Evidence for Non-Hydrostatic Gas Motions in the Hot ISM of Centaurus A

Abstract

We present preliminary results from a deep (600 ks) {\em Chandra} observation of the hot interstellar medium of the nearby early-type galaxy Centaurus A (Cen A). We find a surface brightness discontinuity in the gas $\sim$3.5 kpc from the nucleus spanning a 120${}^{\circ }$ arc. The temperature of the gas is 0.60$\pm$0.05 and 0.68$\pm$0.10 keV, interior and exterior to the discontinuity, respectively. The elemental abundance is poorly constrained by the spectral fits, but if the abundance is constant across the discontinuity, there is a factor of 2.3$\pm$0.4 pressure jump across the discontinuity. This would imply that the gas is moving at 470$\pm$100 km s${}^{-1}$, or Mach 1.0$\pm$0.2 (1.2$\pm$0.2) relative to the sound speed of the gas external (internal) to the discontinuity. Alternatively, pressure balance could be maintained if there is a large (factor of $\sim$7) discontinuity in the elemental abundance. We suggest that the observed discontinuity is the result of non-hydrostatic motion of the gas core (i.e. sloshing) due to the recent merger. In this situation, both gas motions and abundance gradients are important in the visibility of the discontinuity. Cen A is in the late stages of merging with a small late-type galaxy, and a large discontinuity in density and abundance across a short distance demonstrates that the gas of the two galaxies remains poorly mixed even several hundred million years after the merger. The pressure discontinuity may have had a profound influence on the temporal evolution of the kpc-scale jet. The jet could have decollimated crossing the discontinuity and thereby forming the northeast radio lobe.

arXiv comment14 pages, 3 figures, 1 table - accepted for publication in the Astrophysical Journal Letters

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Cited by in corpus (19)

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• The MAGNUM survey: different gas properties in the outflowing and disk components in nearby active galaxies with MUSE
• The X-ray Jets of Active Galaxies
• Triggered star-formation in the inner filament of Centaurus A
• Long Term Monitoring of the Dynamics and Particle Acceleration of Knots in the Jet of Centaurus A
• The Jet-Heated X-ray Filament in the Centaurus A Northern Middle Radio Lobe
• Luminosity functions of LMXBs in Centaurus A: globular clusters versus the field
• The variable and non-variable X-ray absorbers in Compton-thin type-II Active Galactic Nuclei
• The Complex North Transition Region of Centaurus A: A Galactic Wind
• Suzaku view of X-ray Spectral Variability of the Radio Galaxy Centaurus A : Partial Covering Absorber, Reflector, and Possible Jet Component
• The hard X-ray continuum of Cen A observed with INTEGRAL SPI
• Soft band X/K luminosity ratios for gas-poor early-type galaxies
• The multi-phase environment in the centre of Centaurus A
• UVIT view of Centaurus A; a detailed study on positive AGN feedback
• Cosmic Ray Ionization of Low-Excitation Lines in Active Galactic Nuclei and Starburst Galaxies
• The Infrared Jet in 3C31
• A Transient Sub-Eddington Black Hole X-ray Binary Candidate in the Dust Lanes of Centaurus A
• Spectral Properties of X-ray Binaries in Centaurus A