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San Jose State University

2011

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Articles 91 - 107 of 107

Full-Text Articles in Physical Sciences and Mathematics

Wide-Field Precision Kinematics Of The M87 Globular Cluster System, J. Strader, Aaron J. Romanowsky, J. P. Brodie, L. R. Spitler, M. A. Beasley, Jacob A. Arnold, N. Tamura, R. M. Sharples, N. Arimoto Jan 2011

Wide-Field Precision Kinematics Of The M87 Globular Cluster System, J. Strader, Aaron J. Romanowsky, J. P. Brodie, L. R. Spitler, M. A. Beasley, Jacob A. Arnold, N. Tamura, R. M. Sharples, N. Arimoto

Aaron J. Romanowsky

We present the most extensive combined photometric and spectroscopic study to date of the enormous globular cluster (GC) system around M87, the central giant elliptical galaxy in the nearby Virgo Cluster. Using observations from DEIMOS and the Low Resolution Imaging Spectrometer at Keck, and Hectospec on the Multiple Mirror Telescope, we derive new, precise radial velocities for 451 GCs around M87, with projected radii from ~5 to 185 kpc. We combine these measurements with literature data for a total sample of 737 objects, which we use for a re-examination of the kinematics of the GC system of M87. The velocities …

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Diffusive Transport Enhanced By Thermal Velocity Fluctuations, Alejandro Garcia, Aleksandar Donev, Anton De La Fuente, John B. Bell Jan 2011

Diffusive Transport Enhanced By Thermal Velocity Fluctuations, Alejandro Garcia, Aleksandar Donev, Anton De La Fuente, John B. Bell

Alejandro Garcia

We study the contribution of advection by thermal velocity fluctuations to the effective diffusion coefficient in a mixture of two identical fluids. We find good agreement between a simple fluctuating hydrodynamics theory and particle and finite-volume simulations. The enhancement of the diffusive transport depends on the system size L and grows as ln⁡(L/L0) in quasi-two-dimensional systems, while in three dimensions it scales as L0-1-L-1, where L0 is a reference length. Our results demonstrate that fluctuations play an important role in the hydrodynamics of small-scale systems.

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An Extremely Luminous Panchromatic Outburst From The Nucleus Of A Distant Galaxy, A. J. Levan, N. R. Tanvir, S. B. Cenko, D. A. Perley, K. Wiersema, J. S. Bloom, A. S. Fruchter, A. De Urgarte Postigo, P. T. Butler, A. J. Van Der Horst, G. Leloudas, A. N. Morgan, K. Misra, G. C. Bower, J. Farihi, R. L. Tunnicliffe, A. N. Morgan, K. Misra, G. C. Bower, J. Farihi, R. L. Tunnicliffe, M. Modjaz, J. M. Silverman, J. Hjorth, C. Thone, A. Cucchiara, J. M. Castro-Ceron, A. J. Castro-Tirado, J. A. Arnold, M. Bremer, J. P. Brodie, T. Carroll, M. C. Cooper, P. A. Curran, R. M. Cutri, J. Ehle, D. Forbes, J. Fynbo, J. Gorosabel, J. Graham, D. I. Hoffman, S. Guziy, P. Jakobsson, A. Kamble, T. Kerr, M. M. Kasliwal, C. Kouveliotou, D. Kocevski, N. M. Law, P. E. Nugent, E. O. Ofek, D. Poznanski, R. M. Quimby, E. Rol, Aaron J. Romanowsky, R. Sanchez-Ramirez, S. Schulze, N. Singh, L. Van Spaandonk, R.L.C. Starling, R. G. Strom, J. C. Tello, O. Vaduvescu, P. J. Wheatley, J. M. Winters, R.A.M.J. Wijers, D. Xu Jan 2011

