Multiwavelength study of the star-formation in the bar of NGC 2903

¹ Kapteyn Astronomical Institute, PO Box 800, 9700 AV Groningen, The Netherlands e-mail: G.Popping@astro.rug.nl
² Dep. Física Teórica y del Cosmos, Campus de Fuentenueva, Universidad de Granada, 18071 Granada, Spain
³ Instituto Carlos I de Física Teórica y Computación, Spain

Received: 2 February 2010
Accepted: 28 April 2010

Abstract

Aims. The nearby barred spiral NGC 2903 has an active starburst at its centre and H II regions distributed along its bar. We analyse the star-formation properties in the bar region of NGC 2903 and study its links to the typical bar morphological features.

Methods. We combine space and ground-based data from the far-ultraviolet to the sub-millimeter spectral ranges to create a panchromatic view of the NGC 2903 bar. We produce two catalogues: one for the current star-formation regions, as traced by the Hα compact emission, and a second for the ultraviolet (UV) emitting knots, containing positions and luminosities. From them, we obtain ultraviolet colours, star-formation rates, dust attenuation, and Hα EWs, and analyse their spatial distribution. We estimate stellar cluster ages using stellar population synthesis models (Starburst99).

Results. We find NGC 2903 to be a complex galaxy that has a very different morphology in each spectral band. The CO (J = 1–0) and the 3.6 μm emission trace each other in a clear barred structure, while the Hα leads both components and has an s-shape distrib0ution. The UV emission is patchy and does not resemble a bar. The UV emission is also characterised by a number of regions located symmetrically with respect to the galaxy centre, almost perpendicular to the bar, in a spiral shape covering the inner ~2.5 kpc. These regions exhibit a significant amount of neither Hα nor 24 μm emission. We estimate ages for these regions ranging from 150 to 320 Myr, older than the remaining UV knots, which have ages lower than 10 Myr. The SFR calculated from the UV emission is ~0.4  yr^-1, compatible with the SFR derived from Hα calibrations (~1  yr^-1).