Detection of Superluminal Motion in the X-Ray Jet of M87
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Date
2019-06-26
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Citation of Original Publication
Bradford Snios, et.al, Detection of Superluminal Motion in the X-Ray Jet of M87, The Astrophysical Journal, Volume 879, Number 1, https://doi.org/10.3847/1538-4357/ab2119
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This work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.
Public Domain Mark 1.0
Abstract
Chandra HRC observations are investigated for evidence of proper motion and brightness changes in the X-ray jet
of the nearby radio galaxy M87. Using images spanning 5 yr, proper motion is measured in the X-ray knot HST-1,
with a superluminal apparent speed of 6.3 ± 0.4c, or 24.1 ± 1.6 mas yr⁻¹
, and in Knot D, with a speed of
2.4 ± 0.6c. Upper limits are placed on the speeds of the remaining jet features. The X-ray knot speeds are in
excellent agreement with existing measurements in the radio, optical, and ultraviolet. Comparing the X-ray results
with images from the Hubble Space Telescope indicates that the X-ray and optical/UV emitting regions co-move.
The X-ray knots also vary by up to 73% in brightness, whereas there is no evidence of brightness changes in the
optical/UV. Using the synchrotron cooling models, we determine lower limits on magnetic field strengths of
∼ 420 μG and ∼ 230 μG for HST-1 and Knot A, respectively, consistent with estimates of the equipartition fields.
Together, these results lend strong support to the synchrotron cooling model for Knot HST-1, which requires that
its superluminal motion reflects the speed of the relativistic bulk flow in the jet