Browsing by Subject "population"

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Answering the Call
(The Texas Scientist, 2021) The Texas Scientist
The APOGEE Red-Clump Catalog: Precise Distances, Velocities, And High-Resolution Elemental Abundances Over A Large Area Of The Milky Way's Disk
(2014-08) Bovy, Jo; Nidever, David L.; Rix, Hans-Walter; Girardi, Leo; Zasowski, Gail; Chojnowski, S. Drew; Holtzman, Jon; Epstein, Courtney; Frinchaboy, Peter M.; Hayden, Michael R.; Rodrigues, Thaise S.; Majewski, Steven R.; Johnson, Jennifer A.; Pinsonneault, Marc H.; Stello, Dennis; Prieto, Carlos Allende; Andrews, Brett; Basu, Sarbani; Beers, Timothy C.; Bizyaev, Dmitry; Burton, Adam; Chaplin, William J.; Cunha, Katia; Elsworth, Yvonne; Garcia, Rafael A.; Garcia-Hernandez, Domingo A.; Garcia Perez, Ana E.; Hearty, Fred R.; Hekker, Saskia; Kallinger, Thomas; Kinemuchi, Karen; Koesterke, Lars; Meszaros, Szabolcs; Mosser, Benoit; O'Connell, Robert W.; Oravetz, Daniel; Pan, Kaike; Robin, Annie C.; Schiavon, Ricardo P.; Schneider, Donald P.; Schultheis, Mathias; Serenelli, Aldo; Shetrone, Matthew; Aguirre, Victor Silva; Simmons, Audrey; Skrutskie, Michael; Smith, Verne V.; Stassun, Keivan; Weinberg, David H.; Wilson, John C.; Zamora, Olga; Shetrone, Matthew
The Sloan Digital Sky Survey III's Apache Point Observatory Galactic Evolution Experiment (APOGEE) is a high-resolution near-infrared spectroscopic survey covering all of the major components of the Galaxy, including the dust-obscured regions of the inner Milky Way disk and bulge. Here we present a sample of 10,341 likely red-clump stars (RC) from the first two years of APOGEE operations, selected based on their position in color-metallicity-surface-gravity-effective-temperature space using a new method calibrated using stellar evolution models and high-quality asteroseismology data. The narrowness of the RC locus in color-metallicity-luminosity space allows us to assign distances to the stars with an accuracy of 5%-10%. The sample extends to typical distances of about 3 kpc from the Sun, with some stars out to 8 kpc, and spans a volume of approximately 100 kpc(3) over 5 kpc less than or similar to R less than or similar to 14 kpc, vertical bar Z vertical bar less than or similar to 2 kpc, and -15 degrees less than or similar to Galactocentric azimuth less than or similar to 30 degrees. The APOGEE red-clump (APOGEE-RC) catalog contains photometry from the Two Micron All Sky Survey, reddening estimates, distances, line-of-sight velocities, stellar parameters and elemental abundances determined from the high-resolution APOGEE spectra, and matches to major proper motion catalogs. We determine the survey selection function for this data set and discuss how the RC selection samples the underlying stellar populations. We use this sample to limit any azimuthal variations in the median metallicity within the approximate to 45 degrees azimuthal region covered by the current sample to be <= 0.02 dex, which is more than an order of magnitude smaller than the radial metallicity gradient. This result constrains coherent non-axisymmetric flows within a few kiloparsecs from the Sun.
Austin and Its Future: The Challenge of Growth, PRP 3
(LBJ School of Public Affairs, 1973) Haynes, Kingsley E.; Hazleton, Jared E.; Poston, Dudley L.
Before and After Studies on the Effects of a Power Plant Installation on Lake Lyndon B. Johnson: Some Effects of Temperature on the Population Dynamics of Planktonic Rotifers
(University of Texas at Austin, 1976-06) MacRae, J.R.; Maguire, B. Jr.
Bulges Of Nearby Galaxies With Spitzer: Scaling Relations In Pseudobulges And Classical Bulges
(2010-06) Fisher, David B.; Drory, Niv; Fisher, David B.
