five of seven galaxies show a Toomre stability criterion of Q˜3 the others are only marginally stable with Q˜1. (3) We find indications of a nearly constant line-of-sight velocity dispersion in the extended parts of at least three galaxies, implying an increase in the mass-to-light ratio by factors of a few at these radii. We acknowledge support from the NSF (AST-9970780, AST-0307417, AST-0607516), UW Graduate School (PRJ13SL, 050167, and the Vilas Associate award), and NASA/JPL/Spitzer (GO-30894). KBW is currently supported by an NSF International Research Fellowship (OISE-0754437)
Observational Disk Dynamics of Late-Type Galaxies
No full text(Abridged) The primary concern of this thesis is the measurement of the stellar velocity ellipsoid (SVE) in galaxy disks. While a few attempts exist in the literature, we know of no study providing as detailed a discussion of the empirical procedure nor of the associated errors in SVE measurements as that presented herein. This is despite the relevance of the SVE to galaxy-disk dynamics as it quantifies, in gross terms, the stellar phase-space distribution function, but largely due to the observational expense of the measurement. We address the observational obstacles by using the WIYN SparsePak integral-field unit, which is well-suited to measuring line-of-sight kinematics in the low-surface-brightness, low-velocity-dispersion regime presented by galaxy disks. Thus, we obtain ionized gas and stellar kinematics for seven galaxies and characterize the SVE using a set of six decomposition methods resulting from consideration of four dynamical relations pulled from the literature and theories of galactic dynamics. These analyses have resulted in the following conclusions: (1) We find general agreement with the results of previous SVE studies; however, we do not confirm a cold-to-hot progression of "disk temperature'' from late- to early-type (Sa) galaxies due to the dominance of different secular processes. The mean vertical-to-radial axial ratio is 0.66 for our sample. (2) Five of seven galaxies show a Toomre stability criterion of Q˜3 the others are only marginally stable with Q˜1. (3) We find indications of a nearly constant line-of-sight velocity dispersion in the extended parts of at least three galaxies, implying an increase in the mass-to-light ratio by factors of a few at these radii. We acknowledge support from the NSF (AST-9970780, AST-0307417, AST-0607516), UW Graduate School (PRJ13SL, 050167, and the Vilas Associate award), and NASA/JPL/Spitzer (GO-30894). KBW is currently supported by an NSF International Research Fellowship (OISE-0754437)
Observational Disk Dynamics of Late-Type Galaxies
No full text(Abridged) The primary concern of this thesis is the measurement of the stellar velocity ellipsoid (SVE) in galaxy disks. While a few attempts exist in the literature, we know of no study providing as detailed a discussion of the empirical procedure nor of the associated errors in SVE measurements as that presented herein. This is despite the relevance of the SVE to galaxy-disk dynamics as it quantifies, in gross terms, the stellar phase-space distribution function, but largely due to the observational expense of the measurement. We address the observational obstacles by using the WIYN SparsePak integral-field unit, which is well-suited to measuring line-of-sight kinematics in the low-surface-brightness, low-velocity-dispersion regime presented by galaxy disks. Thus, we obtain ionized gas and stellar kinematics for seven galaxies and characterize the SVE using a set of six decomposition methods resulting from consideration of four dynamical relations pulled from the literature and theories of galactic dynamics. These analyses have resulted in the following conclusions: (1) We find general agreement with the results of previous SVE studies; however, we do not confirm a cold-to-hot progression of "disk temperature'' from late- to early-type (Sa) galaxies due to the dominance of different secular processes. The mean vertical-to-radial axial ratio is 0.66 for our sample. (2) Five of seven galaxies show a Toomre stability criterion of Q˜3 the others are only marginally stable with Q˜1. (3) We find indications of a nearly constant line-of-sight velocity dispersion in the extended parts of at least three galaxies, implying an increase in the mass-to-light ratio by factors of a few at these radii. We acknowledge support from the NSF (AST-9970780, AST-0307417, AST-0607516), UW Graduate School (PRJ13SL, 050167, and the Vilas Associate award), and NASA/JPL/Spitzer (GO-30894). KBW is currently supported by an NSF International Research Fellowship (OISE-0754437)
The Nature of This Debate: A Look at the Texas Foreign Corporation Venue Rule and a Method for Analyzing the Premises and Promises of Tort Reform
