Is IC cooling off in galactic_expanding_shell ?

[sona-patel]

Hi @andreatramacere,

'Hadronic pp jez model' page on Jetset-v1.2.2 doc page mentions that IC cooling was switch off to speed up the process. And, testing galactic_expanding_shell branch, it seems that IC cooling is still off, is it correct?

I was going through LHASSO J2108+5157 paper on MWL study, where jestet-1.2.2 is used and mentions about taking into account IC. So, just wondering if its based on some other development or I am doing some goof-up!

Thank a lot :-)

[andreatramacere]

Hi @sona-patel, the IC cooling is off to evaluate the equilibrium state of secondaries but is evaluated in the radiative output, i.e. for the SED. This is also mentioned in the paper where we state: This means that, for each step of the minimization, secondaries pairs temporarily evolve to equilibrium state, taking into account synchrotron radiation and escape timescales.

Indeed, for this source, the synchrotron emission is dominating both the SSC and the bremsstrahlung radiation.

Coming back to the IC emission for the equilibrium of secondaries, obtained by using the integral solution of the FP equation, there is no problem in adding it, but, for the SSC it is not correct. The only way to evaluate the contribution of the SSC to the secondaries equilibrium is by solving numerically the FP equation. This can be done in jetset, but this would increase significantly the computation time for the case of mininization.

The comparison of the two approaches is shown here: https://jetset.readthedocs.io/en/latest/user_guide/documentation_notebooks/hadronic_pp_jet/hadronic_validate_temp_ev.html#hadronic-pp-jet-validation-guide

So to wrap up, as long as the SSC is not dominant, using the integral solution of the FP equation is coccrect, this includes also the external Compton, indeed, the external Compton has no feedback on the synchrotron emission (it affects only the cooling of the electrons) but it does not affect the seed photons (since they are external), whilst, the SSC affects both the electrons, but also the synchrotron seed field, which in turns affect again the SSC emission, causing the feedback which can not be handled by the integral solution of the FP equation, but only by the numerical solution of the FP equation.

In the latest commit of jets galactic_expanding_shell the IC for the EC case is on, at least in the latest commit I pushed,
just check this file: file

Please, take into account, that I am still testing, and I have no help in developing .... :)

Cheers
Andrea