Journal Article

Probing star formation with galactic cosmic rays

Massimo Persic and Yoel Rephaeli

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 403, issue 3, pages 1569-1576
Published in print April 2010 | ISSN: 0035-8711
Published online April 2010 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2009.16218.x
Probing star formation with galactic cosmic rays

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Cosmic-ray energy densities in central regions of starburst galaxies, as inferred from radio and γ-ray measurements of, respectively, non-thermal synchrotron and π0-decay emission, are typically , i.e. typically at least an order of magnitude larger than near the Galactic Centre and in other not-very-actively star-forming galaxies. We first show that these very different energy density levels reflect a similar disparity in the respective supernova (SN) rates in the two environments, which is not unexpected given the SN origin of (Galactic) energetic particles. As a consequence of this correspondence, we then demonstrate that there is partial quantitative evidence that the stellar initial mass function (IMF) in starburst nuclei has a low-mass truncation at ∼2 M, as predicted by theoretical models of turbulent media, in contrast with the much smaller value of 0.1 M that characterizes the low-mass cut-off of the stellar IMF in ‘normal’ galactic environments.

Keywords: cosmic rays; galaxies: spiral

Journal Article.  7536 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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