Photo-dissociation regions in the interstellar medium
25 Apr 2018






interstellar medium.png​Photo-dissociation regions (PDRs) are parts of the interstellar medium where the gas is predominantly neutral but where far-UV photons play a significant role in the chemistry and/or the heating. On one side of the PDR is the hot gas from a young star, on the other, the cold ambient material the PDR is pushing into. 

Studying nearby regions, like the famous Orion bright bar and the Horsehead nebula, gives us knowledge on rapid variations in the dust and gas components as a function of excitation and physical conditions. 

Pamela Klaassen will use the unique capabilities of NIRCam and MIRI on the JWST to study the key spectral features, as well as the main H2 and ionised gas lines at these dissociation fronts.

These studies will then be compared to longer wavelength studies with telescopes such as ALMA​ to study how these photo-dissociation regions interact with the cold gas and dust in the ambient medium.

At the edges of these large PDRs, large scale pillars are being revealed, compressed, and pushed, directly affecting how the next generation of stars are formed.  Such pillars, like the “Seahorse” in Carina (see figure) show clear evidence for forming the next generation, either through dense condensations (shown in blue) or protostellar jets at each knot in the pillar (shown in white), or a combination of the two. Other, similar pillars show now evidence for the next generation of stars, and the most pressing question in this context is: why?

For further information about our research on photo-dissociation regions please contact: Pamela Klaassen​​