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Articles 31 - 60 of 71

Full-Text Articles in Physics

C/2013 R1 (Lovejoy) At Ir Wavelengths And The Variability Of Co Abundances Among Oort Cloud Comets, L. Paganini, M. Mumma, G. Villanueva, J. Keane, G. Blake, B. Bonev, M. Disanti, E. Gibb, K. Meech Aug 2014

C/2013 R1 (Lovejoy) At Ir Wavelengths And The Variability Of Co Abundances Among Oort Cloud Comets, L. Paganini, M. Mumma, G. Villanueva, J. Keane, G. Blake, B. Bonev, M. Disanti, E. Gibb, K. Meech

Physics Faculty Works

We report production rates, rotational temperatures, and related parameters for gases in C/2013 R1 (Lovejoy) using the Near InfraRed SPECtrometer at the Keck Observatory, on six UT dates spanning heliocentric distances (Rh ) that decreased from 1.35 AU to 1.16 AU (pre-perihelion). We quantified nine gaseous species (H2O, OH*, CO, CH4, HCN, C2H6, CH3OH, NH3, and NH2) and obtained upper limits for two others (C2H2 and H2CO). Compared with organics-normal comets, our results reveal highly enriched CO, (at most) slightly enriched CH3OH, C2H6, and HCN, and CH4 consistent with "normal", yet depleted, NH3, C2H2, and H2CO. Rotational temperatures increased from …

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Optical Spectroscopic Studies Of Two Star Forming Regions, Kristen Leilani Erickson Dec 2013

Optical Spectroscopic Studies Of Two Star Forming Regions, Kristen Leilani Erickson

Dissertations

The ρ Ophiuchi and Serpens molecular clouds are sites of low mass star formation. The goals of this study were to identify young stellar objects (YSOs) and estimate ages and masses in order to infer an initial mass function (IMF), investigate disk evolution, and determine the star-forming history. Optical spectroscopic surveys of an unbiased sample of candidate young stars have been completed. Optical images taken in different photometric bands were used to create color-magnitude diagrams from which sources were selected for spectroscopic observation. In combination with published data, 135 association members in ρ Ophiuchi and 63 association members plus 16 …

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The Unexpectedly Bright Comet C/2012 F6 (Lemmon) Unveiled At Near-Infrared Wavelengths, Lucas Paganini, Michael Disanti, Michael Mumma, Geronimo Villanueva, Boncho Bonev, Jacqueline Keane, Erika Gibb, Hermann Boehnhardt, Karen Meech Dec 2013

The Unexpectedly Bright Comet C/2012 F6 (Lemmon) Unveiled At Near-Infrared Wavelengths, Lucas Paganini, Michael Disanti, Michael Mumma, Geronimo Villanueva, Boncho Bonev, Jacqueline Keane, Erika Gibb, Hermann Boehnhardt, Karen Meech

Physics Faculty Works

We acquired near-infrared spectra of the Oort cloud comet C/2012 F6 (Lemmon) at three different heliocentric distances (R h) during the comet's 2013 perihelion passage, providing a comprehensive measure of the outgassing behavior of parent volatiles and cosmogonic indicators. Our observations were performed pre-perihelion at R h = 1.2 AU with CRIRES (on 2013 February 2 and 4), and post-perihelion at R h = 0.75 AU with CSHELL (on March 31 and April 1) and R h = 1.74 AU with NIRSPEC (on June 20). We detected 10 volatile species (H2O, OH* prompt emission, C2H6, CH3OH, H2CO, HCN, CO, CH4, …

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Detection Of Ch4 In The Gv Tau N Protoplanetary Disk, David Horne, Erika Gibb Oct 2013

Detection Of Ch4 In The Gv Tau N Protoplanetary Disk, David Horne, Erika Gibb

Physics Faculty Works

T Tauri stars are low mass young stars that may serve as analogs to the early solar system. Observations of organic molecules in the protoplanetary disks surrounding T Tauri stars are important for characterizing the chemical and physical processes that lead to planet formation. Searches for undetected molecules, particularly in the inner, planet forming regions of these disks are important for testing protoplanetary disk chemical models and for understanding the evolution of volatiles through the star and planet formation process. We used NIRSPEC on Keck 2 to perform a high resolution (λ/Δλ ~ 25,000) L-band survey of T Tauri star …

