Monitoring an Internal Shock Collision in Action in 3C 264
Abstract
3C264 is a nearby radio galaxy with a prominent optical jet. Recent HST observations (May 2014) have revealed not only the fastest-ever superluminal speed (on kpc scales) of 7c for knot B, but also that knot B is in the very early stages of a collision with slow-moving downstream knot C (Meyer et al. 2015, Nature). This remarkable discovery represents the first strong evidence for the internal shock model for particle acceleration, a mechanism proposed to explain sources as diverse as gamma-ray bursts, microquasars, and jetted AGN. While a popular theoretical framework, such a collision has never actually been observed directly in any astrophysical object. Our recent HST imaging has captured the collision in its incipient stages, thus we have a unique opportunity to monitor a major shock collision as it unfolds. We propose 2 epochs of WFC3/UVIS (near-UV, B, and I band) imaging to monitor the optical-UV spectral energy distribution for the colliding knots and continue spatial proper motion measurements of the jet over the next 2-3 years. We also request 1 orbit of polarimetry in F606W with ACS/WFC in each epoch to monitor the polarization structure in the jet for changes as a result of the collision. The collision is expected to manifest in brightening and hardening of the optical spectrum and increasing polarization over the next several years, and our observations will allow us to evaluate the applicability, efficiency and physical characterization of the internal shock mechanism.
- Publication:
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HST Proposal
- Pub Date:
- August 2017
- Bibcode:
- 2017hst..prop15191M