dragon gc simulation project - bao
TRANSCRIPT
DRAGON GC simulation project: million-body simulations of globular clusters
Long Wang PhD student (last year) at Kavli Institute for Astronomy and Astrophysics, Peking University
Collaborator: Rainer Spurzem, Sverre Aarseth, Mirek Giersz, Abbas Askar, Peter Berczik, Thorsten Naab, Riko Schadow and M.B.N. Kouwenhoven
Realistic star cluster simulationsEvolution of maximum star number N
Heggie, 2014, Sexten
GRAPE
GPU (Multi-nodes)
GPU
Heggie, 2014, Sexten
Finished in 2015
Direct N-body code NBODY6++GPU
NBODY6-GPU (single node)
(4 CPU I7-920 cores + 2 GTX 470) NBODY6++GPU (multiple nodes)
Hydra GPU clusters at MPCDF
Nitadori & Aarseth (2012), MNRASWang (2015), MNRAS
https://github.com/nbodyx/Nbody6ppGPU
https://github.com/nbodyx/Nbody6
Dragon GC simulation project
Initial conditions
IMF
Kroupa et al. (1993)
Kroupa (2001)
Chabrier (2003)
Maschberger(2012)
π β
0.1-10 pc
Distribution function
Plummer (1911)
King (1966)
Mass segregation (Subr, 2007)
Rotation (Einsel, 1999)
Primordial binaries
Spatial dist. Orbital dist.
Kroupa (1995)
Uniform Log a
Mass ratio dist.
Random pairing
Kouwenhoven (2007)
Sana (2012)
Build a βsimulation catalogβ of globular clusters (GCs) by direct N-body method with initial large N.For general studies of GC evolution and comparison with observations
Evolution
Single/binary stellar evolution (mass-
loss/transfer)
SSE/BSE (Hurley, 2000 & 2002)
PARSEC (Bressan, 2012)
β¦
Neutron star/Black hole formation
model (kick model)
Hansen (1997)
Hobbs (2005)
ECS
β¦
Tidal field
Tidal shocks
Cluster orbits
For the first step - Initial models
Name DRAGON 1 DRAGON 2 DRAGON 3 DRAGON 4
Label D1-R7-IMF93 D2-R7-IMF01 D3-R7-ROT D4-R3-IMF01
πππ’π 12 Gyr 1.1 Gyr
( π, π£) King π0 = 6 Rotation King π0 = 6
π βπ 7.5 pc 7.56 pc 8.1 pc 3.0 pc
IMF Kroupa (1993) Kroupa (2001)
Binary π1/π2 Random 0.6 π1/π2β0.4 (Kouwenhoven, 2007)
NS Kick 2*VSTAR 265 km/s (Hobbs, 2005)
β’ 160 CPUs + 16 GPUs per simulation on Hydra Cluster (MPCDF)β’ NBODY6++GPU (Wang, 2015)
N 950,000 singles + 50,000 binaries
semi Logarithm uniform distribution (0 .005-50) AU
ecc Thermal distribution
Tidal field Point mass potential (π πΊ = 7.1kpc;ππΊ = 8 Γ 1010πβ)
Neutron star (NS)/black hole (BH) initial velocity (kick models)
No FB
Partial FB
Complete FB
BH final mass vs. zero-age main sequence mass
Initial velocity of NS/BH after supernova explosion vs. final mass of NS/BH
π1βD,NS = 265 km/s (Hobbs, 2005)BH mass fallback (FB; Belczynski, 2002)
Mock observations - Photometry
DRAGON 1 (D1-R7-IMF93) DRAGON 2 (D2-R7-IMF01)
IMF01: πβπΌ
0.08 < π β€ 0.5 πβ; πΌ1 = 1.3π > 0.5 πβ; πΌ2 = 2.3
Johnson B (blue), V (green) and Cousins I (red) using COCOA (Askar, 2014)
MS MSRG RG
AGB AGB
WD WDBinary Binary
BH (245) BH (1037)
Wang (2015), submitted to MNRAS
57.6 pc
IMF93: πβπΌ
0.08 < π β€ 0.5 πβ; πΌ1 = 1.3
0.5 < π β€ 1πβ; πΌ2 = 2.2π > 1πβ; πΌ3 = 2.7
π0 = 4.7 Γ 105πβ
ππΉ = 2.9 Γ 105πβ
ππΉ = 8.8 Γ 105
π0 = 5.9 Γ 105πβ
ππΉ = 2.5 Γ 105πβ
ππΉ = 7.0 Γ 105
40% 60%
BH subsystem evolution
Breen & Heggie (2013)
Mock observations β SBP & VDP
V-band surface brightness profiles (SBPs)
π < 20 πΏβ π > 2.15 πΏβ
line-of-sight velocity dispersion profiles (VDPs)King (1966) model fitting (equal weights of SBP and VDP)King (1966) model fitting (more weight of VDP)
βTwo-coreβ structures - BH & Luminous stellar cores
D2-R7-IMF01
3D2D
Density
Mass to light
Half mass (light) & core radii evolution
β’ Four definitions of core radius:β’ π π: Casertano & Hut (1985) mass-
square weighted method
β’ π ππ: Projected core radius from SBP
β’ π πππ: 3-D core radius from King (1966) model fitting (equal weights of SBP and VDP)
β’ 2-D half light radius π βπ and 3-D half mass radius π β
β’ π ππ (π πππ) and π π ( ) have opposite evolution trends.
β’ π β and π π from Monte-Carlo simulations using MOCCA (MC) are well consistent with NBODY models
D1-R7-IMF93SSE/BSE (Hurley 2000 & 2002)
Mock observations β Color Magnitude Diagram
HST WFPC2 (Piotto, 2002)
Image size scale as π π
β’ Luminosity functionβ’ Cumulative luminosity functionβ’ Completeness function
Summary
β’ We provide the four realistic models of GCs DRAGON1-4 with initially πππ stars for the first time. This is also the first step of Dragon GC simulation project. More GC models will be carried out in the future.
β’ The different IMFs (Kroupa, 1993 & Kroupa, 2001) result in very different concentration features of GCs.
β’ With the BH fallback kick models, large number of BHs are retained in GCs after 12 Gyr and form stable dense BH subsystems in the cluster center.
β’ King (1966) model cannot provide consistent surface brightness profile (SBPs) and velocity dispersion profiles (VDPs) in GCs with BH subsystems. But the inconsistent fitting to SBPs and VDPs can be an observational tool to identify the presence of BH subsystems.
β’ The MOCCA Monte-Carlo models have consistent half-mass radius and core radius evolution as direct N-body models.