Fermi-LAT Analysis of the Coma Cluster a Fabio Zandanel GRAPPA Institute University of Amsterdam f.zandanel@uva.nl In collaboration with S. Ando (GRAPPA) 18 th Symposium on Astroparticle Physics in the Netherlands Leiden 23 th October 2013
Clusters of Galaxies Largest gravitationally bound systems in the Universe with mass of 10 14 10 15 M and radius of few Mpc Actively evolving objects Cosmic energy reservoirs Expected to contain substantial populations of cosmic rays (CRs) and dark matter can generate non-thermal emission from radio to gamma-ray frequencies Powerful cosmological tools to test models on the origin and evolution of the Universe via thermal X-ray emission and Sunyaev-Zel dovich effect 23-10- 2013 Fabio Zandanel (GRAPPA Amsterdam) 2
CRs in Clusters Processes & Emission from Pfrommer et al. 2008 energy and particle sources structure formation AGNs and supernovae acceleration processes turbulence shock waves relativistic populations expected emission 23-10- 2013 Fabio Zandanel (GRAPPA Amsterdam) 3
CRs in Clusters Processes & Emission from Pfrommer et al. 2008 energy and particle sources structure formation AGNs and supernovae acceleration processes turbulence shock waves relativistic populations CR electrons re-acceleration primary CR electrons expected emission 23-10- 2013 Fabio Zandanel (GRAPPA Amsterdam) 4
CRs in Clusters Processes & Emission from Pfrommer et al. 2008 energy and particle sources structure formation AGNs and supernovae acceleration processes turbulence shock waves CR protons relativistic populations CR electrons re-acceleration primary CR electrons expected emission 23-10- 2013 Fabio Zandanel (GRAPPA Amsterdam) 5
CRs in Clusters Processes & Emission from Pfrommer et al. 2008 energy and particle sources structure formation AGNs and supernovae acceleration processes turbulence shock waves HADRONIC INTERACTIONS CR protons relativistic populations CR electrons re-acceleration primary CR electrons secondary CR electrons expected emission π 0 23-10- 2013 Fabio Zandanel (GRAPPA Amsterdam) 6
CRs in Clusters Processes & Emission from Pfrommer et al. 2008 energy and particle sources structure formation AGNs and supernovae acceleration processes turbulence shock waves HADRONIC INTERACTIONS CR protons relativistic populations CR electrons re-acceleration primary CR electrons secondary CR electrons expected emission synchrotron radio IC hard X-ray and gamma-ray π 0 23-10- 2013 Fabio Zandanel (GRAPPA Amsterdam) 7
CRs in Clusters Processes & Emission from Pfrommer et al. 2008 energy and particle sources structure formation AGNs and supernovae acceleration processes turbulence shock waves HADRONIC INTERACTIONS CR protons relativistic populations CR electrons re-acceleration primary CR electrons secondary CR electrons expected emission synchrotron radio IC hard X-ray and gamma-ray π 0 gamma-ray 23-10- 2013 Fabio Zandanel (GRAPPA Amsterdam) 8
Analysis of Fermi-LAT data of the Coma Cluster FZ & Ando 2013, in preparation Analysis of 56 months of Fermi-LAT data on the Coma Cluster Events 100 MeV 100 GeV 14 14 deg pixel = 0.1 deg We test different (diffuse) models: Point Source Disk Pinkze & Pfrommer (2010) FZ, Pfrommer & Prada (2012) Radio Relic template Ring-like Model (Keshet et al. 2012) NO DETECTION so far (TS 4) 23-10- 2013 Fabio Zandanel (GRAPPA Amsterdam) 9
Analysis of Fermi-LAT data Templates FZ & Ando 2013, in preparation some TEMPLATES 23-10- 2013 Fabio Zandanel (GRAPPA Amsterdam) 10
Analysis of Fermi-LAT data Results FZ & Ando 2013, in preparation Analysis of 56 months of Fermi-LAT data on the Coma Cluster Events 100 MeV 100 GeV 14 14 deg pixel = 0.1 deg Model 23-10- 2013 Fabio Zandanel (GRAPPA Amsterdam) 11
Analysis of Fermi-LAT data Results FZ & Ando 2013, in preparation Analysis of 56 months of Fermi-LAT data on the Coma Cluster Events 100 MeV 100 GeV 14 14 deg pixel = 0.1 deg Model[%] Residuals Preliminary 23-10- 2013 Fabio Zandanel (GRAPPA Amsterdam) 12
