DIRT User Input Help
When you start DIRT,
you are presented with a small window from
which you select the parameters of the models you wish to investigate.
When you press Go!,
all the models that match your inputs will be fetched from the database and
scaled to the chosen distance. Currently, only Spherical Envelope
models are available (so you can't set Surface Density Law or
The model files are large, so
it takes about 0.5 - 1 seconds to load each model. If your parameters match
more than about 50 models, expect to wait close to a minute before the
Selecting Model Parameters
Select the model input parameters for which you wish to
institute a database search. The available parameters are:
Model Type - circumstellar Disk or circumstellar spherical Envelope.
Currently the database contains only Envelopes.
Grain Model - the model of dust grains composition and size
distribution. Currently available Grain Models are:
MRN - from
Mathis, Rumpl, & Nordsieck 1977, ApJ, 217, 425,
using graphite and silicate grains distributed in size, a, as
with optical constants from
Draine & Lee 1984, ApJ, 285, 89
Draine & Lee 1987, ApJ, 318, 485
This is pretty much the 'standard' dust model.
Consult the Dust Grain Opacities page
for further details.
Luminosity - the luminosity in solar units of the embedded star
Effective Temperature - The effective temperature in Kelvin of the
Outer Radius - The outer radius of the envelope or disk in cm.
Models with inner radii varying from 1.0E13 cm up to a factor of 10
smaller than the selected outer radius will be returned.
Density Law - (Envelope models only). The power law exponent for
the density structure of the envelope, that is, p where
(ri) is the density at the inner radius.
Surface Density Law - (Disk models only). The power law exponent p for
the disk surface density where
(ri) is the central surface density (or the innermost
surface density if the disk has a hole in the center).
Temperature Law - (Disk models only). The power law exponent q
for the disk temperature where
T(ri) is the central temperature.
Distance - the distance in parsecs to the source. Model fluxes
and luminosities are scaled appropriately for your chosen distance.
What The Messages Mean
After you click Go, the yellow information line tells you what is
happening while you wait for your models to load. Here is the list
of messages and what they mean:
Looking up models - the database is being queried as to the number
and names of the models which match your inputs. The models are
copied to a disk staging area.
Fetching N models from the database - The matched models (N of
them) are now being sucked into the DIRT applet.
Loading models into plotter - the models are being transferred into
the display (aka the Plot Controller).
Pre-filtering display by Inner Radius - too many models makes for a
confusing plot (too many points to see what is going on) and also
slows down the interactive part of the display. So, if necessary,
DIRT will pre-filter the display
to select only one or two inner radii. The entire range of inner
radii is still available to you. Simply unfilter the range you want
back into the display (using the Filter button on the Plot Controller).
Initializing plotter layout - DIRT is constructing the Plot Controller
Cleaning up - when you quit DIRT
or close the Plot Controller, the temporary files in the staging area
won't allow more than one Plot Controller at a time.
Once the Plot Controller is up, the Go button will be disabled. It will be
reenabled after you close the Plot Controller and the staging area is
Please direct comments, criticisms, corrections
and contributions to Marc Pound
Page last modified:
Tuesday, 10-Jun-2003 14:24:10 EDT.