PAH revolution with the James Webb Space Telescope

Today, the world is eagerly awaiting the launch of the James Webb Space Telescope (JWST; launch date Oct 2021). Hailed as the bigger and vastly more sensitive successor to the HST, JWST will similarly inspire the general public and have researchers develop the most innovative approaches to process and analyze observations of unprecedented quality to study the Universe near and far.

JWST observations will be dominated by infrared (IR) emission from large carbonaceous molecules (polycyclic aromatic hydrocarbons, PAHs). This emission encodes a large amount of information about the physical and chemical

environments in which they reside and is a powerful messenger to study astrophysical processes such as star and planet formation and galaxy evolution. The best observations to date of astronomical PAH sources yield spectra averaged over regions with vastly different properties, thus greatly confusing their interpretation. JWST’s incredible spatial resolution and sensitivity will disentangle these regions and allow us unprecedented views on PAH characteristics on small spatial scales.

The first few hundred hours of science time with JWST will be used to carry out 13 so-called Early Release Science (ERS) programs. I am leading one of the 13 successful ERS programs: ID 1288 “Stellar Feedback of massive stars" (http://jwst-ism.org). We will observe a very popular astronomical object, the Orion Bar. These observations will be further complemented by observations from General Observers (GO) programs in which I am involved and other ERS programs.

Our group aims to determine the detailed properties of the PAH population (size, shape, charge, composition) in space and their response to changing environments. Graduate projects involve analyses of observational data using modern data processing and machine-learning techniques to characterize the PAH variability, analyses of the dependence of the observed PAH variability on the local physical parameters (e.g. temperature, density, strength of the radiation field, ...) and/or interpretation of these observational results in terms of the properties of the PAH population (e.g. changes in size, shape, charge and composition) by using the NASA Ames PAH IR database (www.astrochem.org /pahdb). These results will represent an important contribution towards the development of PAH diagnostic tools as well as to a better understanding of the cosmic carbonaceous inventory.