NGC 3603 PDR region

Ultraviolet photons from O and B stars strongly influence the structure and emission spectra of the interstellar medium. The UV photons energetic enough to ionize hydrogen \(h\nu > {\rm 13.6 eV}\) will create the H II region around the star, but lower energy UV photons escape. These far-UV photons (\(6~{\rm eV} < h\nu < {\rm 13.6~eV}\)) are still energetic enough to photodissociate molecules and to ionize low ionization-potential atoms such as carbon, silicon, and sulfur. They thus create a photodissociation region (PDR) just outside the H II region. In aggregate, these PDRs dominates the heating and cooling of the neutral interstellar medium. The gas is heated by photo-electrons from grains and cools mostly through far-infrared fine structure lines like [O I] and [C II].

The PDR Toolbox is a science-enabling tool for the community, designed to help astronomers determine the physical parameters of photodissociation regions from observations. Typical observations of both Galactic and extragalactic PDRs come from ground- and space-based millimeter, submillimeter, and far-infrared telescopes such as ALMA, SOFIA, JWST, Spitzer, and Herschel. Given a set of observations of spectral line or continuum intensities, PDR Toolbox can compute best-fit FUV incident intensity and cloud density based on our models of PDR emission. One can also fit H2 rovibrational emission excitation diagrams to determine temperature and column density.

The current version is 2.1.1 (released August 24, 2021)


Coming Soon: KOSMA-tau PDR models

The next release of pdrtpy (~Sept 2021) will include KOSMA-tau PDR models for both clumpy and non-clumpy media. This will provide users the ability to easily compare their observations to models from different PDR codes using the dandy tools in the PDR Toolbox.


Please remember to cite use of the PDR Toolbox!
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Citing PDR Toolbox

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History

Twenty years ago, when we started the Photodissociation Region Toolbox (PDRT), web programming meant Common Gateway Interface and Perl was King. Single pixel detectors were cutting edge technology and the sub-mm window had just begun to be explored. Airline travel was pleasant and people still smoked cigarettes. We put together PDRT with Perl, HTML, Apache 1.3, FITS files, CVS, shell scripts, thumb tacks, horsehair, and bits of string. The tool filled a need, scratched an itch, developed an international user base. As new telescopes arrived, we added spectral lines and low metallicity models. Web-free scripting interfaces were created by users. Our funding ran out, but we added lines when users requested and kept the service running. Single pixel detectors gave way to pixel arrays and the sub-mm science matured. Recently, we received funding to implement upgrades described here. Let us know which are most important to you and what else you'd like to see!

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