Issue |
A&A
Volume 441, Number 2, October II 2005
|
|
---|---|---|
Page(s) | 491 - 511 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361:20042342 | |
Published online | 19 September 2005 |
Dissecting the spiral galaxy M 83: mid-infrared emission and comparison with other tracers of star formation
1
DSM/DAPNIA/Service d'Astrophysique, CEA/Saclay, 91191 Gif-sur-Yvette Cedex, France e-mail: smadden@cea.fr
2
Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
3
European Southern Observatory, Casilla 19001, Santiago 19, Chile
4
Stockholm Observatory, AlbaNova, 106 91 Stockholm, Sweden
5
XMM-Newton Science Operations Centre, European Space Agency, Villafranca, PO Box 50727, 28080 Madrid, Spain
Received:
9
November
2004
Accepted:
7
July
2005
We present a detailed mid-infrared study of the nearby, face-on
spiral galaxy M 83 based on ISOCAM data. M 83 is a unique case
study, since a wide variety of MIR broad-band filters as well as
spectra, covering the wavelength range of 4 to 18 μm, were observed
and are presented here. Emission maxima trace the nuclear and bulge
area, star-formation regions at the end of the bar, as well as the
inner spiral arms. The fainter outer spiral arms and interarm regions
are also evident in the MIR map. Spectral imaging of the
central (
) field allows
us to investigate five regions of different environments. The various
MIR components (very small grains, polycyclic aromatic hydrocarbon (PAH)
molecules, ionic lines) are analyzed for different regions throughout
the galaxy. In the total λ4 μm to 18 μm wavelength range,
the PAHs dominate the luminosity, contributing between 60% in the
nuclear and bulge regions and 90% in the less active, interarm
regions. Throughout the galaxy, the underlying continuum emission from
the small grains is always a smaller contribution in the total MIR wavelength regime, peaking in the nuclear and bulge components. The
implications of using broad-band filters only to characterize the
mid-infrared emission of galaxies, a commonly used ISOCAM observation
mode, are discussed.
We present the first quantitative analysis of new Hα and λ6 cm VLA+Effelsberg radio continuum maps of M 83. The distribution of the MIR emission is compared with that of
the CO, HI, R band, Hα and λ6 cm radio. A striking
correlation is found between the intensities in the two mid-infrared
filter bands and the λ6 cm radio continuum.
To explain the tight mid-infrared-radio correlation we propose the
anchoring of magnetic field lines in the photoionized shells of gas
clouds.
Key words: galaxies: individual: M 83 / galaxies: spiral / galaxies: ISM / ISM: dust, extinction / ISM: magnetic fields
© ESO, 2005
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