dynamical constraints on the intermediate mass black holes (imbhs)
DESCRIPTION
Dynamical constraints on the Intermediate Mass Black Holes (IMBHs). Michela Mapelli collaborators: Andrea Ferrara, Monica Colpi, Andrea Possenti, Steinn Sigurdsson, Nanda Rea. SISSA. 1. What are the IMBHs?. - PowerPoint PPT PresentationTRANSCRIPT
Dynamical constraints on the Dynamical constraints on the Intermediate Mass Black Holes (IMBHs)Intermediate Mass Black Holes (IMBHs)
Michela MapelliMichela Mapelli
collaborators: collaborators: Andrea Ferrara, Monica Colpi, Andrea Andrea Ferrara, Monica Colpi, Andrea Possenti,Possenti, Steinn Sigurdsson, Nanda ReaSteinn Sigurdsson, Nanda Rea 11
SISSASISSA
What are the IMBHs?What are the IMBHs?
BHs with mass ~ 20- 5 x 10BHs with mass ~ 20- 5 x 1044 Msun Msun
What is their origin?What is their origin?
- runaway collapse of stars in young - runaway collapse of stars in young clusters clusters (Portegies Zwart & McMillan 2002)(Portegies Zwart & McMillan 2002)
- repeated mergers of a binary BH seed - repeated mergers of a binary BH seed with BHs and stars in globular clusters with BHs and stars in globular clusters (Miller & Hamilton 2002)(Miller & Hamilton 2002)
- remnants of first massive stars - remnants of first massive stars (Heger (Heger et al. 2002)et al. 2002)
22
How can we detect IMBHs?How can we detect IMBHs?
Gebhardt, Rich, Ho Gebhardt, Rich, Ho 20052005
G1: G1: the interpretation of the interpretation of
the surface the surface brightness profilebrightness profileand of the velocity and of the velocity
profile on the basis of profile on the basis of axisymmetric general axisymmetric general models suggests the models suggests the
presence of a presence of a 1.8 (+/- 0.5) x 101.8 (+/- 0.5) x 1044
Msun IMBHMsun IMBH
33
How can we detect IMBHs?How can we detect IMBHs?
Van den Bosch et al. Van den Bosch et al. 20052005
M15: M15: the interpretation of the interpretation of
the surface the surface brightness profilebrightness profileand of the velocity and of the velocity
profile on the basis of profile on the basis of axisymmetric general axisymmetric general models suggests the models suggests the
presence of apresence of adark central massdark central mass500 (- 500, +2500) 500 (- 500, +2500)
Msun Msun
44
How can we detect IMBHs?How can we detect IMBHs?
Colpi, Mapelli, Possenti 2003Colpi, Mapelli, Possenti 2003
NGC6752: NGC6752: - high concentration of dark - high concentration of dark matter (1000 Msun) from the matter (1000 Msun) from the
acceleration of the 3 acceleration of the 3 innermost millisecond pulsars innermost millisecond pulsars (Ferraro et al. 2003; D'Amico (Ferraro et al. 2003; D'Amico
et al 2002)et al 2002)
- peculiar position (far from - peculiar position (far from the GC center) of the the GC center) of the
millisecond pulsar A and C:millisecond pulsar A and C:
only 4-body interactions with only 4-body interactions with a binary IMBH can explain the a binary IMBH can explain the
position of PSRAposition of PSRA
55
ULXs?ULXs?
ULXs:= X-ray sources with LX>1039 erg s-1
SMBHs accreting at sub-Eddington rate
HMXBs with mild beaming
Cons: far-off from the galactic center
Cons: ionized nebulae around ULXs
IMBHs
Cons: too exotic..
How can we detect How can we detect IMBHs?IMBHs?
