Browsing by Subject "statistics"

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A Statistical Methodology for Prediction Salinity in Upper Lavaca Bay
(University of Texas at Austin, 1982-06) Hisao Yamada, S.; Armstrong, N.E.
Answering the Call
(The Texas Scientist, 2021) The Texas Scientist
Corwin Zigler
(The Texas Scientist, 2020) The Texas Scientist
GEMS : Galaxy Fitting Catalogs and Testing Parametric Galaxy Fitting Codes : GALFIT and GIM2D
(2007-10) Haeussler, Boris; McIntosh, Daniel H.; Barden, Marco; Bell, Eric F.; Rix, Hans-Walter; Borch, Andrea; Beckwith, Steven V. W.; Caldwell, John A. R.; Heymans, Catherine; Jahnke, Knud; Jogee, Shardha; Koposov, Sergey E.; Meisenheimer, Klaus; Sanchez, Sebastian F.; Somerville, Rachel S.; Wisotzki, Lutz; Wolf, Christian; Caldwell, John A. R.
In the context of measuring the structures of intermediate-redshift galaxies with HST ACS surveys, we tune, test, and compare two widely used fitting codes (GALFIT and GIM2D) for fitting single-component Sersic models to both simulated and real galaxy data. Our study focuses on the GEMS survey with the sensitivity of typical HST survey data, and we include our final catalog of fit results for all 41,495 objects detected in GEMS. Using simulations, we find that fitting accuracy depends sensitively on galaxy profile shape. Exponential disks are well fit and have small measurement errors, whereas fits to de Vaucouleurs profiles show larger uncertainties owing to the large amount of light at large radii. Both codes provide reliable fits with little systematic error for galaxies with effective surface brightnesses brighter than that of the sky; the formal uncertainties returned by these codes significantly underestimate the true uncertainties (as estimated using the simulations). We find that GIM2D suffers significant systematic errors for spheroids with close companions owing to the difficulty of effectively masking out neighboring galaxy light; there appears to be no work-around to this important systematic in GIM2D's current implementation. While this crowding error affects only a small fraction of galaxies in GEMS, it must be accounted for in the analysis of deeper cosmological images or of more crowded fields with GIM2D. In contrast, GALFIT results are robust to the presence of neighbors because it can simultaneously fit the profiles of multiple companions as well as the galaxy of interest. We find GALFIT's robustness to nearby companions and factor of greater than or similar to 20 faster runtime speed are important advantages over GIM2D for analyzing large HST ACS data sets.
The M-Sigma And M-L Relations In Galactic Bulges, And Determinations Of Their Intrinsic Scatter
(2009-06) Gultekin, Kayhan; Richstone, Douglas O.; Gebhardt, Karl; Lauer, Tod R.; Tremaine, Scott; Aller, Monique C.; Bender, Ralf; Dressler, Alan; Faber, S. M.; Filippenko, Alexei V.; Green, Richard; Ho, Luis C.; Kormendy, John; Magorrian, John; Pinkney, Jason; Siopis, Christos; Gebhardt, Karl; Kormendy, John
We derive improved versions of the relations between supermassive black hole mass (MBH) and host-galaxy bulge velocity dispersion (sigma) and luminosity (L; the M-sigma and M-L relations), based on 49 M-BH measurements and 19 upper limits. Particular attention is paid to recovery of the intrinsic scatter (epsilon(0)) in both relations. We find log(M-BH/M-circle dot) = alpha + beta log(sigma/ 200 km s(-1)) with (alpha, beta, epsilon(0)) = (8.12 +/- 0.08, 4.24 +/- 0.41, 0.44 +/- 0.06) for all galaxies and (alpha, beta, epsilon(0)) = (8.23 +/- 0.08, 3.96 +/- 0.42, 0.31 +/- 0.06) for ellipticals. The results for ellipticals are consistent with previous studies, but the intrinsic scatter recovered for spirals is significantly larger. The scatter inferred reinforces the need for its consideration when calculating local black hole mass function based on the M-sigma relation, and further implies that there may be substantial selection bias in studies of the evolution of the M-sigma relation. We estimate the M-L relationship as log(M-BH/M-circle dot) = alpha + beta log(L-V/10(11) L-circle dot,L- V) of (alpha, beta, epsilon(0)) = (8.95 +/- 0.11, 1.11 +/- 0.18, 0.38 +/- 0.09); using only early-type galaxies. These results appear to be insensitive to a wide range of assumptions about the measurement errors and the distribution of intrinsic scatter. We show that culling the sample according to the resolution of the black hole's sphere of influence biases the relations to larger mean masses, larger slopes, and incorrect intrinsic residuals.
