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San Jose State University

Faculty Publications

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Articles 181 - 210 of 332

Full-Text Articles in Physical Sciences and Mathematics

Planetary Nebula Spectrograph Survey Of S0 Galaxy Kinematics – Ii. Clues To The Origins Of S0 Galaxies, A. Cortesi, M. R. Merrifield, L. Coccato, M. Arnaboldi, O. Gerhard, Aaron J. Romanowsky, N. G. Douglass, K. Kuiijken, M. Capaccioli, K. C. Freeman, K. Saha, A. L. Chies-Santos Jan 2013

Planetary Nebula Spectrograph Survey Of S0 Galaxy Kinematics – Ii. Clues To The Origins Of S0 Galaxies, A. Cortesi, M. R. Merrifield, L. Coccato, M. Arnaboldi, O. Gerhard, Aaron J. Romanowsky, N. G. Douglass, K. Kuiijken, M. Capaccioli, K. C. Freeman, K. Saha, A. L. Chies-Santos

Faculty Publications

The stellar kinematics of the spheroids and discs of S0 galaxies contain clues to their formation histories. Unfortunately, it is difficult to disentangle the two components and to recover their stellar kinematics in the faint outer parts of the galaxies using conventional absorption line spectroscopy. This paper therefore presents the stellar kinematics of six S0 galaxies derived from observations of planetary nebulae, obtained using the Planetary Nebula Spectrograph. To separate the kinematics of the two components, we use a maximum-likelihood method that combines the discrete kinematic data with a photometric component decomposition. The results of this analysis reveal that: the …

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The Planetary Nebula Spectrograph Survey Of S0 Galaxy Kinematics. Data And Overview, A. Cortesi, M. Arnaboldi, L. Coccato, M. R. Merrifield, O. Gerhard, S. Bamford, Aaron J. Romanowsky, N. R. Napolitano, N. G. Douglas, K. Kuiijken, M. Capaccioli, K. C. Freeman, A. L. Chies-Santos, V. Pota Jan 2013

The Planetary Nebula Spectrograph Survey Of S0 Galaxy Kinematics. Data And Overview, A. Cortesi, M. Arnaboldi, L. Coccato, M. R. Merrifield, O. Gerhard, S. Bamford, Aaron J. Romanowsky, N. R. Napolitano, N. G. Douglas, K. Kuiijken, M. Capaccioli, K. C. Freeman, A. L. Chies-Santos, V. Pota

Faculty Publications

The origins of S0 galaxies remain obscure, with various mechanisms proposed for their formation, likely depending on environment. These mechanisms would imprint different signatures in the galaxies' stellar kinematics out to large radii, offering a method for distinguishing between them. We aim to study a sample of six S0 galaxies from a range of environments, and use planetary nebulae (PNe) as tracers of their stellar populations out to very large radii, to determine their kinematics in order to understand their origins. Using a special-purpose instrument, the Planetary Nebula Spectrograph, we observe and extract PNe catalogues for these six systems*. We …

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The Sluggs Survey: Wide Field Imaging Of The Globular Cluster System Of Ngc 4278, C. Usher, D. A. Forbes, L. R. Spitler, J. P. Brodie, Aaron J. Romanowsky, J. Strader, K. A. Woodley Jan 2013

The Sluggs Survey: Wide Field Imaging Of The Globular Cluster System Of Ngc 4278, C. Usher, D. A. Forbes, L. R. Spitler, J. P. Brodie, Aaron J. Romanowsky, J. Strader, K. A. Woodley

Faculty Publications

We use multipointing Hubble Space Telescope Advanced Camera for Surveys and wide field Subaru Suprime-Cam imaging to study the globular cluster system of the L* elliptical galaxy NGC 4278. We have also obtained a handful of new globular cluster spectra with the Keck Deep Imaging Multi-Object Spectrograph. We determine the globular cluster surface density profile and use it to calculate the total number of globular clusters, finding the system to be slightly more populous than average for galaxies of its luminosity. We find clear evidence for bimodality in the globular cluster colour distribution and for a colour–magnitude relation in the …

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The Sluggs Survey: Probing The Supermassive Blackhole Connection With Bulges And Haloes Using Red And Blue Globular Cluster Systems, V. Pota, A. W. Graham, D. A. Forbes, Aaron J. Romanowsky, A. J. Brodie, J. Strader Jan 2013

