The X-ray Emissions from the M87 Jet: Diagnostics and Physical Interpretation

Eric S. Perlman; Andrew S. Wilson

doi:10.1086/430340

paper

The X-ray Emissions from the M87 Jet: Diagnostics and Physical Interpretation

arXiv:astro-ph/0503024 · doi:10.1086/430340

Abstract

We reanalyze the deep Chandra observations of the M87 jet, first examined by Wilson & Yang (2002). By employing an analysis chain that includes image deconvolution, knots HST-1 and I are fully separated from adjacent emission. We find slight but significant variations in the spectral shape, with values of $α_{x}$ ranging from $\sim 1.2 - 1.6$ . We use VLA radio observations, as well as HST imaging and polarimetry data, to examine the jet's broad-band spectrum and inquire as to the nature of particle acceleration in the jet. As shown in previous papers, a simple continuous injection model for synchrotron-emitting knots, in which both the filling factor, $f_{a cc}$ , of regions within which particles are accelerated and the energy spectrum of the injected particles are constant, cannot account for the X-ray flux or spectrum. Instead, we propose that $f_{a cc}$ is a function of position and energy and find that in the inner jet, $f_{a cc} \propto E_{γ}^{- 0.4 \pm 0.2} \propto E_{e}^{- 0.2 \pm 0.1}$ , and in knots A and B, $f_{a cc} \propto E_{γ}^{- 0.7 \pm 0.2} \propto E_{e}^{- 0.35 \pm 0.1}$ , where $E_{γ}$ is the emitted photon energy and and $E_{e}$ is the emitting electron energy. In this model, the index $p$ of the injected electron energy spectrum ( $n (E_{e}) \propto E_{e}^{- p}$ ) is $p = 2.2$ at all locations in the jet, as predicted by models of cosmic ray acceleration by ultrarelativistic shocks. There is a strong correlation between the peaks of X-ray emission and minima of optical percentage polarization, i.e., regions where the jet magnetic field is not ordered. We suggest that the X-ray peaks coincide with shock waves which accelerate the X-ray emitting electrons and cause changes in the direction of the magnetic field; the polarization is thus small because of beam averaging.

Accepted for publication in ApJ; 21 pages, 9 figures, 2 tables; abstract shortened for astro-ph; Figures 1, 7 and 8 at reduced resolution

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Ultraviolet HST Observations of the Jet in M87

The X-ray Emissions from the M87 Jet: Diagnostics and Physical Interpretation

Abstract

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