An Extremely Luminous Panchromatic Outburst From The Nucleus Of A Distant Galaxy, A. J. Levan, N. R. Tanvir, S. B. Cenko, D. A. Perley, K. Wiersema, J. S. Bloom, A. S. Fruchter, A. De Urgarte Postigo, P. T. Butler, A. J. Van Der Horst, G. Leloudas, A. N. Morgan, K. Misra, G. C. Bower, J. Farihi, R. L. Tunnicliffe, A. N. Morgan, K. Misra, G. C. Bower, J. Farihi, R. L. Tunnicliffe, M. Modjaz, J. M. Silverman, J. Hjorth, C. Thone, A. Cucchiara, J. M. Castro-Ceron, A. J. Castro-Tirado, J. A. Arnold, M. Bremer, J. P. Brodie, T. Carroll, M. C. Cooper, P. A. Curran, R. M. Cutri, J. Ehle, D. Forbes, J. Fynbo, J. Gorosabel, J. Graham, D. I. Hoffman, S. Guziy, P. Jakobsson, A. Kamble, T. Kerr, M. M. Kasliwal, C. Kouveliotou, D. Kocevski, N. M. Law, P. E. Nugent, E. O. Ofek, D. Poznanski, R. M. Quimby, E. Rol, Aaron J. Romanowsky, R. Sanchez-Ramirez, S. Schulze, N. Singh, L. Van Spaandonk, R.L.C. Starling, R. G. Strom, J. C. Tello, O. Vaduvescu, P. J. Wheatley, J. M. Winters, R.A.M.J. Wijers, D. Xu

Aaron J. Romanowsky

Variable x-ray and γ-ray emission is characteristic of the most extreme physical processes in the universe. We present multiwavelength observations of a unique γ-ray–selected transient detected by the Swift satellite, accompanied by bright emission across the electromagnetic spectrum, and whose properties are unlike any previously observed source. We pinpoint the event to the center of a small, star-forming galaxy at redshift z = 0.3534. Its high-energy emission has lasted much longer than any γ-ray burst, whereas its peak luminosity was ∼100 times higher than bright active galactic nuclei. The association of the outburst with the center of its host galaxy …

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Star Clusters In M31: Old Clusters With Bar Kinematics, H. Morrison, N. Caldwell, R. P. Schiavon, E. Athanassoula, Aaron J. Romanowsky, P. Harding Jan 2011

Star Clusters In M31: Old Clusters With Bar Kinematics, H. Morrison, N. Caldwell, R. P. Schiavon, E. Athanassoula, Aaron J. Romanowsky, P. Harding

Aaron J. Romanowsky

We analyze our accurate kinematical data for the old clusters in the inner regions of M31. These velocities are based on high signal-to-noise Hectospec data. The data are well suited for analysis of M31's inner regions because we took particular care to correct for contamination by unresolved field stars from the disk and bulge in the fibers. The metal-poor clusters show kinematics that are compatible with a pressure-supported spheroid. The kinematics of metal-rich clusters, however, argue for a disk population. In particular the innermost region (inside 2 kpc) shows the kinematics of the x 2 family of bar periodic orbits, …

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Crazy Heart: Kinematics Of The “Star Pile” In Abell 545, R. Salinas, T. Richtler, M. J. West, Aaron J. Romanowsky, E. Llyod-Davies, Y. Schuberth Jan 2011

Crazy Heart: Kinematics Of The “Star Pile” In Abell 545, R. Salinas, T. Richtler, M. J. West, Aaron J. Romanowsky, E. Llyod-Davies, Y. Schuberth

Aaron J. Romanowsky

We study the structure and internal kinematics of the “star pile” in Abell 545 – a low surface brightness structure lying in the center of the cluster. We have obtained deep long-slit spectroscopy of the star pile using VLT/FORS2 and Gemini/GMOS, which is analyzed in conjunction with deep multiband CFHT/MEGACAM imaging. As presented in a previous study the star pile has a flat luminosity profile and its color is consistent with the outer parts of elliptical galaxies. Its velocity map is irregular, with parts being seemingly associated with an embedded nucleus, and others which have significant velocity offsets to the …

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Galaxies In Cdm With Halo Abundance Matching: Luminosity-Velocity Relation, Baryonic Mass-Velocity Relation, Velocity Function, And Clustering, S. Trujillo-Gomez, A. Klypin, J. Primack, Aaron J. Romanowsky Jan 2011

Galaxies In Cdm With Halo Abundance Matching: Luminosity-Velocity Relation, Baryonic Mass-Velocity Relation, Velocity Function, And Clustering, S. Trujillo-Gomez, A. Klypin, J. Primack, Aaron J. Romanowsky

Aaron J. Romanowsky

It has long been regarded as difficult if not impossible for a cosmological model to account simultaneously for the galaxy luminosity, mass, and velocity distributions. We revisit this issue using a modern compilation of observational data along with the best available large-scale cosmological simulation of dark matter (DM). We find that the standard cosmological model, used in conjunction with halo abundance matching (HAM) and simple dynamical corrections, fits—at least on average—all basic statistics of galaxies with circular velocities V circ > 80 km s–1 calculated at a radius of ~10 kpc. Our primary observational constraint is the luminosity-velocity (LV) relation—which generalizes …