We investigate scaling relations of bulges using bulge-disk decompositions at 3.6 mu m and present bulge classifications for 173 E-Sd galaxies within 20 Mpc. Pseudobulges and classical bulges are identified using Sersic index, Hubble Space Telescope morphology, and star formation activity ( traced by 8 mu m emission). In the near-IR pseudobulges have n(b) < 2 and classical bulges have n(b) > 2, as found in the optical. Sersic index and morphology are essentially equivalent properties for bulge classification purposes. We confirm, using a much more robust sample, that the Sersic index of pseudobulges is uncorrelated with other bulge structural properties, unlike for classical bulges and elliptical galaxies. Also, the half-light radius of pseudobulges is not correlated with any other bulge property. We also find a new correlation between surface brightness and pseudobulge luminosity; pseudobulges become more luminous as they become more dense. Classical bulges follow the well-known scaling relations between surface brightness, luminosity, and half-light radius that are established by elliptical galaxies. We show that those pseudobulges (as indicated by Sersic index and nuclear morphology) that have low specific star formation rates are very similar to models of galaxies in which both a pseudobulge and classical bulge exist. Therefore, pseudobulge identification that relies only on structural indicators is incomplete. Our results, especially those on scaling relations, imply that pseudobulges are very different types of objects than elliptical galaxies.
Converting From 3.6 And 4.5 Micron Fluxes To Stellar Mass
(2012-06) Eskew, Michael; Zaritsky, Dennis; Meidt, Sharon; Eskew, Michael
We use high spatial resolution maps of stellar mass and infrared flux of the Large Magellanic Cloud (LMC) to calibrate a conversion between 3.6 and 4.5 mu m fluxes and stellar mass, M-* = 10(5.65) F-3.6(2.85) F-4.5(-1.85) (D/0.05)(2) M-circle dot,where fluxes are in Jy and D is the luminosity distance to the source in Mpc, and to provide an approximate empirical estimate of the fractional internal uncertainty in M* of 0.3 root N/10(6), where N is the number of stars in the region. We find evidence that young stars and hot dust contaminate the measurements, but attempts to remove this contamination using data that are far superior to what are generally available for unresolved galaxies resulted in marginal gains in accuracy. The scatter among mass estimates for regions in the LMC is comparable to that found by previous investigators when modeling composite populations, and so we conclude that our simple conversion is as precise as possible for the data and models currently available. Our results allow for a reasonably bottom-heavy initial mass function, such as Salpeter or heavier, and moderately disfavor lighter versions such as a diet-Salpeter or Chabrier initial mass function.
Discovery of a Large Number of Candidate Protoclusters Traced By Similar to 15 Mpc-Scale Galaxy Overdensities in COSMOS
(2014-02) Chiang, Yi-Kuan; Overzier, Roderick; Gebhardt, Karl; Chiang, Yi-Kuan; Overzier, Roderick; Gebhardt, Karl
To demonstrate the feasibility of studying the epoch of massive galaxy cluster Formation in a more systematic manner using current and future galaxy surveys, we report the discovery of a large sample of protocluster candidates in the 1.62 deg(2) COSMOS/UltraVISTA field traced by optical/infrared selected galaxies using photometric redshifts. By comparing properly smoothed three-dimensional galaxy density maps of the observations and a set of matched simulations incorporating the dominant observational effects (galaxy selection and photometric redshift uncertainties), we first confirm that the observed similar to 15 comoving Mpc-scale galaxy clustering is consistent with Lambda CDM models. Using further the relation between high-z overdensity and the present day cluster mass calibrated in these matched simulations, we found 36 candidate structures at 1.6 < z < 3.1, showing overdensities consistent with the progenitors of M-z=0 similar to 10(15) M-circle dot clusters. Taking into account the significant upward scattering of lower mass structures, the probabilities for the candidates to have at least M-z=0 similar to 10(14) M-circle dot are similar to 70%. For each structure, about 15%-40% of photometric galaxy candidates are expected to be true protocluster members that will merge into a cluster-scale halo by z = 0. With solely photometric redshifts, we successfully rediscover two spectroscopically confirmed structures in this field, suggesting that our algorithm is robust. This work generates a large sample of uniformly selected protocluster candidates, providing rich targets for spectroscopic follow-up and subsequent studies of cluster Formation. Meanwhile, it demonstrates the potential for probing early cluster Formation with upcoming redshift surveys such as the Hobby-Eberly Telescope Dark Energy Experiment and the Subaru Prime Focus Spectrograph survey.
A First Look At The Auriga-California Giant Molecular Cloud With Herschel And The CSO: Census Of The Young Stellar Objects And The Dense Gas
(2013-02) Harvey, Paul M.; Fallscheer, Cassandra; Ginsburg, Adam; Terebey, Susan; Andre, Phillippe; Bourke, Tyler L.; Di Francesco, James; Konyves, Vera; Matthews, Brenda C.; Peterson, Dawn E.; Harvey, Paul M.