Analysis of Fermi-LAT data Implications Kushnir & Waxman (2009) predicted that a flat IC emission from primary electrons from accreting shocks should dominate the gamma-ray emission of clusters F TH >100 MEV 1 10-8 cm -2 s -1 F UL >100 MEV 4 10-9 cm -2 s -1 23-10- 2013 Fabio Zandanel (GRAPPA Amsterdam) 13
Analysis of Fermi-LAT data Implications Kushnir & Waxman (2009) predicted that a flat IC emission from primary electrons from accreting shocks should dominate the gamma-ray emission of clusters F TH >100 MEV 1 10-8 cm -2 s -1 F UL >100 MEV 4 10-9 cm -2 s -1 1. Electrons acceleration efficiency at shocks < 1% 2. However, likely overproduce radio emission 23-10- 2013 Fabio Zandanel (GRAPPA Amsterdam) 14
Analysis of Fermi-LAT data Implications Keshet et al. (2012) claimed the detection of a gamma-ray ring around the Coma cluster in the VERITAS (Arlen et al. 2012) skymap, as predicted by earlier simulations (Keshet et al. 2003) F TH (>100 MEV) 4 10-8 cm -2 s -1 F UL (>100 MEV) 4 10-9 cm -2 s -1 23-10- 2013 Fabio Zandanel (GRAPPA Amsterdam) 15
Analysis of Fermi-LAT data Implications Keshet et al. (2012) claimed the detection of a gamma-ray ring around the Coma cluster in the VERITAS (Arlen et al. 2012) skymap, as predicted by earlier simulations (Keshet et al. 2003) F TH (>100 MEV) 4 10-8 cm -2 s -1 F UL (>100 MEV) 4 10-9 cm -2 s -1 1. No Ring-like structure is present 2. Electrons acceleration efficiency at shocks < 1% 3. Contribution to extragalactic background < 1% 23-10- 2013 Fabio Zandanel (GRAPPA Amsterdam) 16
Analysis of Fermi-LAT data Implications Pinzke & Pfrommer (2010) predicted that pion decays from CR proton-proton interactions with the ambient gas should dominate the gamma-ray emission in clusters by running cosmological hydrodynamic simulations F TH >100 MEV 4.2 10-9 cm -2 s -1 F UL >100 MEV 1.4 10-9 cm -2 s -1 23-10- 2013 Fabio Zandanel (GRAPPA Amsterdam) 17
Analysis of Fermi-LAT data Implications Pinzke & Pfrommer (2010) predicted that pion decays from CR proton-proton interactions with the ambient gas should dominate the gamma-ray emission in clusters by running cosmological hydrodynamic simulations F TH >100 MEV 4.2 10-9 cm -2 s -1 F UL >100 MEV 1.4 10-9 cm -2 s -1 1. Protons maximum acceleration efficiency at shocks < 20% 2. CR-to-thermal pressure < 0.5% 23-10- 2013 Fabio Zandanel (GRAPPA Amsterdam) 18
Analysis of Fermi-LAT data Implications FZ, Pfrommer & Prada (2012) included the possible CR transport phenomena (streaming and diffusion) by merging the advection-dominated simulations (Pinzke & Pfrommer 2010) and analytical (Ensslin et al. 2011) approaches Advection-dominated regime: F TH >100 MEV 3.2 10-9 cm -2 s -1 F UL >100 MEV 1.3 10-9 cm -2 s -1 Streaming-dominated regime: F TH >100 MEV 2.4 10-9 cm -2 s -1 F UL >100 MEV 2.3 10-9 cm -2 s -1 23-10- 2013 Fabio Zandanel (GRAPPA Amsterdam) 19
Analysis of Fermi-LAT data Implications FZ, Pfrommer & Prada (2012) included the possible CR transport phenomena (streaming and diffusion) by merging the advection-dominated simulations (Pinzke & Pfrommer 2010) and analytical (Ensslin et al. 2011) approaches Advection-dominated regime: F TH >100 MEV 3.2 10-9 cm -2 s -1 F UL >100 MEV 1.3 10-9 cm -2 s -1 1. Protons maximum acceleration efficiency at shocks < 20% 2. Overproduce radio for B 0 5 μg max. acc. eff. 5% Streaming-dominated regime: F TH >100 MEV 2.4 10-9 cm -2 s -1 F UL >100 MEV 2.3 10-9 cm -2 s -1 Being challenged, assuming magnetic field from Faraday rotation measurements (B 0 5 μg, α B = 0.5) but 23-10- 2013 Fabio Zandanel (GRAPPA Amsterdam) 20
Conclusions & Future Prospects Gamma-rays (Fermi & IACTs) are starting to put stringent constraints on various acceleration scenarios and on the CR content in clusters of galaxies Detection of cluster gamma-ray emission would be a major scientific discovery Fermi 10 yr CTA Open up a new window to study: non-thermal processes in clusters high-energy physics in the largest and latest structures DM, CR, ICM, and cluster magnetic field formation and evolution of clusters and of the Universe itself 23-10- 2013 Fabio Zandanel (GRAPPA Amsterdam) 21
Gamma-ray Spectrum (Pinzke & Pfrommer 2010) 23-10- 2013 Fabio Zandanel (GRAPPA Amsterdam) 24