Search Publications
New Mass-Loss Measurements from Astrospheric Lyα Absorption
Linsky, J. L.; Redfield, S.; Zank, G. P. +2 more
Measurements of stellar mass-loss rates are used to assess how wind strength varies with coronal activity and age for solar-like stars. Mass loss generally increases with activity, but we find evidence that winds suddenly weaken at a certain activity threshold. Very active stars are often observed to have polar starspots, and we speculate that the…
Star Formation in NGC 5194 (M51a): The Panchromatic View from GALEX to Spitzer
Helou, G.; Roussel, H.; Leitherer, C. +32 more
Far-ultraviolet to far-infrared images of the nearby galaxy NGC 5194 (M51a), from a combination of space-based (Spitzer, GALEX, and Hubble Space Telescope) and ground-based data, are used to investigate local and global star formation and the impact of dust extinction. The Spitzer data provide unprecedented spatial detail in the infrared, down to …
Shock Geometry, Seed Populations, and the Origin of Variable Elemental Composition at High Energies in Large Gradual Solar Particle Events
Cohen, C. M. S.; Mewaldt, R. A.; Maclennan, C. G. +5 more
Above a few tens of MeV per nucleon, large, gradual solar energetic particle (SEP) events are highly variable in their spectral characteristics and elemental composition. The origin of this variability has been a matter of intense and ongoing debate. In this paper, we propose that this variability arises from the interplay of two factors-shock geo…
The Morphology-Density Relation in z ~ 1 Clusters
Ford, H. C.; Demarco, R.; Infante, L. +39 more
We measure the morphology-density relation (MDR) and morphology-radius relation (MRR) for galaxies in seven z~1 clusters that have been observed with the Advanced Camera for Surveys (ACS) on board the Hubble Space Telescope. Simulations and independent comparisons of our visually derived morphologies indicate that ACS allows one to distinguish bet…
A Helium Spread among the Main-Sequence Stars in NGC 2808
D'Antona, F.; Bellazzini, M.; Galleti, S. +3 more
We have made a detailed study of the color distribution of the main sequence of the globular cluster (GC) NGC 2808, based on new deep HST WFPC2 photometry of a field in the uncrowded outskirts of the cluster. The observed color distribution of main-sequence stars is not Gaussian and is wider than expected for a single stellar population, given our…
The Mass Assembly Histories of Galaxies of Various Morphologies in the GOODS Fields
Conselice, Christopher J.; Ellis, Richard S.; Bundy, Kevin
We present an analysis of the growth of stellar mass with cosmic time partitioned according to galaxy morphology. Using a well-defined catalog of 2150 galaxies based, in part, on archival data in the Great Observatories Origins Deep Survey (GOODS) fields, we assign morphological types in three broad classes (ellipticals, spirals, peculiar/irregula…
Decay of Planetary Debris Disks
Bryden, G.; Stapelfeldt, K. R.; Rieke, G. H. +9 more
We report new Spitzer 24 µm photometry of 76 main-sequence A-type stars. We combine these results with previously reported Spitzer 24 µm data and 24 and 25 µm photometry from the Infrared Space Observatory and the Infrared Astronomy Satellite. The result is a sample of 266 stars with mass close to 2.5 Msolar, all detec…
Strong-Lensing Analysis of A1689 from Deep Advanced Camera Images
Herranz, D.; Zheng, W.; Broadhurst, Tom +39 more
We analyze deep multicolor Advanced Camera images of the largest known gravitational lens, A1689. Radial and tangential arcs delineate the critical curves in unprecedented detail, and many small counterimages are found near the center of mass. We construct a flexible light deflection field to predict the appearance and positions of counterimages. …
Multiwavelength Monitoring of the Dwarf Seyfert 1 Galaxy NGC 4395. I. A Reverberation-based Measurement of the Black Hole Mass
Kaspi, Shai; Laor, Ari; Moran, Edward C. +8 more
A reverberation-mapping program on NGC 4395, the least luminous known Seyfert 1 galaxy, undertaken with the Space Telescope Imaging Spectrograph on the Hubble Space Telescope yields a measurement of the mass of the central black hole MBH=(3.6+/-1.1)×105 Msolar. The observations consist of two visits of five orbits …
Direct Observations of the Magnetic Reconnection Site of an Eruption on 2003 November 18
Raymond, J. C.; Ko, Y. -K.; Lin, J. +5 more
We report direct observations of the magnetic reconnection site during an eruptive process that occurred on 2003 November 18. The event started with a rapid expansion of a few magnetic arcades located over the east limb of the Sun and developed an energetic partial-halo coronal mass ejection (CME), a long current sheet, and a group of bright flare…