Jet-Gas Interactions in
Seyfert Galaxies
Mark Whittle (Virginia)
David Rosario (Virginia)
John Silverman (Virginia)
Charlie Nelson (Drake)
Andrew Wilson (Maryland)
Outline
• Brief review of :
AGN & Jets & Emission lines
Reasons to study jet-gas interactions (JGI)
• Case study of Seyfert Galaxy : Mkn 78
Observations & data overview
Heuristic description of JGI
Ionization analysis
Dynamical analysis
Active Galaxies
• All galaxies have nuclear black holes
• Those currently accreting are “active”
• Accretion energy released in two forms
A : Photons
• Thermal & non-thermal processes
• Broad SED : Optical / UV / X-ray
• Large range in luminosity :
LINER  Seyfert  QSO
AGN Spectral Energy Distribution (SED)
Radio
far-IR
optical
EUV
X-ray
Seyferts
(NGC 4151)
Low Luminosity
Quasars
High Luminosity
B : Bipolar Outflows (Jets)
• Origin uncertain (MHD driven ?)
• Velocity uncertain :
– Some relativistic, others not
+
+
• Content uncertain : (p e or e e ?)
– Relativistic component : e- + B  radio
– Other (thermal) components ?
• Large luminosity range :
– Radio loud (radio galaxies/QSRs)
– Radio quiet (Seyferts/QSOs)
Radio Galaxy
3C 296
Flux ~ few Jy
Radio Loud
Seyfert Galaxy
Mkn 573
Flux ~ few mJy
Radio Quiet
Emission Lines
•From ionized gas :
Te ~ 104 K, ne ~ 102 – 109 cm-3
•Ionization mechanism ?
– Photoionization (yes)
– Shock related (maybe with jets?)
•Profiles reveal (Doppler) velocities
BLR (R ~ 10-2pc, V2 ~ GMBH/R)
NLR-1 (R ~ 1 kpc, V2 ~ GMbul/R)
NLR-2 (R ~ 1 kpc, V ~ jet related)
•Nested emission line regions
BH << AD << BLR << NLR << Gal
r/c : min hr
week 103 yr 104 yr
Why study JGI in Seyferts ?
• Jet-gas interactions occur in many contexts
– AGN (ISM/IGM)
– Stellar jets (DMC/ISM)
– Starburst winds (ISM/IGM)
• Laboratory for astrophysical hydrodynamics
• Seyfert ELRs allow important diagnostics
– Gas mass, velocity, KE, momentum, pressure
– Complements radio source pressure/energy
Mkn 78 : jet-gas archetype
Early ground based data suggest
prominent JGI :
• Luminous triple radio source
• Strong double [OIII] profile
• FWHM >> gravitational velocities
Mkn 78
Unfortunately, Mkn 78 is quite distant :
• cz ~ 11,000 km/s  1 arcsec ~ 700pc
• BT ~ 15.2 MB ~ -20.8
• Dull looking early type galaxy
 Need HST resolution
Mkn 78
KPNO 2.1m Red Continuum
30 arcsec
Mkn 78 : HST & VLA Dataset
• VLA : 3.6cm 8hr map
• HST images : (FOC, PC, STIS, NICMOS)
– Continuum : UV/green/near-IR
– Emission line : [OIII] 5007
• HST spectra : (STIS, FOS)
– 4 slits : good spatial coverage
– 4 gratings : low resolution : UV & optical
high resolution : [OIII] 5007
Near IR
STIS CCD clear
Optical
arcsec
NICMOS F160W
Dust lane
[OIII] λ5007
3.6cm radio
4 STIS Slit Positions
STIS low dispersion spectral data
STIS high dispersion [OIII] 5007 data
Mkn 78 Case Study :
Jet-gas interactions
1. Heuristic description
2. Ionization study
3. Dynamical study
4. Jet properties
Overlay : Radio (contours) & [OIII] (image)
STIS high dispersion [OIII] 5007 data
1. Heuristic Description
1. Inner W-knot
Jet ends & disrupts; some gas disturbance
?  DMC enters & disrupts flow; recent interaction
2. Eastern fan
Jet deflected; split lines; “blow-back” shape
?  Cloud inertia deflects jet (doesn’t destroy it)
?  Radial + lateral motion induced (±300 on 400)
?  Intermediate age : begun to disrupt cloud
3. Outer W-lobe
Components; complex velocity ; no bow shock
?  late stage; dispersing cloud remnants; leaky bubble
2. Ionization Study
Low dispersion spectra  many line fluxes
Compare line ratios with :
1. Ionization models (U, Am/i , Shock)
2. Velocities (Vbulk & FWHM)
3. Location (radius)
4.
