parsec-scale jet-environment interactions in agn matthew lister purdue university extragalactic...
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Parsec-Scale Parsec-Scale Jet-Environment Jet-Environment
Interactions in AGNInteractions in AGN
Matthew ListerMatthew Lister
Purdue UniversityPurdue University
Extragalactic Jets, May 2007
Girdwood, AK
Review OutlineReview Outline
1. Evolutionary theories for young radio jets - Gigahertz-peaked spectrum galaxies (CSOs)
2. Numerical jet-cloud simulations
3. VLBA studies of young jets and blazars
Perucho & Marti 02
Self-similar expansion modelsSelf-similar expansion models
CSO 0710+439
• Begelman 96, Kaiser and Alexander 97, Bicknell et al. 97
• Hotspots in ram pressure equilibrium
– evolution depends on radial profile of ISM density
– correlation between hotspot size and overall jet length (Jeyakumar & Saikia 00)
Perucho & Marti 02
CSO 0710+439
• Contemporary view :
– forward hotspot motion >> side-to-side not a “dentist’s drill”
– advancing bow shock interacts with clumpy ISM, creating line emission via shock ionization
– hotspot advance unimpeded
– fast advance speeds of 0.1 - 0.4 c
Self-similar expansion modelsSelf-similar expansion models
Young jet evolutionYoung jet evolution• Evolution models suggest rapid
dimming once jet reaches ~ 1 kpc (e.g., Snellen et al. 00)– CSOs overrepresented in AGN jet
population – cutoff in kinematic age distribution
• ISM interaction to blame?– change in jet polarization
properties past 2-3 kpc (Cotton et al. 03)
– first encounter with clumpy medium? tidal effects? Gugliucci et al. 05
(years)
Kinematic age distribution of CSO jets
shaded = lower limits
GPS Galaxies: Young and not so frustratedGPS Galaxies: Young and not so frustrated• Strong observational evidence for dense environments, but
dense enough?– huge gas masses (1010 Msun) required to halt medium power jets
– HI and X-ray column densities too low • (e.g.,Vermeulen et al. 03, Guaianazzi et al. 06, Vink et al. 06)
• Other evidence against frustration:– ‘burst and stall’ can’t apply in majority of cases advance speeds
are measurable (Polatidis & Conway 92)
– kinematic expansion ages ≈ spectral ages (< 104 y; Murgia et al. 99)
– no IR excess (Fanti et al. 2000)
Intermittent Jet ActivityIntermittent Jet Activity
– 5-10% of GPS galaxies show kpc-scale emission
– X-ray shells around radio galaxies: (e.g. M87, NGC 1275, 3C 317)
– Ultra steep spectrum (fossil) radio galaxies
• “Double-double” radio galaxies– only ~dozen known, all large
radio galaxies
– a few to tens of Myr between jet episodes
– symmetric inner doubles imply stoppage at AGN nucleus, not from cloud collisions (Kaiser et al. 00)
J1835+620180 kpc
Saikia et al. 06
Numerical SimulationsNumerical Simulationsof Jet-Cloud Interactionsof Jet-Cloud Interactions
Jet simulations with clumpy mediumJet simulations with clumpy medium
• 3D pure hydro sims: – extends work of Saxton et al. 05
– light hypersonic jet, η = 10-3
– Mach 26, Γ = 5
• External medium:– hot (107 K) ISM plus 104 K
turbulent, clumpy disk (1010 Msun)
• Main findings:– jet forms channels through weak
points in ISM
– spherical energy-driven bubble
– jet eventually breaks free and recollimates, forming classical bow shock Sutherland & Bicknell, ApJ
submitted
False color = density
Comparisons with CSO 4C 31.04
• Western lobe emission not backflow– flat-spectrum region extended perpendicular to western hotspot– high velocity filaments in simulations: particle acceleration sites– jet near end of breakout phase?
• Eastern lobe perhaps at earlier evolutionary phase
VLBA 5 GHz: Giroletti et al. 03
50 pc
Comparisons with CSO 4C 31.04
• Western lobe emission not backflow– flat-spectrum region extended perpendicular to western hotspot– high velocity filaments in simulations: particle acceleration sites?– jet near end of breakout phase?
