AGN Jets A Review for Comparison with Microquasars

AGN Jets: A Review for Comparison with Microquasars & GRBs Alan Marscher Boston University Research Web Page: www. bu. edu/blazars

Emission Regions in a Radio-Loud AGN Differences with BH X-ray binaries: Inner accretion disk not hot enough to emit X-rays (but can have X-ray emitting ADAF if accretion rate is low) harder X-ray spectrum Core is always present in nearly all radio-loud AGN jets Unbeamed Beamed

Jets of Low-Luminosity AGNs Seyfert Liners Jets often seem to be interacting with clouds Apparent motion usually < c III Zw 2 (Brunthaler et al. 2005, A&A, 435, 497): 0. 6 c at 15 GHz, 1. 2 c at 43 GHz

Blazar Jets: 3 C 279 Superluminal motion between ~5 c & 20 c, bulk Lorentz factor up to 25, Doppler factor up to 50 Changes in apparent speed may be due solely to change in direction of jet by about ± 2 o

Blazar Jets: PKS 1510 -089 Apparent speeds up to 45 c (fastest known blazar containing well-defined superluminal knots) bulk Lorentz factor of at least 45 in jet

Radio-Loud AGN: The General Population Relativistic beaming causes strong selection effect in flux-limited radio surveys Bias toward high- jets pointing almost directly along line-of-sight Population simulation (Lister & Marscher 1997): observed apparent-motion & redshift distribution reproduced if: 1. Radio-galaxy luminosity function measured at low z is valid at higher z 2. Lorentz factor distribution is a power law, N( ) -a, a = 1. 5 -1. 75, with a high- cutoff of 45 (highest observed app) 12 -17% of jets in population have = 10 -45 5 -7% have = 20 -45, 2 -3% have = 30 -45, 0. 5 -0. 9% have = 40 -45 1. Spine-sheath models for compact AGN jets requiring a very high- spine in a typical jet are untenable unless radiation from the spine is suppressed 2. - But such ultra-fast spines should be prodigious emitters of inverse Compton X -rays off ambient photon field (e. g. , CMB)

Intrinsic Half Opening Angles of Jets (Jorstad et al. 2005, AJ, 130, 1418) Side-on radio galaxies: o Opening angles typically 1 -4 Blazars: q 1/ Agrees with models in which jet is focused as it is accelerated over an extended region. (HD: Marscher 1980; MHD: Vlahakis & Königl 2004) Explains why apparent opening angle is uncorrelated with apparent speed

Knots in Jets Polarization: BL Lac objects usually have B ~ transverse to local jet axis well downstream of core stationary 8 c

Knots in Jets Polarization: Quasars generally have oblique direction of B after aberration taken into account

Shock Model for Knots in Jets Best-liked model: Shocks propagating down turbulent jet Magnetic field compressed at shock front Electrons accelerated at shock front Polarization indicates that in general such shocks must be oblique, especially after correcting for aberration Need supersonic relative motion to get shock waves strong shocks are difficult for high- flows with relativistic equation of state (but don’t need very strong shocks for substantial enhancement of radiation)

Bends in Jets Bending: Apparent bends amplified greatly by projection effects Intrinsic bends by only a few degrees 3 C 446 0528+134

Changes in Direction Change in apparent speed can be due solely to change in direction Nonthermal luminosity seems to be related to direction of jet Changes amplified greatly by projection effects Velocity seems ballistic in some jets but seems to follow twisting jet in many others Changes in direction appear to be abrupt, unlike precession (more like an unstable firehose)

The Core of Blazar Jets Frequencies below ~ 40 GHz: ~ 1 surface At higher frequencies: a. Conical standing shock? (Daly & Marscher 1988) - See poster by Cawthorne et al. (e. g. , 1803+784 shown below) -In favor: reproduces polarization pattern if randomly oriented B field is compressed by conical shock -b. End of zone of accelerating flow - Where Doppler factor reaches asymptotic value 1803+784

