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Series

Astrophysics and Astronomy

2015

San Jose State University

Articles 1 - 15 of 15

Full-Text Articles in Physical Sciences and Mathematics

The Sluggs Survey: Globular Cluster Kinematics In A ‘Double Sigma’ Galaxy – Ngc 4473, Adebusola Alabi, Caroline Foster, Duncan Forbes, Aaron Romanowsky, Nicola Pastorello, Jean Brodie, Lee Spitler, Jay Strader, Christopher Usher Sep 2015

The Sluggs Survey: Globular Cluster Kinematics In A ‘Double Sigma’ Galaxy – Ngc 4473, Adebusola Alabi, Caroline Foster, Duncan Forbes, Aaron Romanowsky, Nicola Pastorello, Jean Brodie, Lee Spitler, Jay Strader, Christopher Usher

Faculty Publications

NGC 4473 is a so-called double sigma (2σ) galaxy, i.e. a galaxy with rare, double peaks in its 2D stellar velocity dispersion. Here, we present the globular cluster (GC) kinematics in NGC 4473 out to ∼10Re (effective radii) using data from combined Hubble Space Telescope/Advanced Camera for Surveys and Subaru/Suprime-Cam imaging and Keck/Deep Imaging Multi-Object Spectrograph. We find that the 2σ nature of NGC 4473 persists up to 3Re, though it becomes misaligned to the photometric major axis. We also observe a significant offset between the stellar and GC rotation amplitudes. This offset can be understood as a co-addition of …

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The Sluggs Survey: Inferring The Formation Epochs Of Metal-Poor And Metal-Rich Globular Clusters, Duncan Forbes, Nicola Pastorello, Aaron Romanowsky, Christopher Usher, Jean Brodie, Jay Strader Sep 2015

The Sluggs Survey: Inferring The Formation Epochs Of Metal-Poor And Metal-Rich Globular Clusters, Duncan Forbes, Nicola Pastorello, Aaron Romanowsky, Christopher Usher, Jean Brodie, Jay Strader

Faculty Publications

We present a novel, observationally-based framework for the formation epochs and sites of globular clusters (GCs) in a cosmological context. Measuring directly the mean ages of the metal-poor and metal-rich GC subpopulations in our own Galaxy, and in other galaxies, is observationally challenging. Here we apply an alternative approach utilizing the property that the galaxy mass–metallicity relation is a strong function of redshift (or look-back age) but is relatively insensitive to galaxy mass for massive galaxies. Assuming that GCs follow galaxy mass–metallicity relations that evolve with redshift, one can estimate the mean formation epochs of the two GC subpopulations by …

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Vegas: A Vst Early-Type Galaxy Survey: I. Presentation, Wide-Field Surface Photometry, And Substructures In Ngc 4472, Massimo Capaccioli, Marilena Spavone, Aniello Grado, Enrichetta Iodice, Luca Limatola, Nicola Napolitano, Michele Cantiello, Maurizio Paolillo, Aaron Romanowsky, Duncan Forbes, Thomas Puzia, Gabriella Raimondo, Pietro Schipani Sep 2015

Vegas: A Vst Early-Type Galaxy Survey: I. Presentation, Wide-Field Surface Photometry, And Substructures In Ngc 4472, Massimo Capaccioli, Marilena Spavone, Aniello Grado, Enrichetta Iodice, Luca Limatola, Nicola Napolitano, Michele Cantiello, Maurizio Paolillo, Aaron Romanowsky, Duncan Forbes, Thomas Puzia, Gabriella Raimondo, Pietro Schipani

Faculty Publications

Context. We present the VST Early-type GAlaxy Survey (VEGAS), which is designed to obtain deep multiband photometry in g,r,i, of about one hundred nearby galaxies down to 27.3, 26.8, and 26 mag/arcsec2 respectively, using the ESO facility VST/OmegaCAM.Aims. The goals of the survey are 1) to map the light distribution up to ten effective radii, re; 2) to trace color gradients and surface brightness fluctuation gradients out to a few re for stellar population characterization; and 3) to obtain a full census of the satellite systems (globular clusters and dwarf galaxies) out to 20% of the galaxy virial radius. The …

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Vimos Mosaic Integral-Field Spectroscopy Of The Bulge And Disc Of The Early-Type Galaxy Ngc 4697, C. Spiniello, N. Napolitano, L. Coccato, V. Pota, Aaron Romanowsky, C. Tortora, G. Covone, M. Capaccioli Sep 2015

Vimos Mosaic Integral-Field Spectroscopy Of The Bulge And Disc Of The Early-Type Galaxy Ngc 4697, C. Spiniello, N. Napolitano, L. Coccato, V. Pota, Aaron Romanowsky, C. Tortora, G. Covone, M. Capaccioli

Faculty Publications

No abstract provided.

