RESEARCH

“ Nothing in life is to be feared, it is only to be understood. Now is the time to understand more, so that we may fear less.”

- Marie Curie -

Supernova Remnants Interacting with Molecular Clouds

In gamma rays, middle-aged mixed-morphology (MM) supernova remnants (SNRs) interacting with molecular clouds (MCs), such as IC443, W28, W51C, W44, W49B, were among the first detected SNRs by the Large Area Telescope (LAT) on board Fermi Gamma Ray Space Telescope (Fermi). Interactions of these MM SNRs with MCs were clearly shown by the detection of 1720 MHz OH masers  and near-infrared H2 and [Fe II] lines.

 

MM SNRs interacting with MCs are primary targets for the detection of gamma rays of 'hadronic' origin, where two gamma rays are produced from the decay of a neutral pion (π◦) created in a proton- proton interaction while the SNR shock passes through a dense molecular material. The gamma-ray spectra of these SNRs fall steeply below 250 MeV and at energies greater than 1 GeV they trace the parent proton energy distribution.

The Galactic supernova remnant (SNR) G349.7+0.2 is located about 11.5 kpc away from us. It is an OH maser emitting SNR. Gamma-ray emission is detected from this SNR. In the figures on the right-hand side you see the TS map of G349.7+0.2 spectral data points and the corresponding 'hadronic' model fitted to them. 

Relationship Between Gamma-ray Emission & Recombining X-ray Plasma in Supernova Remnants 

The recombining plasma (RP) observed in X-rays, is characterised with a higher ionisation temperature than an electron temperature (kTz > kTe). Although the origin of RP in supernova remnants (SNRs) has not been understood yet, there is a strong correlation between the RPs and the mixed-morphology SNRs. That the MM SNRs are generally associated with molecular cloud regions and GeV gamma-ray emission indicates that they are mostly located in dense environments. Therefore, it is expected that they are originated in core-collapse supernovae. So, these are the best SNR candidates to search for RP emission. Figures on the left-hand side are related to 3C 391.  

Unidentified Gamma-ray Sources & Extended Gamma-ray Emission

Work under this section includes newly detected gamma-ray sources like supernova remnants (SNRs), e.g. 3C400.2, and unidentified extended gamma-ray sources which were detected during our SNR analyses, such as the extended source, PS J1934.5+1845, that was detected during the 3C400.2 analyses and SourceA, which was detected during the gamma-ray analysis of SNR G306.3−0.9. The left-upper Figure shows the TS map of SNR 3C400.2, the middle Figure is the TS map of unidentified extended source, PS J1934.5+1845, and the bottom  Figure is the TS map of Source A. 

Source A was also observed with Swift, which found 4 X-ray point-like sources within SourceA, which we called srcA, srcB, srcC and srcD on the Figure below.