AGN Outflows: Part II

Outflow Generation Mechanisms: Models and Observations

Leah SimonMay 4, 2006

Review: Unified Model

Review: Outflows exist BALs (Broad Absorption Lines)

Large velocity widths: V(FWHM) > 3000 km/s Within ~60,000km/s of quasar redshift (v ~ 0.2c)

Variability: timescales of ~year(s) Caused by continuum source variability affecting

photoionized clouds Or caused by cloud (outflow) motion across LOS

Partial coverage Continuum source is small! Cloud must be nearby if some continuum source

can pass around cloud to our eye

Review: Acceleration Mechanisms Radiation Pressure (Photoionization)

Line Driving – momentum from radiation field through line opacity

Expect vtransverse

= small

Require very high L/LEdd

Thermal Pressure (Parker Wind) Not strong enough Requires Isothermal wind...

Magnetic Pressure (Magnetocentrifugal Driving) 'Beads on a string' See John Everett (CITA)

MHD vs LD MagnetoHydroDynam

ics Does not necessitate

shielding (over-ionization unimportant)

Expected from collimated radio jets

Predicts high velocity flows, and can move high-density gas

Line Driving Requires shield to

protect wind from inner x-ray radiation

UV flux and wind velocities correlate

Radiative momentum lost from continuum found in BALs

Can explain relative X-ray and UV flux well

Predicts high velocity outflows, but maybe densities too low

Probably a combination of the the two methods (Everett 2005, Proga, 2003).Need to constrain models to distinguish between them!

Proga 2003 simulates MHD+LD using both poloidal and toroidal B-fieldsSimilar to LD, but with faster (slow) dense wind at outer disk

Fluid angular-momentum-conservation

Not magneto-centrifugal wind

Mass loss through LD at inner disk (fast stream)through MHD at outer disk (slow stream)

Observational Evidence: General Results

CIV width relates to Lxray

Proga 2005, Proga + Kallman 2004 Are UV and and X-ray radiatively coupled?

X-ray absorption Gallagher et al. 2006 Hardest X-ray spectra are also weakest – intrinsic

absorption? Shielding and/or Over-ionization Proga, Everett,

Murray et al. 1995 Line driving requires shielding to protect from over-

ionization Hot corona?

What's all the buzz?

Using Gravitational Lensing

Use multiple LOS to compare structural models for BLR Virialized clouds (Kaspi & Netzer 1999) Continuously outflowing wind ( Murray et al. 1995)

How it works observe lensed BALQSOs compare 2 observations Infer geometry based on

variation among LOSD. Chelouche, ApJ 2003

Chelouche finds lensed troughs are similar to within S/N for all but 2 quasars

Single Cloud Model:

lateral size of clouds must be smaller than RS - expected based on partial coverage

For non-varying clouds, must have lateral to radial aspect ratio ~ 10-3 - Would be destroyed on dynamical timescale – no coherent acceleration --NO

Tube model - many (n) identical clouds with aspect ratio also << 1 - alignment of tube over numerous LOS unlikely --NO

Clumpy Wind Model:

Cloudlets imply statistical isotropy: different LOS views same distribution – variation should follow Poissonian distribution

similarities imply nv >>1 and ntot>>100

changes imply change in cloud distribution function –YES

implies isotropy on ~few arcsec scale – BAL Outflow probably one or many sheets or cones with large lateral size – not time- dependent dynamical wind

Evidence for Multiphase Flows de Kool et al. 2001 observe disparate ionization

states at similar velocities-conclude shielded gas at large distances (~1kpc)

Everett et al. 2002 re-evaluate and conclude multiphase flow, with continuous low-density wind and embedded high density clouds at small distances (~4pc) Inner continuous region acts as shield, driven by

MHD or failed LD Outer region is LD outflow, with lower ionizations Lowest ionizations found in dense embedded clouds

→ Centrifugally driven disk wind? Turbulence? Shocks?

Multiphase Flow in NALs?

Observe CIV and CII at same velocitiesInitial distance determinations locate SiII very far from source (~150 kpc)Combine with partial coverage in CIV!Could multiphase flow be a solution?

Variability Test

Observation SeparationPKS 2204 ~ 13 yearsQ 0401 ~ 7 yearsPKS 2044 ~ 17 yearsQ 0249 ~ 14 yearsQ 0334 ~ 14 years

Approximate Variability TimescalesAccretion disk size ~ .1pc Light crossing time ~ .35 yearsViscous time ~ 200 yearsDynamical time ~ 0.3 daysUsing M=108M

sun, R=2x1014 ~3R

S(X-ray source size)

Thanks!