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