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Ice And Dust In The Prestellar Dark Cloud Lynds 183: Preplanetary Matter At The Lowest Temperatures, David Horne, D. Whittet, C Poteet, J. Chiar, L. Paganini, V Bajaj, S. Shenoy, A Adamson Aug 2013

Ice And Dust In The Prestellar Dark Cloud Lynds 183: Preplanetary Matter At The Lowest Temperatures, David Horne, D. Whittet, C Poteet, J. Chiar, L. Paganini, V Bajaj, S. Shenoy, A Adamson

Physics Faculty Works

Dust grains are nucleation centers and catalysts for the growth of icy mantles in quiescent interstellar clouds, the products of which may accumulate into preplanetary matter when new stars and solar systems form within the clouds. In this paper, we present the first spectroscopic detections of silicate dust and the molecular ices H2O, CO, and CO2 in the vicinity of the prestellar core L183 (L134N). An infrared photometric survey of the cloud was used to identify reddened background stars, and we present spectra covering solid-state absorption features in the wavelength range 2-20 μm for nine of them. The mean composition …

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Spectro-Astrometry Of Water In Dr Tauri, Logan Brown, Matthew Troutman, Erika Gibb May 2013

Spectro-Astrometry Of Water In Dr Tauri, Logan Brown, Matthew Troutman, Erika Gibb

Physics Faculty Works

We present high-resolution, near-infrared spectro-astrometric (SA) data for the T Tauri star DR Tau using NIRSPEC at the Keck II telescope. Spectro-astrometry obtains sub-seeing spatial information from emission lines originating in a non-point source object, such as a circumstellar disk. We report the first detection of water SA signatures in a protoplanetary disk. Three water features near 3 μm were averaged together to produce the total signal analyzed. Using a disk model, we constrained the position angle of the disk (~140°), the inclination of the disk (~13°), and the emitting region of the emission lines (~0.056-0.38 AU).

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Handel's Maser-Soliton Theory Of Ball Lightning: The Creation Of Stable Three-Dimensional Cavitons By An Atmospheric Maser Within An Open Resonator, Glenn Andrew Carlson Jan 2013

Handel's Maser-Soliton Theory Of Ball Lightning: The Creation Of Stable Three-Dimensional Cavitons By An Atmospheric Maser Within An Open Resonator, Glenn Andrew Carlson

Dissertations

This dissertation develops details of Handel’s Maser-Soliton Theory of ball lightning. The atmosphere between a thundercloud and the Earth’s surface is modeled as an idealized stable open resonator with water vapor as the active medium and the thundercloud and Earth’s surface as reflecting surfaces. The stable resonator generates a maser beam that narrows to the beam waist at the Earth’s surface, which is assumed to be planar. Two candidate rotational transitions are identified within the v1v2v3 = 010 vibrational band of water having wavelengths of 13.9 cm and 1.12 cm, and relevant spectroscopic parameters are retrieved from the HITRAN 2008 …

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The Characterization Of Volatiles Associated With Young Stellar Objects, Kari Anne Wojtkowski Nov 2012

The Characterization Of Volatiles Associated With Young Stellar Objects, Kari Anne Wojtkowski

Dissertations

In the first portion of this work, we searched for differences in volatiles within a single star forming region, Rho Ophiuchi. We determined the amount, temperature, and composition of two ice features, the bending modes of CO2 and H2O at 15 μm and 6 μm, respectively, toward 28 Young Stellar Objects (YSOs). We found that more than 50% of the YSOs studied contained a portion of crystalline CO2 ice. We also found that some sources with Flat or borderline Class II Spectral Energy Distributions (SEDs) have a larger abundance of CO2 ice with respect to H2O ice. In addition to …

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A Proper Motion Study Of The Haro 6-10 Outflow: Evidence For A Subarcsecond Binary, Bruce Wilking, Kevin Marvel, Mark Claussen, Bradley Gerling, Alwyn Wootten, Erika Gibb Jul 2012

A Proper Motion Study Of The Haro 6-10 Outflow: Evidence For A Subarcsecond Binary, Bruce Wilking, Kevin Marvel, Mark Claussen, Bradley Gerling, Alwyn Wootten, Erika Gibb