We have mapped the Auriga/California molecular cloud with the Herschel PACS and SPIRE cameras and the Bolocam 1.1 mm camera on the Caltech Submillimeter Observatory with the eventual goal of quantifying the star formation and cloud structure in this giant molecular cloud (GMC) that is comparable in size and mass to the Orion GMC, but which appears to be forming far fewer stars. We have tabulated 60 compact 70/160 mu m sources that are likely pre-main-sequence objects and correlated those with Spitzer and WISE mid-IR sources. At 1.1 mm, we find 18 cold, compact sources and discuss their properties. The most important result from this part of our study is that we find a modest number of additional compact young objects beyond those identified at shorter wavelengths with Spitzer. We also describe the dust column density and temperature structure derived from our photometric maps. The column density peaks at a few x 10(22) cm(-2) (N-H2) and is distributed in a clear filamentary structure along which nearly all of the pre-main-sequence objects are found. We compare the young stellar object surface density to the gas column density and find a strong nonlinear correlation between them. The dust temperature in the densest parts of the filaments drops to similar to 10 K from values similar to 14-15 K in the low-density parts of the cloud. We also derive the cumulative mass fraction and probability density function of material in the cloud, which we compare with similar data on other star-forming clouds.
Gemini And Hubble Space Telescope Evidence For An Intermediate-Mass Black Hole In Omega Centauri
(2008-04) Noyola, Eva; Gebhardt, Karl; Bergmann, Marcel; Noyola, Eva; Gebhardt, Karl
The globular cluster omega Centauri is one of the largest and most massive members of the galactic system. However, its classification as a globular cluster has been challenged making it a candidate for being the stripped core of an accreted dwarf galaxy; this together with the fact that it has one of the largest velocity dispersions for star clusters in our galaxy makes it an interesting candidate for harboring an intermediate-mass black hole. We measure the surface brightness profile from integrated light on an HSTACS image of the center, and find a central power-law cusp of logarithmic slope -0.08. We also analyze Gemini GMOS-IFU kinematic data for a 5 '' x 5 '' field centered on the nucleus of the cluster, as well as for a field 1400 away. We detect a clear rise in the velocity dispersion from 18.6 km s(-1) at 1400 to 23 km s(-1) in the center. A rise in the velocity dispersion could be due to a central black hole, a central concentration of stellar remnants, or a central orbital structure that is radially biased. We discuss each of these possibilities. An isotropic, spherical dynamical model implies a black hole mass of 4.0(-1.0)(+0.75) x 10(4) M-circle dot, and excludes the no black hole case at greater than 99% significance. We have also run flattened, orbit-based models and find similar results. While our preferred model is the existence of a central black hole, detailed numerical simulations are required to confidently rule out the other possibilities.
A Generation at Risk: When the baby boomers reach Golden Pond
(Hogg Foundation for Mental Health, 1984) Butler, Robert N.
A Herschel Search for Cold Dust in Brown Dwarf Disks: First Results
(2012-01) Harvey, Paul M.; Henning, Thomas; Menard, Francois; Wolf, Sebastian; Liu, Yao; Cieza, Lucas A.; Evans, Neal J., II; Pascucci, Ilaria; Merin, Bruno; Pinte, Christophe; Harvey, Paul M.; Evans, Neal J., II
We report initial results from a Herschel program to search for far-infrared emission from cold dust around a statistically significant sample of young brown dwarfs. The first three objects in our survey are all detected at 70 mu m, and we report the first detection of a brown dwarf at 160 mu m. The flux densities are consistent with the presence of substantial amounts of cold dust in the outer disks around these objects. We modeled the spectral energy distributions (SEDs) with two different radiative transfer codes. We find that a broad range of model parameters provide a reasonable fit to the SEDs, but that the addition of our 70 mu m, and especially the 160 mu m, detection enables strong lower limits to be placed on the disk masses since most of the mass is in the outer disk. We find likely disk masses in the range of a few x 10(-6) to 10(-4) M(circle dot). Our models provide a good fit to the SEDs and do not require dust settling.
A Herschel Survey Of Cold Dust In Disks Around Brown Dwarfs And Low-Mass Stars
(2012-08) Harvey, Paul M.; Henning, Thomas; Liu, Yao; Menard, Francois; Pinte, Christopher; Wolf, Sebastian; Cieza, Lucas A.; Evans, Neal J.; Pascucci, Ilaria; Harvey, Paul M.