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The Pn.S Elliptical Galaxy Survey: A Standard Cdm Halo Around Ngc 4374?, N. R. Napolitano, Aaron J. Romanowsky, M. Capaccioli, N. G. Douglas, M. Arnaboldi, L. Coccato, O. Gerhard, K. Kuijken, M. R. Merrifield, S. P. Bamford, A. Cortesi, P. Das, K. C. Freeman Jan 2011

The Pn.S Elliptical Galaxy Survey: A Standard Cdm Halo Around Ngc 4374?, N. R. Napolitano, Aaron J. Romanowsky, M. Capaccioli, N. G. Douglas, M. Arnaboldi, L. Coccato, O. Gerhard, K. Kuijken, M. R. Merrifield, S. P. Bamford, A. Cortesi, P. Das, K. C. Freeman

Aaron J. Romanowsky

As part of our current programme to test ΛCDM predictions for dark matter (DM) haloes using extended kinematical observations of early-type galaxies, we present a dynamical analysis of the bright elliptical galaxy NGC 4374 (M84) based on ∼450 planetary nebulae (PNe) velocities from the PN.Spectrograph, along with extended long-slit stellar kinematics. This is the first such analysis of a galaxy from our survey with a radially constant velocity dispersion profile. We find that the spatial and kinematical distributions of the PNe agree with the field stars in the region of overlap. The velocity kurtosis is consistent with zero at almost …

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Unravelling The Origins Of S0 Galaxies Using Maximum Likelihood Analysis Of Planetary Nebulae Kinematics, A. Cortesi, M. R. Merrifield, M. Arnaboldi, O. Gerhard, I. Martinez-Valpuesta, K. Saha, L. Coccato, S. Bamford, N. R. Napolitano, N. G. Douglas, Aaron J. Romanowsky, K. Kuijken, M. Capaccioli, K. C. Freeman Jan 2011

Unravelling The Origins Of S0 Galaxies Using Maximum Likelihood Analysis Of Planetary Nebulae Kinematics, A. Cortesi, M. R. Merrifield, M. Arnaboldi, O. Gerhard, I. Martinez-Valpuesta, K. Saha, L. Coccato, S. Bamford, N. R. Napolitano, N. G. Douglas, Aaron J. Romanowsky, K. Kuijken, M. Capaccioli, K. C. Freeman

Aaron J. Romanowsky

To investigate the origins of S0 galaxies, we present a new method of analysing their stellar kinematics from discrete tracers such as planetary nebulae. This method involves binning the data in the radial direction so as to extract the most general possible non-parametric kinematic profiles, and using a maximum-likelihood fit within each bin in order to make full use of the information in the discrete kinematic tracers. Both disc and spheroid kinematic components are fitted, with a two-dimensional decomposition of imaging data used to attribute to each tracer a probability of membership in the separate components. Likelihood clipping also allows …

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Global Properties Of ‘Ordinary’ Early-Type Galaxies: Photometry And Spectroscopy Of Stars And Globular Clusters In Ngc 4494, C. Foster, L. R. Spitler, Aaron J. Romanowsky, D. A. Forbes, V. Pota, K. Bekki, J. Strader, R. N. Proctor, J. A. Arnold, J. P. Brodie Jan 2011

Global Properties Of ‘Ordinary’ Early-Type Galaxies: Photometry And Spectroscopy Of Stars And Globular Clusters In Ngc 4494, C. Foster, L. R. Spitler, Aaron J. Romanowsky, D. A. Forbes, V. Pota, K. Bekki, J. Strader, R. N. Proctor, J. A. Arnold, J. P. Brodie

Aaron J. Romanowsky

We present a comprehensive analysis of the spatial, kinematic and chemical properties of stars and globular clusters (GCs) in the ‘ordinary’ elliptical galaxy NGC 4494 using data from the Keck and Subaru telescopes. We derive galaxy surface brightness and colour profiles out to large galactocentric radii. We compare the latter to metallicities derived using the near-infrared Calcium Triplet. We obtain stellar kinematics out to ∼3.5 effective radii. The latter appear flattened or elongated beyond ∼1.8 effective radii in contrast to the relatively round photometric isophotes. In fact, NGC 4494 may be a flattened galaxy, possibly even an S0, seen at …

