Search Publications
Hubble Space Telescope Photometry for the Halo Stars in the Leo Elliptical NGC 3377
Stetson, Peter B.; Layden, Andrew C.; Harris, William E. +1 more
We have used the ACS camera on HST to obtain (V,I) photometry for 57,000 red giant stars in the halo of the Leo elliptical NGC 3377, an intermediate-luminosity elliptical. We use this sample of stars to derive the metallicity distribution function (MDF) for its halo field stars and comment on its chemical evolution history compared with both large…
Energetic electrons injected into Saturn's neutral gas cloud
Krupp, N.; Krimigis, S. M.; Mitchell, D. G. +7 more
We demonstrate that the population of 20-410 keV electrons observed in Saturn's inner magnetosphere result principally from recent injections. Electrons at these energies appear to survive only up to a few days in the neutral gas cloud emitted by gas jets in Enceladus's southern hemisphere. Ions of similar energies have much shorter lifetimes in t…
The AGB stars of the intermediate-age LMC cluster NGC 1846. Variability and age determination
Lebzelter, T.; Wood, P. R.
Aims:We investigate variability and we model the pulsational behaviour of AGB variables in the intermediate-age LMC cluster NGC 1846.
Methods: Our own photometric monitoring has been combined with data from the MACHO archive to detect 22 variables among the cluster's AGB stars and to derive pulsation periods. According to the global parameters…
An integral field spectroscopic survey for high redshift damped Lyman-α galaxies
Jahnke, K.; Christensen, L.; Kelz, A. +3 more
Aims:We search for galaxy counterparts to damped Lyman-α absorbers (DLAs) at z > 2 towards nine quasars, which have 14 DLAs and 8 sub-DLAs in their spectra.
Methods: We use integral field spectroscopy to search for Lyα emission line objects at the redshifts of the absorption systems.
Results: Besides recovering two previously confirmed …
The Survey of Nearby Nuclei with the Space Telescope Imaging Spectrograph: Emission-Line Nuclei at Hubble Space Telescope Resolution
Filippenko, Alexei V.; Ho, Luis C.; Shields, Joseph C. +6 more
We present results from a program of optical spectroscopy for 23 nearby galaxies with emission-line nuclei. This investigation takes advantage of the spatial resolution of the Hubble Space Telescope to study the structure and energetics of the central ~10-20 pc, and the resulting data have value for quantifying central black hole masses, star form…
Saturn's satellite Rhea is a homogeneous mix of rock and ice
Anderson, J. D.; Schubert, G.
A close flyby of Saturn's satellite Rhea by the Cassini spacecraft on 26 November 2005 can be used to infer its mass and quadrupole gravity moments. From these data we derive a mean density of 1233 ± 5 kg m-3 for Rhea and an axial moment of inertia consistent with an undifferentiated interior. The small density implies an interior made up of about…
Flight Performance of the AKARI Cryogenic System
Nakagawa, Takao; Murakami, Masahide; Yoshida, Seiji +11 more
We describe the flight performance of the cryogenic system of the infrared astronomical satellite AKARI, which was successfully launched on 2006 February 21 (UT). AKARI carries a 68.5 cm telescope together with two focal plane instruments, Infrared Cameras (IRC) and Far Infrared Surveyor (FIS), all of which are cooled down to cryogenic temperature…
Clathrate hydrates as a sink of noble gases in Titan's atmosphere
Mousis, O.; Thomas, C.; Picaud, S. +1 more
We use a statistical thermodynamic approach to determine the composition of clathrate hydrates which may form from a multiple compound gas whose composition is similar to that of Titan's atmosphere. Assuming that noble gases are initially present in this gas phase, we calculate the ratios of xenon, krypton and argon to species trapped in clathrate…
An Alternative Interpretation of the Relationship between the Inferred Open Solar Flux and the Interplanetary Magnetic Field
Riley, Pete
Photospheric observations at the Wilcox Solar Observatory (WSO) represent an uninterrupted data set of 32 years and are therefore unique for modeling variations in the magnetic structure of the corona and inner heliosphere over three solar cycles. For many years, modelers have applied a latitudinal correction factor to these data, believing that i…
Global Coronal Seismology
Ballai, I.
Following the observation and analysis of large-scale coronal-wave-like disturbances, we discuss the theoretical progress made in the field of global coronal seismology. Using simple mathematical techniques we determine average values for the magnetic field together with a magnetic map of the quiet Sun. The interaction between global coronal waves…