The Sluggs Survey: Probing The Supermassive Blackhole Connection With Bulges And Haloes Using Red And Blue Globular Cluster Systems, V. Pota, A. W. Graham, D. A. Forbes, Aaron J. Romanowsky, A. J. Brodie, J. Strader

Faculty Publications

Understanding whether the bulge or the halo provides the primary link to the growth of supermassive black holes has strong implications for galaxy evolution and supermassive black hole formation itself. In this paper, we approach this issue by investigating extragalactic globular cluster (GC) systems, which can be used to probe the physics of both the bulge and the halo of the host galaxy. We study the relation between the supermassive black hole masses (MBH) and the GC system velocity dispersions (σGC) using an updated and improved sample of 21 galaxies. We exploit the dichotomy of GC system colours, to test …

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Mond And Imf Variations In Early-Type Galaxies From Atlas3d, C. Tortora, Aaron J. Romanowsky, V. F. Cardone, N. R. Napolitano, Ph Jetzer Jan 2013

Mond And Imf Variations In Early-Type Galaxies From Atlas3d, C. Tortora, Aaron J. Romanowsky, V. F. Cardone, N. R. Napolitano, Ph Jetzer

Faculty Publications

No abstract provided.

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The Sluggs Survey: Outer Triaxiality In The Fast Rotator Elliptical Ngc 4473, C. Foster, J. A. Arnold, D. A. Forbes, N. Pastorello, Aaron J. Romanowsky, L. R. Spitler, J. Strader, J. P. Brodie Jan 2013

The Sluggs Survey: Outer Triaxiality In The Fast Rotator Elliptical Ngc 4473, C. Foster, J. A. Arnold, D. A. Forbes, N. Pastorello, Aaron J. Romanowsky, L. R. Spitler, J. Strader, J. P. Brodie

Faculty Publications

Systematic surveys of nearby early-type galaxies using integral field unit (IFU) spectrograph data have revealed that galaxies can hide interesting structures only visible through kinematic studies. As part of their pioneering work, the ATLAS3D team have shown that most morphologically elliptical galaxies are centrally kinematically disc like. Hence, while global morphology suggests that ellipticals are ellipsoidal/triaxial in shape, their central kinematics may be consistent with (inclined) oblate systems. Here, we study the fast rotator elliptical galaxy: NGC 4473. Using slitlets, we obtain galaxy light kinematics out to unprecedentedly large galactocentric radii (2.5 effective radii). While we confirm the IFU results …

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The Densest Galaxy, J. Strader, A. C. Seth, J. P. Brodie, D. A. Forbes, G. Fabbiano, Aaron J. Romanowsky, C. Conroy, N. Caldwell, V. Pota, C. Usher, J. A. Arnold Jan 2013

The Densest Galaxy, J. Strader, A. C. Seth, J. P. Brodie, D. A. Forbes, G. Fabbiano, Aaron J. Romanowsky, C. Conroy, N. Caldwell, V. Pota, C. Usher, J. A. Arnold

Faculty Publications

We report the discovery of a remarkable ultra-compact dwarf galaxy around the massive Virgo elliptical galaxy NGC 4649 (M60), which we call M60-UCD1. With a dynamical mass of 2.0 × 108 M ☉ but a half-light radius of only ~24 pc, M60-UCD1 is more massive than any ultra-compact dwarfs of comparable size, and is arguably the densest galaxy known in the local universe. It has a two-component structure well fit by a sum of Sérsic functions, with an elliptical, compact (rh = 14 pc; n ~ 3.3) inner component and a round, exponential, extended (rh = 49 pc) outer component. …

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Filling The Gap: A New Class Of Old Star Cluster?, D. A. Forbes, V. Pota, C. Usher, Aaron J. Romanowsky, J. Strader, J. P. Brodie, J. A. Arnold, L. R. Spitler Jan 2013

Filling The Gap: A New Class Of Old Star Cluster?, D. A. Forbes, V. Pota, C. Usher, Aaron J. Romanowsky, J. Strader, J. P. Brodie, J. A. Arnold, L. R. Spitler