No full textThe author examines the implications of the Texas venue rule for foreign corporations engaged in litigation. The article critically analyzes how the venue rule interacts with broader tort reform efforts in the state, particularly concerning access to justice and the rights of plaintiffs. By exploring various legal perspectives and case studies, the author identifies key challenges and contradictions within the current framework. The discussion highlights the potential consequences of tort reform on the legal landscape and its impact on both businesses and consumers. Ultimately, the article advocates for a balanced approach that safeguards fair litigation practices while considering the interests of foreign corporations
The DiskMass Survey: III. Stellar Kinematics Via Cross-Correlation
No full textWe describe a new cross-correlation (CC) approach used by our survey to derive stellar kinematics from galaxy-continuum spectroscopy. This approach adopts the formal error analysis derived by Statler, but properly handles spectral masks. Thus, we address the primary concerns regarding application of the CC method to censored data, while maintaining its primary advantage by consolidating kinematic and template-mismatch information toward different regions of the CC function. We identify a systematic error in the nominal CC method of approximately 10% in velocity dispersion incurred by a mistreatment of detector-censored data, which is eliminated by our new method. We derive our approach from first principles, and we use Monte Carlo simulations to demonstrate its efficacy. An identical set of Monte Carlo simulations performed using the well-established penalized-pixel-fitting code of Cappellari & Emsellem compares favorably with the results from our newly implemented software. Finally, we provide a practical demonstration of this software by extracting stellar kinematics from SparsePak spectra of UGC 6918
Metabolic profiling and population screening of analgesic usage in nuclear magnetic resonance spectroscopy-based large-scale epidemiologic studies
No full textThe application of a 1H nuclear magnetic resonance (NMR) spectroscopy-based screening method for determining the use of two widely available analgesics (acetaminophen and ibuprofen) in epidemiologic studies has been investigated. We used samples and data from the cross-sectional INTERMAP Study involving participants from Japan (n = 1145), China (n = 839), U.K. (n = 501), and the U.S. (n = 2195). An orthogonal projection to latent structures discriminant analysis (OPLS-DA) algorithm with an incorporated Monte Carlo resampling function was applied to the NMR data set to determine which spectra contained analgesic metabolites. OPLS-DA preprocessing parameters (normalization, bin width, scaling, and input parameters) were assessed systematically to identify an optimal acetaminophen prediction model. Subsets of INTERMAP spectra were examined to verify and validate the presence/absence of acetaminophen/ibuprofen based on known chemical shift and coupling patterns. The optimized and validated acetaminophen model correctly predicted 98.2%, and the ibuprofen model correctly predicted 99.0% of the urine specimens containing these drug metabolites. The acetaminophen and ibuprofen models were subsequently used to predict the presence/absence of these drug metabolites for the remaining INTERMAP specimens. The acetaminophen model identified 415 out of 8436 spectra as containing acetaminophen metabolite signals while the ibuprofen model identified 245 out of 8604 spectra as containing ibuprofen metabolite signals from the global data set after excluding samples used to construct the prediction models. The NMR-based metabolic screening strategy provides a new objective approach for evaluation of self-reported medication data and is extendable to other aspects of population xenometabolome profiling
Recombination Ghosts in Littrow Configuration: Implications for Spectrographs Using Volume Phase Holographic Gratings
No full textGalaxy disks are submaximal
No full textWe measure the contribution of galaxy disks to the overall gravitational potential of 30 nearly face-on intermediate-to-late-type spirals from the DiskMass Survey. The central vertical velocity dispersion of the disk stars (\u3c3disk z, R = 0) is related to the maximum rotation speed (V max) as \u3c3disk z, R = 0 ~ 0.26V max, consistent with previous measurements for edge-on disk galaxies and a mean stellar velocity ellipsoid axial ratio \u3b1 61 \u3c3 z /\u3c3 R = 0.6. For reasonable values of disk oblateness, this relation implies these galaxy disks are submaximal. We find disks in our sample contribute only 15%-30% of the dynamical mass within 2.2 disk scale lengths (hR ), with percentages increasing systematically with luminosity, rotation speed, and redder color. These trends indicate that the mass ratio of disk-to-total matter remains at or below 50% at 2.2 hR even for the most extreme, fast-rotating disks (V max 65 300 km s\u207b\ub9) of the reddest rest frame, face-on color (B \u2013 K ~ 4 mag), and highest luminosity (MK < \u201326.5 mag). Therefore, spiral disks in general should be submaximal. Our results imply that the stellar mass-to-light ratio and hence the accounting of baryons in stars should be lowered by at least a factor of three.Peer reviewed: YesNRC publication: Ye
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