Physics Faculty Works

We present single-dish and very long baseline interferometry observations of an outburst of water maser emission from the young binary system Haro 6-10. Haro 6-10 lies in the Taurus molecular cloud and contains a visible T Tauri star with an infrared companion 1farcs3 north. Using the Very Long Baseline Array, we obtained five observations spanning three months and derived absolute positions for 20 distinct maser spots. Three of the masers can be traced over three or more epochs, enabling us to extract absolute proper motions and tangential velocities. We deduce that the masers represent one side of a bipolar outflow …

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The Gas/Dust Ratio Of Circumstellar Disks: Testing Models Of Planetesimal Formation, David Horne, Erika Gibb, Terrence Rettig, Sean Brittain, David Tilley, Dinshaw Balsara Jul 2012

The Gas/Dust Ratio Of Circumstellar Disks: Testing Models Of Planetesimal Formation, David Horne, Erika Gibb, Terrence Rettig, Sean Brittain, David Tilley, Dinshaw Balsara

Physics Faculty Works

We present high-resolution, near-infrared NIRSPEC observations of CO absorption toward six class II T Tauri stars: AA Tau, DG Tau, IQ Tau, RY Tau, CW Tau, and Haro 6-5b. 12CO overtone absorption lines originating from the circumstellar disk of each object were used to calculate line-of-sight gas column densities toward each source. We measured the gas/dust ratio as a function of disk inclination, utilizing measured visual extinctions and inclinations for each star. The majority of our sources show further evidence for a correlation between the gas/dust column density ratio and disk inclination similar to that found by Rettig et al.

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Chemical Composition Of Comet C/2007 N3 (Lulin): Another ''Atypical'' Comet, Erika Gibb, Boncho Bonev, Geronimo Villanueva, Michael Disanti, Michael Mumma, Emily Sudholt, Yana Radeva May 2012

Chemical Composition Of Comet C/2007 N3 (Lulin): Another ''Atypical'' Comet, Erika Gibb, Boncho Bonev, Geronimo Villanueva, Michael Disanti, Michael Mumma, Emily Sudholt, Yana Radeva

Physics Faculty Works

We measured the volatile chemical composition of comet C/2007 N3 (Lulin) on three dates from 2009 January 30 to February 1 using NIRSPEC, the high-resolution (λ/Δλ ≈ 25,000), long-slit echelle spectrograph at Keck 2. We sampled nine primary (parent) volatile species (H2O, C2H6, CH3OH, H2CO, CH4, HCN, C2H2, NH3, CO) and two product species (OH* and NH2). We also report upper limits for HDO and CH3D. C/2007 N3 (Lulin) displayed an unusual composition when compared to other comets. Based on comets measured to date, CH4 and C2H6 exhibited "normal" abundances relative to water, CO and HCN were only moderately depleted, …

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The Initial Mass Function And Disk Frequency Of The Ρ Ophiuchi Cloud: An Extinction-Limited Sample, Kristen Erickson, Bruce Wilking, Michael Meyer, John Robinson, Lauren Stephenson Sep 2011

The Initial Mass Function And Disk Frequency Of The Ρ Ophiuchi Cloud: An Extinction-Limited Sample, Kristen Erickson, Bruce Wilking, Michael Meyer, John Robinson, Lauren Stephenson

Physics Faculty Works

We have completed an optical spectroscopic survey of an unbiased, extinction-limited sample of candidate young stars covering 1.3 deg2 of the ρ Ophiuchi star-forming region. While infrared, X-ray, and optical surveys of the cloud have identified many young stellar objects (YSOs), these surveys are biased toward particular stages of stellar evolution and are not optimal for studies of the disk frequency and initial mass function. We have obtained over 300 optical spectra to help identify 135 association members based on the presence of Hα in emission, lithium absorption, X-ray emission, a mid-infrared excess, a common proper motion, reflection nebulosity, and/or …

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Temporal And Spatial Aspects Of Gas Release During The 2010 Apparition Of Comet 103p/Hartley 2, M. Mumma, B. Bonev, G. Villanueva, L. Paganini, M. Disanti, E. Gibb, J. Keane, K. Meech, G. Blake, R. Ellis, M. Lippi, H. Boehnhardt, K. Magee-Sauer Jun 2011

Temporal And Spatial Aspects Of Gas Release During The 2010 Apparition Of Comet 103p/Hartley 2, M. Mumma, B. Bonev, G. Villanueva, L. Paganini, M. Disanti, E. Gibb, J. Keane, K. Meech, G. Blake, R. Ellis, M. Lippi, H. Boehnhardt, K. Magee-Sauer

