Cosmic ray protons in the inner Galaxy and the Galactic Center gamma-ray excess

By E. Carlson, S. Profumo. 2014

135 citations recorded by the source corpus.

A gamma-ray excess over background has been claimed in the inner regions of the Galaxy, triggering some excitement about the possibility that the gamma rays originate from the annihilation of dark matter particles. We point out that the existence of such an excess depends on how the diffuse gamma-ray background is defined, and on the procedure employed to fit such background to observations. We demonstrate that a gamma-ray emission with spectral and morphological features closely matching the observed excess arises from a population of cosmic ray protons in the inner Galaxy, and provides proof of principle and arguments for the existence of such a population, most likely originating from local supernova remnants. Specifically, the ``Galactic center excess'' is readily explained by a recent cosmic ray injection burst, with an age in the 1--10 kilo-year range, while the extended inner Galaxy excess points to mega-year old injection episodes, continuous or impulsive. We conclude that it is premature to argue that there are no standard astrophysical mechanisms that can explain the excess.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/76b2434585852a8694869416b6bcca4f1f7bdb02

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. Christoph Weniger
2. I. Cholis
3. F. Calore
4. J. Gaskins
5. P. Serpico
6. G. Zaharijas
7. Jovana Petrovic
8. I. Grenier

In Nuclear and High Energy Physics

1. J. Gaskins
2. Christoph Weniger
3. I. Cholis
4. F. Calore
5. S. Profumo
6. P. Serpico
7. O. F. Piattella
8. L. Giani

Citations in the corpus

• Galactic Center gamma-ray ``excess'' from an active past of the Galactic Centre? (2014, methodology): “we are grateful to Seth Digel, Dan Hooper, Tim Linden, Tijana Prodanović and Andy Strong for instructive comments and to Stefano Profumo for notifying us of their work [25].”
• The Nine Lives of Cosmic Rays in Galaxies (2015, background): “Possibilities include large numbers of pulsars (millisecond or normal, Yuan & Zhang 2014), CR proton sources (Carlson & Profumo 2014), lepton sources, and darkmatter models.”
• The effects of QCD equation of state on the relic density of WIMP dark matter (2015, background): “It has been claimed that there is evidence for an additional component in the GeV γ flux from near the galactic center which can be explained through WIMP annihilation [54–57], but other interpretations of this additional component exist [58–60].”
• A tale of tails: Dark matter interpretations of the Fermi GeV excess in light of background model systematics (2014, background): “…astrophysical explanations, like the emission from an unresolved population of pointlike sources concentrated in the very center of the Galaxy (see [28 – 31] for relevant discussions) or the injection of leptons and/or protons during a burst event at the GC some kilo-/mega-years ago [32,33].”
• A review of indirect searches for particle dark matter (2016, background): “A similar argument has been made that an injection of cosmic-ray protons in the past could possibly lead to the observed excess [127].”
• An Introduction to Particle Dark Matter (2019, background): “[21] the authors show how using physically-motivated models for the location of the acceleration sites of cosmic rays leads to a significant reduction of the Galactic center excess, as well as to drastic changes to its spectrum and morphology.”