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The Sluggs Survey: Combining Stellar And Globular Cluster Metallicities In The Outer Regions Of Early-Type Galaxies, Nicola Pastorello, Duncan Forbes, Christopher Usher, Jean Brodie, Aaron Romanowsky, Jay Strader, Lee Spitler, Adebusola Alabi, Caroline Foster, Zachary Jennings, Sreeja Kartha, Vincenzo Pota Aug 2015

The Sluggs Survey: Combining Stellar And Globular Cluster Metallicities In The Outer Regions Of Early-Type Galaxies, Nicola Pastorello, Duncan Forbes, Christopher Usher, Jean Brodie, Aaron Romanowsky, Jay Strader, Lee Spitler, Adebusola Alabi, Caroline Foster, Zachary Jennings, Sreeja Kartha, Vincenzo Pota

Faculty Publications

The outer halo regions of early-type galaxies carry key information about their past accretion history. However, spectroscopically probing the stellar component at such galactocentric radii is still challenging. Using the DEep Imaging Multi-Object Spectrograph on the Keck, we have been able to measure the metallicities of the stellar and globular cluster components in 12 early-type galaxies out to more than 10Re. We find similar metallicity gradients for the metal-poor and metal-rich globular cluster subpopulations, suggesting a common formation process for the two subpopulations. This is in conflict with most current theoretical predictions, where the metal-poor globular clusters are thought to …

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The Sluggs Survey: Multipopulation Dynamical Modelling Of The Elliptical Galaxy Ngc 1407 From Stars And Globular Clusters, Vincenzo Pota, Aaron Romanowsky, Jean Brodie, Jorge Peñarrubia, Duncan Forbes, Nicola Napolitano, Caroline Foster, Matthew Walker, Jay Strader, Joel Roediger Jul 2015

The Sluggs Survey: Multipopulation Dynamical Modelling Of The Elliptical Galaxy Ngc 1407 From Stars And Globular Clusters, Vincenzo Pota, Aaron Romanowsky, Jean Brodie, Jorge Peñarrubia, Duncan Forbes, Nicola Napolitano, Caroline Foster, Matthew Walker, Jay Strader, Joel Roediger

Faculty Publications

No abstract provided.

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A Sluggs And Gemini/Gmos Combined Study Of The Elliptical Galaxy M60: Wide-Field Photometry And Kinematics Of The Globular Cluster System, Vincenzo Pota, Jean Brodie, Terry Bridges, Jay Strader, Aaron Romanowsky, Alexa Villaume, Zach Jennings, Favio Faifer, Nicola Pastorello, Duncan Forbes, Ainsley Campbell, Christopher Usher, Caroline Foster, Lee Spitler, Nelson Caldwell, Juan Forte, Mark Norris, Stephen Zepf, Michael Beasley, Karl Gebhardt, David Hanes, Ray Sharples, Jacob Arnold Jun 2015

A Sluggs And Gemini/Gmos Combined Study Of The Elliptical Galaxy M60: Wide-Field Photometry And Kinematics Of The Globular Cluster System, Vincenzo Pota, Jean Brodie, Terry Bridges, Jay Strader, Aaron Romanowsky, Alexa Villaume, Zach Jennings, Favio Faifer, Nicola Pastorello, Duncan Forbes, Ainsley Campbell, Christopher Usher, Caroline Foster, Lee Spitler, Nelson Caldwell, Juan Forte, Mark Norris, Stephen Zepf, Michael Beasley, Karl Gebhardt, David Hanes, Ray Sharples, Jacob Arnold

