Massive star formation in the central regions of spiral galaxies

Abstract

Received ; accepted Abstract. Context The morphology of massive star formation in the central regions of galaxies is an important tracer of the dynamical processes that govern the evolution of disk, bulge, and nuclear activity. Aims We present optical imaging of the central regions of a sample of 73 spiral galaxies in the Hline and in optical broad bands, and derive information on the morphology of massive star formation. Methods We obtained images with the William Herschel Telescope, mostly at a spatial resolution of below one second of arc. For most galaxies, no Himaging is available in the literature. We outline the obser ving and data reduction procedures, list basic properties, and present the I-band and continuum-subtracted Himages. We classify the morphology of the nuclear and circumnuclear Hemission and explore trends with host galaxy parameters. Results We confirm that late-type galaxies have a patchy circumnucle ar appearance in H�, and that nuclear rings occur pri- marily in spiral types Sa-Sbc. We identify a number of previously unknown nuclear rings, and confirm that nuclear rings ar e predominantly hosted by barred galaxies. Conclusions Other than in stimulating nuclear rings, bars do not influenc e the relative strength of the nuclear Hpeak, nor the circumnuclear Hmorphology. Even though our selection criteria led to an over-abundance of galaxies with close massive companions, we do not find any significant influence of the presence or absence of a close com panion on the relative strength of the nuclear Hpeak, nor on the Hmorphology around the nucleus.