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Astrophysics and Astronomy

San Jose State University

Articles 181 - 210 of 320

Full-Text Articles in Physical Sciences and Mathematics

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

Faculty Publications

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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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

Faculty Publications

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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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

Faculty Publications

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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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

Faculty Publications

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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The Dark Halo Of He Hydra I Galaxy Cluster: Core, Cusp, Cosmological? Dynamics Of Ngc 3311 And Its Globular Cluster System, T. Richtler, R. Salinas, I. Misgeld, M. Hilker, G.K. T. Hau, Aaron J. Romanowsky, Y. Schuberth, M. Spolaor Jan 2011

The Dark Halo Of He Hydra I Galaxy Cluster: Core, Cusp, Cosmological? Dynamics Of Ngc 3311 And Its Globular Cluster System, T. Richtler, R. Salinas, I. Misgeld, M. Hilker, G.K. T. Hau, Aaron J. Romanowsky, Y. Schuberth, M. Spolaor

Faculty Publications

Context. Some galaxy clusters exhibit shallow or even cored dark matter density profiles in their central regions rather than the predicted steep or cuspy profiles, conflicting with the standard understanding of dark matter. NGC 3311 is the central cD galaxy of the Hydra I cluster (Abell 1060). Aims. We use globular clusters around NGC 3311, combined with kinematical data of the galaxy itself, to investigate the dark matter distribution in the central region of Hydra I. Methods. Radial velocities of 118 bright globular clusters, based on VLT/VIMOS mask spectroscopy, are used to calculate velocity dispersions which are well defined out …

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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

Faculty Publications

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

Faculty Publications

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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Stellar Mass-To-Light Ratio Gradients In Galaxies: Correlations With Mass, C. Tortora, N. R. Napolitano, Aaron J. Romanowsky, Ph. Jetzer, V. F. Cardone, M. Capaccioli Jan 2011

Stellar Mass-To-Light Ratio Gradients In Galaxies: Correlations With Mass, C. Tortora, N. R. Napolitano, Aaron J. Romanowsky, Ph. Jetzer, V. F. Cardone, M. Capaccioli

Aaron J. Romanowsky

We analyse the stellar mass-to-light ratio (M/L) gradients in a large sample of local galaxies taken from the Sloan Digital Sky Survey, spanning a wide range of stellar masses and morphological types. As suggested by the well-known relationship between M/L values and colours, we show that M/L gradients are strongly correlated with colour gradients, which we trace to the effects of age variations. Stellar M/L gradients generally follow patterns of variation with stellar mass and galaxy type that were previously found for colour and metallicity gradients. In late-type galaxies M/L gradients are negative, steepening with increasing mass. In early-type galaxies …

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The Dark Halo Of He Hydra I Galaxy Cluster: Core, Cusp, Cosmological? Dynamics Of Ngc 3311 And Its Globular Cluster System, T. Richtler, R. Salinas, I. Misgeld, M. Hilker, G.K. T. Hau, Aaron J. Romanowsky, Y. Schuberth, M. Spolaor Jan 2011

The Dark Halo Of He Hydra I Galaxy Cluster: Core, Cusp, Cosmological? Dynamics Of Ngc 3311 And Its Globular Cluster System, T. Richtler, R. Salinas, I. Misgeld, M. Hilker, G.K. T. Hau, Aaron J. Romanowsky, Y. Schuberth, M. Spolaor

Aaron J. Romanowsky

Context. Some galaxy clusters exhibit shallow or even cored dark matter density profiles in their central regions rather than the predicted steep or cuspy profiles, conflicting with the standard understanding of dark matter. NGC 3311 is the central cD galaxy of the Hydra I cluster (Abell 1060). Aims. We use globular clusters around NGC 3311, combined with kinematical data of the galaxy itself, to investigate the dark matter distribution in the central region of Hydra I. Methods. Radial velocities of 118 bright globular clusters, based on VLT/VIMOS mask spectroscopy, are used to calculate velocity dispersions which are well defined out …

