X-ray sources in the starburst spiral galaxy M 83

Free access article

Issue		A&A Volume 384, Number 1, March II 2002


Page(s)		99 - 111
Section		Extragalactic astronomy
DOI		http://dx.doi.org/10.1051/0004-6361:20020026

A&A 384, 99-111 (2002)
DOI: 10.1051/0004-6361:20020026

Nuclear region and discrete source population

R. Soria^{1, 2} and K. Wu^{1, 2}

¹ Mullard Space Science Laboratory, University College London, Holmbury St Mary, Surrey RH5 6NT, UK
e-mail: kw@mssl.ucl.ac.uk
² School of Physics A28, University of Sydney, NSW 2006, Australia

(Received 18 October 2001 / Accepted 4 January 2002 )

Abstract
Chandra has resolved the starburst nuclear region of the face-on grand-design spiral M 83. Eighty-one point sources are detected (above 3.5- $\sigma$ ) in the ACIS S3 image, and 15 of them are within the inner 16´´ region of the galaxy. A point source with $L_{\rm x} \approx 3 \times 10^{38}$ erg s ^-1 in the 0.3-8.0 keV band is found to coincide with the infra-red nuclear photometric peak, one of the two dynamical nuclei of the galaxy. No point-like sources are resolved (at a 2.5- $\sigma$ level) at the centre of symmetry of the outer optical isophote ellipses, suspected to be another dynamical nucleus. About 50% of the total emission in the nuclear region is unresolved; of this, about 70% can be attributed to hot thermal plasma, and the rest is probably due to unresolved point sources (e.g., faint X-ray binaries). The azimuthally-averaged radial distribution of the unresolved emission has a King-like profile, with no central cusp. Strong emission lines are seen in the spectrum of the optically thin plasma component. The high abundances of C, Ne, Mg, Si and S with respect to Fe suggest that the interstellar medium in the nucleus is enriched and heated by type-II supernova explosions and winds from massive stars. The cumulative luminosity distribution of the discrete X-ray sources is neither a single nor a broken power law. Separating the sources in the nuclear region (within a distance of 60´´ from the X-ray centre) from the rest reveals that the two groups have different luminosity distributions. The $\log N({>}S) - \log S$ curve of the sources in the inner region (nucleus and stellar bar) is a single power law, which we interpret as due to continuous, ongoing star formation. Outside the central region, there is a smaller fraction of sources brighter than the Eddington limit for an accreting neutron star.

Key words: galaxies: individual: M 83 (= NGC 5236) -- galaxies: nuclei -- galaxies: spiral -- galaxies: starburst -- X-rays: binaries -- X-rays: galaxies

Offprint request: R. Soria, rs1@mssl.ucl.ac.uk

SIMBAD Objects

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.