ABSORB(1) TIPSY COMMANDS ABSORB(1)
NAME
absorb - calculate spectra
SYNOPSIS
absorb type spatial_bin_number vel_min vel_max vel_bin_number filename
x y
DESCRIPTION
absorb calculates absorption properties along a sight line specified
by x and y. If x is the string "auto", then the sight line is deter-
mined by a mouse click. The properties calculated depend on the type
parameter which can be either "spectra", "column", "velocity", "dark",
or "star".
If type is "dark" or "star" then filename will contain spa-
tial_bin_number lines corresponding to spatial bins along the line of
sight equally spaced across the active box. Each line contains the
line of sight distance to the center of the bin, the mean mass density
of "star" or "dark" (in gm/cc), the mean velocity of the material in
that bin (in physical km/s, that is with Hubble flow included for cos-
mological simulations), and the effective spatial resolution used in
determining the density. The density is determined in the following
way. For each particle, it is determined whether the line of sight
intersects the smoothing kernel (as set by the smooth command), and if
it does the contribution of the spline kernel to the column density of
each bin which overlaps the kernel is integrated along the line of
sight. The mass density for each bin is then the column density
divided by the bin length, the velocity is the mass weighted veloci-
ties (shifted by a Hubble term for cosmological simulations) of the
particles that contribute to the column density, and the resolution is
the mass weighted smoothing lengths ("h" of the spline kernel).
If type is "column" then filename.col will contain spatial_bin_number
lines as above with each line containing the line of sight distance to
the bin, the total gas mass density, the mass weighted velocity, the
mass weighted temperature, the mass density in HI, the velocity of the
HI, the temperature of the HI, the mass density, velocity and tempera-
ture of the HeI, the mass density, velocity and temperature of the
HeII, the effective resolution, and an estimate of the divergence of
the velocity.
If type is "velocity" then filename.vel will contain vel_bin_number
lines corresponding to equally spaced velocity intervals between
vel_min and vel_max. Each line contains the central velocity of the
bin, the column density per velocity interval of HI (in gm/cm2 per
km/s), the total column density of gas (in atoms/cm2/(km/s)), the neu-
tral fraction of the gas that contributes to the HI column den-
sity(??), the mean temperature of the HI gas, the density of the HI
gas (in atoms/cc), the effective resolution of the HI, the mean tem-
perature of the total gas, the mean temperature squared of the gas,
and the divergence of the velocity of the gas. The column densities
are determined in the following way. Each spatial bin along the line
of sight is divided into 10 (a compile time constant "SUBBIN") sub-
bins. The velocity and temperature of these sub-bins are linearly
interpolated from the adjacent bins. A velocity profile is determined
for the gas in this sub-bin based on thermal broadening and damping
wings. This profile is then integrated over each velocity bin to
determine its contribution to the bin.
If type is "spectra", "column", or "velocity" then filename will con-
tain vel_bin_number lines corresponding to equally spaced velocity
intervals between vel_min and vel_max. Each line contains the central
velocity of the bin, the optical depth to HI absorption, the optical
depth to HeI absorption, the optical depth to HeII absorption, the
total optical depth to HI within the velocity interval (no line broad-
ening), and the optical depth to deuterium absorption,
SEE ALSO
KQ Release 2.2.3a 20 JULY 2006 ABSORB(1)
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