2011/03/09 by Michael Malmrose, Michael P. Malmrose, Alan Marscher +5
Earth and Planetary Sciences · Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Blazar #Compton scattering #Cosmic dust #Earth Systems and Cosmic Evolution #Infrared #Luminosity #Photon #Quasar #Scientific Research and Discoveries #Spitzer Space Telescope #Torus #astro-ph.CO #astro-ph.GA
paper · pdf · doi:10.1088/0004-637x/732/2/116
published as ApJ, 732, 116, 2011 · 23 Pages, 5 Figures, 2 Tables, 1 Machine Readable Table. Accepted to ApJ
arxiv created 2011/03/09 · openalex publication_date 2011/04/26 · arxiv updated 2015/05/27 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
A possible source of γ-ray photons observed from the jets of blazars is inverse Compton scattering by relativistic electrons of infrared seed photons from a hot, dusty torus in the nucleus. We use observations from the Spitzer Space Telescope to search for signatures of such dust in the infrared spectra of four γ-ray bright blazars, the quasars 4C 21.35, CTA102, and PKS 1510−089, and the BL Lacertae object ON231. The spectral energy distribution (SED) of 4C 21.35 contains a prominent infrared excess indicative of dust emission. After subtracting a non-thermal component with a power-law spectrum, we fit a dust model to the residual SED. The model consists of a blackbody with temperature ∼1200 K, plus a much weaker optically thin component at ∼660 K. The total luminosity of the thermal dust emission is 7.9 ± 0.2 × 10 45 erg s −1 . If the dust lies in an equatorial torus, the density of infrared photons from the torus is sufficient to explain the γ-ray flux from 4C 21.35 as long as the scattering occurs within a few parsecs of the central engine. We also report a tentative detection of dust in the quasar CTA102, in which the luminosity of the infrared excess is 7 ± 2 × 10 45 erg s −1 . However, in CTA102 the far-infrared spectra are too noisy to detect the 10 μm silicate feature. Upper limits to the luminosity from thermal emission from dust in PKS 1510−089, and ON231, are 2.3 × 10 45 , and 6.6 × 10 43 erg s −1 , respectively. These upper limits do not rule out the possibility of inverse Compton upscattering of infrared photons to γ-ray energies in these two sources. The estimated covering factor of the hot dust in 4C 21.35, 22%, is similar to that of non-blazar quasars; however, 4C 21.35 is deficient in cooler dust.