We compare the details of the distributions of HI, Hα , and far-UV emission in the spiral arms of M81, at a resolution of about 9'' (linear resolution 150 pc at 3.7 Mpc distance). The effects of extinction on the morphology of the Hα and far-UV are shown to be essentially bi-modal, i.e. the extinction is either very small or very large. The

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

The formation of quasar broad-line region (BLR) clouds via thermal instability in the presence of Alfvén heating has been discussed by Gonçalves, Jatenco-Pereira & Opher. In particular, these studies showed the relevance of Alfvén heating in establishing the stability of BLR clouds in the intercloud medium. The present paper shows the results of

I present our recent results on bulge evolution. (1) We have modeled the accretion of satellite galaxies onto disk-bulge-halo galaxies, and show that accretion-driven bulge growth generates two of the observed trends of galaxies along the Hubble sequence, namely the higher Sersic index toward more massive bulges, and the appearance of a thick disk

The particle and event horizons are widely known and studied concepts, but the study of their properties, in particular their evolution, have only been done so far considering a single state equation in a decelerating universe. This paper is the first of two where we study this problem from a general point of view. Specifically, this paper is

Observations with the balloon borne SUNRISE/IMAX instrument provide us with unprecedented high spatial resolution (pixel size 40 km) measurements of the magnetic field in the photosphere of the quiet Sun. To investigate the magnetic structure of the chromosphere and corona we extrapolate these photospheric measurements into the upper solar