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Post Info TOPIC: Pictor A
Blobrana


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RE: Pictor A
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Black hole's twin jets shine bright, somehow

Astronomers have published new images of a bright jet of material, long enough to cross the Milky Way three times, fired into space by the black hole at the heart of a distant galaxy.
The observations confirm the existence of a second jet, blasting in the opposite direction.
The study uses this galaxy, Pictor A, to test ideas about what makes jets like these emit very bright X-rays.
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Blobrana


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ESO 252-18A
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Pictor A (also 2MASX J05194973-4546436, PKS 0518-45, ESO 252-18A and QSO B0518-4549) is a magnitude +15.8 Seyfert 1 galaxy located about 485 million light-years away in the constellation Pictor.

From a supermassive black hole at its centre, a relativistic jet shoots out to an X-ray hot spot 800,000 light years away
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Right ascension05h 19m 49.7s, Declination-45° 46' 44"



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Blobrana


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Title: Deep Chandra observations of Pictor A
Author: M. J. Hardcastle, E. Lenc, M. Birkinshaw, J. H. Croston, J.L. Goodger, H. L. Marshall, E. S. Perlman, A. Siemiginowska, L. Stawarz, D. M. Worrall

We report on deep Chandra observations of the nearby broad-line radio galaxy Pictor A, which we combine with new Australia Telescope Compact Array (ATCA) observations. The new X-ray data have a factor 4 more exposure than observations previously presented and span a 15-year time baseline, allowing a detailed study of the spatial, temporal and spectral properties of the AGN, jet, hotspot and lobes. We present evidence for further time variation of the jet, though the flare that we reported in previous work remains the most significantly detected time-varying feature. We also confirm previous tentative evidence for a faint counterjet. Based on the radio through X-ray spectrum of the jet and its detailed spatial structure, and on the properties of the counterjet, we argue that inverse-Compton models can be conclusively rejected, and propose that the X-ray emission from the jet is synchrotron emission from particles accelerated in the boundary layer of a relativistic jet. For the first time, we find evidence that the bright western hotspot is also time-varying in X-rays, and we connect this to the small-scale structure in the hotspot seen in high-resolution radio observations. The new data allow us to confirm that the spectrum of the lobes is in good agreement with the predictions of an inverse-Compton model and we show that the data favour models in which the filaments seen in the radio images are predominantly the result of spatial variation of magnetic fields in the presence of a relatively uniform electron distribution.

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Blobrana


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Title: Origin of the X-rays and Possible GeV-TeV Emission from the Western Hot Spot Of Pictor A
Authors: Jin Zhang, J. M. Bai, Liang Chen, Xian Yang

Pictor A is a nearby Fanaroff-Riley class II (FR II) radio galaxy with a bright hot spot, the western hot spot. Observation of high polarization in the optical emission of the hot spot indicates that the optical emission could be synchrotron radiation of relativistic electrons in the hot spot. These electrons may be able to produce high energy gamma-ray photons through inverse Compton (IC) scattering. We use single-zone and multi-zone synchrotron + synchrotron-self-Compton (SSC) models to fit the observed spectral energy distribution (SED) from the radio to the X-ray band of the hot spot. Our results show that in the case of a much weaker magnetic field strength than the equipartition magnetic field, both the single-zone and multi-zone models can fit the SED, but the multi-zone model significantly improves the fit. The two models predict the hot spot as a GeV-TeV source, which might be marginally detectable with Fermi/LAT and HESS. The inverse Compton scattering of cosmic microwave background (IC/CMB) is also considered, but its contribution to GeV-TeV emission is negligible. Note that under the equipartition condition, the SED can also be fit with the multi-zone model, but the predicted flux at 10^22 Hz is too weak to be detectable. The detection of TeV gamma-rays from this FR II radio galaxy, if confirmed, would establish a new subclass of extragalactic source in this energy regime since most of the AGNs detected to date at TeV energies are high-energy-peaked BL Lac objects.

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Blobrana


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Title: An X-ray view of Pictor A radio lobes: a spatially resolved study
Authors: G. Migliori, P. Grandi, G.C.G. Palumbo, G. Brunetti, C. Stanghellini

A spatially resolved analysis of the lobes of the radio galaxy Pictor A has been performed for the first time starting from a 50 ksec XMM-Newton observation. Magnetic field, B_{IC}, particle density, particle to magnetic field energy density ratios have been measured. Our study shows that B_{IC} varies through the lobes. On the contrary, a rather uniform distribution of the particles is observed. In both the lobes, the equipartition magnetic field, B_{eq}, is bigger than the Inverse Compton value, B_{IC}, calculated from the radio to X-ray flux ratio.

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