• Eastern lobe likely at an earlier evolutionary phase
VLBA 5 GHz: Giroletti et al. 03
50 pc
65 kyr
Relativistic 3-D Hydro simulationsRelativistic 3-D Hydro simulations
• Choi & Wiita, ApJ ‘07
• Oblique shocks deflect the beam
– no jet deceleration or decollimation
– bend is transient
• Highest deflections expected for low-Mach jets hitting denser clouds
Density
Pressure
cloud/ISM density ratio = 10
Jet Lorentz factor = 2.3
Mach number = 6.4
• Model B: thicker cloud:– less encompassed by
bow shock, so Mach disk interacts sooner
– perpendicular structure similar to 4C 31.04
cloud/ISM density ratio = 100
Jet Lorentz factor = 2.3
Mach number = 6.4
Density
Pressure• Clouds can survive
impact without fragmentation
– may be important star formation sites
VLBA Studies of Jet-Environment VLBA Studies of Jet-Environment Interactions: I. SeyfertsInteractions: I. Seyferts
Jets in Seyfert galaxies
• VLBA resolution: < 104 A.U. at typical Seyfert distances (15-20 Mpc)
• Much lower jet power and speed– more subject to entrainment and disruption (Bicknell et al. 98, de Young 06)
– accretion may be sporadic, leading to random jet axis directions (King & Pringle 07)
Seyfert NGC 4151: Mundell et al. 03Seyfert NGC 4151: Mundell et al. 03red: radio jet
green: molecular hydrogen torus
central black region: ionized gas
- Seyfert 1.5 (nearly face on), 13.3 Mpc
- Possible deflection at site of eastern HI absorption: flat radio spectrum
200 pc
• Numerous [O III] emission clouds near radio jet– some are high
velocity– NLR geometry
suggests radiative excitation from AGN
HST image (Winge et al. 97)+ jet overlay (Mundell et al. 03)
NGC 4151
• Some clouds are high velocity (> 1000 km/s)– cocoon may shock ionize NLR clouds close to the jet
NGC 3079: Middelberg et al. 07NGC 3079: Middelberg et al. 07
• Seyfert 2 at 15 Mpc
• Powerful water maser disk, indicative of thick molecular torus
• Multi-epoch VLBA monitoring:– A and B: compact, SSA/FFA radio spectra– A is moving at 0.1 c away from B– recently slowed and increased in flux density– cpts E and F may represent earlier (branching?) outflow
5 GHz VLBA image
1345+125: A young precessing AGN Jet1345+125: A young precessing AGN Jet• Host galaxy: gas rich ULIRG at z = 0.12
• Tidal tails, young stellar pop., double nucleus recent merger
Stanghellini et al. 2005
• Jet follows a conical helix:– intrinsic speed 0.8 c– cone axis inclined 82
degrees from line of sight
– 280 pc helix wavelength
VLBA 2 cm image (Lister et al. 2003
PKS 1345+125:
Young radio jet at z = 0.1
AGN
– northern jet truncated at site of dense HI absorption (>1022 cm-2; Morganti et al. 05)
• High polarization at bend and jet terminus– shocked regions– Mach disk implies active
hotspot: jet not stifled in this very gas rich galaxy
• Outer (kpc-scale) structure likely remnant of earlier activity cycle
fpol = 10%
fpol > 40%
Lister et al. 03
VLBA Studies of Jet-Enviroment InteractionsVLBA Studies of Jet-Enviroment InteractionsII. BlazarsII. Blazars
Using blazars to probe jet-ISM interactionsUsing blazars to probe jet-ISM interactions
• Small jet viewing angles:– small jet bends exaggerated by projection– less obscured view through hole in torus– trace gas via Faraday rotation of polarization
• Superluminal blobs effectively trace jet flow– century of jet evolution in a few years
MOJAVE / 2 cm Survey (Lister & Homan 05)
more movies at: www.physics.purdue.edu/MOJAVE
50 pc (projected)
Feature C4 moved steadily on linear path for over a decade at 8 c – sudden
acceleration to 13 c and change by 26°
– intrinsic change in direction only ~1°
• Event occurred a few kpc from nucleus:– reconfinement
following flaring of initially overpressured jet?
– deflection by oblique density gradient?
3C279: Homan et al. 2003
3C 1203C 120
• Broad-line Sy 1 galaxy at 145 Mpc (z = 0.033)
• Signs of merger activity
• One-sided pc-scale jet, speeds ~6 c, viewing angle < 20 deg. (Jorstad et al. 05)
• High velocity emission line components suggest jet interaction with gas clouds (Axon et al. 89)
HST archive image: Cheung and Harris
Rosat contours + radio greyscale (Harris)
• Multiepoch, multifrequency VLBA polarimetry of inner jet (Gomez et al. 2000, 2001, 2006, Jorstad et al. 2005)
• Spatial resolution of ~0.1 pc allows resolution across the jet
22 GHz
• Jet features brighten and rotate in polarization as they move along southern half of the jet – changes occur after they have left the nucleus, and no kinematic
accelerations seen– suggestive of medium interaction
Gomez et al. 01
Dynamics of 3C 120’s JetDynamics of 3C 120’s Jet
• Cloud interaction?– occurs at 8 pc
(deprojected) from the nucleus
– jet remains well collimated
– strong and variable RM indicates dynamic interaction
Gómez et al. in prep.Gómez et al. in prep.
