Context. Observing supernova remnants (SNRs) and modelling the shocks they are associated with is the best way to quantify the energy SNRs re-distribute back into the interstellar medium (ISM).
Aims: We present comparisons of shock models with CO observations in the F knot of the W28 supernova remnant. These comparisons constitute a valuable tool to constrain both the shock characteristics and pre-shock conditions.
Methods: New CO observations from the shocked regions with the APEX and SOFIA telescopes are presented and combined. The integrated intensities are compared to the outputs of a grid of models, which were combined from an MHD shock code that calculates the dynamical and chemical structure of these regions and a radiative transfer module based on the large velocity gradient (LVG) approximation.
Results: We base our modelling method on the higher J CO transitions, which unambiguously trace the passage of a shock wave. We provide fits for the blue- and red-lobe components of the observed shocks. We find that only stationary, C-type shock models can reproduce the observed levels of CO emission. Our best models are found for a pre-shock density of 104 cm-3, with the magnetic field strength varying between 45 and 100 μG, and a slightly higher shock velocity for the so-called blue-shock (~25 km s-1) than for the red one (~20 km s-1). Our models also satisfactorily account for the pure rotational H2 emission that is observed with Spitzer.
Astronomy and Astrophysics
- Pub Date:
- June 2012
- ISM: supernova remnants;
- ISM: individual objects: W28;
- ISM: kinematics and dynamics;
- shock waves;
- submillimeter: ISM;
- infrared: ISM;
- Astrophysics - Astrophysics of Galaxies
- 8 pages, 6 figures, 1 table, accepted for A&