The Galactic Center as a laboratory for EMRI dynamics Resonant relaxation
Calibrating resonant relaxation 1
GW inspiral Prompt infall
Inspiral
NR
NR+RR rate / NR rate Q(χ)/Q
10
10
Plunge
0
Rauch & Tremaine 1996
10
−1 −2
10
−1
10
10
0
χ efficiency Resonant relaxation Hopman & Alexander 2005, 2006
10
1
The Galactic Center as a laboratory for EMRI dynamics Resonant relaxation GC constraints on RR
t? vs r
Hopman & Alexander 2006
TNR
104 103 t (Myr)
102 101 10−3
10−2
a (pc)
10−1
1
The Galactic Center as a laboratory for EMRI dynamics Resonant relaxation GC constraints on RR
t? vs r
Hopman & Alexander 2006
TNR
104 103 t (Myr)
102 101
_s
T
10−3
RR
10−2
a (pc)
10−1
1
The Galactic Center as a laboratory for EMRI dynamics Resonant relaxation GC constraints on RR
t? vs r
Hopman & Alexander 2006
TNR
104 103 t (Myr)
102 1
10
_s
T
10−3
Tv RR
RR
10−2
a (pc)
10−1
1
The Galactic Center as a laboratory for EMRI dynamics Resonant relaxation GC constraints on RR
t? vs r
Hopman & Alexander 2006
TNR
104
GW sources
103 t (Myr)
102 1
10
_s
T
10−3
Tv RR
RR
10−2
a (pc)
10−1
1
The Galactic Center as a laboratory for EMRI dynamics Resonant relaxation GC constraints on RR
t? vs r
Hopman & Alexander 2006
TNR
104
GW sources
103 t (Myr)
102 1
10
_s
T
Tv RR
RR
Star disks 10−3
10−2
a (pc)
10−1
1
The Galactic Center as a laboratory for EMRI dynamics Resonant relaxation GC constraints on RR
t? vs r
Hopman & Alexander 2006
TNR
104
GW sources
103 t (Myr)
102 1
10
_s
T
RR
Tv RR
S- stars Star disks
10−3
10−2
a (pc)
10−1
1
The Galactic Center as a laboratory for EMRI dynamics Resonant relaxation GC constraints on RR
t? vs r
Hopman & Alexander 2006
TNR
104
GW sources
103 t (Myr)
102 1
10
_s
T
RR
Tv RR
S- stars Star disks
10−3
10−2
a (pc)
10−1
1
The Galactic Center as a laboratory for EMRI dynamics Resonant relaxation GC constraints on RR
t? vs r
Hopman & Alexander 2006
TNR
104
GW sources
103 t (Myr)
102 1
10
Relaxed giants _s
T
RR
Tv RR
S- stars Star disks
10−3
10−2
a (pc)
10−1
1
The Galactic Center as a laboratory for EMRI dynamics Mass segregation
Mass segregation and the EMRI condition: a0 < acrit
11
10 10
9
0.6 0.4
M
M
S (a)
Fraction of inspirals
r
n (r) [pc−3]; t [Myr]
0.8
0.2 0 −3 10
MS WD NS BH tr
10
WD NS BH
1
10
8
10
7
10
6
10
5
10
4
10
3
10
2
10
1
10
10
−2
(pc) aa [pc] 0
Hopman & Alexander 2006
10
−1
0
10 −4 10
−3
10
10
−2
r [pc]
−1
10
Hopman & Alexander 2006
0
10
The Galactic Center as a laboratory for EMRI dynamics Mass segregation
Mass segregation detection strategies I Direct (Massive objects sinking in) B Dynamical (Rubilar & Eckart 2001; Mouawad et al 2005) I Current upper limit Drain limit (Alexander & Livio 2004)
B X-ray sources (Pessah & Melia 2003; Muno et al 2005) I I Low statistics I Large (∼ 1 pc) scale
B Gravitational lensing (Chanamé et al 2001) I Very low probability (Alexander & Loeb 2001)
B Exotic merger products I Identification? B Collisional destruction I Signature not unique
I Inverse (Light objects floating out) B NSs: radio pulsars (Chanamé & Gould 2002; Pfahl & Loeb 2004) I Hard to detect
B WDs: cataclysmic variables (Muno et al 2003) I Large scale B Horizontal Branch / Red Clump giants
The Galactic Center as a laboratory for EMRI dynamics Mass segregation
Mass segregation detection strategies I Direct (Massive objects sinking in) B Dynamical (Rubilar & Eckart 2001; Mouawad et al 2005) I Current upper limit Drain limit (Alexander & Livio 2004)
B X-ray sources (Pessah & Melia 2003; Muno et al 2005) I I Low statistics I Large (∼ 1 pc) scale
B Gravitational lensing (Chanamé et al 2001) I Very low probability (Alexander & Loeb 2001)
B Exotic merger products I Identification? B Collisional destruction I Signature not unique
I Inverse (Light objects floating out) B NSs: radio pulsars (Chanamé & Gould 2002; Pfahl & Loeb 2004) I Hard to detect
