Multi-frequency study of DEM L299 in the Large Magellanic Cloud
  We have studied the HII region DEM L299 in the Large Magellanic Cloud to
understand its physical characteristics and morphology in different
wavelengths. We performed a spectral analysis of archived XMM-Newton EPIC data
and studied the morphology of DEM L299 in X-ray, optical, and radio
wavelengths. We used H alpha, [SII], and [OIII] data from the Magellanic Cloud
Emission Line Survey and radio 21 cm line data from the Australia Telescope
Compact Array (ATCA) and the Parkes telescope, and radio continuum data from
ATCA and the Molonglo Synthesis Telescope. Our morphological studies imply
that, in addition to the supernova remnant SNR B0543-68.9 reported in previous
studies, a superbubble also overlaps the SNR in projection. The position of the
SNR is clearly defined through the [SII]/H alpha flux ratio image. Moreover,
the optical images show a shell-like structure that is located farther to the
north and is filled with diffuse X-ray emission, which again indicates the
superbubble. Radio 21 cm line data show a shell around both objects. Radio
continuum data show diffuse emission at the position of DEM L299, which appears
clearly distinguished from the HII region N 164 that lies south-west of it. We
determined the spectral index of SNR B0543-68.9 to be alpha=-0.34, which
indicates the dominance of thermal emission and therefore a rather mature SNR.
We determined the basic properties of the diffuse X-ray emission for the SNR,
the superbubble, and a possible blowout region of the bubble, as suggested by
the optical and X-ray data. We obtained an age of 8.9 (3.5-18.1) kyr for the
SNR and a temperature of 0.64 (0.44-1.37) keV for the hot gas inside the SNR,
and a temperature of the hot gas inside the superbubble of 0.74 (0.44-1.1) keV.
We conclude that DEM L299 consists of a superposition of SNR B0543-68.9 and a
superbubble, which we identified based on optical data.