66
PART 1: PART 1:
unvealing binary IMBHs unvealing binary IMBHs in globular clusters in globular clusters
via 3-body encounters via 3-body encounters
PART 2: PART 2:
dynamical constraints on the dynamical constraints on the number of IMBHs in the Milky number of IMBHs in the Milky
WayWay
OUTLINEOUTLINE::
77
PART 1: PART 1:
unvealing binary IMBHs unvealing binary IMBHs in globular clusters in globular clusters
via 3-body encounters via 3-body encounters
88
BASIC IDEA:BASIC IDEA:
BINARY IMBHs are expected to often (~million years)interact with cluster stars
How can we detect How can we detect IMBHs?IMBHs?
Do cluster stars conserve any memory of this interaction (angular momentum, velocity)?
We run 3-body simulations (binary IMBH + incoming star)
99
SIMULATIONS:SIMULATIONS:
What binaries we consider?
- M1+M2 = 60-210 Msun
- M2/M1 = 1/2 – 1/20
- a = 1, 10, 100, 1000 AU
- e =0.7 (thermally averaged value)
What incoming stars?
- m = 0.5 Msun
FEBO (FEw BOdy Interactions; Colpi, Mapelli &
Possenti 2003)Integrator Runge Kutta 5th order
3- and 4-body interactions
1100
SIMULATIONS:SIMULATIONS:
What the host globular cluster?
We consider a DENSE CONCENTRATED cluster (NGC6752)
- v1D = 4.9 km/s (Dubath, Meylan & Mayor 1997)
- n ~ 105 #/pc3
- DOUBLE King!
- indications of a binaryIMBH (Colpi, Mapelli, Possenti 2003)
1111
3-body interactions :3-body interactions :
During a 3-During a 3-body body
interaction interaction with a HARD with a HARD
binary, binary, the incoming the incoming star acquires star acquires kinetic energy kinetic energy
from the from the binary, which binary, which
hardenshardens1122
3-body interactions :3-body interactions :
During a 3-During a 3-body body
interaction interaction with a HARD with a HARD
binary, binary, the incoming the incoming star acquires star acquires kinetic energy kinetic energy
from the from the binary, which binary, which
hardenshardens1313
RESULTS of SIMULATIONS:RESULTS of SIMULATIONS:
- SUPRATHERMAL STARS
-ANGULAR MOMENTUM ALIGNMENT
1414
SUPRATHERMAL STARs:SUPRATHERMAL STARs:
Stars which after the encounter remain bound to the cluster, but acquire HIGH velocity (from 3 sigma to the escape velocity)
1155
ANGULAR MOMENTUM ANGULAR MOMENTUM ALIGNMENT:ALIGNMENT:
IF
THE BINARY TRANSFERS ANGULAR MOMENTUM TO THE INTERACTING STAR
1616
ANGULAR MOMENTUM ANGULAR MOMENTUM ALIGNMENT:ALIGNMENT:
Angular momentum alignment only if Angular momentum alignment only if the binary is wide!the binary is wide!
a =10 AUa =10 AU a =100 AUa =100 AU
1177
ARE ARE SUPRATHERMAL STARS SUPRATHERMAL STARS
AND AND ANGULAR MOMENTUM ANGULAR MOMENTUM
ALIGNMENT ALIGNMENT OBSERVABLE EFFECTS?OBSERVABLE EFFECTS?
