AGN Jets Steve Movit 10 25 2004 ASTRO 597A Credit NASA CXC A Siemiginowska CfA J Bechtold U Arizona Outline Before Chandra Physics of Jets What we expect Emission Processes Types of Jets Surrounding medium Detection How we see them Results What we see Future what we d like to see Before Chandra Jets mainly studied in radio Xray jets thought exotic Einstein and ROSAT had few M87 Cen A NGC 6251 Chandra first light Xray jet PKS 0637 752 Xrays found where no optical emision Synchrotron model breaks down from radio to Xray Now it seems that ALL radio jets have Xray counterparts Synchrotron Review See Rybicki and Lightman Ch 6 2 2 2 2 q u 2 q a a Larmor Formula P 3 3 3 c 3 c For relativity a a is invariant 3 2 Beaming a a a a a B v qB B mc 2 2 2 2 q 4 q B 2 P v 3 2 3 c mc More Synchrotron Review 2 q Classical Electron radius r 0 2 mc 2 B T 8 r 0 3 U B 8 rad E dE dt 2 2 2 Voila dE dt 2 T c U B sin 1 g B 2 2 Critical Freq c 3 2 g sin Synchrotron SDF and Luminosity Critical Freq is 30GHZ From Worrall and Birkinshaw X c F c X X K 5 3 d L F c N d Synchrotron Power Laws and Luminosity The Big Punchline L F c N d N d 2 2 Requires min g max g Analytical Result is a mess However L p d Physics Pret mean probability per cycle that particle remains in jet and is Achterberg et al 2001 shocked again ln 1 P ret Ultarel case 1 ln E f E i Fermi acceleration d u 2 Nonrel case d u 1 Phew Onto Inverse Compton Exact same energy rate loss formula Provided 2 h o me c low energy photons Spectral distribution function differs X 2 4 o 2 F o X f x f x X 1 X 2 X 2 X ln X X X f X dX f X dX 2 1 3 4 3 o When Compton scattering is on synchroton photons from jet is synchrotron self compton Thermal Bremsstrahlung Emission 6 16 e dW 2 Stated ne ni Z g ff v w 3 2 d dV dt 3 3 c m v 2 mv 2 Maxwell Velocity Dist n Isotropic dP v exp dv 2 kT 1 2 For a photon of freq h mv 2 Average dW v d dV dt over the velocity distribution 2 5 h 5 2 2 3 me c 32 2 Z i g ff ni ne me c r o e kT 3 3 kT Integrate over freq convert to P kT cool 2 5 m H FR classification Paper Fanaroff and Riley 1974 MNRAS Cambridge One Mile telescope There is a definite relationship between relative positions of the high and low brightness regions of radio sources and their luminosity Classified by ratio distance between highest central bright regions on either side of nucleus and total extent relative position of hotspots 5 Class II 5 Class I High L Class II Low L Class I Class I more complex structure FR I FR I galaxy 3C 31 note that jets starts right near core FR I physics Low power and a well defined beam head this means good contact with external medium Based on 3C 31 jet has 3 regions narrow jet w relativistic flow flaring region bright in radio outer region with steady deceleration Outer region is where deflection takes place Knots are a mystery Acceleration takes place in knots FR II FR II galaxy 3C 220 1 clear separation of lobes from core high power FR II Physics FR II is supersonic w r t ISM bow shock forms at end of jet we see well collimated jets feeding edge brightened lobes k T c s m H v adv Assume strong shock Rankine Hugoniot M cs Get simple relations 2 P2 4 M 2 2 5 M 1 4 P1 1 M 2 3 2 T2 M 3 2 5 M 1 2 T1 16 M FR I II Physics Difference according to Sambruna lies in jet pressure fits with idea of luminosity discrimination Jet pressure in FRII becomes comparable to ambient farther out this is where shocks form Would expect innemost knot closer to core in FR I than in FRII explore In FRI knots fit radio optical synchrotron spectrum FRI Xray morph Fairly uniform FR I II Physics From Sambruna et al Jet Schematic From Worrall and Birkinshaw Jet terminates at hotspot light gray is radio emitting fluid heats ambient gas producing X rays Jet Structures Jet features defined based on radio Jet narrow feature 4x as long as it is wide Lobe radio emission not in jet Hotspot compact feature in lobe Knot compact feature in jet End of jet end of emission 90 degree change of direction decollimation by 2x Knots are most likely to have X ray counterparts Magnetic Fields Field orient determined by linear polarization in radio 1 L 5 3 Significant pol indicates lack of thermal material otherwise differential between front and back of jet would depolarize it Circular polarization mentioned later also seen in pc scale jets Is this e e Superluminal Motion VLBI obs of AGN show jets w multiple comp around bright cores These comp Expanding separating w Vt 10c Blandford et al 1977 A v t sin D Adapted from Peterson 1997 B v t B v t cos v T D v sin sin T c c t c 1 cos 1 cos Maximize get max T can be arb large Bulk Relativistic Motion Effects Relativistic Doppler Factor 1 2 1 cos R 1 cos J 2 1 cos L nu increases by Boosting by factor of alpha due to blueshift Core dominance R cd cos 0 2 2 R cd 1 cos 1 cos 2 External Medium Jets mostly distinct from nucleus X rays arise from interaction of hot jet gas with cool dense medium Jet is in hydrostatic equilibrium like stellar interior P Ideal Gas P n p k T solar abund 6 Spherical sym X d G M tot r 2 dr r More External Medium Follows Isothermal Beta Model see Cavaliere and Fusco Fermiano 1978 2 1 5 mh GM c r 2 3 0 1 2 kT rc rc Beta depends on ratio of grav pot to thermal E per unit mass NFW say its unphysical measured beta s don t match theory NFW ain t perfect either Bottom line density has power law structure with dimensionless parameter representing balance of gravity and thermal motions More External Medium Surface Brightness and Ion Ratio Density and T of medium can be determined from surface brightness but it s a mess XSPEC uses the magic normalization mentioned in class 1 z S ne n p dV N 2 2 4 D A 1 z Da is angular diameter distance and 1 z is for expanding …