Far Infrared observations of the Seyfert galaxies NGC 3227, NGC 4051 and NGC 4151 are presented. These are the first data from a complete sample of Seyfert galaxies that is being observed by ISO as part of the ISOPHOT guaranteed time. The new ISO data, in combination with the IRAS data, show that the mid to far IR emission in all three objects can

The numerical solution of the idealized, but self-consistent, LTE atmosphere problem posed by the authors has been used to introduce the effect of multiple scattering on the temperature gradient, the spectral distribution of the observed flux and the intensity discontinuities. In the theoretical consideration of the problem, the nature of

In this Letter, we discuss a method to conduct a quantitative study of the star formation history (SFH) of Local Group (LG) galaxies using Hubble Space Telescope (HST) data. This method has proved to be successful in the analysis of the SFH of the same kind of galaxies using ground-based observations. It is based on the comparison of observed CMDs

Based on photometry of deep CCD frames of the central region of the OB cluster Berkeley 86, we derive the cluster mass function. The absence of current star formation, and the cluster's young age of about 6Myrs, leads to the conclusion that the initial mass function (IMF) and the current mass function are identical for stars with m

We argue that heights of formation (HOFs) should not be assigned to spectral lines since a single line my sample very different layers of the atmosphere, depending on the physical parameter of interest and the technique employed to determine it. HOFs should be assigned to specific measurements. General expressions to compute these HOFs for

We obtain the probability distribution for the volume of excursion sets in a three-dimensional Gaussian field, in order to develop the approximation to the cosmic mass function that follows directly from the assumption that the spherical collapse criteria may be applied to field points. We also use this distribution to develop an analytical