The Milky Way Tomography With SDSS. III. Stellar Kinematics
(2010-06) Bond, Nicholas A.; Ivezic, Zeljko; Sesar, Branimir; Juric, Mario; Munn, Jeffrey A.; Kowalski, Adam; Loebman, Sarah; Roskar, Rok; Beers, Timothy C.; Dalcanton, Julianne; Rockosi, Constance M.; Yanny, Brian; Newberg, Heidi J.; Prieto, Carlos Allende; Wilhelm, Ron; Lee, Young Sun; Sivarani, Thirupathi; Majewski, Steven R.; Norris, John E.; Bailer-Jones, Coryn A. L.; Fiorentin, Paola Re; Schlegel, David; Uomoto, Alan; Lupton, Robert H.; Knapp, Gillian R.; Gunn, James E.; Covey, Kevin R.; Smith, J. Allyn; Miknaitis, Gajus; Doi, Mamoru; Tanaka, Masayuki; Fukugita, Masataka; Kent, Steve; Finkbeiner, Douglas; Quinn, Tom R.; Hawley, Suzanne; Anderson, Scott; Kiuchi, Furea; Chen, Alex; Bushong, James; Sohi, Harkirat; Haggard, Daryl; Kimball, Amy; McGurk, Rosalie; Barentine, John; Brewington, Howard; Harvanek, Mike; Kleinman, Scott; Krzesinski, Jurek; Long, Dan; Nitta, Atsuko; Snedden, Stephanie; Lee, Brian; Pier, Jeffrey R.; Harris, Hugh; Brinkmann, Jonathan; Schneider, Donald P.; Prieto, Carlos Allende
We study Milky Way kinematics using a sample of 18.8 million main-sequence stars with r < 20 and proper-motion measurements derived from Sloan Digital Sky Survey (SDSS) and POSS astrometry, including similar to 170,000 stars with radial-velocity measurements from the SDSS spectroscopic survey. Distances to stars are determined using a photometric-parallax relation, covering a distance range from similar to 100 pc to 10 kpc over a quarter of the sky at high Galactic latitudes (|b| > 20 degrees). We find that in the region defined by 1 kpc < Z < 5 kpc and 3 kpc < R < 13 kpc, the rotational velocity for disk stars smoothly decreases, and all three components of the velocity dispersion increase, with distance from the Galactic plane. In contrast, the velocity ellipsoid for halo stars is aligned with a spherical coordinate system and appears to be spatially invariant within the probed volume. The velocity distribution of nearby (Z < 1 kpc) K/M stars is complex, and cannot be described by a standard Schwarzschild ellipsoid. For stars in a distance-limited subsample of stars (< 100 pc), we detect a multi-modal velocity distribution consistent with that seen by HIPPARCOS. This strong non-Gaussianity significantly affects the measurements of the velocity-ellipsoid tilt and vertex deviation when using the Schwarzschild approximation. We develop and test a simple descriptive model for the overall kinematic behavior that captures these features over most of the probed volume, and can be used to search for substructure in kinematic and metallicity space. We use this model to predict further improvements in kinematic mapping of the Galaxy expected from Gaia and the Large Synoptic Survey Telescope.
The Multiwavelength Survey By Yale-Chile (MUSYC) Wide K-Band Imaging, Photometric Catalogs, Clustering, And Physical Properties Of Galaxies At Z Similar To 2
(2008-07) Blanc, Guillermo A.; Lira, Paulina; Barrientos, L. Felipe; Aguirre, Paula; Francke, Harod; Taylor, Edward N.; Quadri, Ryan; Marchesini, Danilo; Infante, Leopoldo; Gawiser, Eric; Hall, Patrick B.; Willis, Jon P.; Herrera, David; Maza, Jose; Blanc, Guillermo A.
We present K-band imaging of two similar to 30' x 30' fields covered by the Multiwavelength Survey by Yale-Chile (MUSYC) Wide NIR Survey. The SDSS 1030+05 and Cast 1255 fields were imaged with the Infrared Side Port Imager (ISPI) on the 4 m Blanco telescope at the Cerro Tololo Inter-American Observatory (CTIO) to a 5 sigma point-source limiting depth of K similar to 20 (Vega). Combining these data with the MUSYC optical UBVRIz imaging, we created multiband K-selected source catalogs for both fields. These catalogs, together with the MUSYC K-band catalog of the Extended Chandra Deep Field South (ECDF-S) field, were used to select K 20 BzK galaxies over an area of 0.71 deg(2). This is the largest area ever surveyed for BzK galaxies. We present number counts, redshift distributions, and stellar masses for our sample of 3261 BzK galaxies (2502 star-forming [sBzK] and 759 passively evolving [pBzK]), as well as reddening and star formation rate estimates for the star-forming BzK systems. We also present two-point angular correlation functions and spatial correlation lengths for both sBzK and pBzK galaxies and show that previous estimates of the correlation function of these galaxies were affected by cosmic variance due to the small areas surveyed. We have measured correlation lengths r(0) of 8.89 +/- 2.03 and 10.82 +/- 1.72 Mpc for sBzK and pBzK galaxies, respectively. This is the first reported measurement of the spatial correlation function of passive BzK galaxies. In the Lambda CDM scenario of galaxy formation, these correlation lengths at z similar to 2 translate into minimum masses of similar to 4 x 10(12) and similar to 9 x 10(12) M(circle dot) for the dark matter halos hosting sBzK and pBzK galaxies, respectively. The clustering properties of the galaxies in our sample are consistent with their being the descendants of bright Lyman break galaxies at z similar to 3, and the progenitors of present-day > 1L* galaxies.
