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Title: Constraining cosmic ray acceleration in young star clusters using multi-wavelength observations
Authors: Gupta, Siddhartha
Nath, Biman B.
Sharma, Prateek
Keywords: hydrodynamics
ISM: bubbles
cosmic rays
star clusters
Issue Date: 1-Oct-2018
Publisher: Oxford University Press on behalf of the Royal Astronomical Society
Citation: Monthly Notices of the Royal Astronomical Society, 2018, Vol. 479; p5220–5234
Abstract: We use 1D and 3D two-fluid cosmic ray (CR) hydrodynamic simulations to investigate the role of CRs in the vicinity of a compact young star cluster. We model a self-gravitating cloud (density profile ρ∝r−1), include important thermal and non-thermal processes, and explore two different CR injection scenarios. We show that if internal shocks in the wind-driving region are the main site for CR acceleration, then the resulting γ-ray luminosity (Lγ) can reach ≈5% of the mechanical luminosity (Lw), independent of the fraction of wind energy (∼1−20%) injected into CRs. In contrast, if the forward/reverse shock of a bubble is the injection site then Lγ increases linearly with the CR injection fraction, as expected analytically. We find that the X-ray luminosity (Lx) in the forward/reverse shock injection scenario is ≳10−3Lw, which is ∼10 times larger than in the central wind-driving injection case. We predict the corresponding range of the synchrotron radio luminosity. We show how multi-wavelength observations can constrain the CR parameters. Comparing the predicted multi-wavelength luminosities with those of 30 Doradus we identify the reverse shock as the most probable CR injection site, and that thermal conduction is important. We do not find significant dynamical impact of CRs in our models.
Description: Restricted Access. An open-access version is available at (one of the alternative locations)
ISSN: 0035-8711
1365-2966 - (online)
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Copyright: 2018 The Author(s)
Appears in Collections:Research Papers (A&A)

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