Physics Faculty Works

We report measurements of eight primary volatiles (H2O, HCN, CH4, C2H6, CH3OH, C2H2, H2CO, and NH3) and two product species (OH and NH2) in comet 103P/Hartley 2 using high-dispersion infrared spectroscopy. We quantified the long- and short-term behavior of volatile release over a three-month interval that encompassed the comet's close approach to Earth, its perihelion passage, and flyby of the comet by the Deep Impact spacecraft during the EPOXI mission. We present production rates for individual species, their mixing ratios relative to water, and their spatial distributions in the coma on multiple dates. The production rates for water, ethane, HCN, …

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Epoxi: Comet 103p/Hartley 2 Observations From A Worldwide Campaign ; Astrophysical Journal Letters, K. Meech, M. A'Hearn, J. Adams, P. Bacci, J. Bai, L. Barrera, M. Battelino, J. Bauer, E. Becklin, B. Bhatt, N. Biver, D. Bockelee-Morvan, D. Bodewits, H. Bohnhardt, J. Boissier, B. Bonev, W. Borghini, J. Brucato, E. Bryssinck, M. Buie, H. Canovas, D. Castellano, S. Charnley, W. Chen, P. Chiang, Y. Choi, D. Christian, Y. Chuang, Anita Cochran, P. Colom, M. Combi, I. Coulson, J. Crovisier, N. Russo, K. Dennerl, K. Dewahl, M. Disanti, M. Facchini, T. Farnham, Y. Fernandez, H. Floren, U. Frisk, T. Fujiyoshi, R. Furusho, T. Fuse, G. Galli, D. Garcia-Hernandez, A. Gersch, Z. Getu Jan 2011

Epoxi: Comet 103p/Hartley 2 Observations From A Worldwide Campaign ; Astrophysical Journal Letters, K. Meech, M. A'Hearn, J. Adams, P. Bacci, J. Bai, L. Barrera, M. Battelino, J. Bauer, E. Becklin, B. Bhatt, N. Biver, D. Bockelee-Morvan, D. Bodewits, H. Bohnhardt, J. Boissier, B. Bonev, W. Borghini, J. Brucato, E. Bryssinck, M. Buie, H. Canovas, D. Castellano, S. Charnley, W. Chen, P. Chiang, Y. Choi, D. Christian, Y. Chuang, Anita Cochran, P. Colom, M. Combi, I. Coulson, J. Crovisier, N. Russo, K. Dennerl, K. Dewahl, M. Disanti, M. Facchini, T. Farnham, Y. Fernandez, H. Floren, U. Frisk, T. Fujiyoshi, R. Furusho, T. Fuse, G. Galli, D. Garcia-Hernandez, A. Gersch, Z. Getu

Physics Faculty Works

Earth- and space-based observations provide synergistic information for space mission encounters by providing data over longer timescales, at different wavelengths and using techniques that are impossible with an in situ flyby. We report here such observations in support of the EPOXI spacecraft flyby of comet 103P/Hartley 2. The nucleus is small and dark, and exhibited a very rapidly changing rotation period. Prior to the onset of activity, the period was ~16.4 hr. Starting in 2010 August the period changed from 16.6 hr to near 19 hr in December. With respect to dust composition, most volatiles and carbon and nitrogen isotope …

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Mutation Size Optimizes Speciation In An Evolutionary Model, Nathan Dees, Sonya Bahar Aug 2010

Mutation Size Optimizes Speciation In An Evolutionary Model, Nathan Dees, Sonya Bahar

Physics Faculty Works

The role of mutation rate in optimizing key features of evolutionary dynamics has recently been investigated in various computational models. Here, we address the related question of how maximum mutation size affects the formation of species in a simple computational evolutionary model. We find that the number of species is maximized for intermediate values of a mutation size parameter μ; the result is observed for evolving organisms on a randomly changing landscape as well as in a version of the model where negative feedback exists between the local population size and the fitness provided by the landscape. The same result …

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Weak Shear Study Of Galaxy Clusters By Simulated Gravitational Lensing, David Raymond Coss May 2010

Weak Shear Study Of Galaxy Clusters By Simulated Gravitational Lensing, David Raymond Coss