Safety In Numbers: Improving the University of Texas’ Security Climate Through the Control and Transmission of Information
(2018-05) Black III, Michael
Campus safety and security is a concern that challenges colleges across the country. This is true also for The University of Texas at Austin (UT Austin). With two recent homicides, a growing awareness of rampant sexual assault, and the political polarization of the student body, the dialogue surrounding UT Austin and its safety environment has become especially urgent and energetic. Interview with campus administrators suggested that one of the most effective ways to create a secure student body is to educate its constituents so that they can make informed decisions about their safety. The purpose of this study was to investigate ways that UT Austin can enhance its ability to create that informed community. The topic was divided into three categories, information, communication, and transparency that were analyzed individually. The first section investigates what information UT Austin is disseminating, how the data are formatted, how the information is contextualized, and what data are often inaccessible to the public. Delaying or withholding information degrades administrative transparency, which can erode student feelings of safety. The final section investigates ways that the University improve that relationship through performance analysis and feedback solicitation. To conduct this analysis, research on campus safety and security from 2000 to 2017 and interviews with campus administrators were synthesized along with a dataset comparing twenty peer institutions across a series of performance metrics. The results indicate that UT Austin currently has substantial growth potential in regards to its safety environment, and the study concludes by suggesting recommendations for the University that include publishing crime data in more open formats, increasing student involvement in campus security, streamlining and formatting online resources, and ensuring the recency of security information.
Scale dependence of the alignment between strain rate and rotation in turbulent shear flow
(2016-10) Fiscaletti, D.; Elsinga, G. E.; Attili, A.; Bisetti, F.; Buxton, O. R. H.; KAUST Supercomputing Laboratory
The scale dependence of the statistical alignment tendencies of the eigenvectors of the strain-rate tensor e(i), with the vorticity vector omega, is examined in the self-preserving region of a planar turbulent mixing layer. Data from a direct numerical simulation are filtered at various length scales and the probability density functions of the magnitude of the alignment cosines between the two unit vectors vertical bar e(i) . (omega) over cap vertical bar are examined. It is observed that the alignment tendencies are insensitive to the concurrent large-scale velocity fluctuations, but are quantitatively affected by the nature of the concurrent large-scale velocity-gradient fluctuations. It is confirmed that the small-scale (local) vorticity vector is preferentially aligned in parallel with the large-scale (background) extensive strain-rate eigenvector e(1), in contrast to the global tendency for omega to be aligned in parallelwith the intermediate strain-rate eigenvector [Hamlington et al., Phys. Fluids 20, 111703 (2008)]. When only data from regions of the flow that exhibit strong swirling are included, the so-called high-enstrophy worms, the alignment tendencies are exaggerated with respect to the global picture. These findings support the notion that the production of enstrophy, responsible for a net cascade of turbulent kinetic energy from large scales to small scales, is driven by vorticity stretching due to the preferential parallel alignment between omega and nonlocal e(1) and that the strongly swirling worms are kinematically significant to this process.
Science Study Break - Sherlock Holmes
(2011-11-10) Bryant, Jim; Gosling, Sam
Shooting for Success: an Analysis of Predictive Basketball Analytics
(2023-05) Geelhoed, Devin
Basketball has changed greatly over recent years, thanks to the data-driven revolution in the way the game is played. Models to predict player and team performance are increasingly popular for team personnel to focus on what they are most successful at, for analysts to break down where advantages and disadvantages are had for different players or teams, and for viewers to create their own opinions on the players or teams they want to succeed or fail and inform betting decisions. This thesis seeks to define where current predictive analytics are lacking with a multimodal examination of three ways we analyze the game: equation-based prediction, machine learning prediction, and human prediction. The thesis focuses on each of these three methods of forecasting in turn, noting their strengths and weaknesses. Additionally, with equation-based prediction, the thesis provides an example model of Expected Points to project the outcome of a certain shot from a certain player. Lastly, the thesis focuses on future developments in predictive analytics and the ways they are shaping the basketball viewing experience.
Some Wholesome Education Statistics
(University of Texas at Austin, 1904-03-01) University of Texas at Austin
Students Who Flex Their Brains Do Better in School
(2020-02-26) Simon, Jeremy M.