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Evidence For Two Phases Of Galaxy Formation From Radial Trends In The Globular Cluster System Of Ngc 1407, D. A. Forbes, L. R. Spitler, J. Strader, Aaron J. Romanowsky, J. P. Brodie, C. Foster Jan 2011

Evidence For Two Phases Of Galaxy Formation From Radial Trends In The Globular Cluster System Of Ngc 1407, D. A. Forbes, L. R. Spitler, J. Strader, Aaron J. Romanowsky, J. P. Brodie, C. Foster

Aaron J. Romanowsky

Here we present the colours of individual globular clusters (GCs) around the massive elliptical galaxy NGC 1407 out to a projected galactocentric radius of 140 kpc or 17 galaxy effective radii (Re). Such data are a proxy for the halo metallicity. We find steep, and similar, metallicity gradients of ∼−0.4 dex dex−1 for both the blue (metal poor) and red (metal rich) GC subpopulations within 5–8.5 Re (40–70 kpc). At larger radii the mean GC colours (metallicity) are constant. A similar behaviour is seen in a wide-field study of M87's GC system, and in our own Galaxy. We interpret these …

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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, …

Go to article

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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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 …

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Cluster Solver For Dynamical Mean-Field Theory With Linear Scaling In Inverse Temperature, Ehsan Khatami, C. Lee, Z. Bai, R. Scalettar, M. Jarrell May 2010

Cluster Solver For Dynamical Mean-Field Theory With Linear Scaling In Inverse Temperature, Ehsan Khatami, C. Lee, Z. Bai, R. Scalettar, M. Jarrell

Faculty Publications

Dynamical mean-field theory and its cluster extensions provide a very useful approach for examining phase transitions in model Hamiltonians and, in combination with electronic structure theory, constitute powerful methods to treat strongly correlated materials. The key advantage to the technique is that, unlike competing real-space methods, the sign problem is well controlled in the Hirsch-Fye (HF) quantum Monte Carlo used as an exact cluster solver. However, an important computational bottleneck remains; the HF method scales as the cube of the inverse temperature, β. This often makes simulations at low temperatures extremely challenging. We present here a method based on determinant …

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Quantum Criticality Due To Incipient Phase Separation In The Two-Dimensional Hubbard Model, Ehsan Khatami, K. Mikelsons, D. Galanakis, A. Macridin, J. Moreno, R. Scalettar, M. Jarrell May 2010

Quantum Criticality Due To Incipient Phase Separation In The Two-Dimensional Hubbard Model, Ehsan Khatami, K. Mikelsons, D. Galanakis, A. Macridin, J. Moreno, R. Scalettar, M. Jarrell

Faculty Publications

We investigate the two-dimensional Hubbard model with next-nearest-neighbor hopping, t′, using the dynamical cluster approximation. We confirm the existence of a first-order phase-separation transition terminating at a second-order critical point at filling nc(t′) and temperature Tps(t′). We find that as t′ approaches zero, Tps(t′) vanishes and nc(t′) approaches the filling associated with the quantum critical point separating the Fermi liquid from the pseudogap phase. We propose that the quantum critical point under the superconducting dome is the zero-temperature limit of the line of second-order critical points.

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A Hybrid Particle-Continuum Method For Hydrodynamics Of Complex Fluids, Alejandro Garcia, A. Donev, J. B. Bell, B. Alder Jan 2010

A Hybrid Particle-Continuum Method For Hydrodynamics Of Complex Fluids, Alejandro Garcia, A. Donev, J. B. Bell, B. Alder

Faculty Publications

A previously developed hybrid particle-continuum method [J. B. Bell, A. Garcia, and S. A. Williams, Multiscale Model. Simul., 6 (2008), pp. 1256–1280] is generalized to dense fluids and two- and three-dimensional flows. The scheme couples an explicit fluctuating compressible Navier–Stokes solver with the isotropic direct simulation Monte Carlo (DSMC) particle method [A. Donev, A. L. Garcia, and B. J. Alder, J. Stat. Mech. Theory Exp., 2009 (2009), article P11008]. To achieve bidirectional dynamic coupling between the particle (microscale) and continuum (macroscale) regions, the continuum solver provides state-based boundary conditions to the particle subdomain, while the particle solver provides flux-based boundary …

