Volume 621, January 2019
|Number of page(s)||8|
|Section||Interstellar and circumstellar matter|
|Published online||10 January 2019|
Comparative study of gamma-ray emission from molecular clouds and star-forming galaxies
Guizhou Provincial Key Laboratory of Radio Astronomy and Data Processing, Guizhou Normal University,
2 School of Astronomy and Space Science, Nanjing University, Nanjing 210093, PR China
3 Guangxi Key Laboratory for Relativistic Astrophysics, Nanning 530004, PR China
4 Key laboratory of Modern Astronomy and Astrophysics, Nanjing University, Ministry of Education, Nanjing 210093, PR China
5 National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, PR China
6 CAS Key Laboratory of FAST, NAOC, Chinese Academy of Sciences, Beijing 100101, PR China
Accepted: 6 November 2018
Star-forming regions on different scales, such as giant molecular clouds in our Galaxy and star-forming galaxies, emit GeV gamma-rays. These are thought to originate from hadronic interactions of cosmic-ray (CR) nuclei with the interstellar medium. It has recently been shown that the gamma-ray luminosity (Lγ) of star-forming galaxies is well correlated with their star formation rates (SFR). We investigated Fermi data of eight Galactic molecular clouds in the Gould belt and found that molecular clouds do not follow the Lγ −SFR correlation of star-forming galaxies. We also compared the scaling relations of gamma-ray luminosity, SFR, and the gas mass for molecular clouds and star-forming galaxies. Using a multiple-variable regression analysis, we found different dependences of gamma-ray emission on SFR or mass for molecular clouds and star-forming galaxies. This suggests that different mechanisms may govern the production of gamma-rays in these two types of sources. Specifically, the strong dependence on mass supports that gamma-ray emission of molecular clouds primarily comes from passive interaction by diffuse Galactic CRs, whereas the strong dependence on SFR supports that gamma-ray emission of star-forming galaxies originates from CRs that are accelerated by local active sources.
Key words: cosmic rays / ISM: clouds / gamma rays: ISM / methods: statistical
© ESO 2019
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.