Herschel Aperture Detection Of Far Infrared Emitted By Hot Spot D In Cygnus A
Far infrared emission from hot spot D in Cygnus A was detected by Herschel Aperture photometry of the source in 5 photometric bands covering the wavelength range of 70–350 micrometres. Because the object's far-infrared spectrum neatly connects to the radio spectrum, the far-infrared emission is attributed to synchrotron radiation from the radio-emitting electron population. The presence of a far-infrared break feature in the radio-to-near-infrared spectrum has been proven. The shift in energy index at the break is regarded as the effect of radiative cooling on an electron distribution supported by constant injection from diffusive shock acceleration. The magnetic field in the hot spot is calculated as a function of its radius within a uniform one-zone model and combined with the high relativistic shock state by assigning the derived break to this cooling break. By assuming that the X-ray spectrum is entirely attributable to synchrotron-self-Compton emission, an independent restriction is obtained. The two parameters are closely regulated by combining these requirements. A closer look at the two situations shows that the X-ray output is mostly caused by synchrotron-self-Compton emission.
This study was carried out by a group of scientists from various research institutes in Japan, led by Yuji Sunada from the Department of Physics at Saitama University in Japan.
The scientists used Herschel data to detect the Far infrared source associated with hot spot D in the radio galaxy Cygnus A for the first time. The spatial analysis revealed that the Far infrared source has been extended, and its peak position has been shifted by 4 arcsec from hot spot D to hot spot E. These characteristics point to a significant contamination from hot spot E. They used SPIRE and PACS photometry to measure the Far infrared source in a circle that included both hot spots D and E. The source's far infrared is measured at 350 micrometres and 160 micrometres, respectively.
The source's far infrared spectrum is found to slightly exceed the extrapolation of hot spot D's radio spectrum, confirming the contamination from hot spot E. By interpolating the radio and near-infrared spectra, the far infrared flux of hot spot E was estimated to be 10% of the overall far infrared source flux. By removing the estimated far infrared flux of hot spot E, the far infrared flux of hot spot D was calculated at 350 and 160 micrometres, smoothly linking hot spot D's radio and near-infrared spectra. The shift in the spectral index agrees with the prediction of the diffusive shock acceleration with continuous energy injection and radiative cooling. The break frequency was calculated using far infrared data while keeping the index change constant.
Naturally, the respite is viewed as a cooling break. The derived break frequency of hot spot D is transformed into the magnetic field strength for the uniform one-zone model with a strong relativistic shock based on the cooling break interpretation. Aside from this estimate, The magnetic field strength was calculated by assuming that the whole recorded X-ray spectrum was magnetic. The magnetic field intensity of hot spot D was determined by integrating the two restrictions. With the electron-to-magnetic-field energy density ratio, this magnetic field strength suggests a non-thermal electron supremacy. Because of the magnetic field from the cooling break scales, the allowable magnetic field intensity is predicted to increase significantly. The allowable magnetic field is expected to be larger if the observed X-ray flow is polluted by emission activities. A close look at the cooling-break, on the other hand, shows that in the case of the uniform one-zone model with the powerful shock, the SSC fraction of the X-ray flux is more than 98%.