B WDs: cataclysmic variables (Muno et al 2003) I Large scale B Horizontal Branch / Red Clump giants
The Galactic Center as a laboratory for EMRI dynamics Mass segregation
Mass segregation detection strategies I Direct (Massive objects sinking in) B Dynamical (Rubilar & Eckart 2001; Mouawad et al 2005) I Current upper limit Drain limit (Alexander & Livio 2004)
B X-ray sources (Pessah & Melia 2003; Muno et al 2005) I I Low statistics I Large (∼ 1 pc) scale
B Gravitational lensing (Chanamé et al 2001) I Very low probability (Alexander & Loeb 2001)
B Exotic merger products I Identification? B Collisional destruction I Signature not unique
I Inverse (Light objects floating out) B NSs: radio pulsars (Chanamé & Gould 2002; Pfahl & Loeb 2004) I Hard to detect
B WDs: cataclysmic variables (Muno et al 2003) I Large scale B Horizontal Branch / Red Clump giants
The Galactic Center as a laboratory for EMRI dynamics Mass segregation
Mass segregation detection strategies I Direct (Massive objects sinking in) B Dynamical (Rubilar & Eckart 2001; Mouawad et al 2005) I Current upper limit Drain limit (Alexander & Livio 2004)
B X-ray sources (Pessah & Melia 2003; Muno et al 2005) I I Low statistics I Large (∼ 1 pc) scale
B Gravitational lensing (Chanamé et al 2001) I Very low probability (Alexander & Loeb 2001)
B Exotic merger products I Identification? B Collisional destruction I Signature not unique
I Inverse (Light objects floating out) B NSs: radio pulsars (Chanamé & Gould 2002; Pfahl & Loeb 2004) I Hard to detect
B WDs: cataclysmic variables (Muno et al 2003) I Large scale B Horizontal Branch / Red Clump giants
The Galactic Center as a laboratory for EMRI dynamics Mass segregation Low mass test particles
The “Red Clump giants” as low-mass test particles -10
Hot
Cold Bright
-9
Mbol [mag] (-2.5 log L)
-8 -7 -6 -5 -4
"Red Clump giants"
0.5-1.9 Mo, He-burning 0.11 Gyr
-3
Detection threshold
-2 -1
1.5 Mo, H-burning 2.90 Gyr
0 1 3.85
1.0 Mo, H-Burning 13 Gyr
3.80
3.75
3.70
3.65 3.60 log Teff [K] Girardi et al 2000
3.55
3.50
3.45
Faint 3.40
The Galactic Center as a laboratory for EMRI dynamics Mass segregation Low mass test particles
Mean mass [Mo]
Window on old low-mass stellar population 9 8 7 6 5 4 3 2 1 0
GC population synthesis model Alexander & Sternberg
All stars
Old stars (t>109 yr) dlog(N)/dK Old star fraction
8
9
10
11
12
13 14 K [mag]
15
16
17
18
1.0 0.5 0.0 19
The Galactic Center as a laboratory for EMRI dynamics Mass segregation Mass segregation in the GC
Mass segregation in the Galactic Center? 0.04 pc
0.12 pc
0.2 pc
0.4 pc
Sch¨odel et al.: Structure of the GC Star Cluster
17
N E Fig. 1. Colour image composed of ISAAC imaging observations at 2.09 µm and in the J-band. The field-of-view is 15000 × 15000 . The field of about 4000 × 4000 that was observed with AO observations is marked by a square. Blue sources are foreground stars. The patchy and highly variable extinction is evident, as well as the minimum of the extinction on the central cluster.
Schödel et al 2006
The Galactic Center as a laboratory for EMRI dynamics Mass segregation Low-eccentricity EMRIs
Binary disruptions 1. Low-e EMRIs
(Miller et al 2005)
Perets, Hopman & Alexander 2006 2
10
Fast capture by massive perturber−induced relaxation GMC1
1
Observed
No. of MS B−Stars
10
GMC2
0
10
Clusters1 Stars
−1
10
Clusters2
−2
10
0.001
2. Obs: 43±31 HVSs
(Brown et al 2005)
3. MP prediction: Rapid Binary MBH mergers
0.004
0.01
0.04
Semi Major Axis (pc)
0.1
0.4
MP prediction: 50–350 HVSs (Perets & Alexander 2006)
The Galactic Center as a laboratory for EMRI dynamics Summary
Summary
I
GC observations probe EMRI dynamics B Resonant relaxation B Mass segregation in a relaxed system B Binary capture and low-e EMRIs
I
The challenges B Observational: Cutting edge observations B Theoretical: Disentangling star formation and evolution from dynamics
