Multi-frequency study of supernova remnants in the Large Magellanic
  Cloud. Confirmation of the supernova remnant status of DEM L205
  We present new X-ray and radio data of the LMC SNR candidate DEM L205,
obtained by XMM-Newton and ATCA, along with archival optical and infrared
observations. We use data at various wavelengths to study this object and its
complex neighbourhood, in particular in the context of the star formation
activity, past and present, around the source. We analyse the X-ray spectrum to
derive some remnant's properties, such as age and explosion energy. Supernova
remnant features are detected at all observed wavelengths: soft and extended
X-ray emission is observed, arising from a thermal plasma with a temperature kT
between 0.2 keV and 0.3 keV. Optical line emission is characterised by an
enhanced [SII]/Halpha ratio and a shell-like morphology, correlating with the
X-ray emission. The source is not or only tentatively detected at near-infrared
wavelengths (< 10 microns), but there is a detection of arc-like emission at
mid and far-infrared wavelengths (24 and 70 micron) that can be unambiguously
associated with the remnant. We suggest that thermal emission from dust heated
by stellar radiation and shock waves is the main contributor to the infrared
emission. Finally, an extended and faint non-thermal radio emission correlates
with the remnant at other wavelengths and we find a radio spectral index
between -0.7 and -0.9, within the range for SNRs. The size of the remnant is
~79x64 pc and we estimate a dynamical age of about 35000 years. We definitely
confirm DEM L205 as a new SNR. This object ranks amongst the largest remnants
known in the LMC. The numerous massive stars and the recent outburst in star
formation around the source strongly suggest that a core-collapse supernova is
the progenitor of this remnant. (abridged)
