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Name

mkgalaxy - McMillan-Dehnen composite Disk-Bulge-Halo models

synopsis

mkgalaxy name=basename [parameter=value]

Description

Script for constructing N-body initial conditions for a disc galaxy according to McMillan and Dehnen (2007, MNRAS, 378, 541).

For more detailed documentation see mkgalaxy_user_guide.pdf

Parameters

The following description of the parameters is taken verbatim from the script, and explain the optional parameters. Only name=basename is required.

If spheroid=filename is given, it is assumed to contain halo & bulge adjusted to disc, so it can skip steps 1 and 2. The user must ensure that the parameters match! 

################################################################################
## body numbers (note that for $Mb>0 the bulge will also add bodies)
set Nh=1200000       # number of bodies in halo
set Nd=200000        # number of disc bodies
################################################################################
## disc parameters
set Md=1             # disc mass
set Rd=1             # disc scale radius
set Zd=0.1           # disc scale height (rho propto sech^2(z/Zd))
set Rsig=0           # if non-zero, rad. vel. disp. sigma propto exp(-R/Rsig)
set Rdmax=4.5        # maximum disc radius
set Q=1.2            # Toomre’s Q (const if Rsig=0, else value Q(Rsig)
set Nbpo=50          # number of disc bodies sampled per orbit
set ni=4             # number of iterations in disc sampling
set epsd=0.01        # gravitational softening length for disc bodies
################################################################################
## halo parameters
set Mh=24            # halo mass 
set innerh=7/9       # halo inner logarithmic density slope
set outerh=31/9      # halo outer logarithmic density slope
set etah=4/9         # halo transition exponent
set Rcoreh=0         # halo core radius
set Rscaleh=
set Rh=6             # halo scale length
set Rth=60           # halo truncation radius
set betah=0          # halo anisotropy parameter
set r_ah=0           # halo anisotropy radius; 0 maps to infinity
set epsh=0.02        # gravitational softening length for halo bodies
################################################################################
## bulge parameters
set Mb=0.2           # bulge mass
set innerb=1         # bulge inner density exponent
set outerb=4         # bulge outer density exponent
set etab=1           # bulge transition exponent
set Rtb=0            # bulge truncation radius
set Rcoreb=0         # bulge core radius
set Rb=0.2           # bulge scale radius
set betab=0          # bulge anisotropy parameter
set r_ab=0           # bulge anisotropy radius; 0 maps to infinity
################################################################################
## Parameters controlling code
set kmax=3           # maximum timestep = 2^-kmax
set kmin=7           # minimum timestep = 2^-kmin
set fac=0.01         # time step control: tau < fac/|acc|
set fph=0.04         # time step control: tau < fph/|phi|
set tgrow=40         # Disc growth time
set seed=1           # seed for RNGs
set nmax=12          # maximum radial "quantum number" in potential expansion
set lmax=8           # maximum angular "quantum number" in potential expansion
set debug=2          # debug level used to run all falcON programs

Example

The script take a fair amount of CPU. Here is an example with 12000 stars in the halo, and 2000 in the disk (which is 1/100 of the script defaults): 
% /usr/bin/time mkgalaxy name=gal1
mkgalaxy:    building a N-body model of a disc galaxy
mkgalaxy: 0  starting falcON and setting parameters
mkgalaxy: 1  Building the initial spheroid models
mkgalaxy:    creating the initial halo with N=600000 in file gal2.h
mkgalaxy:    creating the initial bulge with N=20000 in file gal2.b
mkgalaxy:    stacking initial halo and bulge in file gal2.s
mkgalaxy: 2  Growing the full disc potential
mkgalaxy:    symmetrize initial spheroid snapshot (and doubling body number)
mkgalaxy:    start simulation to grow disc potential from monopole
mkgalaxy:    (log output into gal2.grow) ...
mkgalaxy: 3  Populating the disc
mkgalaxy:    extracting bulge into file gal2.b (needed for bulge potential)
mkgalaxy:    extracting halo into file gal2.h (needed for halo potential)
mkgalaxy:    creating the initial disc with N=200000 in file gal2.d
mkgalaxy:    stacking all components into file gal2.snp
mkgalaxy:    finished. snapshots generated:
             gal2.snp: complete galaxy model ready to use
4586.25user 94.47system 1:18:01elapsed 99%CPU 
% snapmstat gal2.snp
0 0:199999       =  200000 Mass= 5.32538e-06 TotMas= 1.06508 CumMas=  1.06508
1 200000:239999  =   40000 Mass= 5e-06       TotMas= 0.2     CumMas=  1.26508
2 240000:1439999 = 1200000 Mass= 2e-05       TotMas= 24      CumMas= 25.2651
# Found 3 species:
select=0:199999,200000:239999,240000:1439999

Stage 3 takes a long time.

See Also

mkkd95(1NEMO) , magalie(1NEMO) , mkgalaxy2(1NEMO)

https://ui.adsabs.harvard.edu/abs/2007MNRAS.378..541M/abstract

Ads

@ads 2007MNRAS.378..541M

Files

$FALCON/doc mkgalaxy, mkgalaxy_user_guide.pdf 
file         status                content/meaning                    
    
-------------------------------------------------------------------------- 
1. Building the initial spheroid models                                
   
$name.prm    generated             accfile for "Monopole"              
   
$name.h      generated & deleted   snapshot: initial halo               
  
$name.b      generated & deleted   snapshot: initial bulge              
  
$name.s      generated             snapshot: initial bulge + halo      
   
2.  Growing the full disc potential                                    
    
$name.prm    required  & deleted   accfile for "Monopole"               
  
$name.s      required  & deleted   snapshot: initial bulge + halo       
  
$name.sym    generated & deleted   snapshot: symmetrised $name.s         
 
$name.grow   generated             logfile of gyrfalcON run            
   
$name.S2     generated             snapshot: final bulge + halo
3,  Populating the disc                                               
      
$spheroid    required              snapshot: final bulge + halo       
     
$name.d      generated & deleted   snapshot: initial disc               
   
$name.snp    generated             snapshot: final disc + bulge + halo

Author

Paul McMillan, Walter Dehnen (2007-2010)

History


2007  original version   (PM/WD)
7-feb-2021 Fixes for name collision on Mac   PJT

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