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rotcurves - rotation curve of a composite potential
rotcurves
name1=potential [parameter=value] ...
rotcurves computes the
rotation curve of a composite mass model. Each component must be supplied
in the form of a potential (see potential(5NEMO)
) from which the forces
determine a rotation curves assuming centrifugal balance. Optionally a Lindblad
diagram can be selected for viewing using mode=omega, and the location
of Lindblad resonances is determined. A choice is also given between a
plot and a table for further processing. An experimental LV option can be
used for radial velocity table along the line of sight distance.
In case
a true rotation curve is requested (mode=velocity) the table contains r,
v, v1, v2, ..., whereas the Lindblad option with mode=omega tabulates r, v,
omega, kappa, omega+kappa/2, omega-kappa/2.
The following parameters
are recognized:
- name1=potname
- Name of first potential, in standard potential(5EMO)
format. No default allowed.
- pars1=potpars
- Parameters for first potential.
Defaults as defined by the potential itself.
- file1=potfile
- Optional file
for first potential. Defaults as defined by the potential itself.
- name2=
- See name1= for second potential
- pars2=
- See pars1=
- file2=
- See file1=
- name3=
- See name1= for third potential
- pars3=
- See pars1=
- file3=
- See file1=
- name4=
- See name1= for fourth potential
- pars4=
- See pars1=
- file4=
- See file1=
NOTE that because of the specific code implementation, you cannot re-use
the same potential, since they share their static code data.
- radii=r1,r2,...
- Radii where to compute the rotation curve. [default: 0:2:0.1].
- axis=x|y|z
- Choice
of axis to compute rotation curve along. The rotation curve is defined from
circular orbits balancing the local gravitational force. [default: x].
- mode=option
- Mode can be velocity or omega, the former selecting the true rotation curve,
the latter a Lindblad diagram. In a Lindblad diagram only the total curve
is given, not the individual components. If a finite pattern speed is given,
it also computes the lindblad resonances, but make sure the OLR is included,
else the program will abort. [default: velocity].
- n=
- For angular velocity
diagrams (mode=omega) this gives the Lindblad resonance to be computed.
By default the classical n=2 is used, from which the ILR and OLR can be
derived. For n=4 the two UHR can be determined etc. [Default: 2]
- r0l=r0,l,radii
- Solar radius, galactic longitude and a list of radii (distances along
the line of sight) to calculate radial velocity for. Experimental, only
in lv mode
- dr=
- If given, the forces along the selected cardinal direction
(see dir=) will be computed via a first order numerical derivative from
two points
- plot=t|f
- Select viewing in form of a plot. [Default: t]
- tab=t|f
- Select viewing in form of a table. [Default: f]
- format=
- printf(3)
style
format specification for each of the columns in tabular output. [Default:
%g]
- xrange=xmin,xmax|xmin
- Range in plot for X-axis, always radius. Two (min
and max), one (min) or zero (autoscaling) values can be given. [default:
autoscaling]
- yrange=ymin,ymax|ymin
- Range in plot for Y-axis, either velocity
or omega. See also xrange=. [default: autoscaling]
- headline=plotlabel_text
- Any optional text, plotted at the top of the plot for identification purposes.
The default is a list of nameX(parsX)
....
- in=table_file
- If supplied, it should
be a table (a file) consisting of velocities (colum 2) vs. radius (column
1) to be checking with the composite model supplied earlier. Some kind of
statistics will be calculated from which the goodness of fit can be derived.
[default: not used].
- cols=rcol,vcol,drcol,dvcol
- The columns must be provided
here in which columns the radius, velocity, error in radius and error in
velocity can be found. The error columns are optional, and if provided error
bars will be plotted on top of the data. A 0 can be used if an column is
not present in the data, although radius and velocity must always be present.
[Default: 1,2].
potrot(1NEMO)
, potlist(1NEMO)
, runbulgerot(1NEMO)
,
potential(5NEMO)
, perorb(1NEMO)
, ROTMAS(1GIPSY)
galfit: https://users.obs.carnegiescience.edu/peng/work/galfit/galfit.html
galphot: http://www.astro-wise.org/portal/howtos/man_howto_galphot/man_howto_galphot.shtml
Sometimes Lindblad diagrams require more resolution in radius near
the center, so radii=0.0001,0.001,0.01,0.02:1:0.02 may do a better job than
radii=0:1:0.02.
Although not really a bug, but a limitation, this program
assumes symmetric potentials, and that circular orbits exist in the selected
plane. For non-axisymmetric potentials the obtained rotation curve is bogus,
and one has to resort to a periodic orbit searching program such as perorb(1NEMO)
.
You can also try and average the results along the X and Y axes, and average.
Rotating potentials are not implemented, except for the search for Lindblad
resonances in mode=omega.
Potentials (name1,2,....) cannot be re-used. Since loadobj(3NEMO)
is used to load the potentials, their static code data is shared. One possible
solution would be to make a physical copy of the .so file from $NEMOOBJ/potential
in the local directory with different names
Peter Teuben
~/src/orbit/potential rotcurves.c
xx-oct-90 V1.0 derived from potlist PJT
28-oct-90 V1.1 spline fit -> lindblad option PJT
8-nov-90 V1.2 in= table implemented PJT
16-nov-90 V1.3 cols= to select optional error colums PJT
12-nov-93 V1.4 added n= PJT
8-apr-97 V1.6 search for lindblad resonances if omega>0 PJT
7-jul-02 V1.7 added format= PJT
mar-2021 V1.2 added dr= to allow for forceless potentials PJT
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