franco_vazza

#paperday (sort of): here is the final accepted version of our

"On the interpretation of XRISM X-ray measurements of #turbulence in the intracluster medium: a comparison with cosmological simulations" by myself and G. Brunetti

https://arxiv.org/abs/2507.04727

I did an earlier thread here: https://mastodon.social/@franco_vazza/114816701059679474

The paper only have a useful appendix, which explains why homogenous kolmogorov turbulent models are useful, until they get too simplistic! #astrophysics #astronomy #science

Nov 21 at 9:14amWeb
Show threadfranco_vazzaNov 21

This aspect will keep being relevant as long as people will continue to just rely on homogenous model to interpret too much in detail complex observations. here a killer example:
we initialised a spherically homogeneous density profile perfectly matching the coma cluster (and the simulation) and added on top of it a distribution of velocity fluctuations randomly drawn from a Kolmogorov spectrum - this is also very close to the simulated one.

Then...

Show threadfranco_vazzaNov 21
...then we computed the distribution of line-of-sight broadenings of emission Iron lines in the two cases, which is the quantity that you can now finally measure with the XRISM satellite. The difference is significant: homogenous models produce a factor ~50-70% higher dispersion **even if the kinetic energy in the full simulation, and in the homogenous model is the same by construction**. Why? Because realistic turbulent is intermittent, i.e. more energy can be concentrated in less volume.
Show threadfranco_vazzaNov 21
So our interpretation is that the line broadening currently measured by XRISM (which is anyway limited to extremely tiny 90 x 90 kpc^2 spots, in the case of COMA) is actually probing a kinetic energy which is at least a factor ~2 higher than they think.
This is important if you want to really understand the level of "non-thermal" energy in the intracluster medium!
Show threadfranco_vazzaNov 21
Finally, I take pride of this extra bit in the acknowledgments:
Show threadThomas ConnorNov 21
@franco_vazza I love it! I'm going to have to copy that next time I write a paper
Show threadfranco_vazzaNov 21
@thomasconnor Let's start a resistance movement in papers right here!