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rhobocop - density bootstrap computing program


rhobocop < parameter_file


rhobocop (Density BOotstrap COmputing Program) is a standard F77 program to evaluate several quantities of interest in N-body systems. It gives you the density and velocity profiles in spherical shells centered on the density maximum of the system considered. For each measured quantity it gives the associated error due to finite N-sampling. This is made employing standard bootstrap method (see Efron & Tibshirani:’An Introduction to the Bootstrap’, Chapman & Hall, 1993; Heyl, Hernquist & Spergel Apj, 427,165). Multi system data (e.g. cosmological simulations containing many separate halos) can be examined.

Comments and feedback are welcome! (see AUTHOR below)

Input file must be in SNAP205 ASCII or TIPSY ASCII format. Output files are in ASCII.

Input Parameters

The input parameters can be entered interactively, as the program reads from standard input. You can also prepare an input parameter file, and run the program in ’batch’ mode as given on the SYNOPSIS line. The input parameters are, in order:
Input file:
name of input file
Root name:
4 chars identifying the root of output files’ names
First & last:
first and last indexes of particles in the input file considered by RhoBoCoP
multi system option:
1 if you need to translate to a particular region. If you use this, two new keywords are introduced:

x,y,z: coordinates of

the subsystem center

radius: cutoff radius for particles to be examined (i.e. the radius if the individual system under study

nmin,facr & radius:
the center of the system under study is found iteratively removing the external particles starting at "radius" and obtaining the center of mass at each step reducing the radius by a factor "facr" (<1 !!) until the number of particles remaining in the sphere considered is less then or equal to "nmin".

nmin best value is strongly dependent from the steepness of the density profile, for homogeneous systems is recommanded to use nmin near the total number of particles, otherwise the center of density will be chosen in an almost random way!!

particles per bin:
number of particles in each shell (min number is really problem dependent, but usually > 32)
Number of resamplings:
number of reboot cycles, usually a number comparable to the number of particles for individual shells
Random seed:
a (big) integer used to initialize pseudo-random generator.

An example paramter file:

king           input file name
1            input file name type
king          root file name
1 4096          first and last
0              multi-system option
256,0.95,3    nmin, facr & radius
128         particles per bin
64          number of resamplings
1234567890    random seed

Output Files

Several (ASCII) output files are created (xxxx is the root input filename)
xxxxrho        r    r^1/4    Log(r)    rho(r)    errrho(r)    m(r)    errm(r)
xxxxrms        r    vrmsr    err    Vrmsth    err    Vrmsph    err
xxxxvel       r    <vr>    err      <vtheta>    err    <vphi>    err
xxxxsigma    r    sigmar    err    sigmat    err    sigmaph    err    beta    err
r            = mean radius of particles belonging to each shell
rho(r)       = density in each shell
errrho(r)    = 1-sigma error on density of each shell
m(r)         = cumulative mass function
errm(r)      = 1-sigma error on m(r)
vrmsr        = root mean square of radial velocity at radius r
vrmsth       = root mean square of theta velocity  at radius r
vrmsph       = root mean square of phi   velocity  at radius r
err          = 1-sigma error of previous estimated quantity
<vr>         = mean radial velocity  at radius r
<vtheta>     = mean theta  velocity  at radius r
<vphi>       = mean phi    velocity  at radius r
sigmar       = standard deviation (sigma)  for radial velocity at radius r
sigmat       = standard deviation (sigma)  for theta velocity at radius r
sigmaph      = standard deviation (sigma)  for phi velocity at radius r
beta          = anisotropy parameter as in Jeans Equation;
           beta=1-(sigmath**2/sigmar**2)In source file, expressions for
           formulations of anisotropy parameters are available; since a
bootstrap is 
           made, beta is not simply the result of a calculation on other
columns in
           file; ( f(<q>) not always equal to <f(q)>!!).


$NEMO/usr/governato/    (location in NEMO)
 rhobocop.f    the source code
 rhobocop.doc    this document
 king            King model W0=7 N=4096 (SNAP205 format)
 rbpar        parameters for analysis of king


F. Leoni (contact: & F. Governato


10-dec-1994       V1.1 released version    FL&FG 

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