Other things (radio/color/dust)
Ionization mechanisms
Three basic contexts explored :
1. U – sequence : AGN photoionization
2. Am/i – sequence : AGN photoionization
3. Shock – sequence : shock ionization
Cartoon illustrates these

1)
2)
U sequence
Am/i sequence
Neutral
Back
Ionized
front
Optically
Thin clouds
AGN
AGN
UV
Optically
Thick Clouds
Only
Optically
Thick & Thin
Clouds
UV
Ferland’s,
CLOUDY
U = Ni/Ne ~ 10-2 – 10-3
3)
Binette et al : ‘96
Am/i = Am/Ai ~ 0.1 – 10
Vsh
Shock sequence
Auto-ionizing
Shocks
Collisionally ionized
& photo-ionized
post-shock gas
Vsh = 100 – 800 km/s
shock
UV
Photo-ionized
precursor
Doptia & Sutherland : ‘95, ‘96, ‘03
Line ratios vs models
a) General excitation/ionization
b) Discriminators to separate Sh & U+Am/i
c) Discriminators to separate U & Am/i
d) [ [OI] 6300 anomalous line ]
e) [ Nuclear nitrogen enhancement ]
Excitation :
All models OK
U ~ 10-2 – 10-3
A ~ 30% – 90%
Sh ~ 500 – 300 km/s
U
Am/i
Sh
U
Am/i
Sh
Discriminators 1
Trends follow U & A
Don’t follow shocks
Discriminators 2
e.g. [NeV], HeII,
& [OIII]4363
U poor, favours Am/i
trend fits nicely
Note : weak [NeV]
U
Am/i
Sh
in Mkn 78
requires new Am/i
Ratios vs models :
Summary
1.
2.
3.
4.
Clean results because enough data to show trends
Current shock models are excluded
Photoionization by the AGN dominates
Gas contains both optically thick & thin clouds
Now consider ratios vs gas velocity 
Excitation vs FWHM
Excitation vs V –Vsys
Shock
Shock
Results summary 
Ratios vs velocity :
Summary
1. Essentially no (v. weak) correlations :
 ionization conditions independent of velocity
2. Shock model predictions very poor
Now consider ratios vs radius 
Excitation vs Radius
Radius :
• Strong correlation
 photoionization
• U drops ~ r –1
 density ~ r –1
[SII] difficult to confirm
• Am/i drops with r
 more thin @ small r
Final check : UV Luminosity
• Check photoionization :
– Can UV luminosity power emission lines ?
• But UV is invisible/obscured ?!
• Take FIR luminosity = reprocessed UV
– LUV ~ LFIR ~ 4πd2FFIR ~ 4πd2 [2.6S60+ S100]
 Check :
– LUV ~ Lem ~ 10 x L5007 as observed
– U ~ NUV/ne ~ 10-2.5 as observed
3. Dynamical Study
To go beyond heuristic description :
–
–
–
–
Need physical properties
Aim to evaluate these throughout regions
First consider ionized gas
Then consider other components
Slit B : kinematic measurements
Peak Velocity
FWHM
-2
East
-1
0
Nuc
+1
+2
+3
West
Extinction
Density
Line flux
Mass
Momentum
KE
Simple Properties
Three regions : Inner knot / East fan / West lobe
Region Age :
•
Age ~ size/velocity : ~ 0.4 / 4 / 8 Myr
Ionized gas :
•
Mass : ~ 0.4 / 1.0 / 1.1 x 106 Msun
•
Filling factor : ~ 30 / 1.5 / 0.5 x 10-4
•
Covering factor : ~ 0.5 / 0.5 / 0.5
Consider other components 
The Various Components
Relativistic gas :
ffrel; Prel ~ B2/8π
Line Emitting gas :
ffem; nem; Pem; Vem
Assume/show : Prel ~ Pth ~ Pem ~ Pism
Thermal gas :
nth; Pth; Tth
ISM
nism~ 1
Pressures : Prel, Pem, Pth, Prad
•
•
Log P/k ~ 6.5 / 6.0 / 5.5 K cm-3
–
Quite high > radio galaxy lobes
–
All components deep within galaxy ISM
All pressures drop with radius (~ r -1)
–
As expected for galaxy ISM context
•
Approximate pressure balance between
•
different components : Prel ~ Pem (~ Pth)
Relativistic & radiation pressure too low
to accelerate ionized gas (by ~ x10)
–
Need dynamical (ram) pressure of jet
Energy Comparisons
Relative energies in different parts :
– UV (FIR)
~ 1000 (~1043 erg/s)
–
–
–
–
–
~ 1000
~1
~1
~1
~ 0.2
Emission lines
Kinetic
Relativistic
Expansion /lobe
Radio
Simple inferences 
Conclusions from energy comparisons
1. Photons dominate by x1000 ; Lem ~ LUV
 supports photo- over shock ionization
