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| .TH DISKSPECTRUM 1NEMO "28 November 0024" | ||
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| .SH "NAME" | ||
| diskspectrum \- global spectrum of a rotating thin disk | ||
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| .SH "SYNOPSIS" | ||
| \fBdiskspectrum out=\fPsnapshot [parameters=values ...] | ||
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| .SH "DESCRIPTION" | ||
| \fIdiskspectrum\fP sets up a ``cold'' disk of test particles | ||
| in the gravitational potential of a user-supplied potential in | ||
| \fIpotential(5NEMO)\fP format. The disk is imagined to be inclined by | ||
| a given inclination and a global spectral profile is computed. | ||
| .PP | ||
| This program was cloned from \fImkdisk(1NEMO)\fP, with which it shares | ||
| a number of keywords. Instead of producing a \fIsnapshot(5NEMO)\fP, it | ||
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| .SH "PARAMETERS" | ||
| The following parameters are recognized in any order if the keyword is also | ||
| given: | ||
| .TP 25 | ||
| \fBout=\fIout_file\fP | ||
| The data are written to this file in \fIsnapshot(5NEMO)\fP | ||
| format . Currently the potential and total energy are stored in the | ||
| Potential and Aux slots of the snapshot. [no default]. | ||
| .TP | ||
| \fBnbody=\fInum_bodies\fP | ||
| Number of bodies particles [default: \fB2048\fP] | ||
| .TP | ||
| \fBpotname=\fIpotential_name\fP | ||
| name of the potential, see \fB$NEMOOBJ/potential\fP for the current | ||
| object repository. The user can supply his own, see \fIpotential(5NEMO)\fP. | ||
| [no default]. | ||
| .TP | ||
| \fBpotpars=\fIpot_pars\fP | ||
| Paramaters to the user supplied potential. The number of parameters | ||
| depends on the potential supplied, the first parameter is reserved | ||
| for the pattern speed. | ||
| [default: not supplied, parameters as defined by potential(5)]. | ||
| .TP | ||
| \fBpotfile=\fIpot_data\fP | ||
| Optional data file(s) to the user supplied potential. | ||
| The number of files depends | ||
| on the potential supplied. | ||
| [default: not supplied, or datafile(s) defined by potential(5)]. | ||
| .TP | ||
| \fBrmin=\fImin_disk_radius\fP | ||
| Inner cutoff radius of test-particle disk. [Default: \fB0\fP]. | ||
| .TP | ||
| \fBrmax=\fImax_disk_radius\fP | ||
| Outer cutoff radius of test-particle disk. [Default: \fB1\fP]. | ||
| .TP | ||
| \fBmass=\fItot_mass\fP | ||
| Total mass of the disk. The default total mass is 0, since this is a | ||
| testdisk. Since there are a few programs that will not like mass-less | ||
| particles, this keyword can be used, or \fIsnapmass\fP | ||
| will have to be used before further action is taken. | ||
| [default: \fB0\fP]. | ||
| .TP | ||
| \fBfrac=\fIfraction\fP | ||
| The fraction that the local velocity dispersion has w.r.t. | ||
| the local rotation velocity. If a number is given, radial and tangential velocity are | ||
| by default taken to be the same, with no Z-velocities. If two numbers are given, | ||
| the first one is the radial dispersion, the second one the tangential | ||
| (currently wihtout any 2*Omega/Kappa correction), and the Z dispersion 0. | ||
| Finally, when 3 numbers are given, random motions in Z are also added. | ||
| [Default: \fB0\fP] | ||
| .TP | ||
| \fBseed=\fIrandom_seed\fP | ||
| Use random number seed. If 0 is given, a random number is generated | ||
| from the time of the day. [default: \fB0\fP]. | ||
| .TP | ||
| \fBsign=-1|1\fP | ||
| Sign of the angular momentum. 1 means counter clockwise rotation in the | ||
| XY-plane (in case you were wondering, | ||
| our galaxy has sign=-1). [Default: \fB1\fP]. | ||
| .TP | ||
| \fBin=\fIinfile\fP | ||
| Input file, in \fIsnapshot(5NEMO)\fP format, of which the positions | ||
| are used as initial conditions. [Default: not used]. | ||
| *** \fI lost the implementation ** \fP | ||
| .TP | ||
| \fBangle=t|f\fP | ||
| Normally the particles are distributed randomly in phase, but setting this | ||
| to true, they will be regularly spread between 0 and TWO_PI. | ||
| Default: f | ||
| .TP | ||
| \fBvrad=\fP | ||
| A constant radial velocity (>0 means outward motion) added to all particles. | ||
| Default: 0. | ||
| .TP | ||
| \fBenergy=t|f\fP | ||
| If random motions are added (see frac=), the energy of each particle will | ||
| change. By setting \fBenergy=t\fP the energy is conserved and the "circular" | ||
| speed will be reduced. This way the guiding center for epicyclic orbits | ||
| will also be conserved. Note that this only applies to motion in XY. | ||
| For stars with too much random motion (if \fBfrac\fP too high), the | ||
| random number generator is run again to ensure conserving the planar | ||
| motion kinetic energy. Default: false. | ||
| .TP | ||
| \fBabs=t|f\fP | ||
| Use absolute value of velocity dispersion instead of fractional. | ||
| Default: f | ||
| .TP | ||
| \fBz0=z0_d,z0_v\fP | ||
| Scaleheight for density dropoff, and circular velocity dropoff. Default: 0,0 | ||
| .TP | ||
| \fBvloss=\fP | ||
| (deprecated) Fractional loss in circular streaming as z increased. Use z0_v now. | ||
| .TP | ||
| \fBheadline=\fImessage\fP | ||
| Text headline for output file [default: not used]. | ||
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| .SH "SEE ALSO" | ||
| mkdisk(1NEMO) | ||
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| .SH "UPDATE HISTORY" | ||
| .nf | ||
| .ta +1.5i +4.5i | ||
| 28-nov-2024 V0.1: cloned of mkdisk to check performance PJT | ||
| .fi |