Variability and Proper Motion of X-Ray Knots in the Jet of Centaurus A

Bradford Snios, Sarka Wykes, Paul E. J. Nulsen, Ralph P. Kraft, Eileen T. Meyer, Mark Birkinshaw, Diana M. Worrall, Martin J. Hardcastle, Elke Roediger, William R. Forman, Christine Jones

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Abstract

We report results from Chandra observations analyzed for evidence of variability and proper motion in the X-ray jet of Centaurus A. Using data spanning 15 yr, collective proper motion of 11.3 +/- 3.3 mas yr(-1), or 0.68 +/- 0.20c, is detected for the fainter X-ray knots and other substructure present within the jet. The three brightest knots (AX1A, AX1C, and BX2) are found to be stationary to an upper limit of 0.10c. Brightness variations up to 27% are detected for several X-ray knots in the jet. For the fading knots, BX2 and AX1C, the changes in spectral slope expected to accompany synchrotron cooling are not found, ruling it out and placing upper limits of similar or equal to 80 mu G for each of their magnetic field strengths. Adiabatic expansion can account for the observed decreases in brightness. Constraints on models for the origin of the knots are established. Jet plasma overrunning an obstacle is favored as the generator of stationary knots, while moving knots are likely produced either by internal differences in jet speed or the late stages of jet interaction with nebular or cloud material.

Original languageEnglish
Article number248
Number of pages11
JournalAstrophysical Journal
Volume871
Issue number2
DOIs
Publication statusPublished - 1 Feb 2019

Cite this

Snios, B., Wykes, S., Nulsen, P. E. J., Kraft, R. P., Meyer, E. T., Birkinshaw, M., ... Jones, C. (2019). Variability and Proper Motion of X-Ray Knots in the Jet of Centaurus A. Astrophysical Journal, 871(2), [248]. https://doi.org/10.3847/1538-4357/aafaf3
Snios, Bradford ; Wykes, Sarka ; Nulsen, Paul E. J. ; Kraft, Ralph P. ; Meyer, Eileen T. ; Birkinshaw, Mark ; Worrall, Diana M. ; Hardcastle, Martin J. ; Roediger, Elke ; Forman, William R. ; Jones, Christine. / Variability and Proper Motion of X-Ray Knots in the Jet of Centaurus A. In: Astrophysical Journal. 2019 ; Vol. 871, No. 2.
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Snios, B, Wykes, S, Nulsen, PEJ, Kraft, RP, Meyer, ET, Birkinshaw, M, Worrall, DM, Hardcastle, MJ, Roediger, E, Forman, WR & Jones, C 2019, 'Variability and Proper Motion of X-Ray Knots in the Jet of Centaurus A' Astrophysical Journal, vol. 871, no. 2, 248. https://doi.org/10.3847/1538-4357/aafaf3

Variability and Proper Motion of X-Ray Knots in the Jet of Centaurus A. / Snios, Bradford; Wykes, Sarka; Nulsen, Paul E. J.; Kraft, Ralph P.; Meyer, Eileen T.; Birkinshaw, Mark; Worrall, Diana M.; Hardcastle, Martin J.; Roediger, Elke; Forman, William R.; Jones, Christine.

In: Astrophysical Journal, Vol. 871, No. 2, 248, 01.02.2019.

Research output: Contribution to journalArticle

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T1 - Variability and Proper Motion of X-Ray Knots in the Jet of Centaurus A

AU - Snios, Bradford

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AU - Kraft, Ralph P.

AU - Meyer, Eileen T.

AU - Birkinshaw, Mark

AU - Worrall, Diana M.

AU - Hardcastle, Martin J.

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AU - Forman, William R.

AU - Jones, Christine

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N2 - We report results from Chandra observations analyzed for evidence of variability and proper motion in the X-ray jet of Centaurus A. Using data spanning 15 yr, collective proper motion of 11.3 +/- 3.3 mas yr(-1), or 0.68 +/- 0.20c, is detected for the fainter X-ray knots and other substructure present within the jet. The three brightest knots (AX1A, AX1C, and BX2) are found to be stationary to an upper limit of 0.10c. Brightness variations up to 27% are detected for several X-ray knots in the jet. For the fading knots, BX2 and AX1C, the changes in spectral slope expected to accompany synchrotron cooling are not found, ruling it out and placing upper limits of similar or equal to 80 mu G for each of their magnetic field strengths. Adiabatic expansion can account for the observed decreases in brightness. Constraints on models for the origin of the knots are established. Jet plasma overrunning an obstacle is favored as the generator of stationary knots, while moving knots are likely produced either by internal differences in jet speed or the late stages of jet interaction with nebular or cloud material.

AB - We report results from Chandra observations analyzed for evidence of variability and proper motion in the X-ray jet of Centaurus A. Using data spanning 15 yr, collective proper motion of 11.3 +/- 3.3 mas yr(-1), or 0.68 +/- 0.20c, is detected for the fainter X-ray knots and other substructure present within the jet. The three brightest knots (AX1A, AX1C, and BX2) are found to be stationary to an upper limit of 0.10c. Brightness variations up to 27% are detected for several X-ray knots in the jet. For the fading knots, BX2 and AX1C, the changes in spectral slope expected to accompany synchrotron cooling are not found, ruling it out and placing upper limits of similar or equal to 80 mu G for each of their magnetic field strengths. Adiabatic expansion can account for the observed decreases in brightness. Constraints on models for the origin of the knots are established. Jet plasma overrunning an obstacle is favored as the generator of stationary knots, while moving knots are likely produced either by internal differences in jet speed or the late stages of jet interaction with nebular or cloud material.

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KW - galaxies: individual (Centaurus A)

KW - galaxies: jets

KW - X-rays: galaxies

KW - PARTICLE-ACCELERATION

KW - CHANDRA OBSERVATIONS

KW - RADIO JETS

KW - DECELERATION

KW - SIMULATIONS

KW - COUNTERJET

KW - EMISSION

KW - DYNAMICS

KW - MODELS

KW - SHOCKS

U2 - 10.3847/1538-4357/aafaf3

DO - 10.3847/1538-4357/aafaf3

M3 - Article

VL - 871

JO - The Astrophysical Journal

JF - The Astrophysical Journal

SN - 0004-637X

IS - 2

M1 - 248

ER -

Snios B, Wykes S, Nulsen PEJ, Kraft RP, Meyer ET, Birkinshaw M et al. Variability and Proper Motion of X-Ray Knots in the Jet of Centaurus A. Astrophysical Journal. 2019 Feb 1;871(2). 248. https://doi.org/10.3847/1538-4357/aafaf3