Search Publications
Dual-spacecraft observation of large-scale magnetic flux ropes in the Martian ionosphere
Gurnett, D. A.; Winningham, J. D.; Frahm, R. A. +5 more
We here report the first dual-spacecraft detection of planetary flux ropes in the ionosphere of Mars. The Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS), on board Mars Express, can measure the magnetic field magnitude near the spacecraft. Typically, these measurements track the known crustal magnetic field strength very well; …
Ultraviolet and X-ray Variability of the Seyfert 1.5 Galaxy Markarian 817
Brandt, W. N.; Schneider, Donald P.; Shull, J. Michael +9 more
We present an investigation of the ultraviolet and X-ray spectra of the Seyfert 1.5 galaxy Markarian 817. The ultraviolet analysis includes two recent observations taken with the Cosmic Origins Spectrograph (COS) in 2009 August and December, as well as archival spectra from the International Ultraviolet Explorer and the Hubble Space Telescope. Twe…
The Angular Diameter and Fundamental Parameters of Sirius A
Tuthill, P. G.; Davis, J.; Ireland, M. J. +3 more
The Sydney University Stellar Interferometer (SUSI) has been used to make a new determination of the angular diameter of Sirius A. The observations were made at an effective wavelength of 694.1nm and the new value for the limb-darkened angular diameter is 6.048+/-0.040mas (+/-0.66%). This new result is compared with previous measurements and is fo…
Unveiling the Mask on the ULIRG-to-QSO Transition Object [H89]1821+643 at z = 0.3: A Gas-poor/Gas-rich Galaxy Merger and the Implications for Co-based Dynamical Mass Estimates
Aravena, M.; Wagg, J.; Papadopoulos, P. P. +1 more
We report the detection of the 12CO J = 1-0 emission line in [H89]1821+643, one of the most optically luminous quasi-stellar objects (QSOs) in the local universe, and a template ULIRG-to-QSO transition object, located in a rich, cool-core cluster at z = 0.297. The CO emission is likely to be extended, highly asymmetric with respect to t…
Vertical and lateral collapse of Tharsis Tholus, Mars
Neukum, G.; Platz, T.; Dumke, A. +4 more
Tharsis Tholus, a more than 3.9 Ga old composite shield volcano to the east of the major Tharsis Montes, has experienced a complex history of growth and destruction. On the basis of new high resolution images we analysed the morphology as well as the tectonic structures of the Tharsis Tholus volcano in detail. From morphological data, cross-cuttin…
The role of weathering in the formation of bedrock valleys on Earth and Mars: A numerical modeling investigation
Pelletier, Jon D.; Baker, Victor R.
Numerical models of bedrock valley development generally do not include weathering explicitly. Nevertheless, weathering is an essential process that acts in concert with the transport of loose debris by seepage and runoff to form many bedrock valleys. Here we propose a numerical model for bedrock valley development that explicitly distinguishes we…
The Globular Cluster Population of NGC 7457: Clues to the Evolution of Field S0 Galaxies
Brodie, Jean P.; Strader, Jay; Rhode, Katherine L. +1 more
In this paper, we present the results of a wide-field imaging study of the globular cluster (GC) system of the field S0 galaxy NGC 7457. To derive the global properties of the GC system, we obtained deep BVR images with the WIYN 3.5 m telescope and Minimosaic Imager and studied the GC population of NGC 7457 to a projected radius of ~30 kpc. Our gr…
Mode visibilities in radial velocity and photometric Sun-as-a-star helioseismic observations
García, R. A.; Ballot, J.; Salabert, D.
We analyze more than 5000 days of high-quality Sun-as-a-star, radial velocity GOLF and photometric VIRGO/SPM helioseismic observations to extract precise estimates of the visibilities of the low-degree p modes and the m-height ratios of the l = 2 and 3 multiplets in the solar acoustic spectrum. The mode visibilities are shown to be larger during t…
The hierarchical build-up of the Tully-Fisher relation
Thomas, Daniel; Maraston, Claudia; Silk, Joseph +4 more
We use the semi-analytic model GalICS to predict the Tully-Fisher relation in the B, I and K bands, and its evolution with redshift, up to z∼ 1. We refined the determination of the disc galaxies rotation velocity, with a dynamical recipe for the rotation curve, rather than a simple conversion from the total mass to maximum velocity. The new recipe…
Supercorotating return flow from reconnection in Saturn's magnetotail
Coates, A. J.; Dougherty, M. K.; Thomsen, M. F. +4 more
Detecting plasma dynamics in Saturn's magnetosphere is essential for understanding energy flow through the system. It has been proposed that both the Dungey and Vasyliunas cycles operate at Saturn, and the competition between these cycles has been debated. We examine data taken by the Cassini spacecraft in Saturn's post-dawn magnetosphere, ∼17.5 S…