Jet Acceleration over Extended Region Theory: A jet with > ~10 cannot propagate out of nuclear region (Phinney 1987) HD: Pressure gradient p r-a Lorentz factor increases with cross-sectional radius R: Γ R p-1/4 ra/4 If a < 4/(3 +1) and viewing angle is small, brightest emission is where Γ reaches its asymptotic value MHD: Models still being developed Vlahakis & Königl (2004, Ap. J) solution appears similar to HD solution, except that Γ decreases away from jet axis & there is no distinct boundary If viewing angle is large, brightest emission is at lowest r where high-E electrons are accelerated (Marscher 1980 Ap. J) Predicts toroidal field, but perhaps only close to central engine, where opacity is too high to image In either case, energy density at base of jet must exceed ~ 2Γρc 2 Might require a magnetosphere (pulsar or ergosphere of spinning BH)

Cygnus A (Bach et al. 2004, 2005) FR II radio galaxy, jet at large angle to l. o. s. Counter-core Core Gap between core & counterjet < 0. 7 mas Apparent speed increases with distance from core

Evidence for Collimation of Jets Well Outside Central Engine • VLBA observations of M 87: jet appears broad near core → Flow appears to be collimated on scales ~1000 Rs Junor et al. 2000 Nature

The FR I Radio Galaxy 3 C 120 (z=0. 033) Sequence of VLBA images (Marscher et al. 2002) Scale: 1 mas = 0. 64 pc = 2. 1 lt-yr HST image (Harris & Cheung) (Ho=70) • Superluminal apparent motion, ~5 c (1. 8 -2. 8 milliarcsec/yr) • X-ray spectrum similar to Seyferts • Mass of central black hole ~ 3 x 107 solar masses (Marshall, Miller, & Marscher 2004; Wandel et al. 1999)

X-Ray Dips in 3 C 120 Superluminal ejections follow Xray dips Similar to microquasar GRS 1915+105 Radio core must lie at least 0. 4 pc from black hole to produce the observed X-ray dip/superluminal ejection delay of ~ 60 days

Comparison of GRS 1915+105 with 3 C 120 Light Curves BH mass of 3 C 120 ~2 x 106 times that of GRS 1915+105, so timescales of hours to months in the former are similar to the scaled-up quasi-periods (0. 15 to 10 s) & duration of X-ray dips in the latter. Typical fractional amplitude of dips is also similar Long, deep dips not yet seen in 3 C 120 blow-up 150 s of blow-up should scale up to ~10 yr in 3 C 120 if timescales Mbh Below: X-ray light curve of 3 C 120 over 2. 2 yr ← GRS 1915+105 over 3000 s on 9/9/97 Light curve (top) & PSD (bottom) (Taken from Markwardt et al. 1999 Ap. JL) Perhaps low-hard X-ray state corresponds to 3 C 120

FR II Radio Galaxy 3 C 111 (z=0. 0485) Seems to Do the Same 1 mm flare May 2004 1 milliarcsec August 2004 New knot Superluminal ejection follows minimum of deep X-ray by 0. 3 yr Radio core must lie at least 0. 4 pc from black hole to produce the observed X-ray dip/superluminal ejection delay

Accretion States of AGNs Power spectral density of Seyferts similar to high-soft state of Cygnus X-1 (Mc. Hardy et al. 2004) -Weak jets of Seyferts consistent with weak/no jet in high-soft state of GRS 1915+105 (Fender & Belloni 2004) -Inner accretion disk not hot enough to emit X-rays spectrum not so soft (mean spectral index of 0. 9) Seyfert PSDs from Mc. Hardy et al. (2004) X-ray spectra of radio galaxies 3 C 120 (FR 1) & 3 C 111 (FR 2) flatter than this - Suggestive of low-hard state with ~ steady, optically thick jet seen in GRS 1915+105 Liners and low-luminosity Seyferts may have ADAFs near black hole High break timescales approximately linearly with mass

Sketch of Physical Structure of Jet, AGN CORE

Relation of AGN jets to XRBs & GRBs • Bulk Lorentz factors of jet flows can exceed 40 c - not too dissimilar to GRBs - but only rarely → Ultra-fast ( > 10) spines cannot be general feature in AGN → Blandford-Payne type jet launching might be sufficient in high fraction of AGN • X-ray variability of high-luminosity Seyferts has similar PSD to XRBs in high-soft state, with weak jets • X-ray spectrum of radio galaxies with strong jets flatter than in Seyferts, similar to low-hard state • Evidence for acceleration & focusing of jet over an extended region is mounting → Conforms with HD & some MHD models for jet launching