Massive star formation in the central regions of spiral galaxies

Free access article

Issue		A&A Volume 448, Number 2, March III 2006


Page(s)		489 - 498
Section		Extragalactic astronomy
DOI		10.1051/0004-6361:20053928

A&A 448, 489-498 (2006)
DOI: 10.1051/0004-6361:20053928

Massive star formation in the central regions of spiral galaxies

J. H. Knapen¹, L. M. Mazzuca², T. Böker³, I. Shlosman⁴, L. Colina⁵, F. Combes⁶ and D. J. Axon^{1, 7}

¹ Centre for Astrophysics Research, University of Hertfordshire, Hatfield, Herts AL10 9AB, UK
e-mail: j.knapen@star.herts.ac.uk
² NASA Goddard Space Flight Center, Code 441, Greenbelt, MD 20771, USA
³ ESA/ESTEC, Keplerlaan 1, 2200 AG Noordwijk, The Netherlands
⁴ Department of Physics and Astronomy, University of Kentucky, Lexington, KY 40506-0055, USA
⁵ Instituto de Estructura de la Materia, CSIC, Serrano 119, 28006 Madrid, Spain
⁶ Observatoire de Paris, 61 Av. de l'Observatoire, 75014 Paris, France
⁷ Department of Physics, Rochester Institute of Technology, 84 Lomb Memorial Drive, Rochester, NY 14623, USA

(Received 27 July 2005 / Accepted 27 October 2005)

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 H $\alpha$ line 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 H $\alpha$ imaging is available in the literature. We outline the observing and data reduction procedures, list basic properties, and present the I-band and continuum-subtracted H $\alpha$ images. We classify the morphology of the nuclear and circumnuclear H $\alpha$ emission and explore trends with host galaxy parameters. Results. We confirm that late-type galaxies have a patchy circumnuclear appearance in H $\alpha$ , and that nuclear rings occur primarily in spiral types Sa-Sbc. We identify a number of previously unknown nuclear rings, and confirm that nuclear rings are predominantly hosted by barred galaxies. Conclusions. Other than in stimulating nuclear rings, bars do not influence the relative strength of the nuclear H $\alpha$ peak, nor the circumnuclear H $\alpha$ morphology. Even considering that 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 companion on the relative strength of the nuclear H $\alpha$ peak, nor on the H $\alpha$ morphology around the nucleus.

Key words: galaxies: spiral -- galaxies: structure -- galaxies: nuclei

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