Technology Diffusion Through the Lens of Central Bank Digital Currencies
(2021-05) Leake, Avery
This paper seeks to examine the ways policy, technology, commercial environment, and global interaction contribute to the ways national governments are approaching and developing of Central Bank Digital Currencies (CBDCs). This research has a number of applications: 1) the state of global technological diffusion, which can be forecast based on national disposition towards CBDCs, a benchmark that allows to compare all nations using their approach to currency, 2) the shifting landscape of global reserve currencies, and 3) the ways governments are adapting to an increasingly digitalized and technologically advanced global financial system. This paper maps the initiation of CBDC projects around the world and develops a logistic regression model to describe the set of circumstances that need to occur for a given country to begin developing a CBDC. This paper analyzes the influence various indicators might have on future monetary technology development and will forecast the landscape of Central Bank Digital Currencies in coming years.
The Texas Mathematics Teachers' Bulletin, Volume XVI, Number 1
(University of Texas at Austin, 1932-02-08) University of Texas at Austin
Turbulence-Induced Relative Velocity Of Dust Particles. III. The Probability Distribution
(2014-09) Pan, Lubin B.; Padoan, Paolo; Scalo, John; Scalo, John
Motivated by its important role in the collisional growth of dust particles in protoplanetary disks, we investigate the probability distribution function (PDF) of the relative velocity of inertial particles suspended in turbulent flows. Using the simulation from our previous work, we compute the relative velocity PDF as a function of the friction timescales, tau(p1) and tau(p2), of two particles of arbitrary sizes. The friction time of the particles included in the simulation ranges from 0.1 tau(eta) to 54T(L), where tau(eta) and T-L are the Kolmogorov time and the Lagrangian correlation time of the flow, respectively. The relative velocity PDF is generically non-Gaussian, exhibiting fat tails. For a fixed value of tau(p1), the PDF shape is the fattest for equal-size particles (tau(p2) = tau(p1)), and becomes thinner at both tau(p2) < tau(p1) and tau(p2) > tau(p1). Defining f as the friction time ratio of the smaller particle to the larger one, we find that, at a given f in (1/2) less than or similar to f less than or similar to 1, the PDF fatness first increases with the friction time tau(p,h) of the larger particle, peaks at tau(p,h) similar or equal to tau(eta), and then decreases as tp, h increases further. For 0 <= f less than or similar to (1/4), the PDF becomes continuously thinner with increasing tau(p,h). The PDF is nearly Gaussian only if tau(p,h) is sufficiently large (>> T-L). These features are successfully explained by the Pan & Padoan model. Using our simulation data and some simplifying assumptions, we estimated the fractions of collisions resulting in sticking, bouncing, and fragmentation as a function of the dust size in protoplanetary disks, and argued that accounting for non-Gaussianity of the collision velocity may help further alleviate the bouncing barrier problem.
Update on the Fishes of Texas Project
(2017-03-04) Cohen, Adam; Hendrickson, Dean A.; Urban, Tomislav; Walling, David; Gentle, John; Garrett, Gary; Casarez, Melissa; Martin, F. Douglas
The Fishes of Texas project (www.fishesoftexas.org), originating in 2006, remains the most reliable (quality controlled) and data rich site for acquiring occurrence data for Texas fishes, holding over 124,000 records from 42 institutions. Among many discoveries, the project is responsible for detecting at least 3 freshwater species not previously known from the state. We continue making improvements, but substantial updates so far have been onerous for our developers for various reasons. A recent major update reduces coding redundancies, points the website to a new massively restructured and more fully normalized PostgreSQL database (was MySQL), and places the code in a versioning environment. These changes have little immediate effect on user experience, but will greatly accelerate development. PostgreSQL allows for complex spatial queries which will allow users to quickly map occurrence data alongside many more political/environmental layers than currently possible. While our database/web designers have been implementing these changes and fixing bugs etc., we’ve been preparing resources for them to integrate into the website. Some highlights to expect: 1 new updates to the state Species of Greatest Concern list; 2 expert opinion-determined nativity spatial layers for all freshwater fishes displaying in our new mapping system; 3 dynamic statistical summaries; 4 new data types from the literature (>14,900 records), citizen science (>4,300), anglers (>37,000), and agency databases (>1,000,000); 5 new museum records, many derived from our gap sampling (~19,000, 4 museums); 6 more specimen examinations (>400) and photographs (1000); 7 document archive with “smart” text search tools (currently in beta testing using TPWD fisheries reports). So be patient and keep your eyes open for updates.
Using Open Source Tools to Improve DSpace Statistics
(2019-05) Borrego, Gilbert; Liu, Chia-Hui; Hill, Natalie; Lyon, Colleen
Vital Statistics
(The Texas Scientist, 2017) Airhart, Marc