Volume 569, September 2014
|Number of page(s)||19|
|Section||Interstellar and circumstellar matter|
|Published online||26 September 2014|
APEX observations of supernova remnants
Argelander Institut für Astronomie, Universität Bonn,
Auf dem Hügel, 71,
2 Univ. Grenoble Alpes, IPAG, 38000 Grenoble, France
3 CNRS, IPAG, 38000 Grenoble, France
4 LERMA, UMR 8112 du CNRS, Observatoire de Paris, École Normale Supérieure, 24 rue Lhomond, 75231 Paris Cedex 05, France
5 Max Planck Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
Accepted: 22 July 2014
Context. When supernova blast waves interact with nearby molecular clouds, they send slower shocks into these clouds. The resulting interaction regions provide excellent environments for the use of MHD shock models to constrain the physical and chemical conditions in these regions.
Aims. The interaction of supernova remnants (SNRs) with molecular clouds gives rise to strong molecular emission in the far-IR and sub-mm wavelength regimes. The application of MHD shock models in the interpretation of this line emission can yield valuable information on the energetic and chemical impact of SNRs.
Methods. New mapping observations with the APEX telescope in 12CO (3–2), (4–3), (6–5), (7–6), and 13CO (3–2) towards two regions in the SNR W44 are presented. Integrated intensities are extracted on five different positions, corresponding to local maxima of CO emission. The integrated intensities are compared to the outputs of a grid of models, which combine an MHD shock code with a radiative transfer module based on the large velocity gradient approximation.
Results. All extracted spectra show ambient and line-of-sight components as well as blue- and red-shifted wings indicating the presence of shocked gas. Basing the shock model fits only on the highest-lying transitions that unambiguously trace the shock-heated gas, we find that the observed CO line emission is compatible with non-stationary shocks and a pre-shock density of 104 cm-3. The ages of the modelled shocks scatter between values of ~1000 and ~3000 years. The shock velocities in W44F are found to lie between 20 km s-1 and 25 km s-1, while in W44E fast shocks (30–35 km s-1) as well as slower shocks (~20 km s-1) are compatible with the observed spectral line energy diagrams. The pre-shock magnetic field strength components perpendicular to the line of sight in both regions have values between 100 μG and 200 μG. Our best-fitting models allow us to predict the full ladder of CO transitions, the shocked gas mass in one beam as well as the momentum and energy injection.
Key words: ISM: supernova remnants / ISM: individual objects: W44 / ISM: kinematics and dynamics / shock waves / submillimeter: ISM / infrared: ISM
© ESO, 2014
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