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Deep Chandra observations of Pictor A

Deep Chandra observations of Pictor A
Deep Chandra observations of Pictor A
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 of 4 more exposure than observations previously presented and span a 15 yr 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.
0035-8711
3526-3545
Hardcastle, M.J.
23b43806-5ee7-46e3-b29b-98f7442dd263
Lenc, E.
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Birkinshaw, M.
f84791f0-587f-42dc-adbd-4568ec9e66c1
Croston, J.H.
b10aa3fb-620e-4ec2-93e5-8594748d4822
Goodger, J.L.
9b17f409-db04-4209-894e-a769a5b9b6e0
Marshall, H.L.
42b839a2-32ca-44ec-a587-e4488dbe6e38
Perlman, E.S.
012ac90a-4814-4921-88af-01942cdde65f
Siemiginowska, A.
56ff624a-15bf-42f3-928f-4b5af590cc45
Stawarz, Ł.
82eb8ceb-f211-4e6e-bc78-1b34cd5e6fad
Worrall, D.M.
af83a5a9-e50d-4b28-ad03-92baf3726d56
Hardcastle, M.J.
23b43806-5ee7-46e3-b29b-98f7442dd263
Lenc, E.
89efb04e-a2ea-4ebd-92f0-83ca96b6303e
Birkinshaw, M.
f84791f0-587f-42dc-adbd-4568ec9e66c1
Croston, J.H.
b10aa3fb-620e-4ec2-93e5-8594748d4822
Goodger, J.L.
9b17f409-db04-4209-894e-a769a5b9b6e0
Marshall, H.L.
42b839a2-32ca-44ec-a587-e4488dbe6e38
Perlman, E.S.
012ac90a-4814-4921-88af-01942cdde65f
Siemiginowska, A.
56ff624a-15bf-42f3-928f-4b5af590cc45
Stawarz, Ł.
82eb8ceb-f211-4e6e-bc78-1b34cd5e6fad
Worrall, D.M.
af83a5a9-e50d-4b28-ad03-92baf3726d56

Hardcastle, M.J., Lenc, E., Birkinshaw, M., Croston, J.H., Goodger, J.L., Marshall, H.L., Perlman, E.S., Siemiginowska, A., Stawarz, Ł. and Worrall, D.M. (2016) Deep Chandra observations of Pictor A. Monthly Notices of the Royal Astronomical Society, 455 (4), 3526-3545. (doi:10.1093/mnras/stv2553).

Record type: Article

Abstract

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 of 4 more exposure than observations previously presented and span a 15 yr 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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Accepted/In Press date: 28 October 2015
e-pub ahead of print date: 30 November 2015
Published date: 1 February 2016
Organisations: Astronomy Group

Identifiers

Local EPrints ID: 402014
URI: http://eprints.soton.ac.uk/id/eprint/402014
ISSN: 0035-8711
PURE UUID: 5e50b646-ccf5-4362-8199-99a480c85bfb

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Date deposited: 26 Oct 2016 13:26
Last modified: 16 Dec 2019 19:39

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