Research Area: SNRs

This research project was connected with the starburst phenomenon and its constituents at a smaller scale size---the investigation of supernova remnants (SNRs) in our Galaxy, especially their interaction with the surrounding interstellar medium.

The results comprised a radio polarization map of the first quadrant of the Galactic plane (Junkes et al. 1987), and the identification of a number of new SNRs in that area (Reich et al. 1988). Follow-up observations of selected SNRs were performed at several radio frequencies and compared to the FIR emission (IRAS). A spectroscopic investigation in the molecular line of CO (115 GHz) with two radio telescopes (3m-KOSMA telescope, 30m-IRAM telescope) shows the interaction with the interstellar medium. For the extended SNR G54.4-0.3 we found a surrounding molecular shell from the CO observations and developed a scenario for the expansion of this SNR in a surrounding stellar wind bubble, with star formation in the interaction zone (proven by compact HII regions and molecular clouds with bipolar structure at the positions of FIR point sources). The results were published in two papers in A&A (Junkes et al. 1992a, 1992b); this project is supplementing the investigation of starbursts and its constituents (SNRs and formation of new stars) in more detail in our Galaxy.

A similar project was started during a ten months residence at ATNF (Sydney/Australia) with the investigation of SNRs in the Large Magellanic Cloud (LMC) and their interaction with the interstellar medium. We successfully applied for high-resolution radio observations of two SNRs (N49, N63A) at the edge of the supergiant shell LMC-4 with the Australia Telescope (AT). The resolution of the AT of a few arcsec at convenient radio frequencies enables a detailed comparison with optical as well as high-resolution X-ray data. Results of the AT observations were presented for N49 (Dickel et al. 1995) and for N63A (Dickel et al. 1993).

The X-ray structure of SNRs G54.4-0.3 has been investigated in a mosaic of pointed ROSAT observations taken with the PSPC detector. The X-ray image of the SNR displays hot thermal gas filling the interior of the remnant in anti-coincidence to the molecular shell surrounding the SNR. The X-ray emission can be fitted with a thermal plasma model (Raymond-Smith) with significant foreground absorption in the Galactic plane. Taking into account the results from the ROSAT observations, we successfully applied for X-ray observations of G54.4-0.3 with ASCA; the observations (80 ksec) have been performed and the data are available in the ASCA archive.

Results of the X-ray analysis, also in comparison with a complete high-resolution map of neutral hydrogen (including zero spacings) of the SNR which has been observed with the DRAO Synthesis Telescope (Penticton/Canada), were presented at the IAU General Assembly in The Hague (Junkes 1996).

Last modified on Tuesday, March 15th, 2022.
Norbert Junkes ( )
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