Dissertations

Gravitational lensing has been simulated for numerical galaxy clusters in order to characterize the effects of substructure and shape variations of dark matter halos on the weak lensing properties of clusters. In order to analyze realistic galaxy clusters, 6 high-resolution Adaptive Refinement Tree N-body simulations of clusters with hydrodynamics are used, in addition to a simulation of one group undergoing a merger. For each cluster, the three-dimensional particle distribution is projected perpendicular to three orthogonal lines of sight, providing 21 projected mass density maps. The clusters have representative concentration and mass values for clusters in the concordance cosmology. Two gravitational …

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Co And H3 + Toward Mwc 1080, Mwc 349, And Lkhα 101, Erika Gibb, S. Brittain, T Rettig, M Troutman, Theodore Simon, C Kulesa May 2010

Co And H3 + Toward Mwc 1080, Mwc 349, And Lkhα 101, Erika Gibb, S. Brittain, T Rettig, M Troutman, Theodore Simon, C Kulesa

Physics Faculty Works

We present high-resolution, near-infrared NIRSPEC observations of the fundamental rovibrational CO and H+ 3 R(1,0), R(1,1) u , and Q(1,0) transitions toward three early-type young stars: MWC 1080, MWC 349, and LkHα 101. These observations were performed for the purpose of constraining the physical characteristics of the interstellar material along each line of sight. Toward MWC 1080, we detected strong CO absorption and determined a column density upper limit of 1.4 × 1014 cm–2 for H+ 3. We infer that there is very little diffuse material along the line of sight toward MWC 1080 and that the CO absorption is …

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Comet C/2004 Q2 (Machholz): Parent Volatiles, A Search For Deuterated Methane, And Constraint On The Ch4 Spin Temperature, Boncho Bonev, Michael Mumma, Erika Gibb, Michael Disanti, Geronimo Villanueva, Karen Magee-Sauer, Richard Ellis Jul 2009

Comet C/2004 Q2 (Machholz): Parent Volatiles, A Search For Deuterated Methane, And Constraint On The Ch4 Spin Temperature, Boncho Bonev, Michael Mumma, Erika Gibb, Michael Disanti, Geronimo Villanueva, Karen Magee-Sauer, Richard Ellis

Physics Faculty Works

High-dispersion (λ/δλ ≈ 25,000) infrared spectra of Comet C/2004 Q2 (Machholz) were acquired on 2004 November 28-29, and 2005 January 19 (UT dates) with the Near InfraRed echelle SPECtrograph (NIRSPEC) at the Keck-2 telescope on Mauna Kea. We detected H2O, CH4, C2H2, C2H6, CO, H2CO, CH3OH, HCN, and NH3 and we conducted a sensitive search for CH3D. We report rotational temperatures, production rates, and mixing ratios (with respect to H2O) at heliocentric distances of 1.49 AU (2004 November) and 1.21 AU (2005 January). We highlight three principal results. (1) The mixing ratios of parent volatiles measured at 1.49 AU and …

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Characterization And Synthesis Of Nanoscale Materials, Jinfeng Wang Jan 2009

Characterization And Synthesis Of Nanoscale Materials, Jinfeng Wang

Dissertations

This dissertation focuses on the systematic study of techniques for characterization and synthesis of nanoscale materials. We have achieved several goals. Firstly, high number density uniform zinc oxide nanostructure growth has been achieved using thermal evaporation, through control of experimental parameters that include source material temperature, substrate temperature, substrate material, gas flow rate, and choice of catalyst. Aligned zinc oxide nanowires, randomly oriented zinc oxide nanowires, zinc oxide container-shaped structures, and zinc oxide nanobelts have been synthesized with high yield. Secondly, using a one parameter family of lattice fringe geometry curves, we show how to examine the epitaxial relationship between …

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Time-Resolved Au-Scale Jets Traced By Masers In The Iras 4a/B Regions Of Ngc 1333, Bruce Wilking, Kevin Marvel, Mark Claussen, Alwyn Wootten Sep 2008

Time-Resolved Au-Scale Jets Traced By Masers In The Iras 4a/B Regions Of Ngc 1333, Bruce Wilking, Kevin Marvel, Mark Claussen, Alwyn Wootten

