1 research outputs found
Variability of extragalactic X-ray jets on kiloparsec scales
Unexpectedly strong X-ray emission from extragalactic radio jets on
kiloparsec scales has been one of the major discoveries of Chandra, the only
X-ray observatory capable of sub-arcsecond-scale imaging. The origin of this
X-ray emission, which appears as a second spectral component from that of the
radio emission, has been debated for over two decades. The most commonly
assumed mechanism is inverse Compton upscattering of the Cosmic Microwave
Background (IC-CMB) by very low-energy electrons in a still highly relativistic
jet. Under this mechanism, no variability in the X-ray emission is expected.
Here we report the detection of X-ray variability in the large-scale jet
population, using a novel statistical analysis of 53 jets with multiple Chandra
observations. Taken as a population, we find that the distribution of p-values
from a Poisson model is strongly inconsistent with steady emission, with a
global p-value of 1.96e-4 under a Kolmogorov-Smirnov test against the expected
Uniform (0,1) distribution. These results strongly imply that the dominant
mechanism of X-ray production in kpc-scale jets is synchrotron emission by a
second population of electrons reaching multi-TeV energies. X-ray variability
on the time-scale of months to a few years implies extremely small emitting
volumes much smaller than the cross-section of the jet.Comment: Published in Nature Astronomy 29 May 2023; Supplemental Information
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