Future research avenuesFuture research avenues
• Finding the youngest AGN jets:– only ~ 40 currently identified CSOs– large area radio surveys above 15 GHz: ATCA 20 GHz, 9th Cambridge, Planck– large VLBA surveys: VIPS, VCS
• Studies of low-power CSOs:– intermediate stage before classical FR II?– very few currently known, especially at scales > 1 kpc: (e.g., Giroletti et al. 06, Augusto et al. 06)– identification a challenge for VLBA: science driver for space VLBI
• Can we identify the beamed CSOs?– how relativistic are young radio jets? similarities with blazars?
SummarySummary• VLBI studies indicate clumpy, asymmetric ISM
– jet evolution likely affected, but not stifled on pc-scale
• Drop-off in jet population at ~1 kpc size:– jet disruption, or central engine turn off?
• Variety of powerful tools available:– x-ray and radio absorption measures– high resolution optical emission line imaging– VLBA polarimetry– numerical simulations
• The VLBA offers unparalleled means of probing dynamics of jet-cloud interactions on sub-decade timescales
Future research avenuesFuture research avenues
• Finding the youngest AGN jets:– only ~ 40 currently identified CSOs– large area radio surveys above 15 GHz: ATCA 20 GHz, 9th Cambridge, Planck– large VLBA surveys: VIPS, VCS
• Studies of low-power CSOs:– intermediate stage before classical FR II?– very few currently known, especially at scales > 1 kpc: (e.g., Giroletti et al. 06, Augusto et al. 06)– identification a challenge for VLBA: science driver for space VLBI
• Can we identify the beamed CSOs?– how relativistic are young radio jets? similarities with blazars?
Nagging Questions For DiscussionNagging Questions For Discussion
• Is the ~kpc size cutoff related to merger activity/fueling, or jet stifling?
• Where does deceleration of GPS lobes occur? – classical radio galaxies have much slower hotspot
advance speeds
• Could more powerful jets be evolving in less clumpy environments? – role of Roche tidal radius?
X = 10
Γ = 7.1
M = 11.6
Seyfert 2: NGC 1068 (Das et al. 06)Seyfert 2: NGC 1068 (Das et al. 06)
• Seyfert 2
Jet precession and interactionJet precession and interaction
• well established phenomenon in microquasars (eg. SS 433, GRO J 1655-40)
• jets constantly encountering new material• S-shaped morphologies more common in CSOs than blazars• causes:
– KH instability– current driven instability– pressure-driven instability– precession of jet nozzle
• merger• binary BH• accretion disk warp (Lai 03, Quillen 01, Pringle 96)
• Lu 1990: offset accretion disk exerts torque– Peck and Taylor 01 find offset torus needed to explain HI absorption
distribution in CSO 1946+708
Precession and interactionPrecession and interaction
• Jet precession periods too short to be from warped accretion disks (Bardeen-Peterson effect; Lodato & Pringle 06)
• Binary BH have been proposed in several AGN:– OJ 287 (Valtonen XXX)– 3C 345 (Lobanov and Roland 05)– 0402+379 (Rodriguez et al. 06)
EntrainmentEntrainment• Entrainment of external material
excites K-H surface instabilities that can penetrate jet and disrupt lower Mach flows (Perucho et al. 05, de Young 06)
• Slower speed, turbulent surface mixing layer forms (Aloy et al. 99, Laing & Bridle 02,06, Attridge et al. 99)
• Difficult to study observationally
de Young 2006
Brown & Roshko 74
• Limb brightening in resolved jets:– Centaurus A (Kataoka et al. 06)– 3C 353 (Swain et al. 98)– M87 (Ly et al. 07, Kovalev et al. in prep)
• Possible major sites of particle acceleration (Stawarz & Ostrowski 02)– implications for beaming models of high energy emission
Chandra X-ray: Kataoka et al. 06VLBA 7 mm: Ly et al. 07
Centaurus A
M87
Jet-medium interactions in Seyfert galaxies
• Much lower jet power and speed– more subject to
entrainment and disruption
– accretion may be sporadic, leading to random jet axis directions (King & Pringle 07)
• VLBA resolution: < 104 A.U. at typical Seyfert distances (15-20 Mpc).