Physics Faculty Works

We present results of VLBI observations of the water masers associated with IRAS 4A and IRAS 4B in the NGC 1333 star-forming region taken in four epochs over a two month period. Both objects have been classified as extremely young sources, and each source is known to be a multiple system. Using the Very Long Baseline Array, we detected 35 masers in epoch I, 40 masers in epoch II, 35 in epoch III, and 24 in epoch IV. Only one identified source in each system is associated with these masers. These data are used to calculate proper motions for the …

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The Peculiar Volatile Composition Of Comet 8p/Tuttle: A Contact Binary Of Chemically Distinct Cometesimals?, Boncho Bonev, Michael Mumma, Yana Radeva, Michael Disanti, Erika Gibb, Geronimo Villanueva Jun 2008

The Peculiar Volatile Composition Of Comet 8p/Tuttle: A Contact Binary Of Chemically Distinct Cometesimals?, Boncho Bonev, Michael Mumma, Yana Radeva, Michael Disanti, Erika Gibb, Geronimo Villanueva

Physics Faculty Works

We report measurements of eight native (i.e., released directly from the comet nucleus) volatiles (H2O, HCN, CH4, C2H2, C2H6, CO, H2CO, and CH3OH) in comet 8P/Tuttle using NIRSPEC at Keck 2. Comet Tuttle reveals a truly unusual composition, distinct from that of any comet observed to date at infrared wavelengths. The prominent enrichment of methanol relative to water contrasts with the depletions of other molecules, especially C2H2, HCN, and H2CO. We suggest that the nucleus of 8P/Tuttle may contain two cometesimals characterized by distinct volatile composition. The relative abundances C2/CN, C2/OH, and CN/OH in 8P/Tuttle (measured at optical/near-UV wavelengths) differ …

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Thermal Roots Of Correlation-Based Complexity, Philip Fraundorf Jan 2008

Thermal Roots Of Correlation-Based Complexity, Philip Fraundorf

Physics Faculty Works

Bayesian maxent lets one integrate thermal physics and information theory points of view in the quantitative study of complex systems. Since net surprisal (a free energy analog for measuring “departures from expected”) allows one to place second law constraints on mutual information (a multimoment measure of correlations), it makes a quantitative case for the role of reversible thermalization in the natural history of invention, and suggests multiscale strategies to monitor standing crop as well. It prompts one to track evolved complexity starting from live astrophysically observed processes, rather than only from evidence of past events. Various gradients and boundaries that …

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Electron Beam Characterization Of Carbon Nanostructures, Eric Samuel Mandell Dec 2007

Electron Beam Characterization Of Carbon Nanostructures, Eric Samuel Mandell

Dissertations

Atom-thick carbon nanostructures represent a class of novel materials that are of interest to those studying carbon's role in fossil fuel, hydrogen storage, scaled-down electronics, and other nanotechnology. Electron microscope images of "edge-on" graphene sheets show linear image features due to the projected potential of the sheets. Here, intensity profiles along these linear features can measure the curvature of the sheet, as well as the shape of the sheet (i.e. hexagonal, triangular). Also, electron diffraction powder profiles calculated for triangular graphene sheet shapes show a broadening of the low-frequency edge of diffraction rings, in comparison to those calculated for hexagonal …

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Depleted Carbon Monoxide In Fragment C Of The Jupiter-Family Comet 73p/Schwassmann-Wachmann 3, M. Disanti, W. Anderson, G. Villanueva, B. Bonev, K. Magee-Sauer, E. Gibb, M. Mumma May 2007

Depleted Carbon Monoxide In Fragment C Of The Jupiter-Family Comet 73p/Schwassmann-Wachmann 3, M. Disanti, W. Anderson, G. Villanueva, B. Bonev, K. Magee-Sauer, E. Gibb, M. Mumma

Physics Faculty Works

Carbon monoxide emission was targeted in fragment C of the recently split Jupiter-family comet 73P/Schwassmann-Wachmann 3 during its 2006 apparition, using the Cryogenic Echelle Spectrograph (CSHELL) at the NASA IRTF on Mauna Kea, Hawaii. Simultaneous sounding with H2O near 4.65 μm revealed highly depleted CO, consistent with a mixing ratio of 0.5% ± 0.13%. Along with depleted CH3OH but nearly normal HCN, this may indicate that this comet formed in the inner giant planets' region or, alternatively, that it formed relatively late, after significant clearing of the protosolar nebula.