Faculty Publications

It is not understood whether long-lived star clusters possess a continuous range of sizes and masses (and hence densities) or if rather, they should be considered as distinct types with different origins. Utilizing the Hubble Space Telescope to measure sizes and long exposures on the Keck 10 m telescope to obtain distances, we have discovered the first confirmed star clusters that lie within a previously claimed size–luminosity gap dubbed the ‘avoidance zone’ by Hwang et al. The existence of these star clusters extends the range of sizes, masses and densities for star clusters, and argues against current formation models that …

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The Sluggs Survey: The Globular Cluster Systems Of Three Early-Type Galaxies Using Wide-Field Imaging, S. S. Kartha, D. A. Forbes, L. R. Spitler, Aaron J. Romanowsky, J. A. Arnold, J. P. Brodie Jan 2013

The Sluggs Survey: The Globular Cluster Systems Of Three Early-Type Galaxies Using Wide-Field Imaging, S. S. Kartha, D. A. Forbes, L. R. Spitler, Aaron J. Romanowsky, J. A. Arnold, J. P. Brodie

Faculty Publications

We present the results from a wide-field imaging study of globular cluster (GC) systems in three early-type galaxies. Combinations of Subaru/Suprime-Cam, CFHT/MegaCam and HST/WFPC2/ACS data were used to determine the GC system properties of three highly flattened galaxies NGC 720, NGC 1023 and NGC 2768. This work is the first investigation of the GC system in NGC 720 and NGC 2768 to very large galactocentric radius (∼ 100 kpc). The three galaxies have clear blue and red GC subpopulations. The radial surface densities of the GC systems are fitted with Sersic profiles, and detected out to 15, 8 and 10 …

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Angular Momentum And Galaxy Formation Revisited: Effects Of Variable Mass-To-Light Ratios, S. M. Fall, Aaron J. Romanowsky Jan 2013

Angular Momentum And Galaxy Formation Revisited: Effects Of Variable Mass-To-Light Ratios, S. M. Fall, Aaron J. Romanowsky

Faculty Publications

We rederive the relation between the specific angular momentum j sstarf and the mass M sstarf of the stellar matter in galaxies of different morphological types. This is a revision of the j sstarf-M sstarf diagram presented in our recent comprehensive study of galactic angular momentum. In that work, we estimated j sstarf from kinematic and photometric data that extended to large radii and M sstarf from near-infrared luminosities LK with an assumed universal mass-to-light ratio M sstarf/LK . However, recent stellar population models show large variations in M sstarf/LK correlated with B – V color. In the present work, …

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The Sluggs Survey: Wide-Field Stellar Kinematics Of Early-Type Galaxies, J. A. Arnold, Aaron J. Romanowsky, J. P. Brodie, D. A. Forbes, J. Strader, C. Foster, S. S. Kartha, N. Pastorello, V. Pota, C. Usher, K. A. Woodley Jan 2013

The Sluggs Survey: Wide-Field Stellar Kinematics Of Early-Type Galaxies, J. A. Arnold, Aaron J. Romanowsky, J. P. Brodie, D. A. Forbes, J. Strader, C. Foster, S. S. Kartha, N. Pastorello, V. Pota, C. Usher, K. A. Woodley

Faculty Publications

No abstract provided.

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The Paucity Of Globular Clusters Around The Field Elliptical Ngc 7507, J. P. Caso, T. Richtler, L. P. Bassino, R. Salinas, R. R. Lane, Aaron J. Romanowsky Jan 2013

The Paucity Of Globular Clusters Around The Field Elliptical Ngc 7507, J. P. Caso, T. Richtler, L. P. Bassino, R. Salinas, R. R. Lane, Aaron J. Romanowsky

Faculty Publications

There is strong evidence that globular cluster systems (GCSs) of massive galaxies are largely assembled by infall/accretion processes. Therefore, we expect the GCSs of isolated elliptical galaxies to be poor. Alhough not completely isolated, NGC 7507 is a massive field elliptical galaxy with an apparently very low dark matter content. Aims: We determine the richness, the colour distribution, and the structural properties of the GCS of NGC 7507. Methods: We perform wide-field Washington photometry with data obtained with the MOSAIC II camera at the 4m-Blanco telescope, CTIO. Results: The GCS is very poor with S_N ~ 0.6. We identify three …

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The Sluggs Survey: Kinematics For Over 2500 Globular Clusters In Twelve Early-Type Galaxies, V. Pota, D. A. Forbes, Aaron J. Romanowsky, J. P. Brodie, L. R. Spitler, J. Strader, C. Foster, J. A. Arnold, A. Benson, C. Blom, J. R. Hargis, K. L. Rhode, C. Usher Jan 2013

