Modeling the Multi-wavelength Polarization and Spectral Energy Distributions of Blazars
Abstract
In the radio through optical-UV/X-ray regime, blazars emit highly polarized (nonthermal) synchrotron emission. Emission from the dusty torus, broad line region, accretion disk and host galaxy is of thermal origin and unpolarized. In some cases, their contribution is visible in spectropolarimetry wherein the unpolarized thermal emission dilutes the synchrotron polarization. However, partially ordered magnetic fields decreasing with distance along the jet from a shock also yield a decrease of polarization towards longer wavelengths in some sources. A target-of-opportunity Large Science Program "Observing the Transient Universe" using the Southern African Large Telescope provides target-of-opportunity spectropolarimetry observations of gamma-ray bright blazars, indicating a decrease in the total degree of polarization towards shorter or longer wavelengths in many sources. The program includes co-ordinated multi-wavelength observations from the Las Cumbres Observatory, the Swift-XRT and the Fermi -LAT. A shock acceleration model including the effects of magnetic-field compression and gradual restoration of the original magnetic-field configuration behind the shock is applied to reproduce the multi-wavelength spectral energy distributions and spectropolarimetry of blazars observed in steady states. Specifically, the model is applied to 3C 273, 3C 279 and 4C+01.02. Spectropolarimetry enables predictions for high-energy polarization, most notably for scheduled IXPE observations of 3C 273 and 3C 279.
- Publication:
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44th COSPAR Scientific Assembly. Held 16-24 July
- Pub Date:
- July 2022
- Bibcode:
- 2022cosp...44.1869S