Outflow or galactic wind: The fate of ionized gas in the halos of dwarf galaxies

Context: H\alpha images of star bursting irregular galaxies reveal a large amount of extended ionized gas structures, in some cases at kpc-distance away from any place of current star forming activity. A kinematic analysis of especially the faint structures in the halo of dwarf galaxies allows insights into the properties and the origin of this gas component. This is important for the chemical evolution of galaxies, the enrichment of the intergalactic medium, and for the understanding of the formation of galaxies in the early universe. Aims: We want to investigate whether the ionized gas detected in two irregular dwarf galaxies (NGC 2366 and NGC 4861) stays gravitationally bound to the host galaxy or can escape from it by becoming a freely flowing wind. Methods: Very deep H\alpha images of NGC 2366 and NGC 4861 were obtained to detect and catalog both small and large scale ionized gas structures down to very low surface brightnesses. Subsequently, high-resolution long-slit echelle spectroscopy of the H\alpha line was performed for a detailed kinematic analysis of the most prominent filaments and shells. To calculate the escape velocity of both galaxies and to compare it with the derived expansion velocities of the detected filaments and shells, we used dark matter halo models. Results: We detected a huge amount of both small scale (up to a few hundred pc) and large scale (about 1-2 kpc of diameter or length) ionized gas structures on our H\alpha images. Many of the fainter ones are new detections. The echelle spectra reveal outflows and expanding bubbles/shells with velocities between 20 and 110 km/s. Several of these structures are in accordance with filaments in the H\alpha images. A comparison with the escape velocities of the galaxies derived from the NFW dark matter halo model shows that all gas features stay gravitationally bound.Comment: 15 pages, 13 figures, accepted for publication in A&

SN2002kg -- the brightening of LBV V37 in NGC 2403

SN2002kg is a type IIn supernova, detected in October 2002 in the nearby spiral galaxy NGC 2403. We show that the position of SN2002kg agrees within the errors with the position of the LBV V37. Ground based and HST ACS images however show that V37 is still present after the SN2002kg event. We compiled a lightcurve of V37 which underlines the variablity of the object, and shows that SN2002kg was the brightening of V37 and not a supernova. The recent brightening is not a giant eruption, but more likely part of an S Dor phase. V37 shows strong Halpha +[NII] emission in recent images and in the SN2002kg spectrum, which we interprete as the signature of the presence of an LBV nebula. A historic spectrum lacks emission, which may hint that we are witnessing the formation of an LBV nebula.Comment: 4 pages, 5 figures, accepted in A&A Letter, paper with images in full resolution at http://www.astro.ruhr-uni-bochum.de/kweis/publications.htm

Detection of low energy single ion impacts in micron scale transistors at room temperature

We report the detection of single ion impacts through monitoring of changes in the source-drain currents of field effect transistors (FET) at room temperature. Implant apertures are formed in the interlayer dielectrics and gate electrodes of planar, micro-scale FETs by electron beam assisted etching. FET currents increase due to the generation of positively charged defects in gate oxides when ions (121Sb12+, 14+, Xe6+; 50 to 70 keV) impinge into channel regions. Implant damage is repaired by rapid thermal annealing, enabling iterative cycles of device doping and electrical characterization for development of single atom devices and studies of dopant fluctuation effects

Articular cartilage collagen: an irreplaceable framework?

Adult articular cartilage by dry weight is two-thirds collagen. The collagen has a unique molecular phenotype. The nascent type II collagen fibril is a heteropolymer, with collagen IX molecules covalently linked to the surface and collagen XI forming the filamentous template of the fibril as a whole. The functions of collagens IX and XI in the heteropolymer are far from clear but, evidently, they are critically important since mutations in COLIX and COLXI genes can result in chondrodysplasia syndromes. Here we review what is known of the collagen assembly and present new evidence that collagen type III becomes covalently added to the polymeric fabric of adult human articular cartilage, perhaps as part of a matrix repair or remodelling process