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The Relationships Among Compact Stellar Systems: A Fresh View Of Ultra Compact Dwarfs, J. P. Brodie, Aaron J. Romanowsky, J. Strader, D. A. Forbes Jan 2011

The Relationships Among Compact Stellar Systems: A Fresh View Of Ultra Compact Dwarfs, J. P. Brodie, Aaron J. Romanowsky, J. Strader, D. A. Forbes

Aaron J. Romanowsky

We use a combined imaging and spectroscopic survey of the nearby central cluster galaxy, M87, to assemble a sample of 34 confirmed ultracompact dwarfs (UCDs) with half-light radii of gsim10 pc measured from Hubble Space Telescope images. This doubles the existing sample in M87, making it the largest such sample for any galaxy, while extending the detection of UCDs to unprecedentedly low luminosities (MV = –9). With this expanded sample, we find no correlation between size and luminosity, in contrast to previous suggestions, and no general correlation between size and galactocentric distance. We explore the relationships between UCDs, less luminous …

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The Fossil Record Of Two-Phase Galaxy Assembly: Kinematics And Metallicities In The Nearest S0 Galaxy, J, A, Arnold, Aaron J. Romanowsky, J. P. Brodie, L. Chomiuk, L. R. Spitler, J. Strader, A. J. Benson, D. A. Forbes Jan 2011

The Fossil Record Of Two-Phase Galaxy Assembly: Kinematics And Metallicities In The Nearest S0 Galaxy, J, A, Arnold, Aaron J. Romanowsky, J. P. Brodie, L. Chomiuk, L. R. Spitler, J. Strader, A. J. Benson, D. A. Forbes

Aaron J. Romanowsky

We present a global analysis of kinematics and metallicity in the nearest S0 galaxy, NGC 3115, along with implications for its assembly history. The data include high-quality wide-field imaging from Suprime-Cam on the Subaru telescope, and multi-slit spectra of the field stars and globular clusters (GCs) obtained using Keck-DEIMOS/LRIS and Magellan-IMACS. Within two effective radii, the bulge (as traced by the stars and metal-rich GCs) is flattened and rotates rapidly (v/σ gsim 1.5). At larger radii, the rotation declines dramatically to v/σ ~ 0.7, but remains well aligned with the inner regions. The radial decrease in characteristic metallicity of both …

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Speciation, Luminescence, And Alkaline Fluorescence Quenching Of 4-(2-Methylbutyl)Aminodipicolinic Acid (H2mebadpa), Gilles Muller, A. J. Ingram, A. G. Dunpal, R. Dipietro Jan 2011

Speciation, Luminescence, And Alkaline Fluorescence Quenching Of 4-(2-Methylbutyl)Aminodipicolinic Acid (H2mebadpa), Gilles Muller, A. J. Ingram, A. G. Dunpal, R. Dipietro

Faculty Publications, Chemistry

4-(2-Methylbutyl)aminodipicolinic acid (H2MEBADPA) has been synthesized and fully characterized in terms of aqueous phase protonation constants (pKa's) and photophysical measurements. The pKa's were determined by spectrophotometric titrations, utilizing a fully sealed titration system. Photophysical measurements consisted of room temperature fluorescence and frozen solution phosphorescence as well as quantum yield determinations at various pH, which showed that only fully deprotonated MEBADPA2– is appreciably emissive. The fluorescence of MEBADPA2– has been determined to be quenched by hydroxide and methoxide anions, most likely through base-catalyzed excited-state tautomerism or proton transfer. This quenching phenomenon has been quantitatively explored through steady-state and time-resolved fluorescence measurements. …

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A Bulk Water-Dependent Desolvation Energy Model For Analyzing The Effects Of Secondary Solutes On Biological Equilibria, Daryl K. Eggers Jan 2011

A Bulk Water-Dependent Desolvation Energy Model For Analyzing The Effects Of Secondary Solutes On Biological Equilibria, Daryl K. Eggers

Daryl K. Eggers

A new phenomenological model for interpreting the effects of solutes on biological equilibria is presented. The model attributes changes in equilibria to differences in the desolvation energy of the reacting species that, in turn, reflect changes in the free energy of the bulk water upon addition of secondary solutes. The desolvation approach differs notably from that of other solute models by treating the free energy of bulk water as a variable and by not ascribing the observed shifts in reaction equilibria to accumulation or depletion of solutes next to the surfaces of the reacting species. On the contrary, the partitioning …