The Sluggs Survey: Kinematics For Over 2500 Globular Clusters In Twelve Early-Type Galaxies, V. Pota, D. A. Forbes, Aaron J. Romanowsky, J. P. Brodie, L. R. Spitler, J. Strader, C. Foster, J. A. Arnold, A. Benson, C. Blom, J. R. Hargis, K. L. Rhode, C. Usher

Faculty Publications

We present a spectrophotometric survey of 2522 extragalactic globular clusters (GCs) around 12 early-type galaxies, nine of which have not been published previously. Combining space-based and multicolour wide-field ground-based imaging, with spectra from the Keck/DEep Imaging Multi-Object Spectrograph (DEIMOS) instrument, we obtain an average of 160 GC radial velocities per galaxy, with a high-velocity precision of ∼15 km s−1 per GC. After studying the photometric properties of the GC systems, such as their spatial and colour distributions, we focus on the kinematics of metal-poor (blue) and metal-rich (red) GC subpopulations to an average distance of ∼8 effective radii from the …

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Using Marine Snails To Teach Biogeography And Macroevolution: The Role Of Larvae And Dispersal Ability In The Evolution And Persistence Of Species, Jonathan R. Hendricks Dec 2012

Using Marine Snails To Teach Biogeography And Macroevolution: The Role Of Larvae And Dispersal Ability In The Evolution And Persistence Of Species, Jonathan R. Hendricks

Faculty Publications

While some marine animals are capable of traveling great distances, many have limited mobility as adults and spend the majority of their lifetimes in a small geographical area or may even be cemented to a single place. While it might be expected that species with limited mobility would have small geographic distributions, some nevertheless occur over very large areas. This is the case for some marine snails (gastropods). A key factor that impacts the geographic distribution of marine snails is the type of larvae they have during the phase of their life history that follows hatching from an egg. Because …

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Bioactive Trace Metal Distributions And Biogeochemical Controls In The Southern Ocean, Christopher Measures, Mariko Hatta, Maxime Grand Sep 2012

Bioactive Trace Metal Distributions And Biogeochemical Controls In The Southern Ocean, Christopher Measures, Mariko Hatta, Maxime Grand

Faculty Publications

Extensive sampling in many regions of the Southern Ocean has demonstrated that surface water concentrations of dissolved Fe are low enough to limit phytoplankton growth. In contrast, there is currently no evidence that other bioactive elements (e.g., Mn, Zn, Co) are similarly limiting. Although atmospheric input of dissolved Fe to Southern Ocean surface waters appears to be low, resuspension of sediments from shallow regions around islands and the Antarctic coastline can inject significant amounts of Fe into the surrounding waters, stimulating primary production and providing a natural laboratory for studying the response of biological systems to natural Fe fertilization processes. …

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Effect Of Particle Statistics In Strongly Correlated Two-Dimensional Hubbard Models, Ehsan Khatami, Marcos Rigol Aug 2012

Effect Of Particle Statistics In Strongly Correlated Two-Dimensional Hubbard Models, Ehsan Khatami, Marcos Rigol

Faculty Publications

We study the onset of particle statistics effects as the temperature is lowered in strongly correlated two-dimensional Hubbard models. We utilize numerical linked-cluster expansions and focus on the properties of interacting lattice fermions and two-component hard-core bosons. In the weak-coupling regime, where the ground state of the bosonic system is a superfluid, the thermodynamic properties of the two systems at half filling exhibit very large differences even at high temperatures. In the strong-coupling regime, where the low-temperature behavior is governed by a Mott insulator for either particle statistics, the agreement between the thermodynamic properties of both systems extends to regions …

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Student-Teacher Interactions For Bringing Out Student Ideas About Energy, Benedikt W. Harrer, Michael Wittmann, Rachel Scherr Aug 2012

Student-Teacher Interactions For Bringing Out Student Ideas About Energy, Benedikt W. Harrer, Michael Wittmann, Rachel Scherr

Faculty Publications

Modern middle school science curricula use group activities to help students express their thinking and enable them to work together like scientists. We are studying rural 8th grade science classrooms using materials on energy. Even after spending several months with the same curriculum on other physics topics, students' engagement in group activities seems to be restricted to creating lists of words that are associated with energy. Though research suggests that children have rich and potentially valuable ideas about energy, our students don't seem to spontaneously use and express their ideas in the classroom. Only within or after certain interactions with …