1188
NUMBER OF SUPRATHERMAL NUMBER OF SUPRATHERMAL STARS:STARS:
f = fraction of suprathermal (from our simulations)
Total number of interacting stars
N ~ 130 - 300
1199
IMPORTANT TIMESCALES:IMPORTANT TIMESCALES:
HARDENING TIMESCALE (Quinlan 1996)
HALF MASS RELAXATION TIMESCALE (Binney & Tremaine 1987)
GRAVITATIONAL WAVE TIMESCALE (Peters 1964; Quinlan 1996)
2200
IMPORTANT TIMESCALES:IMPORTANT TIMESCALES:A binary IMBH can form only in the early stages of the GC life
Because of the hardening, current IMBH binaries have a <= 1 AU
Because of the gravitational wave emission a >= 0.2 AU
Because of the half mass relaxation time, only suprathermal produced in the last 2-3 trh survive
No angular momentum No angular momentum alignmentalignment
N ~ 90-180N ~ 90-1802211
SELECTION EFFECTS:SELECTION EFFECTS:
-PROJECTION EFFECTS: 80 % of suprathermals
-only MS, HB and RGB STARS with 0.6< m/msun < 0.9 are observable: 45 % of suprathermals
N ~ 30-60number of observable supra-thermal stars
2222
RADIAL DISTRIBUTION of suprathermal RADIAL DISTRIBUTION of suprathermal stars:stars:
How do suprathermal stars evolve in the cluster How do suprathermal stars evolve in the cluster beforebeforethermalization and what is their radial thermalization and what is their radial distribution?distribution?We integrate the dynamics of suprathermal, We integrate the dynamics of suprathermal, accounting for:accounting for:
- cluster potential;- cluster potential;- dynamical friction;- dynamical friction;- kick interactions with other stars;- kick interactions with other stars;
We use an upgraded version of the code by We use an upgraded version of the code by Sigurdsson & Phinney (1995)Sigurdsson & Phinney (1995)
2233
RADIAL DISTRIBUTION of suprathermal RADIAL DISTRIBUTION of suprathermal stars:stars:
~ 30 (half of the ~ 30 (half of the total) suprathermal total) suprathermal stars are within 6 stars are within 6 core radii !core radii !
No substantial No substantial difference with difference with respect to the respect to the distribution of RGBs distribution of RGBs in the clusterin the cluster
2244
SummarySummary The main effects of 3-body interactions The main effects of 3-body interactions between a binary IMBH and cluster stars between a binary IMBH and cluster stars are:are: - suprathermal stars;- suprathermal stars; -angular momentum -angular momentum alignment.alignment. The angular momentum alignment is The angular momentum alignment is significant only if the binary is wide significant only if the binary is wide is not observable for current IMBH is not observable for current IMBH binariesbinaries
The observable suprathermal stars are The observable suprathermal stars are only 30-60only 30-60 very difficult to observe!very difficult to observe!
2255
FuturFuture:e: Are OBSERVATIONS possible?Are OBSERVATIONS possible?
- HST/STIS had a error of 1-2 km/s- HST/STIS had a error of 1-2 km/s
- HST/WFPC2 and HST/ACS can achieve a - HST/WFPC2 and HST/ACS can achieve a median error ~ 6 km/s in proper motion median error ~ 6 km/s in proper motion measurements for NGC6752measurements for NGC6752
the resolution of current telescopes is the resolution of current telescopes is sufficient.sufficient. The problem is that suprathermal are The problem is that suprathermal are few!few! Van den Bosch et al. (2005)Van den Bosch et al. (2005) find that M15 find that M15 has a high concentration of dark mass and has a high concentration of dark mass and rotates.rotates. They search for suprathermal stars; but do They search for suprathermal stars; but do not find anything.not find anything.
2266
PART 2: PART 2:
dynamical constraints dynamical constraints on the number of IMBHson the number of IMBHs
in the Milky Wayin the Milky Way
2277
How many IMBHs are hidden in the Milky How many IMBHs are hidden in the Milky Way?Way?
••= = bb- -
LL~ 0.02~ 0.02
R. P. van der Marel (2004)
OUR IDEA:OUR IDEA:
CONSTRAIN THE DENSITY OF IMBHs CONSTRAIN THE DENSITY OF IMBHs using the using the
LINK between ULXs and IMBHsLINK between ULXs and IMBHs
Van der Marel (2004)Van der Marel (2004)
2288
ULXs can be IMBHs accreting:
In binary systems
GAS in MOLECULAR CLOUDs (Mii & Totani GAS in MOLECULAR CLOUDs (Mii & Totani 2005)2005)
PROBLEMs:1. LX>1040 erg s-1 only for ~ 1 Myr
3. Few ULXs have certain optical identification with companion stars (Liu et al. 2005)
Only 1 galaxy in 103-104 may harbor 1 ULX with LX>1040 erg s-1 (Madhusudhan et
al. 2005) 2. Simulations of accreting IMBHs show too many high luminosity (LX>1040 erg s-1 ) ULXs (Madhusudhan et al. 2005)
2299
No ULXs are detected in the Milky Way.No ULXs are detected in the Milky Way.
