4 papers
A New Mass Degeneracy in Gravitational Lenses: Is there a crisis between a large and the time delay by a large lens halo?
HongSheng Zhao, Bo Qin
Isothermal models and other simple smooth models of dark matter halos of gravitational lenses often predict a dimensionless time delay much too small to be comfortable with…
Probing Galaxy Formation with High Energy Gamma-Rays
Joel R. Primack
I discuss how measurements of the absorption of -rays from GeV to TeV energies via pair production on the extragalactic background light (EBL) can probe important issues in gala…
The GHz-Peaked Spectrum radio galaxy 2021+614: Detection of slow motion in a compact symmetric object
Wolfgang Tschager, Richard T. Schilizzi, Huub J. A. R"ottgering +2
We have analysed VSOP (VLBI Space Observatory Programme) data at 5 GHz and ground-based VLBI (Very Long Baseline Interferometry) data at 15 GHz for the GHz-Peaked Spectrum (GPS) ra…
Baryonic Dark Matter: Limits from HST and ISO
Gerard Gilmore, IoA Cambridge, UK
Recent HST and ISO observations provide very severe limits on any compact baryonic contributions to galactic (dark) halos. When combined with Milky Way Galaxy microlensing results,…