Search results for "galaxies: active"
showing 5 items of 35 documents
VLBA polarimetric monitoring of 3C 111
2018
Context. While studies of large samples of jets of active galactic nuclei (AGN) are important in order to establish a global picture, dedicated single-source studies are an invaluable tool for probing crucial processes within jets on parsec scales. These processes involve in particular the formation and geometry of the jet magnetic field as well as the flow itself. Aims. We aim to better understand the dynamics within relativistic magneto-hydrodynamical flows in the extreme environment and close vicinity of supermassive black holes. Methods. We analyze the peculiar radio galaxy 3C 111, for which long-Term polarimetric observations are available. We make use of the high spatial resolution of…
High-energy monitoring of NGC 4593 II. Broad-band spectral analysis: testing the two-corona model
2019
It is widely believed that the primary X-ray emission of AGN is due to the Comptonisation of optical-UV photons from a hot electron corona, while the origin of the 'soft-excess' is still uncertain and matter of debate. A second Comptonisation component, called warm corona, was therefore proposed to account for the soft-excess, and found in agreement with the optical-UV to X-ray emission of a sample of Seyfert galaxies. In this context, we exploit the broadband XMM-Newton and NuSTAR simultaneous observations of the Seyfert galaxy NGC 4593 to further test the so called "two corona model". The NGC 4593 spectra are well reproduced by the model, from the optical/UV to the hard X-rays. Moreover, …
Testing warm Comptonization models for the origin of the soft X-ray excess in AGNs
2018
The X-ray spectra of many active galactic nuclei (AGN) show a soft X-ray excess below 1-2 keV on top of the extrapolated high- energy power law. The origin of this component is uncertain. It could be a signature of relativistically blurred, ionized reflection, or the high-energy tail of thermal Comptonization in a warm (kT $\sim$ 1 keV), optically thick ($\tau\simeq$ 10-20) corona producing the optical/UV to soft X-ray emission. The purpose of the present paper is to test the warm corona model on a statistically significant sample of unabsorbed, radio-quiet AGN with XMM-newton archival data, providing simultaneous optical/UV and X-ray coverage. The sample has 22 objects and 100 observations…
Faint γ-ray sources at low redshift: the radio galaxy IC 1531
2018
We present amultiwavelength study of IC 1531 (z=0.02564), an extragalactic radio source associated with the γ -ray object 3FGL J0009.9-3206 and classified as a blazar of uncertain type in the Third Fermi-Large Area Telescope AGN catalog (3LAC). A core-jet structure, visible in radio and X-rays, is enclosed within a ~220 kpc wide radio structure. The morphology and spectral characteristics of the kiloparsec jet in radio and X-rays are typical of Fanaroff-Riley type I galaxies. The analysis of the radio data and optical spectrum and different diagnostic methods based on the optical, infrared, and γ -ray luminosities also support a classification as a low-power RG seen at moderate angles (θ = …
Sub-milliarcsecond imaging of a bright flare and ejection event in the extragalactic jet 3C 111
2020
Context. Flares in radio-loud active galactic nuclei are thought to be associated with the injection of fresh plasma into the compact jet base. Such flares are usually strongest and appear earlier at shorter radio wavelengths. Hence, very long baseline interferometry (VLBI) at millimeter(mm)-wavelengths is the best-suited technique for studying the earliest structural changes of compact jets associated with emission flares. Aims. We study the morphological changes of the parsec-scale jet in the nearby (z = 0.049) γ-ray bright radio galaxy 3C 111 following a flare that developed into a major radio outburst in 2007. Methods. We analyse three successive observations of 3C 111 at 86 GHz with th…