We present optical and near-infrared colour maps of the central regions of bulges of S0 and spiral galaxies obtained with WFPC2 and NICMOS on the Hubble Space Telescope (HST). By combined use of HST and ground-based data, the colour information spans a region from a few tens of pc to a few kpc. In almost all galaxies, the colour profiles in the

The Hipparcos mission has made it possible to constrain the positions of nearby field stars in the colour-magnitude diagram with very high accuracy. These positions can be compared with the predictions of stellar evolutionary calculations to provide information on the basic parameters of the stars: masses, radii, effective temperatures, ages, and

Not Available

Not Available

Not Available

The brighter water masers of NGC 1068 appear to trace molecular gas in a parsec-scale disk surrounding the central engine. We find evidence that these masers are reverberating in response to a central, common pump source, presumably the central engine. Firstly, the luminosities of individual maser features are correlated on time-scales as fine as