What is the maximum density of IMBHs for which no ULX is What is the maximum density of IMBHs for which no ULX is expected to form in the Galaxy due to IMBHs accreting expected to form in the Galaxy due to IMBHs accreting
molecular gas?molecular gas?
BASIC IDEA:BASIC IDEA:
3300
SIMULATIONS:SIMULATIONS:
Milky Way model with embedded IMBHs Milky Way:- 1.3 x1012 Msun NFW rigid halo
- 4 x 1010 Msun disk
- 1 010 Msun bulge
Public code GADGET 2 (Springel 2005)
3311
SIMULATIONS:SIMULATIONS:
Milky Way model with embedded IMBHs
Free code GADGET 2 (Springel 2005)
IMBHs:
- HALO population: NFW or Diemand, Madau & Moore (2005; DMM) for IMBHs born in a fluctuation
- 1 04 Msun each one
- different densities: 0.1-10-5 b
(106 - 500 IMBHs)
3322
Deriving the NUMBER of ULXs:Deriving the NUMBER of ULXs:
Our simulation with the IMBHs: • = 10-3 b DMM
3333
Deriving the NUMBER of ULXs:Deriving the NUMBER of ULXs:
We define a molecular disk: z=75 pc; R~20 kpc
And we select the IMBHs which are passing through this disk
3344
Deriving the NUMBER of ULXs:Deriving the NUMBER of ULXs:
We define a molecular disk: z=75 pc; R~20 kpcVolume fraction of molecular disk occupied by clouds: f~0.017 (Agol & Kamionkowski 2002)
We extract from our simulations a fraction f of the IMBHs passing through the molecular diskand derive for them the Bondi-Hoyle luminosity:
If Lx > 1039 erg s-1 we consider them
ULXs3355
What is the expected What is the expected efficiency of the efficiency of the
accretion?accretion?IMBHs are able to transfer angular momentum to the gas if their velocity is <~100 km/s (Agol & Kamionkowski)
They are expected to form an ACCRETION DISK
What kind of accretion disk?
THIN accretion disk (Shakura-Sunyaev):efficiency = 0.1
ADAF accretion disk (Quataert & Narayan):efficiency = 0.001
3366
• = 10-3 b DMM NULX = 0.2 +/- 0.2
• = 10-1 b DMM NULX = 40 +/- 6
• = 10-3 b NFW NULX ~ 0
• = 10-1 b NFW NULX = 0.5 +/- 0.5
The upper limit is The upper limit is • • = 10= 10-3-3 bb for a DMM profile for a DMM profile
or or • • = 10= 10-1-1 bb for a NFW profile for a NFW profile
Results for the THIN accretion Results for the THIN accretion disk:disk:
3377
ULX radial and luminosity distribution:
Disagreement with Liu & Bregman 2005
agreement with observations (Brassington 2005)
Results for the THIN accretion Results for the THIN accretion disk:disk:
3388
• = 10-3 b DMM NULX = 0.002 +/- 0.002
• = 10-1 b DMM NULX = 0.5 +/- 0.5
• = 10-3 b NFW NULX ~ 0
• = 10-1 b NFW NULX = 0.007 +/- 0.007
The upper limit is The upper limit is • • = 10= 10-1-1 bb for a DMM profile for a DMM profile
or or • • >> 10 10-1-1 bb for a NFW profile for a NFW profile
Results for the ADAF accretion Results for the ADAF accretion disk:disk:
3399
Can we derive stronger Can we derive stronger constrains, if we constrains, if we
consider the other X-ray consider the other X-ray sources (not only ULXs)?sources (not only ULXs)?