Relativistic 3-D Hydro simulationsRelativistic 3-D Hydro simulations
• Choi & Wiita 07
• Off-axis collision
• X = cloud/ISM density ratio
• Γ = jet Lorentz factor
• M = Mach number
X = 10
Γ = 2.3
M = 6.4
Density
Pressure
Γ
• Model B: thick cloud:– less encompassed by
bow shock– Mach disk interacts
sooner– stronger oblique
shocks deflect the beam
– perpendicular structure similar to 4C 31.04
X = 100
Γ = 2.3
M = 6.4
Density
Pressure
Γ
ISM
cloudbowshockshock n
nvv
• Beam deflected in all models
– oblique shocks form, but do not decelerate or decollimate the jet, unlike non-relativistic sims (Wang et al. 00, Higgins et al. 99)
– bends appear to be transient
• Deflection angle more dependent on cloud density than jet Mach number
– highest deflection expected for low-Mach jets hitting denser clouds
• Clouds can survive impact without fragmentation
– large cloud/jet density contrast suppresses K-H instabilities
– may be important star formation sites
X = 100
Γ = 7.1
M = 11.6
• Model C: faster jet– Mach disk further offset from bow shock– thinner backflow cocoon
Density
Pressure
Γ
Compact Steep-Spectrum Sources (CSS)Compact Steep-Spectrum Sources (CSS)
• Sizes up to a few kpc
• Spectral turnovers < 100 MHz
• Strong evidence for jet/ISM interaction:
– asymmetric jets (Saikia et al. 02, 03)
– high rotation measures and depolarization
– high-velocity emission line systems and jet alignments (Gelderman & Whittle 94, Labiano et al. 05, de Vries et al. 99)
Schoenmakers et al. 00
Radio galaxy B1450+333
Important issues addressed via pc-scale jet-Important issues addressed via pc-scale jet-medium interaction studiesmedium interaction studies
• How is AGN jet activity triggered?
• What is the nature of the ISM in AGN hosts, and how does it affect jet evolution?
• Which young jets evolve into classical radio galaxies? (And how?)
• Model B: thicker cloud:– less encompassed by
bow shock, so Mach disk interacts sooner
– perpendicular structure similar to 4C 31.04
cloud/ISM density ratio = 100
Jet Lorentz factor = 2.3
Mach number = 6.4
Density
Pressure
ISM
cloudbowshockshock n
nvv
• Clouds can survive impact without fragmentation
– may be important star formation sites
Double-double radio Double-double radio galaxiesgalaxies
• No hotspots in inner double expected if jets propagating through previous cocoon material – would be difficult to observe (Marecki et al. 06, Clarke et al. 92)
– restarted jet may encounter warm, dense clouds from previous cocoon backflow (Kaiser et al. 00)
Is CSO growth affected by dense gas?Is CSO growth affected by dense gas?
• Gupta et al. 06 find no dependence of jet morphology on HI properties– HI in obscuring torus, not
interacting with jet?
• NGC 1052: nearly identical jet&counterjet, yet significant absorption (Vermeulen et al. 03)
• 1345+125: well collimated jet in very dense environment (Lister et al. 03) Gupta et al. 06
The youngest AGN JetsThe youngest AGN Jets
• Gigahertz-Peaked Spectrum (GPS) galaxies:– 5% of AGN selected at 5 GHz– large intrinsic radio
luminosities (not beamed)– many host galaxies have
distorted morphologies / close companions (O’Dea et al. 96)
• Compact Symmetric Objects (CSOs):– misnomer? jet asymmetries
are common– miniature versions of two-
sided radio galaxies (1000x smaller)
– jets oriented near sky planeGugliucci et al. 2005
Size – HI absorption anti-correlationSize – HI absorption anti-correlation• Pihlström et al. fit trend with power
law ISM, index ≈ -2
– similar slope to predictions of expansion models
– total HI gas masses ~ 108 Msun
– no trend of HI with jet asymmetry though (Gupta et al. 06) HI in torus?
• Vink et al. 06: NLR may be still forming in young CSOs
– lower [OIII] luminosities than larger jets
– collimated jet and hotspots must form very soon after AGN turn-on
– supported by NLR size and lobe expansion speed of J1503+4528 (Inskip et al. 06)
Pihlström et al. 2003
Basic forms of jet-medium interactionBasic forms of jet-medium interaction
A. Entrainment- jet instabilities, sheaths, deceleration
B. Hotspot & bow shock advance- effects of intermittent jet activity- encounters with varying external medium
C. Jet/cloud collisions- bending and disruption