{"content":[{"text":"A multi-wavelength view of star-forming galaxies","bbox":{"left":0.139999,"top":0.062221,"width":0.328446,"height":0.016282999999999992}},{"text":"P. Kornecki","bbox":{"left":0.774839,"top":0.061212,"width":0.08516199999999996,"height":0.017312000000000008}},{"text":"1.","bbox":{"left":0.139999,"top":0.107142,"width":0.015062999999999993,"height":0.020718}},{"text":"Introduction","bbox":{"left":0.17157,"top":0.107142,"width":0.10905300000000001,"height":0.020718}},{"text":"Galaxies with high star formation rate (SFR) are often associated to an enhanced rate of \n supernovae (SNe). The bulk of galactic cosmic rays (CRs) is expected to be accelerated at supernova \n remnant shocks [1], so that high star forming galaxies (SFGs) are naturally expected to be also \n powerful CR sources. In addition, the large amount of gas, photon density and the high level \n of turbulence produced by SNe create unique conditions for the transport of CRs in the SFG \n environment. CRs are, in fact, likely to lose most of their energy before being able to escape. \n Indeed, SFGs are known to radiate non-thermal emission in several bands of the electromagnetic \n spectrum from radio to 훾-rays [2, 3], and their observed non-thermal luminosity is in a tight \n correlation with the SFR. Such a correlation is expected to hold in calorimetric sources, namely \n in environments where most of the injected power in CRs is radiated as non-thermal photons. \n However, the observed correlations extend to SFGs with very low SFR, for which most of the \n injected particles escape their host galaxy. Investigating this phenomenology can shed light on the \n transport properties of electrons and protons, possibly highlighting some scaling properties ranging \n from the strongest calorimeters down to the most quiescent spiral galaxies. \n The X-ray band is one of the most complex energy bands to decipher in SFGs. This is mainly \n due to the fact that their X-ray spectrum has various contributions: 1) thermal emission of the \n hot interstellar medium (ISM) phase; 2) point-like sources such as X-ray binaries; 3) AGN and \n unidentiﬁed SNRs (see e.g. [4]); 4) high-energy electrons and positrons interacting with galactic \n ﬁelds. In particular, the level at which high-energy particles can contribute to the X-ray ﬂux is \n hard to constrain and has been poorly investigated. In the soft X-ray range (∼ 0.2–2 keV), the \n emission is inferred to be dominated by the hot ISM phase and by the hot circumgalactic medium, \n whereas at higher energies the dominant component of the hard X-ray ﬂux has not been clearly \n identiﬁed yet [19]. In the range ∼ 2–10 keV, it has been proposed that the emission in low-redshift \n SFGs is mainly dominated by unresolved emission from low-mass X-ray binaries. Nonetheless, the \n contribution from Inverse Compton (IC) scattering of galactic leptons with the infrared (IR) ﬁeld \n can also be relevant. At higher photon energies (> 30 keV) this IC emission is inferred to be the \n main contribution, especially in starburst galaxies [19, 20]. \n More recently, [2, 21, 26] pointed out the importance of studying the X-ray band as a signature \n of the calorimetry level in galaxies with high SFR. In particular, in the context of individual sources, \n they explored the possible role played by synchrotron radiation from hadronic secondaries at 1– \n 10 keV. In the MeV range the constraints on the non-thermal emission are more uncertain due to \n the lack of observations. In particular, the latter energy band can be of great interest for future \n observational campaigns and for phenomenological investigations of possible marker of presence \n of an non-jetted AGN in galaxies detected in 훾-rays [5]. [18] explored the observed correlation \n between X-ray and SFR on the 0.5–8 keV energy range, while [4] built a model to explain this X-ray \n luminosity–SFR correlation at higher redshift. \n Here we improve upon former investigations by including more sophisticated global galaxy \n quantities scaling with the SFR (as the magnetic ﬁelds and the optical ﬁeld from stars). We also \n include in our calculations the tertiary electrons, namely electron-positron pairs produced by the \n 훾-훾 absorption. We discuss the diﬀuse hard (10–79 keV) X-ray emission and investigate the main \n contribution to the MeV energy range in SFGs. The hard X-ray band can unveil crucial aspects on","bbox":{"left":0.139999,"top":0.142597,"width":0.720009,"height":0.727598}},{"text":"PoS(ICRC2021)456","bbox":{"left":0.908144,"top":0.263658,"width":0.06293700000000002,"height":0.34204300000000004}},{"text":"2","bbox":{"left":0.495417,"top":0.892877,"width":0.009163000000000032,"height":0.017311999999999994}}],"images_bbox":[],"images_bbox_not_text_overlap":[]}