EDP Sciences Journals List
Advanced Search
Subscriber Authentication Point
Home All issues Volume 372/ 2 Article

Free access article

Issue A&A
Volume 372, Number 2, June III 2001
Page(s) 427 - 437
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20010498



A&A 372, 427-437 (2001)
DOI: 10.1051/0004-6361:20010498

The relationship between star formation rates and mid-infrared emission in galactic disks

H. Roussel1, M. Sauvage1, L. Vigroux1 and A. Bosma2

1  DAPNIA/Service d'Astrophysique, CEA/Saclay, 91191 Gif-sur-Yvette Cedex, France
2  Observatoire de Marseille, 2 place Le Verrier, 13248 Marseille Cedex 4, France

(Received 2 February 1999 / Accepted 19 March 2001 )

Abstract
The H$\alpha$ and mid-infrared mean disk surface brightnesses are compared in a sample of nearby spirals observed by ISOCAM. This shows that, in spiral disks, dust emission at 7 and 15 $\mu$m provides a reasonable star formation tracer. The fact that the 15 to 7 $\mu$m flux ratio is nearly constant in various global exciting conditions indicates a common origin, namely the aromatic infrared band carriers, and implies that at these wavelengths, dust emission from the disks of normal galaxies is dominated by photodissociation regions and not by HII regions themselves. We use this newly-found correlation between the mid-infrared and the H$\alpha$ line to investigate the nature of the link between the far-infrared (60 and 100 $\mu$m) and H$\alpha$. Although the separation of the central regions from the disk is impossible to achieve in the far-infrared, we show that a circumnuclear contribution to the dust emission, having no equivalent counterpart in H$\alpha$, is most likely responsible for the well-known non-linearity between far-infrared and H$\alpha$ fluxes in spiral galaxies. We derive a calibration of 7 and 15 $\mu$m fluxes in terms of star formation rates from a primary calibration of H$\alpha$ in the literature, and also outline the applicability limits of the proposed conversion, which should not be blindly extrapolated to objects whose nature is unknown.


Key words: galaxies: spiral -- galaxies: ISM -- stars: formation -- infrared: ISM

Offprint request: H. Roussel, hroussel@cea.fr

SIMBAD Objects



© ESO 2001

What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.
  • If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
  • You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
  • You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.