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Young Stellar clusters
Gamma-ray emission (blue, Fermi-LAT) and infrared emission (Green, Spitzer ; Red, WISE) from the region of RCW 38 [figure by G. Peron, adapted from Peron et al., Nat. Astr.,1-8 (2024)]
We managed to demonstrate that stellar clusters are able to accelerate a fraction of the Galactic cosmic rays. This was possible thanks to the idea of targeting very young star clusters, which are not yet contaminated by the emission of supernova remnants. The latter in fact, are inevitably exploding in these systems, thus preventing us from isolating the contribution due to stars only.
This study was a pilot that then lead to other important results: thanks to a statistical analysis, we were able to demonstrate that there is actually a correlation between gamma-ray unidentified sources and embedded star clusters. The results emerged by looking into data from infrared emission, rather than at the optical emission.
Further confirmation came by the deeper investigation of some of these clusters with dedicated gamma-ray observations: the morphological coincidence of the two radiation demonstrate that the same physical phenomena (winds of stars) are powering both the infrared and the gamma-ray emission.
Molecular Clouds
The Orion A molecular cloud as seen with Fermi-LAT [image credit: G. Peron]
We managed to derive the cosmic-ray distribution in several different locations of the Galaxy at GeV energies, through the analysis of Fermi-LAT data in the direction giant molecular clouds. Although this had already been done for a few objects, mostly local/high latitude ones, we refined the analysis method for extending the observational horizon to the inner part of the Galaxy hence obtaining the largest probing of GCRs far from the Earth. While we confirm a general trend that predicts a higher emissivity in the inner Galaxy, we also find important exceptions in this region where the flux matches the locally measured one.
We also make prediction for extending this study to future gamma-ray facilities
Galactic Diffuse Emission
Galactic diffuse emission in the Fermi LAT energy range [credit: Fermi-LAT collaboration]
The Galactic diffuse emission embeds the entire information about the cosmic-ray diffusion from sources, however its emission is contaminated by those sources that are too faint to be distinguished from the background (these are called unresolved sources). Detail modeling of the diffuse emission contributed by the latter, allows us to put severe constraints on the propagation of Galactic cosmic rays.
Seyfert galaxies
Composite image of the Seyfer galaxy NGC 4151 [credit: X-ray: NASA/CXC/CfA/J.Wang et al.; Optical: Isaac Newton Group of Telescopes, La Palma/Jacobus Kapteyn Telescope, Radio: NSF/NRAO/VLA]
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