Accretion wake of recoiled black holes Roya Mohayaee CNRS, Institut d’Astrophysique de Paris Jacques Colin Observatoire de la Côte d’Azur, Nice

Joe Silk University of Oxford

astro-ph/07093321 J-P Lasota conference, Wroclaw 2007

Galaxy (black hole) mergers

BHs at the centre of many galaxies

Galaxy mergers

BH mergers

Emission of gravitational waves

formation of a new

central BH

HST : colliding galaxies in Canis MajorNGC 2207 –IC 2163

Black hole & dark matter

Adiabatic accretion:

ffinal(Efinal,Lfinal) = finitial(Einitial,Linitial)

Initially : initial ~ r-

Black hole & dark matter

(Young 1980, Gondolo & Silk 1999)

Without BH : initial ~ r-

With BH : final ~ r-(9-2)/(4-)

Absolute luminosity (L) of BH in -rays +

L = luminosity factor x ∫2 dV /s luminosity factor = [N <v>/m

2] c4/cm 3/s/Gev2

For M31: Fornasa et al

2007

Galaxy (black hole) mergers

BHs at the centre of many galaxies

Galaxy mergers

BH mergers

Emission of gravitational waves

If isotropic

formation of a new

central BH

HST : colliding galaxies in Canis MajorNGC 2207 –IC 2163

Galaxy (black hole) mergers

BHs at the centre of many galaxies

Galaxy mergers

BH mergers

Emission of gravitational waves

Ejection of the

BH

From the galaxy

If isotropic If anisotropic

formation of a new

central BH

HST : colliding galaxies in Canis MajorNGC 2207 –IC 2163

Ejection of a black hole during galaxies mergers

Ejection of a black hole during galaxies mergers

€

η =m1m2

(m1 + m2)2

=X

(1+ X)2

Spin=zero

X=0.38

Ejection of a black hole during galaxies mergers

spin ≠ 0

recoil velocity 4000 km/s

Campanelli et al 2007

Orbit of an ejected BH

Virial radius

V~0

low high v

high

Density profile of the accretion wake

Cold medium >Bondi-Hoyle accretion (1944) Two-body problem +mass conservation

V

r

(q) dq

(x) dx=(q) dq

Density profile of the accretion wake

Analytic solution for stationary BHs : (r)~ 1/√r

hot medium (e.g. Maxwellian velocity distribution) > Danby & Camm (1957)

V

Jean’s theorem numerical solution for density

Wake density : radius of influence

Wake density : hot versus cold medium

Hot environment

Wake density : hot versus cold medium

Hot environment Cold environment

Constant density contours : large

Constant density contours : reducing

Wake density contoursWake density contours, small

Highest density at the apapsis passage

Virial radius

V~0

low high v

high

Time to reach the apapsis

Initial velocity of BH / escape velocity

Absolute luminosity of a recoiled BH in -rays

L(M,z) = [N <v>/m2] ∫2 dV /s

L= 1025 (1+z)4 (M/Mo) R2cutoff

/s

LBH /L host

galaxy

Diffused -ray background

BH Mass function

Press & Schechter (1974)Density peaks in initially random gaussian field collapse to form ‘‘galaxies’’

Number density of galaxies of mass M at redsift z N(M,z)

Diffused -ray background=H0 ∫∫ t(M,z) L(M,z) N(M,z) dM dr(z)

Time the BH spends at apapsis

1025 (1+z)4 (M/Mo) R2cutofff /s

Press-Schechter mass function

Time spent at apapsis

=H0 ∫∫ t(M,z) L(M,z) N(M,z) dM dr(z)

> 10 -8 cm-2 s-1 sr-1

Future Prospects: Confronting the observations

Future Prospects: Confronting the observations

HESS, VERITAS

MAGIC

GLAST

EGRET

10-

12

10-7

10-11

10-10

10-9

10-8

cm-2 s-1 sr-1

> 10 -8 cm-2 s-1 sr-1