We report the complete photometric results from our Herschel study which is the first comprehensive program to search for far-infrared emission from cold dust around young brown dwarfs (BDs). We surveyed 50 fields containing 51 known or suspected BDs and very low mass stars that have evidence of circumstellar disks based on Spitzer photometry and/or spectroscopy. The objects with known spectral types range from M3 to M9.5. Four of the candidates were subsequently identified as extragalactic objects. Of the remaining 47 we have successfully detected 36 at 70 mu m and 14 at 160 mu m with signal-to-noise ratio (S/N) greater than 3, as well as several additional possible detections with low S/N. The objects exhibit a range of [24]-[70] mu m colors suggesting a range in mass and/or structure of the outer disk. We present modeling of the spectral energy distributions of the sample and discuss trends visible in the data. Using two Monte Carlo radiative transfer codes we investigate disk masses and geometry. We find a very wide range in modeled total disk masses from less than 10(-6) M-circle dot up to 10(-3) M-circle dot with a median disk mass of the order of 3 x 10(-5) M-circle dot, suggesting that the median ratio of disk mass to central object mass may be lower than for T Tauri stars. The disk scale heights and flaring angles, however, cover a range consistent with those seen around T Tauri stars. The host clouds in which the young BDs and low-mass stars are located span a range in estimated age from similar to 1-3 Myr to similar to 10 Myr and represent a variety of star-forming environments. No obvious dependence on cloud location or age is seen in the disk properties, though the statistical significance of this conclusion is not strong.
In Vivo Growth Rates Are Poorly Correlated With Phage Therapy Success In A Mouse Infection Model
(2012-02) Bull, J. J.; Otto, G.; Molineux, I. J.; Bull, J. J.; Otto, G.; Molineux, I. J.
Two classes of phages yield profoundly different levels of recovery in mice experimentally infected with an Escherichia coli O18:K1:H7 strain. Phages requiring the K1 capsule for infection (K1-dep) rescue virtually all infected mice, whereas phages not requiring the capsule (K1-ind) rescue modest numbers (similar to 30%). To rescue infected mice, K1-ind phages require at least a 10(6)-fold-higher inoculum than K1-dep phages. Yet their in vivo growth dynamics are only modestly inferior to those of K1-dep phages, and competition between the two phage types in the same mouse reveals only a slight growth advantage for the K1-dep phage. The in vivo growth rate seems unlikely to be the primary determinant of phage therapy success. An alternative explanation is that the success of K1-dep phages is due substantially to their proteomic composition. They encode an enzyme that degrades the K1 capsule, which has been shown in other work to be sufficient to cure infection in the complete absence of phages.
Innovative Initiatives in Growth Management and Open Space Preservation: A National Study, PRP 145
(LBJ School of Public Affairs, 2003) Wilson, Robert H.; Paterson, Robert
It's all about the money: An analysis of spending in U.S. Senate races
(2014) Jones, Braydon K.
Letter to F.Stearns MacNeil from Preston E. Cloud, Jr. on 1958-05-12
(1958-05-12) Cloud, Preston E., Jr.
Letter to H.B. Stenzel from Ernst Mayr on 1948-11-05
(1948-11-05) Mayr, Ernst
Letter to Henryk B. Stenzel from Horace Sawin on 1969-01-01
(1969-01-01) Sawin, Horace
M31N-2007-06B: A Nova in the M31 Globular Cluster Bol 111
(2007-12) Shafter, A. W.; Quimby, R. M.; Quimby, R. M.
We report spectroscopic observations of the nova M31N-2007-06b, which was found to be spatially coincident with the M31 globular cluster Bol 111. This nova is the first out of more than 700 discovered in M31 over the past century to be associated with one of the galaxy's globular clusters. A total of three spectra of the nova were obtained 3, 6, and 36 days after discovery. The data reveal broad (FWHM similar to 3000 km s(-1)) Balmer, N II, and N III emission lines and show that the nova belongs to the He/N spectroscopic class. The He/N class of novae are relatively rare, making up roughly 15% of the novae with measured spectra in M31 and roughly 20% - 25% of the Galactic novae for which spectroscopic data are available. The implications of a nova, particularly an He/N nova, occurring in a globular cluster are discussed.
Municipal Public Reporting in Texas
(University of Texas at Austin, 1936-07-15) University of Texas at Austin