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Computational Fluctuating Fluid Dynamics, Alejandro Garcia, J. B. Bell, S. Williams Jan 2010

Computational Fluctuating Fluid Dynamics, Alejandro Garcia, J. B. Bell, S. Williams

Faculty Publications

This paper describes the extension of a recently developed numerical solver for the Landau-Lifshitz Navier-Stokes (LLNS) equations to binary mixtures in three dimensions. The LLNS equations incorporate thermal fluctuations into macroscopic hydrodynamics by using white-noise fluxes. These stochastic PDEs are more complicated in three dimensions due to the tensorial form of the correlations for the stochastic fluxes and in mixtures due to couplings of energy and concentration fluxes (e.g., Soret effect). We present various numerical tests of systems in and out of equilibrium, including time-dependent systems, and demonstrate good agreement with theoretical results and molecular simulation

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The Globular Cluster System Of Ngc 1399. V. Dynamics Of The Cluster System Out To 80 Kpc, Y. Schuberth, T. Richtler, M. Hilker, B. Dirsch, L. Bassino, Aaron J. Romanowsky, L. Infante Jan 2010

The Globular Cluster System Of Ngc 1399. V. Dynamics Of The Cluster System Out To 80 Kpc, Y. Schuberth, T. Richtler, M. Hilker, B. Dirsch, L. Bassino, Aaron J. Romanowsky, L. Infante

Faculty Publications

Globular clusters (GCs) are tracers of the gravitational potential of their host galaxies. Moreover, their kinematic properties may provide clues for understanding the formation of GC systems and their host galaxies. We use the largest set of GC velocities obtained so far of any elliptical galaxy to revise and extend the previous investigations (Richtler et al. 2004) of the dynamics of NGC 1399, the central dominant galaxy of the nearby Fornax cluster of galaxies. The GC velocities are used to study the kinematics, their relation with population properties, and the dark matter halo of NGC 1399. We have obtained 477 …

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Central Dark Matter Content Of Early-Type Galaxies: Scaling Relations And Connections With Star Formation Histories, N. R. Napolitano, Aaron J. Romanowsky, A. J. Tortora Jan 2010

Central Dark Matter Content Of Early-Type Galaxies: Scaling Relations And Connections With Star Formation Histories, N. R. Napolitano, Aaron J. Romanowsky, A. J. Tortora

Faculty Publications

We examine correlations between masses, sizes and star formation histories for a large sample of low-redshift early-type galaxies, using a simple suite of dynamical and stellar population models. We confirm an anticorrelation between the size and stellar age and go on to survey for trends with the central content of dark matter (DM). An average relation between the central DM density and galaxy size of 〈ρDM〉∝R−2eff provides the first clear indication of cuspy DM haloes in these galaxies – akin to standard Λ cold dark matter haloes that have undergone adiabatic contraction. The DM density scales with galaxy mass as …

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The Globular Cluster System Of Ngc 1399. V. Dynamics Of The Cluster System Out To 80 Kpc, Y. Schuberth, T. Richtler, M. Hilker, B. Dirsch, L. Bassino, Aaron J. Romanowsky, L. Infante Jan 2010

The Globular Cluster System Of Ngc 1399. V. Dynamics Of The Cluster System Out To 80 Kpc, Y. Schuberth, T. Richtler, M. Hilker, B. Dirsch, L. Bassino, Aaron J. Romanowsky, L. Infante

Aaron J. Romanowsky

Globular clusters (GCs) are tracers of the gravitational potential of their host galaxies. Moreover, their kinematic properties may provide clues for understanding the formation of GC systems and their host galaxies. We use the largest set of GC velocities obtained so far of any elliptical galaxy to revise and extend the previous investigations (Richtler et al. 2004) of the dynamics of NGC 1399, the central dominant galaxy of the nearby Fornax cluster of galaxies. The GC velocities are used to study the kinematics, their relation with population properties, and the dark matter halo of NGC 1399. We have obtained 477 …

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