Faculty Publications

We present new wide-field photometry and spectroscopy of the globular clusters (GCs) around NGC 4649 (M60), the third brightest galaxy in the Virgo cluster. Imaging of NGC 4649 was assembled from a recently obtained Hubble Space Telescope/Advanced Camera for Surveys mosaic, and new Subaru/Suprime-Cam and archival Canada–France–Hawaii Telescope/MegaCam data. About 1200 sources were followed up spectroscopically using combined observations from three multi-object spectrographs: Keck/Deep Imaging Multi-Object Spectrograph, Gemini/Gemini Multi-Object Spectrograph and Multiple Mirror Telescope/Hectospec. We confirm 431 unique GCs belonging to NGC 4649, a factor of 3.5 larger than previous data sets and with a factor of 3 improvement in …

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How Elevated Is The Dynamical-To-Stellar Mass Ratio Of The Ultracompact Dwarf S999?, Joachim Janz, Duncan Forbes, Mark Norris, Jay Strader, Samantha Penny, Martina Fagioli, Aaron Romanowsky May 2015

How Elevated Is The Dynamical-To-Stellar Mass Ratio Of The Ultracompact Dwarf S999?, Joachim Janz, Duncan Forbes, Mark Norris, Jay Strader, Samantha Penny, Martina Fagioli, Aaron Romanowsky

Faculty Publications

No abstract provided.

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Vegas-Sss. A Vst Early-Type Galaxy Survey: Analysis Of Small Stellar Systems: Testing The Methodology On The Globular Cluster System In Ngc 3115⋆, Michele Cantiello, Massimo Capaccioli, Nicola Napolitano, Aniello Grado, Luca Limatola, Maurizio Paolillo, Enrica Iodice, Aaron Romanowsky, Duncan Forbes, Gabriella Raimondo, Marilena Spavone, Francesco La Barbera, Thomas Puzia, Pietro Schipani Apr 2015

Vegas-Sss. A Vst Early-Type Galaxy Survey: Analysis Of Small Stellar Systems: Testing The Methodology On The Globular Cluster System In Ngc 3115⋆, Michele Cantiello, Massimo Capaccioli, Nicola Napolitano, Aniello Grado, Luca Limatola, Maurizio Paolillo, Enrica Iodice, Aaron Romanowsky, Duncan Forbes, Gabriella Raimondo, Marilena Spavone, Francesco La Barbera, Thomas Puzia, Pietro Schipani

Faculty Publications

We present a study of globular clusters (GCs) and other small stellar systems (SSSs) in the field of NGC 3115, observed as part of the ongoing wide-field imaging survey VEGAS, carried out with the 2.6 m VST telescope. We used deep g and i observations of NGC 3115, a well-studied lenticular galaxy that is covered excellently well in the scientific literature. This is fundamental to test the methodologies, verify the results, and probe the capabilities of the VEGAS-SSS. Leveraging the large field of view of the VST allowed us to accurately study the distribution and properties of SSSs as a …

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Detection Of A Distinct Metal-Poor Stellar Halo In The Early-Type Galaxy Ngc 3115*, Mark Peacock, Jay Strader, Aaron Romanowsky, Jean Brodie Feb 2015

Detection Of A Distinct Metal-Poor Stellar Halo In The Early-Type Galaxy Ngc 3115*, Mark Peacock, Jay Strader, Aaron Romanowsky, Jean Brodie

Faculty Publications

We present the resolved stellar populations in the inner and outer halo of the nearby lenticular galaxy NGC 3115. Using deep Hubble Space Telescope observations, we analyze stars 2 mag fainter than the tip of the red giant branch (TRGB). We study three fields along the minor axis of this galaxy, 19, 37, and 54 kpc from its center—corresponding to 7, 14, and 21 effective radii (re ). Even at these large galactocentric distances, all of the fields are dominated by a relatively enriched population, with the main peak in the metallicity distribution decreasing with radius from [Z/H] ~ –0.5 …

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The Sluggs Survey: Globular Cluster Stellar Population Trends From Weak Absorption Lines In Stacked Spectra, Christopher Usher, Duncan Forbes, Jean Brodie, Aaron Romanowsky, Jay Strader, Charlie Conroy, Caroline Foster, Nicola Pastorello, Vincenzo Pota, Jacob Arnold Jan 2015

