SEARCH FOR COSMIC-RAY-INDUCED GAMMA-RAY EMISSION IN GALAXY CLUSTERS

By M. Ackermann, M. Ajello, A. Albert, A. Allafort, W. Atwood, L. Baldini, J. Ballet, G. Barbiellini, D. Bastieri, K. Bechtol and 116 more. 2013

134 citations recorded by the source corpus.

Current theories predict relativistic hadronic particle populations in clusters of galaxies in addition to the already observed relativistic leptons. In these scenarios hadronic interactions give rise to neutral pions which decay into γ rays that are potentially observable with the Large Area Telescope (LAT) on board the Fermi space telescope. We present a joint likelihood analysis searching for spatially extended γ-ray emission at the locations of 50 galaxy clusters in four years of Fermi-LAT data under the assumption of the universal cosmic-ray (CR) model proposed by Pinzke & Pfrommer. We find an excess at a significance of 2.7σ, which upon closer inspection, however, is correlated to individual excess emission toward three galaxy clusters: A400, A1367, and A3112. We discuss these cases in detail and conservatively attribute the emission to unmodeled background systems (for example, radio galaxies within the clusters).Through the combined analysis of 50 clusters, we exclude hadronic injection efficiencies in simple hadronic models above 21% and establish limits on the CR to thermal pressure ratio within the virial radius, R 200, to be below 1.25%–1.4% depending on the morphological classification. In addition, we derive new limits on the γ-ray flux from individual clusters in our sample.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/a2a05ce6f88e5ade38dd196e20d108d45a3bbc57

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Citations in the corpus

2FHL: THE SECOND CATALOG OF HARD FERMI-LAT SOURCES (2015, background): “The count map reported in Figure 1 shows that Fermi-LATobserves many point-like sources and large-scale diffuse emission in the direction of our Galaxy, some of which appears coincident with the so-called Fermi bubbles (Su et al. 2010; Ackermann et al. 2014b).”
Diffuse Radio Emission from Galaxy Clusters (2019, methodology): “…limits on mini-halos come from the observations of the Major Atmospheric Gamma Imaging Cherenkov (MAGIC) telescopes of Perseus (Aleksić et al. 2010, 2012; Ahnen et al. 2016), and from the combined likelihood analysis of HIFLUGCS clusters with the Fermi -LAT satellite data (Ackermann et al. 2014).”
Sensitivity projections for dark matter searches with the Fermi large area telescope (2016, methodology): “[210] by the √ t and accounting for the improved sensitivity with Pass 8 data.”