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Quantum Quenches In Disordered Systems: Approach To Thermal Equilibrium Without A Typical Relaxation Time, Ehsan Khatami, Marcos Rigol, Armando Relaño, Antonio García-García May 2012

Quantum Quenches In Disordered Systems: Approach To Thermal Equilibrium Without A Typical Relaxation Time, Ehsan Khatami, Marcos Rigol, Armando Relaño, Antonio García-García

Faculty Publications

We study spectral properties and the dynamics after a quench of one-dimensional spinless fermions with short-range interactions and long-range random hopping. We show that a sufficiently fast decay of the hopping term promotes localization effects at finite temperature, which prevents thermalization even if the classical motion is chaotic. For slower decays, we find that thermalization does occur. However, within this model, the latter regime falls in an unexpected universality class, namely, observables exhibit a power-law (as opposed to an exponential) approach to their thermal expectation values.

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The 1, 2-Conjecture For Graphs With Relatively Small Chromatic Number, Sogol Jahanbekam, Douglas West Mar 2012

The 1, 2-Conjecture For Graphs With Relatively Small Chromatic Number, Sogol Jahanbekam, Douglas West

Faculty Publications

No abstract provided.

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Particle Transport Over Rough Hillslope Surfaces By Dry Ravel: Experiments And Simulations With Implications For Nonlocal Sediment Flux, Emmanuel Gabet, Morgan Mendoza Feb 2012

Particle Transport Over Rough Hillslope Surfaces By Dry Ravel: Experiments And Simulations With Implications For Nonlocal Sediment Flux, Emmanuel Gabet, Morgan Mendoza

Faculty Publications

Past studies of hillslope evolution have typically assumed that soil creep processes are governed by a linear relationship between local hillslope angle and transport distance. The assumption of “linear diffusion” has fallen out of favor because, when coupled with an expression of mass continuity, it yields unrealistic hillslope profiles. As a consequence, a better understanding of the mechanics of sediment transport is needed. Here we report results from a series of flume experiments performed to investigate sediment transport by dry ravel, a common soil creep process in arid and semiarid environments. We find that, at gentle slopes, transport distances follow …

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Numerical Study Of The Thermodynamics Of Clinoatacamite, Ehsan Khatami, Joel Helton, Marcos Rigol Feb 2012

Numerical Study Of The Thermodynamics Of Clinoatacamite, Ehsan Khatami, Joel Helton, Marcos Rigol

Faculty Publications

We study the thermodynamic properties of the clinoatacamite compound, Cu2(OH)3Cl, by considering several approximate models. They include the Heisenberg model on (i) the uniform pyrochlore lattice, (ii) a very anisotropic pyrochlore lattice, and (iii) a kagome lattice weakly coupled to spins that sit on a triangular lattice. We utilize the exact diagonalization of small clusters with periodic boundary conditions and implement a numerical linked-cluster expansion approach for quantum lattice models with reduced symmetries, which allows us to solve model (iii) in the thermodynamic limit. We find a very good agreement between the experimental uniform susceptibility and the numerical results for …

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Elements Of Proximal Formative Assessment In Learners’ Discourse About Energy, Benedikt W. Harrer, Rachel E. Scherr, Michael C. Wittmann, Hunter G. Close, Brian W. Frank Jan 2012

Elements Of Proximal Formative Assessment In Learners’ Discourse About Energy, Benedikt W. Harrer, Rachel E. Scherr, Michael C. Wittmann, Hunter G. Close, Brian W. Frank

Faculty Publications

Proximal formative assessment, the just-in-time elicitation of students' ideas that informs ongoing instruction, is usually associated with the instructor in a formal classroom setting. However, the elicitation, assessment, and subsequent instruction that characterize proximal formative assessment are also seen in discourse among peers. We present a case in which secondary teachers in a professional development course at SPU are discussing energy flow in refrigerators. In this episode, a peer is invited to share her thinking (elicitation). Her idea that refrigerators move heat from a relatively cold compartment to a hotter environment is inappropriately judged as incorrect (assessment). The "instruction" (peer …

