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Feedback under the microscope: thermodynamic structure and AGN driven shocks in M87 | | E. T. Million
; N. Werner
; A. Simionescu
; S. W. Allen
; P. E. J. Nulsen
; A. C. Fabian
; H. Bohringer
; J. S. Sanders
; | | Date: |
29 Jun 2010 | | Abstract: | (abridged) Using a deep Chandra exposure (574 ks), we present high-resolution
thermodynamic maps created from the spectra of $sim$16,000 independent
regions, each with $sim$1,000 net counts. The excellent spatial resolution of
the thermodynamic maps reveals the dramatic and complex temperature, pressure,
entropy and metallicity structure of the system. Excluding the ’X-ray arms’,
the diffuse cluster gas at a given radius is strikingly isothermal. This
suggests either that the ambient cluster gas, beyond the arms, remains
relatively undisturbed by AGN uplift, or that conduction in the intracluster
medium (ICM) is efficient along azimuthal directions. We confirm the presence
of a thick ($sim$40 arcsec or $sim$3 kpc) ring of high pressure gas at a
radius of $sim$180 arcsec ($sim$14 kpc) from the central AGN. We verify that
this feature is associated with a classical shock front, with an average Mach
number M = 1.25. Another, younger shock-like feature is observed at a radius of
$sim$40 arcsec ($sim$3 kpc) surrounding the central AGN, with an estimated
Mach number M > 1.2. As shown previously, if repeated shocks occur every
$sim$10 Myrs, as suggested by these observations, then AGN driven weak shocks
could produce enough energy to offset radiative cooling of the ICM. A high
significance enhancement of Fe abundance is observed at radii 350 - 400 arcsec
(27 - 31 kpc). This ridge is likely formed in the wake of the rising bubbles
filled with radio-emitting plasma that drag cool, metal-rich gas out of the
central galaxy. We estimate that at least $sim1.0 imes10^6$ solar masses of
Fe has been lifted and deposited at a radius of 350-400 arcsec; approximately
the same mass of Fe is measured in the X-ray bright arms, suggesting that a
single generation of buoyant radio bubbles may be responsible for the observed
Fe excess at 350 - 400 arcsec. | | Source: | arXiv, 1006.5484 | | Services: | Forum | Review | PDF | Favorites | |
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