AGN OUTFLOWS

Observations and Physical Parameters

Leah SimonFeb. 3, 2006

Absorption: Types

● Unassociated/Associated: Redshift relative to quasar emission lines

● Intrinsic/Extrinsic: Ejected from Quasar or part of host galaxy OR external to quasar

● Broad Absorption Lines(BALs)/Narrow Absorption Lines(NALs) (mini-BALs): line widths FWHM

● Outflows come from Intrinsic Lines of all types● Outflows occur in ~ 50% of all quasars!

Quasar Spectrum

Rodriguez-Hidalgo, private communication

BALs

● V (FWHM)> 3000 km/s● Redshifts from quasar up ~0.2c -> winds!● HiBALS: high ionizations species

– CIV, NV, SiIV● LoBALS: low ionization species

– CII, MgII,

NALs

● V spread (FWHM)< 100-200 km/s● CIV doublet resolvable● V shift < 5000 km/s -> associated (probably part

of quasar/host)

Intrinsic Absorption:Strong Indicators● BALs

– Large velocity widths– Within ~60,000km/s of quasar redshift

● 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

Variability

Rodriguez-Hidalgo, private communication

Partial Coverage

Barlow, Hamann, Sargent, 1997

Partial Coverage Cont.

I I 0

=1−C f C f e

Hamann, Sabra, 2004

Intrinsic Absorption: Weaker Indicators

● Chemical signatures– Fine structure lines place density limits -> intrinsic

systems (probably) have higher densities● Requires low ionizations – not observed often

– High Ionization and/or Metallicity - N(NV)/N(HI)● Line profiles: broad and smooth ● Statistics: over-density of low-z (w/respect to

quasar) NALs implies these are intrinsic● Properties observed in intrinsic NALs appear

correlated with quasar properties (radio loudness, L etc.

Physical Parameters of Outflows

● Column density ~1022 – 1025 cm-3

● Velocity: 0 < v < 0.2c● Mass loss rate roughly correlated with line

strengths ● Mass loss due

to line driving:● Physical scale: calculate small region, however

variability not observed on short enough time scales (~months) – something else is at work

● Abundances and ionization levels

N =me c

e2 f

M w≃4GM e th

k /31/

Uncertainties in Interpretation● Orientation Angle

– Possibly degenerate with age+evolution– Needed to understand physical environment of QSO!

● Age + Evolution– Shorter lifetimes allow a mixture of ages, evolutionary

states at any given redshift● Lifetimes

– Duty Cycle?

● Shielding/self shielding Uinner

nγ/n ~ 5 – 10

– Set such that gas at inner edge of wind is at ionizations low enough to be pushed by UV flux (Murray + Chiang, 1995)

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)

Comparison to BH accretion

● Probably Mdotoutflow

~ Mdotaccretion

● Mass loss rate from accretion : Lacc

= η Mdot c2

● Mass loss rate in winds:

Very uncertain! M w≃4GM e th

k /31/

References1)T.A. Barlow, F. Hamann, W.L.W. Sargent, 1997

astro-ph/9705048

2)D.M. Crenshaw, S.B. Kraemer, I.M. George, 2003 ARAA, 41:117

3)F. Hamann, B. Sabra, 2003 astro-ph/0310668

4)N. Murray, J. Chiang, 1995 ApJ 454: L105

5)N. Murray, J. Chiang, S.A. Grossman, G.M. Voit, 1995 ApJ 451: 498

6)D. Proga, J.M. Stone, T.R. Kallman, 2000 ApJ 543: 686

7)M. Urry, P. Padovani, 1995 PASP 107:803

8)R.J. Weymann, R.F. Carswell, M.G. Smith, 1981 ARAA, 19:41