Transcript Perlman
Insights on Jet Physics & HighEnergy Emission Processes from Optical Polarimetry Eric S. Perlman Florida Institute of Technology Collaborators: C. A. Padgett, M. Georganopoulos (UMBC), F. Dulwich, D. M. Worrall, M. Birkinshaw (Bristol), A. S. Wilson (UMCP), W. B. Sparks, J. A. Biretta (STScI), C. O’Dea, S. Baum (RIT) + several others… Radiation Processes in Jets e- Synchrotron radiation emitted by relativistic particles in magnetic field B Jet “beam” Inverse-Compton – scattering interaction between photon and a relativistic particle that results in a higher-energy photon. Radiation from jets emitted by two processes: synchrotron and inverse-Compton. For inverse-Compton, the ‘scattered’ photon can be either from within the jet (often called synchrotron self-Compton) or some external source (e.g, the cosmic microwave background or emission line regions). Important questions: What does the magnetic field configuration look like? Does it change as one goes up in energy? What clues can the magnetic field configuration and ordering give us to radiation and physical mechanisms involved in producing high-energy emissions? Perlman et al. 1999 Comparing jet width in Radio, optical, X-rays… X-ray jet is narrowest Optical jet is next Radio jet is widest Perlman & Wilson 2005 Stratified jet… High energy particles nearer jet axis Low energy particles evenly distributed B gets compressed, becomes to jet in shocks inside jet Shocks accelerate particles, so they brighten optical emission but not radio Further development of magnetic field depends on two scale lengths: Magnetic field coherence length lB Perlman et al. 1999 Synchrotron cooling length lcool lB = lcool Perlman, Georganopoulos & Kazanas, in progress lB=2lcool 3C15 Optical and radio jet roughly similar but optical jet narrower 2 knots in X-ray, one coincident with knot C, the other not coincident with radio/opt (A’) Knot A’ X-ray max corresponds to a feature seen in UV but not in any other r/o band 3C 15 Polarimetry differences more subtle than M87 In all X-ray maxima, there are interesting radio-optical polzn differences in the neighborhood Resolution marginal Optical spectrum hardens too But still indicate stratification 2-component plasma, relativistic spine, slower sheath Knot C is a torsional compression of the jet where X-ray emission is triggered 3C 264 Wide-angle tail type source. Bend about 4” from nucleus Optical emission dims markedly after 1” X-ray emission both from inner jet as well as optically fainter outer jet 3C 264 Resolution of Chandra data too low to firmly associate inner jet X-ray emission with optical feature But polarization anomalies at 0.8” from nuclueus, just upstream of “ring” Outer jet emission -optically faint, hard to tell 3C 346 Kinked jet seen in both radio and optical Major bend may be the result of the passage of a companion galaxy X-ray emission from ~0.3” before kink Major change in polarization characteristics near kink 3C 346 Increase in polarization near X-ray maximum. Small rotation in position angles, only in optical, at that point. Hardening of optical spectrum at X-ray max. Synchrotron X-ray emission with associated compression? 3C 371 3C 371 Optical shows low polarization in 2 Xray maxima, high polarization in one. Significant rotations seen in optical also Neither is seen in radio Summary In all cases, *something* happens in polarimetry at loci of X-ray emission What happens appears different in each jet and each component Usually associated with an increase in radio-optical polarimetry differences Optical spectrum seems to harden at X-ray flux max X-ray emission from only a small part of jet “crosssection” Optical Polarimetry can serve as a diagnostic for Xray emission mechanism This is crying out to be done for higher-power jets!