Initial and boundary conditions
Our aim is to choose a model displaying an interesting interplay
of stellar and dynamical evolution, and doable by as many groups as possible.
Useful guidance is offered by Hurley et al, MNRAS, 2001, 323,
630, whose model with Ns = Nb = 5000
took 1 month on a GRAPE 4.
Specification
Structure
-
King, W0=5
-
no initial mass segregation
Boundary condition
-
rt = 27.9pc (initially)
-
tidal cutoff
Single stars
-
Ns = 12288
-
IMF of single stars: KTG3*, 0.1M<m< 100M, where M is 1 solar mass
*Kroupa, Tout & Gilmore, MNRAS, 1993, 262, 545; eq.(14) & Table
10 with alpha1=1.3
Primordial binaries
-
Nb = 4096
-
f(e) = 2e
-
total binary mass: KTG1 (see Hurley et al, eq.(1)), range [0.2M,200M]
-
mass ratio q<1, uniform in range giving masses in [0.1M, 100M]
-
a: uniform in log a in a range such that a(1-e) > 2(R1+R2)
and energy exceeds 10kT. Here radii are fromEggleton, Fitchett &
Tout, 1989, ApJ, 347, 998
Stellar evolution
Discussion (under construction)
N = 20480, fb = 0.25m, Ns + Nb
= 16K
For the initial data generated for this project, the total mass is
approximately 10174M. For a point-mass galaxy, galactocentric
distance RG=8.5kpc, circular velocity vG = 220km/s,
rt = 27.9pc approximately.
=> M ± 813000MM
=> lifetime ± 7.6Gyr (V&H)
(=>30% in [10kT,100kT])
Possible sources:
Single stars: Eggleton, Fitchett & Tout, 1989, ApJ, 347,
998
Binary stars: Tout, Aarseth, Pols, 1997, MNRAS, 291, 732
Portegies Zwart, McMillan, Hut, Makino, 2001,
MNRAS, 321, 199 (and references therein)