Table of Contents

Name

GalPot - galactic potential descriptor

Description

The GalPot potential (potname=GalPot) describes the Milky Way potential as published in Dehnen & Binney (1998). A number of standard models have been implemented via datafiles in $NEMODAT/GalPot.

The Dehnen & Binney model contains three components: a disk, bulge and halo. The disk is made up of three components: ISM, thin and thick stellar disk, each of them a double (in R and |z|) exponential disk. The bulge and halo are both parameterized flattened spheroids.

Units

There are two implementations of GalPot in falcON:

Units-1

Taken from falcON/src/public/acc/GalPot.cc:
The units differ from those used in class GalPot: we have             
   
                                                                      
   
quantity              | here          | GalPot        | unit             

-----------------------+---------------+---------------+--------------    
unit of length         | 1             | 1             | kpc             

unit of time           | 1 E+9         | 1 E+6         | yr              

unit of mass           | 2.2228847 E+5 | 1             | solar masses     
unit of velocity       | 0.9777753     | 9.777753  E+2 | km/s             
unit of potential      | 0.95604457    | 9.5604457 E+5 | (km/s)^2         
unit of acceleration   | 0.9777753 E-9 | 0.977753  E-6 | km/s/yr          
                                                                      
   
The implied size of Newton’s constant G are                            
  
G = 1                 here                                            
   
G = 4.49865897 E-12   in GalPot units                                   
 

Units-2

Taken from falcON/inc/acc/GalPot.h
The unit system used throughout the classes and functions defined here
and 
in included files is based on the following basic units               
    
    unit of length:        1 kilo parsec (kpc)                        
    unit of time:        1 mega year   (Myr)                        
     unit of mass:        1 solar mass  (Msun)                       
This implies the following dimensions                                 
    
quantity        dimension / seize                using other units    
    
---------------------------------------------------------------------------
angular vel.  1 Myr^-1                 = 977.775320024919 km/s/kpc 
velocity      1 kpc/Myr                         = 977.775320024919 km/s
action/mass   1 kpc^2/Myr                       = 977.775320024919 kpc*km/s

potential     1 kpc^2/Myr^2                     = 956044.576449833 (km/s)^2

acceleration  1 kpc/Myr^2                                              
    
G             4.49865897 E-12 kpc^3/Myr^2/Msun                            
 
4 Pi G        5.65318158 E-11 kpc^3/Myr^2/Msun                            
 

Standard Models

1-4 are their standard models. 2a-i and 4a-i are deviations from standard model 2 and 4.
pot.1    Rd/R0=0.25
pot.2    Rd/R0=0.30
pot.3    Rd/R0=0.35
pot.4    Rd/R0=0.40
pot.2a    Rd/R0=0.30
pot.2b
pot.2c
pot.2d
pot.2e
pot.2f
pot.2g
pot.2h
pot.2i
pot.4a    Rd/R0=0.40
pot.4b
pot.4c
pot.4d
pot.4e
pot.4f
pot.4g
pot.4h
pot.4i
pot.2.1        these an remaining ones are not mentioned in their 1998 paper.
pot.2.2
pot.2.3
pot.2.4
pot.4.1
pot.4.2
pot.4.3
pot.4.4
pot.10
pot.20
pot.40

Examples


  % potlist GalPot potfile=$NEMODAT/GalPot/pot.1 x=1

Environment

The environment variable ACCPATH can be used to search for accelerations in other than the local directory.

See Also

acceleration(3NEMO) , potential(5NEMO)
1998MNRAS.294..429D : Mass models of the Milky Way : Dehnen, Walter; Binney,
James 

Author

Walter Dehnen

Files


$NEMODAT/GalPot        directory with GalPot descriptors

Update History


8-nov-08    created        PJT


Table of Contents