4400
NON-ULX sources due to IMBH NON-ULX sources due to IMBH accreting MOLECULAR or ATOMIC accreting MOLECULAR or ATOMIC
GAS:GAS:
3-phases of atomic gas:
COLD and neutral: T~102 K, n ~ 1 cm-3
WARM: T~104 K, n ~ 0.03cm-3
HOT: T~106 K, n ~10-3 cm-3
Non ULX sources can be due to the accretion of not only molecular, but also atomic, less dense gas
How to model the atomic How to model the atomic gas?gas?
4411
NON-ULX sources due to IMBH NON-ULX sources due to IMBH accreting MOLECULAR or ATOMIC accreting MOLECULAR or ATOMIC
GAS:GAS:
We define an atomic hydrogen disk: z=100pc, R~20kpc
Volume fraction of atomic H disk occupied by COLD H : fCH~0.48 (Agol & Kamionkowski 2002)
Volume fraction of atomic H disk occupied by WARM H : fWH~0.2 (Rosen & Bregman 1995)We extract from our simulations a fraction fCH + fWH of
the IMBHs passing through the atomic H diskand derive their Bondi-Hoyle luminosity
4422
NON-ULX sources due to IMBH NON-ULX sources due to IMBH accreting MOLECULAR or ATOMIC accreting MOLECULAR or ATOMIC
GAS:GAS:Results for the THIN accretion Results for the THIN accretion
disk:disk:
4433
NON-ULX sources due to IMBH NON-ULX sources due to IMBH accreting MOLECULAR or ATOMIC accreting MOLECULAR or ATOMIC
GAS:GAS:Results for the ADAF accretion Results for the ADAF accretion
disk:disk:
4444
Comparison with observations: Comparison with observations:
These are non-pulsated, variable, maybe transient sources, with 1031<Lx<1039 erg s-1 and faint optical counterpart (absorption)
What kind of observed Galactic sources What kind of observed Galactic sources could correspond to them?could correspond to them?
4455
Comparison with observations: Comparison with observations:
We cannot consider all the sources with 1031<Lx<1039 erg s-1 , because we require completeness.
We consider the 2nd IBIS/ISGRI CATALOGUE (Bird We consider the 2nd IBIS/ISGRI CATALOGUE (Bird et al. 2005): survey of the 50% of the Galaxy, from et al. 2005): survey of the 50% of the Galaxy, from
20 to 40 KeV20 to 40 KeV
We consider sources with 1036<Lx<1039 erg s-1 , where the IBIS/ISGRI catalogue is complete
We exclude all the sources identified as HMXBs or LMXBs andall the sources whose spectrum is typical of a NS
ONLY 3 SOURCES in the IBIS/ISGRI ONLY 3 SOURCES in the IBIS/ISGRI catalogue catalogue
(6 expected in the Galaxy)(6 expected in the Galaxy)have 10have 103636<Lx<10<Lx<103939 erg s erg s-1-1 , and are no , and are no
HMXBs/LMXBsHMXBs/LMXBs4466
Comparison with observations: Comparison with observations: THIN DISK THIN DISK ONLY 3 SOURCES in the IBIS/ISGRI catalogue ONLY 3 SOURCES in the IBIS/ISGRI catalogue
(6 expected in the Galaxy)(6 expected in the Galaxy)have 10have 103636<Lx<10<Lx<103939 erg s erg s-1-1 , and are no HMXBs/LMXBs , and are no HMXBs/LMXBs
Sources with 10Sources with 103636<Lx<10<Lx<103939 erg s erg s-1-1 , in our , in our simulations:simulations:
• = 10-3 b DMM NX = 18 +/- 7
• = 10-1 b DMM NX = 1650 +/- 70
• = 10-3 b NFW NX = 0.4 +/- 0.4
• = 10-1 b NFW NX = 148 +/- 21
The upper limit is The upper limit is • • = 10= 10-4-4-10-10-3-3 bb for a DMM profile for a DMM profile
