Black Hole Outflows

Andrew King

Theoretical Astrophysics Group, University of Leicester, UK

Rome, March 2011

P Cygni profile of iron K- alpha: outflow with v 0.1c

PG1211 + 143 (Pounds & Reeves, 2009)

measured ionization parameter

=> mass outflow rate

=> momentum outflow rate

=> photons scatter ~ once before escaping: Eddington outflow has τ ∼ 1

ξ =Li

NR2∼ 104

Mout = 4πbmpNR2v ∼ 1M⊙ yr−1 ∼ MEdd

Moutv 0.1MEddc ηMEddc =LEdd

c

Pounds et al., 2003; King & Pounds, 2003:

b = Ω/4π > 0.6Tombesi et al., 2010a,b: > 35% of a sample of 50 AGN show similar outflows: solid angle factor

disc

Super-Eddington Accretion

disc

Super-Eddington Accretion

most mass expelled as outflow

disc

most photons eventually escape along cones near axis

Super-Eddington Accretion

most mass expelled as outflow

disc

most photons eventually escape along cones near axis

on average photons give up all momentum to outflow after ~ 1 scattering

Super-Eddington Accretion

most mass expelled as outflow

disc

most photons eventually escape along cones near axis

on average photons give up all momentum to outflow after ~ 1 scattering

Super-Eddington Accretion

most mass expelled as outflow

Eddington outflow X—ray lines with v ∼ 0.1c↔

conversely if we assume Eddington outflow, then mass and momentum conservation =>

v ∼ ηc, ξ ∼ 104

effect on galaxy must be significant

SMBH binding energy

exceeds bulge binding energy

ηMc2

ηMbσ2

swept-up ambient gas, mildly shocked

ambient gas Eddington wind, v ~ 0.1c

SMBH

cooling shocked wind (`momentum – driven’)

outer shock driven into ambient gas

(single scattering limit)

shock pattern near AGN

wind from SMBH

cooling shocked wind snowplough interstellar gas

inner (wind) shock

contact discontinuity

outer (ISM) shock

density

velocity

SMBH

temperature

King, 2010

NGC 4051 Pounds & Vaughan, 2011

evidence for shock structure: other velocity components are present

ionization parameter decreases with outflow velocity as required by mass conservation

evidence for cooling shock

NGC 4051, Pounds & Vaughan, 2011

Pounds & Vaughan, 2011

104 5000 0 5000 104

05×

104

103

coun

ts s

1 bin

1

velocity (km s 1)

self-absorption in limb-brightened shell

blueshifted absorption of continuum

Pounds & Vaughan, 2011

O VIII L velocity profile in PG1211+143 α

effect on galaxy: M – sigma relation (simple derivation)

matter originally distributed so that

with

at radius R total weight of shell is

BH mass grows until Eddington thrust matches this weight, i.e.

or (King, 2003; 2005)

NB: no free parameter

relation is upper limit to (Bacheldor, 2010)

(need to resolve SMBH sphere of influence )

AGN black holes should be below this limit

SMBH – host connection

SMBH in every large galaxy, grown by luminous accretion (Soltan)

but only a small fraction of galaxies are AGN

  SMBH should grow at ~ Eddington rate in AGN

AGN should show outflows

AGN black holes should be underweight

NB: many BH mass estimates assume ! M − σ

-- tendency to overestimate mass and underestimate Eddington factor

frequency of Eddington outflows

Tombesi et al 2010 a, b:

22/42 radio—quiet AGN, 3/5 BLRGs show outflows with

and hence , with very large momentum rates

high frequency solid angles large, : ~ 50% of sample have super—Eddington episodes with significant duty cycles

Rin

observed X—ray column fixed by inner boundary of flow

so if outflow stopped a time ago, we have

Rin

NH 1024m3

bη2

0.1(Rin/100Rs)cm−2

toff 0.2m3M8

bη20.1N23

yr

toff

intermittent outflow

recent!

SMBH – host connection

SMBH in every large galaxy, grown by luminous accretion (Soltan)

but only a small fraction of galaxies are AGN

  SMBH should grow at ~ Eddington rate in AGN

AGN should show outflows

AGN black holes should be underweight

SMBH – host connection

SMBH in every large galaxy, grown by luminous accretion (Soltan)

but only a small fraction of galaxies are AGN

  SMBH do grow at ~ Eddington rate in AGN

AGN do show outflows

AGN black holes are underweight

SMBH – host connection

SMBH in every large galaxy, grown by luminous accretion (Soltan)

but only a small fraction of galaxies are AGN

  SMBH do grow at ~ Eddington rate in AGN

AGN do show outflows

AGN black holes are underweight

X-ray outflows are key to SMBH-galaxy formation link