The Sluggs Survey: Globular Cluster Stellar Population Trends From Weak Absorption Lines In Stacked Spectra, Christopher Usher, Duncan Forbes, Jean Brodie, Aaron Romanowsky, Jay Strader, Charlie Conroy, Caroline Foster, Nicola Pastorello, Vincenzo Pota, Jacob Arnold

Faculty Publications

As part of the SAGES Legacy Unifying Globulars and GalaxieS (SLUGGS) survey, we stack 1137 Keck DEIMOS (Deep Imaging Multi-Object Spectrograph) spectra of globular clusters from 10 galaxies to study their stellar populations in detail. The stacked spectra have median signal-to-noise ratios of ∼90 Å−1. Besides the calcium triplet, we study weaker sodium, magnesium, titanium and iron lines as well as the Hα and higher order Paschen hydrogen lines. In general, the stacked spectra are consistent with old ages and a Milky Way-like initial mass function. However, we see different metal line index strengths at fixed colour and magnitude, and …

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Spectroscopic Confirmation Of The Existence Of Large, Diffuse Galaxies In The Coma Cluster, Pieter Van Dokkum, Aaron Romanowsky, Roberto Abraham, Jean Brodie, Charlie Conroy, Marla Geha, Allison Merritt, Alexa Villaume, Jielai Zhang Jan 2015

Spectroscopic Confirmation Of The Existence Of Large, Diffuse Galaxies In The Coma Cluster, Pieter Van Dokkum, Aaron Romanowsky, Roberto Abraham, Jean Brodie, Charlie Conroy, Marla Geha, Allison Merritt, Alexa Villaume, Jielai Zhang

Faculty Publications

No abstract provided.

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Small Scatter And Nearly Isothermal Mass Profiles To Four Half-Light Radii From Two-Dimensional Stellar Dynamics Of Early-Type Galaxies, Michele Cappellari, Aaron Romanowsky, Jean Brodie, Duncan Forbes, Jay Strader, Caroline Foster, Sreeja Kartha, Nicola Pastorello, Vincenzo Pota, Lee Spitler, Christopher Usher, Jacob Arnold Jan 2015

Small Scatter And Nearly Isothermal Mass Profiles To Four Half-Light Radii From Two-Dimensional Stellar Dynamics Of Early-Type Galaxies, Michele Cappellari, Aaron Romanowsky, Jean Brodie, Duncan Forbes, Jay Strader, Caroline Foster, Sreeja Kartha, Nicola Pastorello, Vincenzo Pota, Lee Spitler, Christopher Usher, Jacob Arnold

Faculty Publications

No abstract provided.

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Ngc 3628-Ucd1: A Possible Ω Cen Analog Embedded In A Stellar Stream, Zachary Jennings, Aaron Romanowsky, Jean Brodie, Joachim Janz, Mark Norris, Duncan Forbes, David Martinez-Delgado, Martina Fagioli, Samantha Penny Jan 2015

Ngc 3628-Ucd1: A Possible Ω Cen Analog Embedded In A Stellar Stream, Zachary Jennings, Aaron Romanowsky, Jean Brodie, Joachim Janz, Mark Norris, Duncan Forbes, David Martinez-Delgado, Martina Fagioli, Samantha Penny

Faculty Publications

No abstract provided.

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Hiding In Plain Sight: Record-Breaking Compact Stellar Systems In The Sloan Digital Sky Survey, Michael Sandoval, Richard Vo, Aaron Romanowsky, Jay Strader, Jieun Choi, Zachary Jennings, Charlie Conroy, Jean Brodie, Caroline Foster, Alexa Villaume, Mark Norris, Joachim Janz, Duncan Forbes Jan 2015

Hiding In Plain Sight: Record-Breaking Compact Stellar Systems In The Sloan Digital Sky Survey, Michael Sandoval, Richard Vo, Aaron Romanowsky, Jay Strader, Jieun Choi, Zachary Jennings, Charlie Conroy, Jean Brodie, Caroline Foster, Alexa Villaume, Mark Norris, Joachim Janz, Duncan Forbes

Faculty Publications

No abstract provided.

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