We examine using numerical examples and conservative assumptions, the consequences of the fractal structure of the interstellar medium in a disk galaxy in permitting the propagation of the ionizing radiation emitted by its massive stellar population. We compare the Strömgren sphere in a homogeneous medium with its equivalent in a clumpy medium

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We propose the use of the break in the HII region luminosity function (LF) as a possible refined powerful standard candle for extragalactic distances. The invariance and high luminosity of the LF break has been proposed in previous studies as a possible secondary standard candle, but it is calibrated here for the first time using the LFs of NGC 925

Sunrise is a 1m balloon-borne solar telescope. It is equipped with a spectrograph polarimeter which combines vector-polarimetry in the visible with diagnostic spectroscopy in the visible and the UV, down to 200 nm. The instrumentation includes a filter-magnetograph and a medium-band filtergraph. The wavelength bands of the latter include the CH

Nuclear rings in barred spiral galaxies offer an opportunity to study starburst properties, as well as the evolution of star formation in the central regions of galaxies. To further our understanding in these areas, a large imaging survey of over 80 galaxies with previous evidence for the existence of nuclear ring structure has been performed in

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