COLLECTIVE EVIDENCE FOR INVERSE COMPTON EMISSION FROM EXTERNAL PHOTONS IN HIGH-POWER BLAZARS

Author/Creator ORCID

Date

2012-05-18

Department

Program

Citation of Original Publication

Eileen T. Meyer et al., COLLECTIVE EVIDENCE FOR INVERSE COMPTON EMISSION FROM EXTERNAL PHOTONS IN HIGH-POWER BLAZARS, The Astrophysical Journal Letters, Volume 752, Number 1, doi: 10.1088/2041-8205/752/1/l4

Rights

This item is likely protected under Title 17 of the U.S. Copyright Law. Unless on a Creative Commons license, for uses protected by Copyright Law, contact the copyright holder or the author.
© 2012. The American Astronomical Society. All rights reserved.

Subjects

Abstract

We present the first collective evidence that Fermi-detected jets of high kinetic power (L kin) are dominated by inverse Compton emission from upscattered external photons. Using a sample with a broad range in orientation angle, including radio galaxies and blazars, we find that very high power sources (L kin > 10⁴⁵·⁵ erg s⁻¹) show a significant increase in the ratio of inverse Compton to synchrotron power (Compton dominance) with decreasing orientation angle, as measured by the radio core dominance and confirmed by the distribution of superluminal speeds. This increase is consistent with beaming expectations for external Compton (EC) emission, but not for synchrotron self-Compton (SSC) emission. For the lowest power jets (L kin < 10⁴³·⁵ erg s⁻¹), no trend between Compton and radio core dominance is found, consistent with SSC. Importantly, the EC trend is not seen for moderately high power flat spectrum radio quasars with strong external photon fields. Coupled with the evidence that jet power is linked to the jet speed, this finding suggests that external photon fields become the dominant source of seed photons in the jet comoving frame only for the faster and therefore more powerful jets.