A Photometric System for Metallicity Mapping in Galaxies

A new photometric system suitable for deep, precise and quick metallicity mapping in galaxies is proposed. We find a linear correlation between our metallicity index and the Mg₂ index for stellar, globular-cluster, and early-type galaxy spectra, and model spectral energy distributions of the simple stellar populations. This revised version was published online in July 2006 with corrections to the Cover Date.     

X-ray,Hα, and radio observations of the two-ribbon flare of 16 May, 1981

The paper is a contribution to the study of two-ribbon flares. A variety of observational material, i.e. Hα pictures, radio spectrum in the frequency band of 150–1000 MHz, radio map at 6 cm, fluxes at other frequencies, magnetograms and X-ray flux in a broad energy interval, enabled us to study the development of the 16 May, 1981 flare. The onset of the flare could be described by the model of Van Tend and Kuperus. A diminishing of the magnetic shear during the activation of the filament was observed. From radio and X-ray data it was found that pulsed acceleration took place in the region under the rising filament, the electrons propagating in a limited region both upwards to greater heights and downwards into the footpoints. Internal oscillations of the filament were observed. A manifestation of the primary process of interplanetary shock-wave generation was found. The 6 cm radio sources could be localized in the footpoints of magnetic loops.     

Mean surface brightness as a criterion for or against the expansion of the Universe

Using the well-known relation for the mean surface brightness, the author gives the concept of the decision regarding the expansion of the Universe. The most serious obstacle on this way was the low precision of parameter measurements which one could achieve in the past. This paper brings the first step for eventual judgement if the Universe expand or not because the accuracy of measurements has advanced. In this sence, we need some more determinations with present accuracy to give the decisive result because the mean surface brightness must faint by 1.46 mag per square arc sec for red shift of 0.4, and this is sufficient to measure and statistically elaborate it.     

Image recovering from the modulated CCD imagers

The CCD imagers have a spatial resolution comparable to the size of a constituent photosensitive cell. The modulation by means of a rotating Ronchi grating helps to exceed this limit. While the grating rotates in front of the CCD imager the counts of each cell are modulated thus producing a time-varying modulation pattern. The small systematic variations of the form of the pattern encode the fragment of the image pertaining to the cell. The images can be recovered from the modulation patterns by means of the least-squares as well as maximum entropy reconstruction technique. Both methods are able to decode the modulation patterns having high signal-to-noise ratio, however, maximum entropy reconstruction seems to be more robust. A gain in spatial resolution may be of the order of magnitude under favourable circumstances.