We present bidimensional, long-slit spectroscopic mapping of the prototypical low-metallicity dwarf galaxy I Zw 18. A total of eight spaced slit positions were observed, covering most of the body of the galaxy and part of the extended envelope of the diffuse ionized halo seen in deep Hα images of I Zw 18. Spectroscopic maps of the galaxy have been

Far Infrared observations of the Seyfert galaxies NGC 3227, NGC 4051 and NGC 4151 are presented. These are the first data from a complete sample of Seyfert galaxies that is being observed by ISO as part of the ISOPHOT guaranteed time. The new ISO data, in combination with the IRAS data, show that the mid to far IR emission in all three objects can

Context: Current atmospheric models cannot reproduce some of the characteristics of the transition between the L dwarfs with cloudy atmospheres and the T dwarfs with dust-depleted photospheres. It has been proposed that a majority of the L/T transition brown dwarfs could actually be a combinaison of a cloudy L dwarf and a clear T dwarf. Indeed

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