or or • • = 10= 10-3-3-10-10-2-2 bb for a NFW profile for a NFW profile
4477
Comparison with observations: ADAF Comparison with observations: ADAF disk disk ONLY 3 SOURCES in the IBIS/ISGRI catalogue ONLY 3 SOURCES in the IBIS/ISGRI catalogue
(6 expected in the Galaxy)(6 expected in the Galaxy)have 10have 103636<Lx<10<Lx<103939 erg s erg s-1-1 , and are no HMXBs/LMXBs , and are no HMXBs/LMXBs
Sources with 10Sources with 103636<Lx<10<Lx<103939 erg s erg s-1-1 , in our , in our simulations:simulations:
• = 10-3 b DMM NX = 1.2 +/- 1.0
• = 10-1 b DMM NX = 236 +/- 15
• = 10-3 b NFW NX ~ 0
• = 10-1 b NFW NX = 5 +/- 3
The upper limit is The upper limit is • • = 10= 10-3-3-10-10-2-2 bb for a DMM profile for a DMM profile
or or • • = 10= 10-1-1 bb for a NFW profile for a NFW profile
4488
Conclusions: Conclusions: We studied IMBHs accreting molecular/atomic gas through N-body simulations of the Milky Way.
The upper limit of the IMBH density obtained by requiring that no ULX is present in our simulation is 1010-3-3 bb (DMM profile;104 IMBHs in the Milky Way)
for the THIN DISK model and 1010-1-1 bb (DMM profile;
106 IMBHs in the Milky Way) for the ADAF model
If we also consider NON-ULTRA-LUMINOUS X-ray sources, the upper limit is ~1010-3-3 bb (DMM) for the
THIN DISK model and 1010-3-3 -10 -10-2-2 bb (DMM) for the
ADAF
The main uncertainty is the radiative efficiency: do the IMBHs accrete via THIN or ADAF disk (if any) ?
4499
Future: Future:
Our limit is the mass of IMBHS (104 Msun) in our simulations.
Approximatively, we can extend our results (for the ULXs) to lower BH masses using an equation by Mii & Totani (2005)
However, we need higher resolution, in our simulations, to consider lower IMBH masses and to study the effects of DYNAMICAL FRICTION
5500
Thank youThank you
What are the IMBHs?What are the IMBHs?
BHs with mass ~ 20- 5 x 10BHs with mass ~ 20- 5 x 1044 Msun Msun
What is their origin?What is their origin?
- runaway collapse of stars in young - runaway collapse of stars in young clusters clusters (Portegies Zwart & McMillan 2002)(Portegies Zwart & McMillan 2002)
- repeated mergers of a binary BH seed - repeated mergers of a binary BH seed with BHs and stars in globular clusters with BHs and stars in globular clusters (Miller & Hamilton 2002)(Miller & Hamilton 2002)
- remnants of first massive stars - remnants of first massive stars (Heger (Heger et al. 2002)et al. 2002)
5151
SIMULATIONS:SIMULATIONS:
Milky Way model with embedded IMBHs
Free code GADGET 2 (Springel 2005)
IMBHs: - HALO population: NFW or Diemand, Madau & Moore (2005; DMM)
for IMBHs born in a fluctuation
5252
SIMULATIONS:SIMULATIONS:
Milky Way model with embedded IMBHs
Free code GADGET 2 (Springel 2005)
IMBHs: - DENSITY of IMBHs (Volonteri et al. 2003):
- NUMBER of IMBHs in the Milky Way
- 1 04 Msun each one:
- different densities: 0.1-10-5 b (106 - 500 IMBHs)
5353
Mii & Totani (2005)Mii & Totani (2005)
The constraint (THIN DISK)•• =10=10-3-3 bb
corresponding to 104Msun IMBHs
becomes•• =10=10-2-2 bb if we consider 103Msun IMBHs
Can we extend to lower IMBH Can we extend to lower IMBH masses?masses?
