Please use this identifier to cite or link to this item:
http://hdl.handle.net/20.500.12386/34516
Title: | The double signature of local cosmic-ray acceleration in star-forming regions | Authors: | Padovani, Marco Marcowith, Alexandre GALLI, Daniele HUNT, Leslie Kipp FONTANI, FRANCESCO |
Issue Date: | 2021 | Journal: | ASTRONOMY & ASTROPHYSICS | Number: | 649 | First Page: | A149 | Abstract: | Context. Recently, there has been an increased interest in the study of the generation of low-energy cosmic rays (< 1 TeV) in shocks situated on the surface of a protostar or along protostellar jets. These locally accelerated cosmic rays offer an attractive explanation for the high levels of non-thermal emission and ionisation rates observed close to these sources. Aims: The high ionisation rate observed in some protostellar sources is generally attributed to shock-generated UV photons. The aim of this article is to show that when synchrotron emission and a high ionisation rate are measured in the same spatial region, a locally shock-accelerated cosmic-ray flux is sufficient to explain both phenomena. Methods: We assume that relativistic protons and electrons are accelerated according to the first-order Fermi acceleration mechanism, and we calculate their emerging fluxes at the shock surface. These fluxes are used to compute the ionisation rate and the non-thermal emission at centimetre wavelengths. We then apply our model to the star-forming region OMC-2 FIR 3/FIR 4. Using a Bayesian analysis, we constrain the parameters of the model and estimate the spectral indices of the non-thermal radio emission, the intensity of the magnetic field, and its degree of turbulence. Results: We demonstrate that the local cosmic-ray acceleration model makes it possible to simultaneously explain the synchrotron emission along the HOPS 370 jet within the FIR 3 region and the ionisation rate observed near the FIR 4 protocluster. In particular, our model constrains the magnetic field strength (∼250−450 μG), its turbulent component (∼20−40 μG), and the jet velocity in the shock reference frame for the three non-thermal sources of the HOPS 370 jet (between 350 km s-1 and 1000 km s-1). Conclusions: Beyond the modelling of the OMC-2 FIR 3/FIR 4 system, we show how the combination of continuum observations at centimetre wavelengths and molecular transitions is a powerful new tool for the analysis of star-forming regions: These two types of observations can be simultaneously interpreted by invoking only the presence of locally accelerated cosmic rays, without having to resort to shock-generated UV photons. | URI: | http://hdl.handle.net/20.500.12386/34516 | URL: | https://www.aanda.org/articles/aa/full_html/2021/05/aa39918-20/aa39918-20.html | ISSN: | 0004-6361 | DOI: | 10.1051/0004-6361/202039918 | Bibcode ADS: | 2021A&A...649A.149P | Fulltext: | open |
Appears in Collections: | 1.01 Articoli in rivista |
Files in This Item:
File | Description | Size | Format | |
---|---|---|---|---|
Padovani (2021a).pdf | Pdf editoriale | 3.33 MB | Adobe PDF | View/Open |
doublesig.pdf | postprint | 3.35 MB | Adobe PDF | View/Open |
Page view(s)
86
checked on Feb 19, 2025
Download(s)
23
checked on Feb 19, 2025
Google ScholarTM
Check
Altmetric
Altmetric
Items in DSpace are published in Open Access, unless otherwise indicated.