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Changes In Apparent Molar Water Volume And Dkp Solubility Yield Insights On The Hofmeister Effect, Daryl K. Eggers, A. Y. Payumo, R. M. Huijon, D. D. Mansfield, L. M. Belk, A. K. Bui, A. E. Knight Jan 2011

Changes In Apparent Molar Water Volume And Dkp Solubility Yield Insights On The Hofmeister Effect, Daryl K. Eggers, A. Y. Payumo, R. M. Huijon, D. D. Mansfield, L. M. Belk, A. K. Bui, A. E. Knight

Daryl K. Eggers

This study examines the properties of a 4 × 2 matrix of aqueous cations and anions at concentrations up to 8.0 M. The apparent molar water volume, as calculated by subtracting the mass and volume of the ions from the corresponding solution density, was found to exceed the molar volume of ice in many concentrated electrolyte solutions, underscoring the nonideal behavior of these systems. The solvent properties of water were also analyzed by measuring the solubility of diketopiperazine (DKP) in 2.000 M salt solutions prepared from the same ion combinations. Solution rankings for DKP solubility were found to parallel the …

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Proximity Of The Superconducting Dome And The Quantum Critical Point In The Two-Dimensional Hubbard Model, S. Yang, H. Fotso, S.-Q. Su, D. Galanakis, Ehsan Khatami, J.-H. She, J. Moreno, J. Zaanen, M. Jarrell Jan 2011

Proximity Of The Superconducting Dome And The Quantum Critical Point In The Two-Dimensional Hubbard Model, S. Yang, H. Fotso, S.-Q. Su, D. Galanakis, Ehsan Khatami, J.-H. She, J. Moreno, J. Zaanen, M. Jarrell

Faculty Publications

We use the dynamical cluster approximation to understand the proximity of the superconducting dome to the quantum critical point in the two-dimensional Hubbard model. In a BCS formalism, Tc may be enhanced through an increase in the d-wave pairing interaction (Vd) or the bare pairing susceptibility (χ0d). At optimal doping, where Vd is revealed to be featureless, we find a power-law behavior of χ0d(ω=0), replacing the BCS log, and strongly enhanced Tc. We suggest experiments to verify our predictions.

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The Relationships Among Compact Stellar Systems: A Fresh View Of Ultra Compact Dwarfs, J. P. Brodie, Aaron J. Romanowsky, J. Strader, D. A. Forbes Jan 2011

The Relationships Among Compact Stellar Systems: A Fresh View Of Ultra Compact Dwarfs, J. P. Brodie, Aaron J. Romanowsky, J. Strader, D. A. Forbes

Faculty Publications

We use a combined imaging and spectroscopic survey of the nearby central cluster galaxy, M87, to assemble a sample of 34 confirmed ultracompact dwarfs (UCDs) with half-light radii of gsim10 pc measured from Hubble Space Telescope images. This doubles the existing sample in M87, making it the largest such sample for any galaxy, while extending the detection of UCDs to unprecedentedly low luminosities (MV = –9). With this expanded sample, we find no correlation between size and luminosity, in contrast to previous suggestions, and no general correlation between size and galactocentric distance. We explore the relationships between UCDs, less luminous …

Go to article

Changes In Apparent Molar Water Volume And Dkp Solubility Yield Insights On The Hofmeister Effect, Daryl K. Eggers, A. Y. Payumo, R. M. Huijon, D. D. Mansfield, L. M. Belk, A. K. Bui, A. E. Knight Jan 2011

Changes In Apparent Molar Water Volume And Dkp Solubility Yield Insights On The Hofmeister Effect, Daryl K. Eggers, A. Y. Payumo, R. M. Huijon, D. D. Mansfield, L. M. Belk, A. K. Bui, A. E. Knight

Faculty Publications, Chemistry

This study examines the properties of a 4 × 2 matrix of aqueous cations and anions at concentrations up to 8.0 M. The apparent molar water volume, as calculated by subtracting the mass and volume of the ions from the corresponding solution density, was found to exceed the molar volume of ice in many concentrated electrolyte solutions, underscoring the nonideal behavior of these systems. The solvent properties of water were also analyzed by measuring the solubility of diketopiperazine (DKP) in 2.000 M salt solutions prepared from the same ion combinations. Solution rankings for DKP solubility were found to parallel the …

Go to article

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