Web Infrared Tool ShedMark Wolfire and Marc Pound (UMd)

Funded by NASA non-SIRTF money for development

Funded by Legacy project for SIRTF specific calculations

There are two parts:

1. Dust Infrared Toolbox

2. Photodissociation Region Toolbox

Dust Infrared Toolbox

What is it: A web-based tool for fitting data to a pre-calculated database of models and for accessing detail of the models.

Models: The models are currently spherically symmetric cores with central heating sources. There are a broad range of luminosities, Av’s and outer radii, and modest range of density gradients.

And fits: The tool allows minimum chi-squared fitting of observations to a user specified range of models within the database.

SIRTF specific: Models have been calculated with many frequency points across the SIRTF bands and integrated over the response curve.

wits.ipac.caltech.edu or dustem.astro.umd.edu

Opening Page

Details

More DetailsTotal flux versus wavelength with choice of units in axes. Fluxes include both stellar and dust emission.

Intensity versus distance from center for selected wavelengths

Fitting Data to Models

Chi-square calculated for selected model database then best fitted model is flagged and its details can be displayed.

We could automate the data feeding and fitting.

Current Status• Models are being calculated from 10-5 to 5 x

105 solar luminosities• Gas density power laws from 0 to –2 in

steps of 0.5• Central effective temperatures of 1000 K to

40,000 K• Outer radii of 1011 to 5 x 1018 cm• Av of 1 to 5000

The model database is roughly 50% calculated.

It will occupy roughly 12 GB of disk when complete.

Access is not quick due to the large number of I-nodes.

DIRT’s SIRTF Extensions• Luminosities: Extending low luminosity sources down to 10-5 solar luminosities.

• Bands and beams: Model SIRTF fluxes are calculated integrated over the filter functions and using the expected PSF’s.

• Input/output: SIRTF specific interface for data is being planned.

• Dust types: Current calculations are for Draine and Lee dust properties with an MRN distribution (bare grains). New calculations can be done for 1 or 2 additional grain types.

• Non-spherical: Preparations are underway for disk models. Either using Barbara Whitney’s Monte Carlo code or a simple model based on a Goldriech and Chang disk.

What do we expect to see?At distances of 160 pc and 300 pc, the dust emission from low

luminosity YSO envelopes and disks should be unresolved with the SIRTF PSF’s at all wavelengths.

– 1 solar luminosity gives ~45K dust at 100 AU– IRAC PSF is ~2” at 4-8 microns or 300-600 AU– 8 microns emission comes from ~500 K dust– 70 microns emission arises from ~55 K dust but the beam is ~20”

or 3000-6000 AU

The shorter wavelength bands will be great tracers of multiplicity in embedded systems.

– Interesting quantities are luminosities and dust masses. Do we want tools tailered to deriving likely values and uncertainties?

Shocked gas in outflows could be very interesting.– Do we want slab models?

Disk versus spherical model fits fundamentally differ due to the extinction caused by the overlying dust.

– Should we explore combinations of data that highlight this effect?

Our Wish List

• Contour plots of model SIRTF fluxes and flux ratios for various combinations of physical quantities. For example dust mass on the x-axis and central luminosity on the y-axis.

• At least one other dust type. Which one? These calculations take several months to complete due to the large number of models

• What else?

• And more?

wits.ipac.caltech.edu or dustem.astro.umd.edu