HTML automatically generated with rman

## Name

mktabdisk - create a test disk with density, circular velocity and dispersion given by a table

## Synopsis

mktabdisk [parameter=value]

## Description

mktabdisk creates an idealized test disk with a given tabular form of density, circular velocity and velocity dispersion as function of radius. It can also optionally compute the asymmetric drift correction.

For clarity the Asymmetric Drift Correction output is split in three: a density, velocity and dispersion related component. They are linear, but recall they are added (or subtracted) in quadrature, so we print the sign of the correction as well. See EXAMPLES below. The three are (many references in the literature with some assumptions of isotropicity):

```     adc_D^2 = S^2 dlnD/dlnR
adc_V^2 = S^2 (1-dlnV/dlnR) / 2

```
Normally only the adc_V^2 term increases the rotation curve, the other two act like an outward bound force, and subtract from the rotation curve to give the observed streaming velocity.

## Parameters

The following parameters are recognized in any order if the keyword is also given:
in=
out=
Output file name in standard snapshot(5NEMO) format.
nbody=
Number of disk particles [2048]
rmin=
rmax=
mass=
Rescale total mass to this?. By default not scaled, if a positive value given, this will be the total mass [1.0]
seed=
sign=
Sign of Z-angular momentum vector of disk. +1 means counter clock wise. [1]
Produce a table of Asymmetric Drift Corrections. If choosen, a simple ascii table with 7 columns is printed: rad, den (D), vel (V), sig (S), adc_D, adc_V, adc_S, vobs [f]
mode=
Select mode of initial conditions. 1: regular in Radius, but random in Theta. nbody= will be exact. 2: cartesian grid, but keeping within rmax. nbody= will be approximate. [1].
sigmaz=
Scaling factor by which the vertical velocity dispersions are computed compared to the (isotropic) planar. Remember this is a toy model. The default is 3D isotropic, but use sigmaz=0 if you want a truly planar disk in all phase space coordinates [1].
Text headline for output file [default: not used].

## Examples

Here is an example of producing the ADC table of an exponential disk with an isothermal halo rotation curve and constant velocity dispersion at 10% of the peak velocity:
```     nemoinp 0:5:0.2 | tabmath - - ’exp(-%1),%1/sqrt(1+%1**2),0.1’ > tab1
0.2  0.818731   0.196116  0.1  -0.0447318 0.0145238 0      0.191498
0.4  0.67032    0.371391  0.1  -0.0632403 0.0261482 0      0.3669
0.6  0.548812   0.514496  0.1  -0.0774612 0.036386  0      0.509931
...
4.6  0.0100518  0.977176  0.1  -0.214485  0.0690972 0      0.955847
4.8  0.00822975 0.97898   0.1  -0.219031  0.0692244 0      0.956671
5.0  0.00673795 0.980581  0.1  -0.223867  0.0693351 0      0.957199
```
or a colorful plot with various velocity components plotted, and where the V/sigma < 1 in the nuclear region
```     nemoinp 0.001,0.1:15:0.1 | tabmath - - ’exp(-%1),%1/sqrt(1+%1**2),0.4-0.3*%1/(1+%1)’
> tab2
tabplot tab2.adc 1 3,4,5,6,7,8 0 16 -0.5 1.1 line=1,1,1,1,1,2 color=3,4,2,3,4,3
ycoord=0 xcoord=1
```

## Caveats

The current version distributes particles regularly by radius, but randomnly in angle.

mkdisk(1NEMO) , snapshot(5NEMO)

## Files

\$NEMO/src/nbody/init/mktabdisk.c

Peter Teuben

## Update History

```16-may-2020    V0.1 drafted    PJT