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Short-Range Correlations And Cooling Of Ultracold Fermions In The Honeycomb Lattice, Baoming Tang, Thereza Paiva, Ehsan Khatami, Marcos Rigol Jan 2012

Short-Range Correlations And Cooling Of Ultracold Fermions In The Honeycomb Lattice, Baoming Tang, Thereza Paiva, Ehsan Khatami, Marcos Rigol

Faculty Publications

We use determinantal quantum Monte Carlo simulations and numerical linked-cluster expansions to study thermodynamic properties and short-range spin correlations of fermions in the honeycomb lattice. We find that, at half filling and finite temperatures, nearest-neighbor spin correlations can be stronger in this lattice than in the square lattice, even in regimes where the ground state in the former is a semimetal or a spin liquid. The honeycomb lattice also exhibits a more pronounced anomalous region in the double occupancy that leads to stronger adiabatic cooling than in the square lattice. We discuss the implications of these findings for optical lattice …

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Numerical Linked-Cluster Expansion For The Distorted Kagome Lattice Heisenberg Model, Ehsan Khatami, Marcos Rigol Jan 2012

Numerical Linked-Cluster Expansion For The Distorted Kagome Lattice Heisenberg Model, Ehsan Khatami, Marcos Rigol

Faculty Publications

Motivated by experimental results for the thermodynamic properties of the Rb2Cu3SnF12 material and the discovery of its valence-bond solid ground state, we utilize the numerical linked-cluster expansions (NLCEs) and devise an expansion tailored to solve the Heisenberg model on a pinwheel-distorted kagome lattice. Using the exchange interactions that are relevant to Rb2Cu3SnF12, we calculate its uniform spin susceptibility and find a very good agreement with experiment. Next, we focus on the ground state of a simplified model of the distorted kagome lattice and take advantage of a zero-temperature Lanczos-based NLCE to study the approach to the ground state of the …

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Testing Yukawa-Like Potentials From F(R)-Gravity In Elliptical Galaxies, N. R. Napolitano, S. Capozziello, Aaron J. Romanowsky, M. Capaccioli, C. Tortora Jan 2012

Testing Yukawa-Like Potentials From F(R)-Gravity In Elliptical Galaxies, N. R. Napolitano, S. Capozziello, Aaron J. Romanowsky, M. Capaccioli, C. Tortora

Faculty Publications

We present the first analysis of extended stellar kinematics of elliptical galaxies where a Yukawa-like correction to the Newtonian gravitational potential derived from f(R)-gravity is considered as an alternative to dark matter. In this framework, we model long-slit data and planetary nebula data out to 7 R eff of three galaxies with either decreasing or flat dispersion profiles. We use the corrected Newtonian potential in a dispersion-kurtosis Jeans analysis to account for the mass-anisotropy degeneracy. We find that these modified potentials are able to fit nicely all three elliptical galaxies and the anisotropy distribution is consistent with that estimated if …

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Evidence For Inhomogeneous Reionization In The Local Universe From Metal-Poor Globular Cluster Systems, L. R. Spitler, Aaron J. Romanowsky, J. Diemand, J. Strader, D. A. Forbes, B. Moore, J. P. Brodie Jan 2012

Evidence For Inhomogeneous Reionization In The Local Universe From Metal-Poor Globular Cluster Systems, L. R. Spitler, Aaron J. Romanowsky, J. Diemand, J. Strader, D. A. Forbes, B. Moore, J. P. Brodie

Faculty Publications

Exploiting a fundamental characteristic of galaxy assembly in the Λ cold dark matter paradigm, the observed spatial biasing and kinematics of metal-poor globular star clusters are used to constrain the local reionization epoch around individual galaxies. Selecting three galaxies located in different environments, the first attempt at constraining the environmental propagation of reionization in the local Universe is carried out. The joint constraint from the three galaxies (Graphic) agrees remarkably well with the latest Wilkinson Microwave Anisotropy Probe constraint on zreion for a simple instantaneous reionization model. More importantly, the range of zreion values found here is consistent with the …

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The Ongoing Assembly Of A Central Cluster Galaxy: Phase-Space Substructures In The Halo Of M87, Aaron J. Romanowsky, J. Strader, J. P. Brodie, C. Mihos, L. R. Spitler, D. A. Forbes, C. Foster, J. A. Arnold Jan 2012

