This particular object I began looking more into right around the time I was also preparing for the written qualification exams at Clemson University. PHEW that is a stressful time to look back on. Maybe I’ll write more about the PhD process in the program in another blog post but, for now, let’s focus on the second Fermi object I investigated. I had a task to gather data for 12 newly detected very high energy sources – or VHE, which we will define at an energy E > 50 GeV which is among the highest energy for light, the gamma-ray range. The gamma-ray space telescope, Fermi, had just discovered these sources and were reported in 2016 (free and public pdf version available here). I was looking at multiple sources at once but, one particular source, led me somewhat down a rabbit hole and led to my second paper (in review but hopefully close to acceptance and publishing!) on the multi-wavelength analysis of the supernova remnant, G3447.1-0.1, which is found to be a likely origin for the newly discovered gamma-ray emission at the edge of the remnant. Does this sound familiar? It should! My first report was also on the discovery of gamma-ray emission on the edge of the Vela supernova remnant (SNR). Coincidence? Yes. Lol. Though this time the physics was a little more complicated but, all the more exciting!

Admittedly my only experience so far with gamma-ray objects was the emission we identified as a shock-cloud interaction on the west edge of the Vela SNR and, so far, I was looking at another SNR with gamma-ray emission appearing on the west edge which overlapped with bright radio emission and a strong infrared filament. The bright radio emission can be seen in the left panel above. The green color is showing you where the radio emission brightens which is seen to be on the north and western regions. Similarly, we see brighten infrared emission in the northern-central and western regions as shown in the middle panel. Do you see the red filament in the middle panel? This coincides with the gamma-ray position and bright radio emission. Interesting.

 

By the way, the above images can be found in the following reports: (left) Eagle et al., 2020 (arXiv pdf version here), (middle) Combi et al., 2010 (arXiv pdf version here), and (right) available here. 

So what does this mean, exactly? Well, in general, where one might see increased emission accompanying high energy emission, like this gamma-ray source, points to some kind of interaction that would accelerate these particles to radiate at the varying wavelengths. Each wavelength provides us different information about the particles responsible for the radiation and how they must be interacting with their environment. This also means we can infer what that environment is made up of.

 

Recall my first report we were able to determine the presence of a small neutral hydrogen cloud that was found to coincide precisely with the western wall of the Vela SNR that paired with the observed gamma-ray emission there. We can plausibly describe the gamma-ray emission as arising between the remnant’s forward shock – that is, it’s outer layer that was blast into the interstellar medium first at the time of explosion – is running into its surroundings and is colliding with and disturbing the material.

Let’s break down my first findings:

• There is bright radio emission to the west of the SNR G344.7-0.1 as can be seen in the left panel above. This may suggest the remnant is interacting with its surroundings, much like the scenario just described.
• There is a bright infrared filament that outlines the west wall of the remnant, overlapping with the bright radio emission seen and also coincides with the X-ray boundary of the SNR (we will see in the next post that the radio emission mostly follows the filled X-ray center appearance of the SNR).