probing non-thermal cluster emission with gamma-ray and radio data
DESCRIPTION
Probing Non-thermal Cluster Emission with Gamma-Ray and Radio Data. Tesla Jeltema University of California, Santa Cruz. Non-Thermal Emission - Sources. Cosmic Rays: accelerated in accretion and merger shocks, AGN, and supernovae - CR protons can survive for a long time - PowerPoint PPT PresentationTRANSCRIPT
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Probing Non-thermal Cluster Emission with Gamma-Ray and Radio Data
Tesla JeltemaUniversity of California, Santa Cruz
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Cosmic Rays: accelerated in accretion and merger shocks, AGN, and supernovae
- CR protons can survive for a long time- CR electrons lose energy quickly
Dark Matter: annihilation or decay of WIMPs to Standard Model particles Star Formation: emission associated to cosmic rays accelerated by supernovae in cluster galaxies
AGN: (not discussed here)
Non-Thermal Emission - Sources
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Non-Thermal Emission - Mechanisms
Cosmic Rays
Hadronic production
or
turbulent reacceleration of lower energy e-
Dark Matter
or
(models for positron fraction)
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Non-Thermal Emission - Observations
Emission from synchrotron (radio), IC scattering of CMB (X-ray or gamma-ray), and π0 decay (gamma-ray).
Radio: Mpc scale radio emission insome, but not all clusters
implies active e- production over a large area limits e- production in non-detections
Gamma-ray: diffuse emission not yet found
limits CR protons, dark matter, and total star formation
Preliminary
Zimmer for Fermi-LAT, TeV PA 2011
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Constraints - Cosmic Rays The Fermi non-detection of clusters implies:
low cosmic ray densities of < 1-10% of the thermal energy density in nearby clusters.
high B fields in the hadronic model of radio halos. Turbulent acceleration model preferred.
Fermi limits to low CR densities and high magnetic fields
Jeltema & Profumo 2011
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Constraints - Dark Matter The non-detection of both radio and gamma-ray emission limits the DM annihilation cross-section
conservative limits exclude thermal cross-section for low DM mass
excludes much of parameter space fitting e+ excess
Storm, Jeltema, Profumo, & Rudnick 2013
NFW only
best Fermi cluster limits
Example Radio Limits Example Fermi Limits
Ackermann et al. 2010
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Star Formation - Predictions
Storm, Jeltema, & Profumo 2012
Gamma-ray luminosity correlates strongly with star formation rate (total IR or radio luminosity) for galaxies
Gives predicted minimum gamma-ray emission from cluster galaxies.
Ackermann et al. 2012
Star formation should account for at least 10% of gamma-ray emission from some clusters.