Offsets between X-ray and Radio Components in X-ray Jets: The AtlasX
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Date
2022-12-05
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Attribution 4.0 International (CC BY 4.0)
Attribution 4.0 International (CC BY 4.0)
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Abstract
The X-ray emission mechanism of powerful extragalactic jets, which has important
implications for their environmental impact, is poorly understood. The X-ray/radio
positional offsets in individual features of jets provide important clues. Extending
the previous work in Reddy et al. 2021, we present a detailed comparison between
X-ray maps deconvolved using the Low Count Image Reconstruction and Analysis
(LIRA) tool and radio maps of 164 components from 77 Chandra-detected X-ray
jets. We detect 94 offsets (57%), with 58 new detections. In FR II-type jet knots,
the X-rays peak and decay before the radio in about half the cases, disagreeing with
the predictions of one-zone models. While a similar number of knots lack statistically
significant offsets, we argue that projection and distance effects result in offsets below
the detection level. Similar de-projected offsets imply that X-rays could be more
compact than radio for most knots, and we qualitatively reproduce this finding with
a ‘moving-knot’ model. The bulk Lorentz factor (Γ) derived for knots under this
model is consistent with previous radio-based estimates, suggesting kpc-scale jets are
only mildly relativistic. An analysis of X-ray/radio flux ratio distributions does not
support the commonly invoked mechanism of X-ray production from inverse Compton
scattering of the cosmic microwave background but does show a marginally significant
trend of declining flux ratio as a function of distance from the core. Our results imply
the need for multi-zone models to explain the X-ray emission from powerful jets. We
provide an interactive list of our X-ray jet sample at http://astro.umbc.edu/Atlas-X.