Supermassive black holes with masses of millions to billions of solar masses are commonly found in the centers of galaxies. Astronomers seek to image jet formation using radio interferometry but still suffer from insufficient angular resolution. An alternative method to resolve small structures is to measure the time variability of their emission

Blue compact dwarf galaxies (BCDs) take up the low end of the distribution of metallicity and nitrogen-to-oxygen (N/O) ratio as derived using collisional emission lines in ionized gaseous nebulae. This chemical status is well explained by chemical evolution models. Nevertheless, there is a subsample of BCDs with large values of N/O which cannot be

Infrared photometry in the J, H and K bands, performed on a sample of 33 blue stragglers (BS) belonging to 8 open clusters is presented. This photometry has been combined with published Johnson UBV photometry to search for possible cold companions among the BS, as expected for Case B close binary evolution. Probable binaries were identified by

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Breaks in the radial luminosity profiles of galaxies have until now been mostly studied averaged over disks. Here, we study separately breaks in thin and thick disks in 70 edge-on galaxies using imaging from the Spitzer Survey of Stellar Structure in Galaxies. We built luminosity profiles of the thin and thick disks parallel to midplanes and we

A search for bright galaxies associated with radio sources from the WENSS minisurvey has been carried out. A galaxy counterpart was found for 402 of almost 10,000 radio sources. Of these a radio and optically complete sample, with a flux density limit at 325 MHz of 30 mJy and a limiting red magnitude of 16, can be constructed, which contains 119