The Location of the Snow Line in Protostellar Disks

The snow line in a gas disk is defined as the distance from the star beyond which the water ice is stable against evaporation. Since oxygen is the most abundant element after hydrogen and helium, the presence of ice grains can have important consequences for disk evolution. However, determining the position of the snow line is not simple. I discuss some of the important processes that affect the position of the snow line.Comment: 8 pages, 5 figures. Invited talk at IAU Symposium 263 - Icy Bodies in the Solar System. Rio de Janeiro, Aug. 200

Many-body wave scattering by small bodies

Scattering problem by several bodies, small in comparison with the wavelength, is reduced to linear algebraic systems of equations, in contrast to the usual reduction to some integral equations

Future Possibilities for Observing HI at High Redshift

We briefly review the beginnings of HI astronomy, proceed to an assessment of our current capabilities in this area, and continue by considering what will be necessary to push back the frontier to cosmological distances. We then consider how such a leap in performance might be realized.Comment: 8 page LaTeX requires crckapb.sty and psfig.sty, 9 compressed and tarred postscript figures (750kB) available at ftp://ftp.nfra.nl/pub/outgoing/rbraun/futposhi/figs.tar.Z Complete compressed postscript paper (790kB) available at ftp://ftp.nfra.nl/pub/outgoing/rbraun/futposhi/paper.ps.Z To appear in "Cold Gas at High Redshift", Eds. M.Bremer et al. (Kluwer, Dordrecht

Multiple scattering in plane atmosphere

Studies on multiple scattering and radiative transfer began early in this century by the work of Schwarzschild, Miln e, and Eddington. In the 1950's the important books of Chandrasekhar, Kourganoff and Sobolev on this subject appeared. In spite of the fact that almost all important questions in this very classical problem have now been solved, it often takes long to obtain the numerical answer to a simple question. For that reason I stated some years ago to prepare a book which should contain many tables and graphs together with a condensed text. In the course of this work it was found useful to deviate from normal usage in some respects, which I shall briefly review.Asociación Argentina de Astronomí

Radio astronomy at Leiden University

The radiotelescope of 25-meter diameter at Dwingeloo is now 10 years in almost continuous operation. The Observatories of Leiden and Groningen share the observing time. A doctor's thesis is often based on several thousand hours of observation, not all taken by the man himself. A good part of the registration and reduction is automatic. In the following a selection of some recent results is presented.Asociación Argentina de Astronomí

Observing the interstellar magnetic field

Before coming to a more detailed discussion, let us see what ways exist to establish the presence of a magnetic field In the galaxy at all. (Table 1). We shall briefly review these methods one by one.Asociación Argentina de Astronomí

Multiple scattering in plane atmosphere

Studies on multiple scattering and radiative transfer began early in this century by the work of Schwarzschild, Miln e, and Eddington. In the 1950's the important books of Chandrasekhar, Kourganoff and Sobolev on this subject appeared. In spite of the fact that almost all important questions in this very classical problem have now been solved, it often takes long to obtain the numerical answer to a simple question. For that reason I stated some years ago to prepare a book which should contain many tables and graphs together with a condensed text. In the course of this work it was found useful to deviate from normal usage in some respects, which I shall briefly review.Asociación Argentina de Astronomí

Radio astronomy at Leiden University

The radiotelescope of 25-meter diameter at Dwingeloo is now 10 years in almost continuous operation. The Observatories of Leiden and Groningen share the observing time. A doctor's thesis is often based on several thousand hours of observation, not all taken by the man himself. A good part of the registration and reduction is automatic. In the following a selection of some recent results is presented.Asociación Argentina de Astronomí

Radio astronomy at Leiden University

The radiotelescope of 25-meter diameter at Dwingeloo is now 10 years in almost continuous operation. The Observatories of Leiden and Groningen share the observing time. A doctor's thesis is often based on several thousand hours of observation, not all taken by the man himself. A good part of the registration and reduction is automatic. In the following a selection of some recent results is presented.Asociación Argentina de Astronomí

Star formation and the interstellar medium in low surface brightness galaxies. II. Deep CO observations of low surface brightness disk galaxies

We present deep, pointed $^{12}$CO($J=2-1$) observations of three late-type LSB galaxies. The beam-size was small enough that we could probe different environments (\HI maximum, \HI mininum, star forming region) in these galaxies. No CO was found at any of the positions observed. We argue that the implied lack of molecular gas is real and not caused by conversion factor effects. The virtual absence of a molecular phase may explain the very low star formation rates in these galaxies.Comment: 9 pages, 3 figure, uses aa.cls. Typos in Tables and text correcte