Supernovae Are Natural Large Hadron Colliders?

[Paracelsus]

Via The Astrophysical Journal: http://www.journals.uchicago.edu/ApJ...171032051Guest

The nonthermal supernova remnant (SNR) RX J1713.7-3946 has recently been shown to be a site of cosmic-ray (CR) electron acceleration to TeV energies. Here we present evidence that this remnant is also accelerating CR nuclei. Such energetic nuclei can interact with ambient interstellar gas to produce high-energy gamma rays via the decay of neutral pions. We associate the unidentified EGRET GeV gamma-ray source, 3EG J1714-3857, with a very massive (∼3 × 105 M&odot and dense (∼500 nucleons cm-3) molecular cloud interacting with SNR RX J1713.7-3946. Direct evidence for such interaction is provided by observations of the lowest two rotational transitions of CO molecules in the cloud; as in other clear cases of interaction, the CO (J = 2 → 1)/CO (J = 1 → 0) ratio is significantly enhanced. Since the cloud is of low radio and X-ray brightness, electrons cannot be responsible for the bulk of the GeV emission there. A picture thus emerges in which both electrons and nuclei are being accelerated by the SNR: whereas the relativistic electrons dominate the local nonthermal radio, X-ray, and TeV emission, the shock-accelerated CR protons and ions (hadrons) are exposed through their interactions in the adjacent massive cloud, leading to the observed GeV emission via the gamma decay of neutral pions.

Two questions:

How does the ratio of rotational transitions of CO molecules in a molecular cloud provide evidence for relativistic accelerations of nuclei? I would think that particles accelerated to ~TeV energies would tend to break C-O bonds..

What is a 'non-thermal remnant'?

[StupendousMan]

Via The Astrophysical Journal: http://www.journals.uchicago.edu/ApJ...171032051Guest



Two questions:

How does the ratio of rotational transitions of CO molecules in a molecular cloud provide evidence for relativistic accelerations of nuclei? I would think that particles accelerated to ~TeV energies would tend to break C-O bonds..

The region of interest is a complex place consisting of several interacting entities. There is a source of relativistic electrons and nuclei, and there is a large cloud of cool molecular gas. Some of the relativistic particles are impinging on the very large cloud. When a relativistic electron or nucleus strikes a CO molecule directly, then of course the CO dissociates. But the products of such a primary collision then go off and strike other atoms and molecules, which strike other atoms and molecules, and so on in a cascade. The final collisions involve such small energies that any CO molecules involved simply are excited to a higher energy level.

What is a 'non-thermal remnant'?

A remnant, the spectrum of which does not have a shape given by the Planck function. In other words, a (supernova) remnant which is not simply a cloud of gas emitting radiation according to the black-body formula.

There are many other processes which can give rise to radiation: bremmstrahlung, synchrotron, etc. If those other processes dominate over simple collisions between particles with a common kinetic energy, then the result is a non-thermal spectrum.

[Paracelsus]

The region of interest is a complex place consisting of several interacting entities. There is a source of relativistic electrons and nuclei, and there is a large cloud of cool molecular gas. Some of the relativistic particles are impinging on the very large cloud. When a relativistic electron or nucleus strikes a CO molecule directly, then of course the CO dissociates. But the products of such a primary collision then go off and strike other atoms and molecules, which strike other atoms and molecules, and so on in a cascade. The final collisions involve such small energies that any CO molecules involved simply are excited to a higher energy level.

A remnant, the spectrum of which does not have a shape given by the Planck function. In other words, a (supernova) remnant which is not simply a cloud of gas emitting radiation according to the black-body formula.

There are many other processes which can give rise to radiation: bremmstrahlung, synchrotron, etc. If those other processes dominate over simple collisions between particles with a common kinetic energy, then the result is a non-thermal spectrum.

Thanks, StupendousMan!

Question from your response: why wouldn't the information as to the energies of the initial collisions be 'lost' in the subsequent noise of all of the secondary & tertiary collisions, as non-high energy collisions between cold CO molecules would also produce excited states, correct?

[StupendousMan]

Thanks, StupendousMan!

Question from your response: why wouldn't the information as to the energies of the initial collisions be 'lost' in the subsequent noise of all of the secondary & tertiary collisions, as non-high energy collisions between cold CO molecules would also produce excited states, correct?

The point is that if there were only collisions between the molecules in the cloud, then the radiation from those molecules would reflect the thermal motions of the molecules. But when high-energy particles enter the cloud, they create certain excited states which would never occur due to ordinary collisions. Those excited states, and the exact ratios of the lower-energy states, reveal the presence of non-thermal particles and collisions.

[Paracelsus]

OIC. Understood.