 should not derive Ljet from Lem (see later)
2. Expansion / KE / Relativistic all similar
 flows can accelerate gas & power radio source
4. Jet Properties
Estimating jet energy and momentum :
Use emission line & lobe properties :
• Ej ~ KEem + αe Elobe ~ 2-5 Elobe
αe = synchrotron loss; adiabatic loss; ffrel
Lj = Ej/Tage ~ 2-5 x 1040 erg/s
• Gj ~ αm Gem ~ 2-5 Gem
αm = covering factor loss ; drag loss
Fj = Gj/Tage ~ 2-5 x 1033 dyne
JET LUMINOSITY
EKE ~ Σ½M V2
Lj
Lj ~ (EKE + αeErel )/tage
JET MOMENTUM
Elobe~ PV
~ αeErel
Gem ~ ΣM V
Fj
Fj ~ αmGem / tage
αe ~ αsyn αad αff ~ 2 – 10
αm ~ αdrag αlcf ~ 2 – 5
Jet Properties (model)
• Components :
– Relativistic & thermal; ratio defined by ffrel
– Both move at Vj
• Pressure balance : Prel ~ Pth
2
– We know Prel from radio physics ~ Bme/8π
• Energy : Ej ~ KEth + Wth + Wrel
– Wrel = (4/3)Prel ; Wth = (5/2) Pth
• Momentum : Gj ~ Gth + Grel = Gth
– Relativistic component has ~zero inertia
Jet Properties (derived)
Use Lj Gj Pj Aj to derive many properties (>100pc)
• Thermal material dominates jet energy and momentum
– Relativistic gas has little/no momentum
– KEj/Uj ~ Fj/Aj/Pj ~ 10 / 3 / 2  KE dominates energy
• Jet velocity ~ 1-few x Vgas
– 2Lj/Fj ~ Vj ~ 300 – 3000 km s-1
• Ram pressure dominates : Pram ~ 30 / 7 / 4
x
Prel
– Can accelerate to Vem over Tage for Ncol ~ 1021 cm-2
– Only mild shocks : Pram ~ ρemVsh2  Vsh ~ 10-50 km s-1
– Not acceleration by impulsive shocks; maybe wind/ablation
Jet Properties (derived)
• Jet density (thermal) : 0.1 - 5 cm-3
– Consistent with entrained ISM
• Jet temperature : Tj ~ Pj/njk ~ 106 K
– ~ 0.1-0.7 Temperature from thermalized Vj
– again consistent with entrained ISM
• Jet Mach number : 5 / 2.5 / 2  transonic
– Consistent with entrainment and decollimation
• Jet mass flux : ~ Mem over region lifetime
– Could be entrained ISM
– Could become ‘thermal’ component of lobe
Comparison with previous work
Many partial interpretations
One thorough analysis :
 Bicknell, Dopita & Sutherland ’98
They use shocks to infer jet properties,
in particular : jet energy & momentum
This yields significantly different results
JET LUMINOSITY
EKE ~ Σ½M V2
Our analysis
Lj
Lj ~ (EKE + αErel )/tage
Bicknell et al ‘98
Shock
Elobe~ PV
~ αErel
Emission
Lines : Lem
Lj
Lj ~ Lem ~ 100 x L5007
For Mkn 78 & other Seyferts : Lj (them) ~ 1000 x Lj (us)
JET MOMENTUM
Our analysis
Gem ~ ΣM V
Fj
Gradual
acceleration
Fj ~ αGem / tage
Bicknell et al ‘98
Shock
2
ρemVsh
Pram ~ ρjVj2
nem~ 103 cm-3
2
ρjVj ~ ρemVsh
2
Vsh~Vem~ 500 km/s
Emission Line
Cloud
Impulsive acceleration
For Mkn 78 & other Seyferts : Fj (them) ~ 100 x Fj (us)
Jet Property
Our Jet
Bicknell et al
Energy flux : Lj
Momentum flux Fj
Velocity : Vj
x1
x 1000
x1
x 100
300 – 3000 km/s
(1 – few Vem)
0.1 – 5 cm-3
x1
10 – 50 km/s
~ 106 K
2–5
15 – 90 x103 km/s
(0.05c – 0.3c)
0.1 – 5 cm-3
x 100
500 – 1000 km/s
~ 109 K
1 – few
Density : nj
Ram pressure : Pj
Cloud shock : Vsh
Temperature : Tj
Mach No. : Mj
Comparison : Ours is a kinder, gentler jet.
Maybe more plausible ?
Summary
1. Jet-gas interactions (JGI) are important
2. VLA & HST data on Seyfert with dominant JGI
3. Inspection reveals likely JGI scenario
–
3 regions suggest temporal development
4. Ionization study rejects role of shocks
–
AGN photoionization of thick & thin components
5. Data provide information on jet properties :
–
–
–
relatively low power, low speed, transonic, dense jet
dominated by thermal gas, at Tj ~ 0.5 x T(Vj)
ram pressure ~ 2-10 x internal pressure
6. Overall context : thermal jet/wind driven ablata
New HST Project :
1 or 2 slits on six
other objects with
evidence for JGI.