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The Shape Of Galaxy Cluster Dark Matter Haloes: Systematics Of Its Imprint On Cluster Gas And Comparison To Observations, Ricardo Flores, Brandon Allgood, Andrey Kravtsov, Joel Primack, David Buote, James Bullock May 2007

The Shape Of Galaxy Cluster Dark Matter Haloes: Systematics Of Its Imprint On Cluster Gas And Comparison To Observations, Ricardo Flores, Brandon Allgood, Andrey Kravtsov, Joel Primack, David Buote, James Bullock

Physics Faculty Works

We study predictions for galaxy cluster observables that can test the statistics of dark matter halo shapes expected in a flat Λ cold dark matter (CDM) universe. We present a simple analytical model for the prediction of cluster-scale X-ray observations, approximating clusters as isothermal systems in hydrostatic equilibrium, and dark matter haloes as ellipsoids with uniform axial ratios (homeoidal ellipsoids). We test the model against high-resolution, hydrodynamic cluster simulations to gauge its reliability. We find that this simple prescription does a good job of predicting cluster X-ray ellipticities compared to the simulations as long as one focuses on cluster regions …

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Warm Hcn, C2h2, And Co In The Disk Of Gv Tau, Erika Gibb, K. Van Brunt, S. Brittain, T Rettig May 2007

Warm Hcn, C2h2, And Co In The Disk Of Gv Tau, Erika Gibb, K. Van Brunt, S. Brittain, T Rettig

Physics Faculty Works

We present the first high-resolution, ground-based observations of HCN and C2H2 toward the T Tauri binary star system GV Tau. We detected strong absorption due to HCN ν3 and weak C2H2 [ν3 and ν2 + (ν4 + ν5)img1.gif] absorption toward the primary (GV Tau S) but not the infrared companion. We also report CO column densities and rotational temperatures, and present abundances relative to CO of HCN/CO ~ 0.6% and C2H/CO ~ 1.2% and an upper limit for CH4/CO < 0.37% toward GV Tau S. Neither HCN nor C2H2 were detected toward the infrared companion, and results suggest that abundances may differ between the two sources.

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The Abundance Of Carbon Dioxide Ice In The Quiescent Intracloud Medium, D. Whittet, S. Shenoy, E. Bergin, J. Chiar, P. Gerakines, E. Gibb, G. Melnick, D. Neufeld Jan 2007

The Abundance Of Carbon Dioxide Ice In The Quiescent Intracloud Medium, D. Whittet, S. Shenoy, E. Bergin, J. Chiar, P. Gerakines, E. Gibb, G. Melnick, D. Neufeld

Physics Faculty Works

We present new observations with the Infrared Spectrograph on board the Spitzer Space Telescope of the solid-CO2 absorption feature near 15 μm in the spectra of eight field stars behind the Taurus complex of dark clouds. Solid CO2 is detected in six lines of sight. New results are combined with previous data to investigate the correlation of CO2 column density with those of other major ice constituents (H2O and CO) and with extinction. CO2 is shown to display a "threshold extinction" effect, i.e., a minimum extinction (A0 = 4.3 ± 1.0 mag) required for detection, behavior similar to that previously …

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Rank-Ordering Protein-Ligand Binding Affinity By A Quantum Mechanics/ Molecular Mechanics/Poisson-Boltzmann-Surface Area Model, Mingliang Wang, Chung Wong Jan 2007

Rank-Ordering Protein-Ligand Binding Affinity By A Quantum Mechanics/ Molecular Mechanics/Poisson-Boltzmann-Surface Area Model, Mingliang Wang, Chung Wong

Chemistry & Biochemistry Faculty Works

The authors describe a quantum mechanics/molecular mechanics/Poisson-Boltzmann-surface area model for rank-ordering protein-ligand binding affinity in aqueous solution. Unlike many classical continuum electrostatics calculations in which the protein and ligand are treated as a uniform dielectric, this model uses quantum mechanics to explicitly describe the electronic polarization of the ligand by its environment. In solving the Poisson-Boltzmann equation, the authors use the quantum mechanical charge density directly rather than the common point-charge approximation. The authors show that useful results can be obtained by using experimental structure, by choosing a protein dielectric constant that is smaller than that typically used in classical …

