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Articles 1 - 14 of 14
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
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
Aaron J. Romanowsky
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 …
Mond And Imf Variations In Early-Type Galaxies From Atlas3d, C. Tortora, Aaron J. Romanowsky, V. F. Cardone, N. R. Napolitano, Ph Jetzer
Mond And Imf Variations In Early-Type Galaxies From Atlas3d, C. Tortora, Aaron J. Romanowsky, V. F. Cardone, N. R. Napolitano, Ph Jetzer
Aaron J. Romanowsky
No abstract provided.
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
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
Aaron J. Romanowsky
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 …
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
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
Aaron J. Romanowsky
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 …
Angular Momentum And Galaxy Formation Revisited: Effects Of Variable Mass-To-Light Ratios, S. M. Fall, Aaron J. Romanowsky
Angular Momentum And Galaxy Formation Revisited: Effects Of Variable Mass-To-Light Ratios, S. M. Fall, Aaron J. Romanowsky
Aaron J. Romanowsky
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, …
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
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
Aaron J. Romanowsky
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 …
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
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
Aaron J. Romanowsky
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 …
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
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
Aaron J. Romanowsky
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 …
An Inventory Of The Stellar Initial Mass Function In Early-Type Galaxies, C. Tortora, Aaron J. Romanowsky, N. R. Napolitano
An Inventory Of The Stellar Initial Mass Function In Early-Type Galaxies, C. Tortora, Aaron J. Romanowsky, N. R. Napolitano
Aaron J. Romanowsky
Given a flurry of recent claims for systematic variations in the stellar initial mass function (IMF), we carry out the first inventory of the observational evidence using different approaches. This includes literature results, as well as our own new findings from combined stellar population synthesis (SPS) and Jeans dynamical analyses of data on ~4500 early-type galaxies (ETGs) from the SPIDER project. We focus on the mass-to-light ratio mismatch relative to the Milky Way IMF, δIMF, correlated against the central stellar velocity dispersion, σsstarf. We find a strong correlation between δIMF and σsstarf, for a wide set of dark matter (DM) …
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
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
Aaron J. Romanowsky
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 …
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
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
Aaron J. Romanowsky
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. …
The Sluggs Survey: Wide-Field Stellar Kinematics Of Earlytype 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
The Sluggs Survey: Wide-Field Stellar Kinematics Of Earlytype 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
Aaron J. Romanowsky
No abstract provided.
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
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
Aaron J. Romanowsky
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 …
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
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
Aaron J. Romanowsky
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 …