Mapping the rapidly evolving interstellar medium of emerging young star clusters

Thanks to JWST’s game-changing capabilities the critical but poorly understood process of star cluster emergence from their natal clouds can be observed at parsec scales in a range of extragalactic environments beyond the Local Group (distances larger than 1 Mpc), enabling to study a broader range of environments more representative of the star-forming galaxies accessible in the Universe.

Our FEAST-NIRCAm imaging studies sampling stellar continua and Paschen alpha(Paa, 1.87 micron) and Bracket alpha(Bra, 4.05 micron) of the spiral galaxy NGC628 reveal ~1800 candidate emerging clusters (eYSCs).

Within this large sample, variations in their spectral energy distribution (SED) and mid-infrared colors suggest a rapid evolutionary sequence of the HII (ionised gas) and photo-dissociation regions (PDRs) as the clusters clear their surroundings. The details of this fundamental process can only be established through spectroscopy.

In Cycle 2, I have secured observing time (GO3503, PI Adamo) with JWST NIRSPEC multi-object spectroscopy (MOS).

A representative example of ~100 eYSCs will be simultanesouly observed by acquiring spectroscopy of their 1-5 micron SED in NGC 628. This newly created FEAST-NIRSPec project is the first of its kind in terms of observing strategy and science goals.

The requested SNSA fundings will support a 3-year postdoc position (100%) within my group and a fraction of my research time (20%). The post-doc will work in close collaboration with a large international team.

The goals of this research project are: 1) Diagnose stellar feedback (e.g., photoionisation and shocks) using hydrogen and helium recombination lines and de-excited iron transition. 2) Explore the properties of warm molecular gas from molecular hydrogen (H2) emission and its relationships to the rapidly evolution of the PDRs during the dissolution of the natal molecular material. 3) Extend our understanding of PAH properties by resolving the strengths of the 3.35 micron PAH emission in its fundamental (aromatic and aliphatic) components as a way to chart the evolution of dust properties as clusters emerge.

These unprecedented results can only be achieved with JWST spectroscopy and will be fundamental to inform our understanding of the separation of star clusters from their molecular fuel supplies while also informing radiative models used to study the larger scale IR emission of local and distant galaxies.