2023/09/04 by Pierre-Olivier Petrucci, Petrucci, P. O., V. Piétu +23
Physics and Astronomy · #Astrophysical Phenomena and Observations #Astrophysics and Cosmic Phenomena #Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #High Energy Astrophysical Phenomena (astro-ph.HE) #Pulsars and Gravitational Waves Research
paper · pdf · doi:10.48550/arxiv.2309.01804
openalex publication_date 2023/09/04 · openalex created_date 2023/09/09 · openalex updated_date 2026/07/28
Most of the Active Galactic Nuclei (AGN) are radio-quiet (RQ) and, differently from radio-loud (RL) AGN, do not show signature of large-scale and powerful jets. The physical origin of their radio emission remains then broadly unclear. The observation of flat/inverted radio spectra at GHz frequencies seems to support however the presence of an unresolved synchrotron self-absorbed region in the close environment of the supermassive black hole. Its size could be as small as that of the X-ray corona. Since synchrotron self absorption decreases strongly with frequency, these sources need to be observed in the millimetric (mm) domain. We report here a 12h simultaneous mm-X-ray observation of the RQ AGN MCG+08-11-11 by NOEMA and NuSTAR. The mm flux shows a weak but clear increase along the pointing with a fractional variability of 2.0±0.1%. The 3-10 keV flux of NuSTAR also increases and shows a fractional variability of 7.0±1.5%. A structure function analysis shows a local maximum in the mm light curve corresponding to 2-3% of variability on timescale of ∼2×104 seconds (100-300 Rg light crossing time). Assuming an optically thick mm emitting medium, this translates into an upper limit of its size of ∼1300 Rg. The observation of fast variability in radio-mm and X-ray wavelengths, as well as a similar variability trend, well support the mm emission to be emitted by a region close, and potentially related to, the X-ray corona like an outflow/weak jet.