Search Publications
Saturn's Icy Moon Rhea: A Prediction for its Bulk Chemical Composition and Physical Structure at the Time of the Cassini Spacecraft First Flyby
Prentice, Andrew J. R.
I report a model for the formation of Saturn's family of mid-sized icy moons to coincide with the first flypast of Rhea by the Cassini spacecraft on 2005 November 26. It is proposed that the moons had condensed from a concentric family of orbiting gas rings that were shed some 4.6 × 109 yr ago by the proto-Saturnian (hereafter p-Sat) cl…
Ultra-Compact Dwarf Galaxies in Galaxy Clusters
Ferguson, Henry C.; Drinkwater, Michael J.; Gregg, Michael D. +5 more
We review the evidence that the ultra-compact dwarf (UCD) galaxies we recently discovered in the Fornax Cluster form a new, previously unknown class of galaxies and we discuss possible scenarios for their formation. We then present recent results that UCDs are also present in the Virgo Cluster, and that there is a much larger than expected populat…
Cosmic Helium Production
Flynn, Chris
K-dwarfs are very long lived, slowly evolving stars, so that their present day helium Y and metal content (metallicity Z) is essentially the same as when they were born. K-dwarfs thus contain a fossil record of the amount of helium and metals which has been produced in successive stellar generations over the lifetime of the Galaxy. We here estimat…
The Geneva-Copenhagen Survey of the Solar Neighbourhood
Pont, F.; Holmberg, J.; Nordström, B. +3 more
We report on a new survey of metallicities, ages, and Galactic orbits for a complete, magnitude-limited, and kinematically unbiased all-sky sample of 16682 nearby F- and G-dwarfs. Our~63000 new, accurate radial velocities for nearly 13500 of the stars, combined with Hipparcos parallaxes and Tycho-2 proper motions, complete the kinematic data for 1…
The Stellar Populations of dE Galaxies in Nearby Groups
Da Costa, G. S.
In this contribution Gemini-North NIRI J,K-observations are used to investigate the upper-Asymptotic Giant Branch (AGB) intermediate-age population in the M81 Group dwarf elliptical (dE) F8D1. Hubble Space Telescope (HST) `snapshot' V,I-observations are also analysed to investigate the upper-AGB populations in two other M81 Group dEs, DDO 71 and k…
Comprehensive Analysis of RGU Photometry in the Direction to M5
Bilir, S.; Karaali, S.; Buser, R.
The RGU-photographic investigation of an intermediate latitude field in the direction to the Galactic centre is presented. 164 extra-galactic objects, identified by comparison of Minnesota and Basel charts, are excluded from the program. Also, a region with size 0.104 square-degrees, contaminated by cluster (M5) stars and affected by background li…
Solar Neighbourhood Age-Metallicity Relation Based on Hipparcos Data
Ibukiyama, Akihiko
We derive age-metallicity relations (AMRs) and orbits for the 1658 solar neighbourhood stars for which accurate distances are measured by the Hipparcos satellite. The sample comprises 1382 thin disk stars, 229 thick disk stars, and 47 halo stars according to their orbital parameters. We find a considerable scatter for thin disk AMRs along the one-…
Jet-Cloud Interactions in Compact Steep Spectrum Radio Sources
Capetti, A.; Koekemoer, A. M.; Morganti, R. +8 more
We have obtained HST/STIS long slit spectroscopy of the aligned emission line nebulae in three compact steep spectrum (CSS) radio sources - 3C67, 3C277.1, and 3C303.1. We find systematic offsets (~300-500kms) of the emission line velocities on one or both sides of the radio sources. We also see evidence for broad lines (FWHM~500kms) and complex em…
HST/STIS Spectroscopy of CSS sources: Kinematics and Ionisation of the Aligned Nebulae
Capetti, A.; Koekemoer, A. M.; Morganti, R. +9 more
We have obtained long slit spectra of 3C67 and 3C277.1 with the HST/STIS spectrograph. We present our preliminary results on the diagnostic emission line ratios along the radio source axes in 3C67 and 3C277.1.
Optical and UV Spectral Diagnostics for GPS and CSS Sources
Dopita, Michael A.
In this paper I examine the use of optical and UV spectral diagnostic ratios to distinguish between gas which is locally shock-excited by the interaction with a jet and that which is photoionised by the central engine. In many cases key UV lines remain unobserved except in the case of high redshift radio galaxies. However, in one case, the nearby …