The Ongoing Assembly Of A Central Cluster Galaxy: Phase-Space Substructures In The Halo Of M87, Aaron J. Romanowsky, J. Strader, J. P. Brodie, C. Mihos, L. R. Spitler, D. A. Forbes, C. Foster, J. A. Arnold

Faculty Publications

The halos of galaxies preserve unique records of their formation histories. We carry out the first combined observational and theoretical study of phase-space halo substructure in an early-type galaxy: M87, the central galaxy in the Virgo cluster. We analyze an unprecedented wide-field, high-precision photometric and spectroscopic data set for 488 globular clusters (GCs), which includes new, large-radius Subaru/Suprime-Cam and Keck/DEIMOS observations. We find signatures of two substructures in position-velocity phase space. One is a small, cold stream associated with a known stellar filament in the outer halo; the other is a large shell-like pattern in the inner halo that implies …

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The Sluggs Survey: Ngc 3115, A Critical Test Case For Metallicity Bimodality In Globular Cluster Systems, J. P. Brodie, C. Usher, C. Conroy, J. Strader, J. A. Arnold, D. A. Forbes, Aaron J. Romanowsky Jan 2012

The Sluggs Survey: Ngc 3115, A Critical Test Case For Metallicity Bimodality In Globular Cluster Systems, J. P. Brodie, C. Usher, C. Conroy, J. Strader, J. A. Arnold, D. A. Forbes, Aaron J. Romanowsky

Faculty Publications

Due to its proximity (9 Mpc) and the strongly bimodal color distribution of its spectroscopically well-sampled globular cluster (GC) system, the early-type galaxy NGC 3115 provides one of the best available tests of whether the color bimodality widely observed in GC systems generally reflects a true metallicity bimodality. Color bimodality has alternatively been attributed to a strongly nonlinear color-metallicity relation reflecting the influence of hot horizontal-branch stars. Here, we couple Subaru Suprime-Cam gi photometry with Keck/DEIMOS spectroscopy to accurately measure GC colors and a CaT index that measures the Ca II triplet. We find the NGC 3115 GC system to …

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The Sluggs Survey: Globular Cluster System Kinematics And Substructure In Ngc 4365, C. Blom, D. A. Forbes, J. P. Brodie, C. Foster, Aaron J. Romanowsky, L. R. Spitler, J. Strader Jan 2012

The Sluggs Survey: Globular Cluster System Kinematics And Substructure In Ngc 4365, C. Blom, D. A. Forbes, J. P. Brodie, C. Foster, Aaron J. Romanowsky, L. R. Spitler, J. Strader

Faculty Publications

We present a kinematic analysis of the globular cluster (GC) system of the giant elliptical galaxy NGC 4365 and find several distinct kinematic substructures. This analysis is carried out using radial velocities for 269 GCs, obtained with the DEIMOS (DEep Imaging Multi-Object Spectrograph) instrument on the Keck II telescope as part of the SAGES Legacy Unifying Globulars and Galaxies Survey (SLUGGS). We find that each of the three (formerly identified) GC colour subpopulations reveal distinct rotation properties. The rotation of the green GC subpopulation is consistent with the bulk of NGC 4365's stellar light, which ‘rolls’ about the photometric major …

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The Sluggs Survey: Calcium Triplet-Based Spectroscopic Metallicites For Over 900 Globular Clusters, C. Usher, D. A. Forbes, J. P. Brodie, C. Foster, L. R. Spitler, J. A. Arnold, Aaron J. Romanowsky, J. Strader, V. Pota Jan 2012

The Sluggs Survey: Calcium Triplet-Based Spectroscopic Metallicites For Over 900 Globular Clusters, C. Usher, D. A. Forbes, J. P. Brodie, C. Foster, L. R. Spitler, J. A. Arnold, Aaron J. Romanowsky, J. Strader, V. Pota

Faculty Publications

Although the colour distribution of globular clusters in massive galaxies is well known to be bimodal, the spectroscopic metallicity distribution has been measured in only a few galaxies. After redefining the calcium triplet index–metallicity relation, we use our relation to derive the metallicity of 903 globular clusters in 11 early-type galaxies. This is the largest sample of spectroscopic globular cluster metallicities yet assembled. We compare these metallicities with those derived from Lick indices finding good agreement. In six of the eight galaxies with sufficient numbers of high-quality spectra we find bimodality in the spectroscopic metallicity distribution. Our results imply that …

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