5454
Agol & Kamionkowski Agol & Kamionkowski (2002)(2002)Formation of an accretion disK:
Accreted angular momentum
Accretion radius
Density fluctuations of the gas
Keplerian angular momentum due to the BH
5555
Comparison with observations: Comparison with observations:
• = 10-3 b DMM NX = 45 +/-
12• = 10-1 b DMM NX = 4056
+/- 125
• = 10-3 b NFW NX = 5 +/- 4
• = 10-1 b NFW NX = 495 +/-
39These are non-pulsated, variable sources, maybe transient, with 1031<Lx<1039 erg s-1 and faint optical counterpart (absorption)
What kind of observed Galactic sources What kind of observed Galactic sources could correspond to them?could correspond to them?
5656
LUMINOSITY FUNCTIONS:
Mii & Totani (2005) 5757
BH SPECTRUM (no accretion disc):
Beskin & Karpov 2005
5858
DMM profile :
Diemand, Madau, Moore 20055959
DMM profile :
NFW:
DMM:
Diemand, Madau, Moore 2005
Navarro, Frenk, White 1996
6060
Luminosity distributionLuminosity distributionComparison with Comparison with
observations:observations:
+= Antennae (Brassington et al. 2005)
•• = simulations 6161
IMBH density:IMBH density:
Volonteri et al. (2003)
Shapiro (2005); Volonteri & Rees (2005) 6262
SIMULATIONS:SIMULATIONS:
Milky Way model with embedded IMBHs
Milky Way:- 1.3 x1012 Msun NFW rigid halo- 4 x 1010 Msun disk- 1 010 Msun bulge
Free code GADGET 2 (Springel 2005)
IMBHs: - HALO population: NFW or Diemand, Madau & Moore (2005; DMM)
- 1 04 Msun each one
- different densities: 0.1-10-5 b
(106 - 500 IMBHs)6363
Van den Bosch et al. Van den Bosch et al. 20052005
6464
SIMULATIONS:SIMULATIONS:
What the host globular cluster?
We consider a LOOSE cluster (M4)
- v1D = 3.5 km/s (Peterson, Rees & Cudworth1995)
- n ~ 2 x 10^4 #/pc^3
- nearest GC!
- data from Richer et al. 2004
6565
SUPRATHERMAL STARs:SUPRATHERMAL STARs:
Energetic exchanges:
M1=100 Msun; M2=50 Msun
6666
SUPRATHERMAL STARs:SUPRATHERMAL STARs:
Energetic exchanges:
M1=50-100 Msun; M2=10-50 Msun 6767
SIMULATIONS:SIMULATIONS:
The choice of the maximum impact parameter (bmax)
6868
HARD HARD BINARIES :=BINARIES :=
FINAL FINAL VELOCITIES:VELOCITIES:
6969
SIMULATIONS:SIMULATIONS:
FEBO (FEw BOdy Interactions; Colpi, Mapelli &
Possenti 2003)Integrator Runge Kutta 5th order
INITIAL PARAMETERs:
- imperturbed relative velocity u between binary CM and star homogeneous in u
- impact parameter homogeneous in b2
- 3 orientation angles
- phasis of the binary (Hut & Bahcall 1983)
3- and 4-body interactions
7070
SIMULATIONS:SIMULATIONS:
The choice of the maximum impact parameter (bmax)All the events with non-negligible energetic exchange must be considered
We find bmax from the cross-sections by imposing thatall the encounterswith E/E >10-3
are simulated
7171
SIMULATIONS:SIMULATIONS:
What binaries we consider?
- M1+M2 = 60-210 Msun
- M2/M1 = 1/2 – 1/20
- a = 1, 10, 100, 1000 AU
- e =0.7 (thermally averaged value)
What incoming stars?
- m = 0.5 Msun
7272