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Structural Fingerprinting In The Transmission Electron Microscope : Overview And Opportunities To Implement Enhanced Strategies For Nanocrystal Identification Jan 2007

Structural Fingerprinting In The Transmission Electron Microscope : Overview And Opportunities To Implement Enhanced Strategies For Nanocrystal Identification

Physics Faculty Works

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[Accepted Article Manuscript Version (Postprint)] Testing The Inverse-Compton Catastrophe Scenario In The Intra-Day Variable Blazar S5 0716+71. I. Simultaneous Broadband Observations During November 2003, Bruce Wilking, L. Ostorero, S Wagner, J. Gracia, E. Ferrero, T Krichbaum, S. Britzen, A. Witzel, K. Nilsson, M. Villata, U. Bach, D. Barnaby, S. Bernhart, M Carini, C Chen, W. Chen, S. Ciprini, S. Crapanzano, V. Doroshenko, N Efimova, D. Emmanoulopoulos, L. Fuhrmann, K Gabanyi, A. Giltinan, V. Hagen-Thorn, M. Hauser, J. Heidt, A Hojaev, T. Hovatta, F. Hroch, M. Ibrahimov, V. Impellizzeri, R Ivanidze, D. Kachel, A. Kraus, O. Kurtanidze, A. Lähteenmäki, L. Lanteri, V. Larionov, Z Lin, E. Lindfors, F. Munz, M. Nikolashvili, G. Nucciarelli, A. O’Connor, J. Ohlert, M. Pasanen, C. Pullen, C. Raiteri, T Rector, R. Robb, L. Sigua, A. Sillanpää, L. Sixtova, N. Smith, P. Strub, S. Takahashi, L. Takalo, C. Tapken, J. Tartar, M. Tornikoski, G. Tosti, M. Tröller, R. Walters, W. Wills, I. Agudo, H. Aller, M. Aller, E. Angelakis, J. Klare, E. Körding, R Strom, H. Teräsranta, H. Ungerechts, B. Vila-Vilaró Jun 2006

[Accepted Article Manuscript Version (Postprint)] Testing The Inverse-Compton Catastrophe Scenario In The Intra-Day Variable Blazar S5 0716+71. I. Simultaneous Broadband Observations During November 2003, Bruce Wilking, L. Ostorero, S Wagner, J. Gracia, E. Ferrero, T Krichbaum, S. Britzen, A. Witzel, K. Nilsson, M. Villata, U. Bach, D. Barnaby, S. Bernhart, M Carini, C Chen, W. Chen, S. Ciprini, S. Crapanzano, V. Doroshenko, N Efimova, D. Emmanoulopoulos, L. Fuhrmann, K Gabanyi, A. Giltinan, V. Hagen-Thorn, M. Hauser, J. Heidt, A Hojaev, T. Hovatta, F. Hroch, M. Ibrahimov, V. Impellizzeri, R Ivanidze, D. Kachel, A. Kraus, O. Kurtanidze, A. Lähteenmäki, L. Lanteri, V. Larionov, Z Lin, E. Lindfors, F. Munz, M. Nikolashvili, G. Nucciarelli, A. O’Connor, J. Ohlert, M. Pasanen, C. Pullen, C. Raiteri, T Rector, R. Robb, L. Sigua, A. Sillanpää, L. Sixtova, N. Smith, P. Strub, S. Takahashi, L. Takalo, C. Tapken, J. Tartar, M. Tornikoski, G. Tosti, M. Tröller, R. Walters, W. Wills, I. Agudo, H. Aller, M. Aller, E. Angelakis, J. Klare, E. Körding, R Strom, H. Teräsranta, H. Ungerechts, B. Vila-Vilaró

Physics Faculty Works

Context. Some intra-day variable, compact extra-galactic radio sources show brightness temperatures severely exceeding 1012 K, the limit set by catastrophic inverse-Compton (IC) cooling in sources of incoherent synchrotron radiation. The violation of the IC limit, actually possible under non-stationary conditions, would lead to IC avalanches in the soft-γ-ray energy band during transient periods.Aims. For the first time, broadband signatures of possible IC catastrophes were searched for in a prototypical source, S5 0716+71.Methods. A multifrequency observing campaign targetting S5 0716+71 was carried out during November 06-20, 2003. The observations, organized under the framework of the European Network for the Investigation of …

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