天体物理学

I discuss the physics of polarization in models with early reionization. For sufficiently high optical depth to recombination the polarization is boosted on large scales while it is suppressed on smaller scales. New peaks appear in the…

The clustering of baryons and cold dark matter induced by a single moving string is analyzed numerically making use of a new three-dimensional Eulerian cosmological hydro code$^{1)}$ which is based on the PPM method to track the baryons and…

In this study we use simulations of 128$^3$ particles to study the ellipticity and orientation of clusters of galaxies in N-body simulations of differing power-law initial spectra (P(k) \propto k^n ,n = +1, 0, -1, -2$), and density…

We examine how the Sunyaev-Zel'dovich (SZ) effect of clusters can probe $\Omega_{o}$. Using self-consistent models of X-ray clusters in the context of hierarchical models of structure formation, we show that both the mean Compton {\it y}…

In a recent Letter (astro-ph/9605001), Cowsik et al. claim that a self-consistent treatment of the dark Galactic halo requires that the local velocity dispersion of dark-matter particles be $600$ km~s$^{-1}$ or greater, more than a factor…

I report on recent developments in the theory of cosmic background radiation perturbations. I describe ways of modeling alternatives to the canonical Gaussian theories within the standard framework of cosmological perturbation theory. Some…

We analyse the surface density of very faint galaxies at the limit of the sky background noise in the field of the cluster of galaxies Cl0024+1654. The radial variation of their number density in the magnitude bins $B=26-28$ and $I=24-26.5$…

We show that it is possible to image the structure of a distant quasar on scales of $\sim 1\,$AU by constructing a telescope which uses a nearby dwarf star as its ``primary lens'' together with a satellite-borne ``secondary''. The image…

We present a WWW-version of the {\it Scenario Machine} - a computer code designed to calculate the evolution of close binary stellar systems. The Internet users can directly access to the code and calculate binary evolutionary tracks with…

As part of a long term effort to understand pre-main sequence Li burning, we have obtained high resolution spectroscopic observations of 14 late type stars (G0--M1) in the young open cluster IC~4665. Most of the stars have \ha filled-in and…

We propose a simple model for the origin and evolution of \lya clouds based on cosmological conductive/cooling fronts. In this model the \lya arises in the interfaces between the IGM and cold clouds that could be tentatively identified with…

I review the present status of nonperturbative studies on the nature of the finite temperature QCD transition on the lattice, with the special attention to the determination of the order of the transition. [Talk given at the International…

Using the near infrared fluxes of local galaxies derived from COBE/DIRBE J(1.25 $\mu$m) K (2.2 $\mu$m) \& L (3.5 $\mu$m) band maps and published Cepheid distances, we construct Tully-Fisher (TF) diagrams for the nearby galaxies. The…

We have made an attempt to compile all currently available data on optically identified QSO absorber systems (Lindner et al. 1996) to establish the status quo of absorber galaxy data as a basis for the investigation of galaxy evolution. We…

A comprehensive set of all available magnitudes, colors and redshifts for optically identified QSO absorbers is compiled from the literature. This results in a largely unbiased sample of galaxies at high redshifts, the size of the sample…

Using the fact that molecular gas is distributed in the inner disk while HI in the outer disk, we have derived most-completely sampled rotation curves by combining HI and CO position-velocity diagrams. We show that inner rotation curves…

We investigated the thermal evolution of non-spherical primordial gas clouds of mass $ M=10^6M_\odot $. We studied two cases: 1) prolate and oblate clouds without angular momentum, 2) initially spherical, oblate and prolate clouds with…

Recently, Cottingham, Kalafatis and Vinh Mau proposed, in the framework of the Lee-Wick model, a scenario of formation of quark stars in the cosmological quark-hadron phase transition with high degree of supercooling. We show here that the…

IC 1396 is a relatively nearby (750 pc), large (>2 deg), HII region ionized by a single O6.5V star and containing bright-rimmed cometary globules. We have made the first arcmin resolution images of atomic hydrogen toward IC 1396, and have…

Microlensing observations have now become a useful tool in searching for non--luminous astrophysical compact objects (brown dwarfs, faint stars, neutron stars, black holes and even planets). Originally conceived for establishing whether the…