The observational projects C1 to C3 and related theory projects C5 and C6 cover observations of the habitats of massive stars from tens of parsec to Mpc scales in “typical”, starburst, and AGN host galaxies over 13 billion years of the history of the universe, critically complementing the other project areas in scales, diversity of environments, and cosmic time. A combination of the most sensitive facilities like ALMA and JWST with new wide-field observatories like FYST/CCAT-prime make it possible to reach both the level of detail and statistical robustness to push these studies to the next level. To prepare for the future, critical detector and readout technology development is delivered by projects C7 and C8, as necessary to build a new generation of instruments that speed up the FYST/CCAT-prime surveys in C2 and C3 by an order of magnitude in the later funding phases. In tandem with these developments, the laboratory spectroscopy and modelling of molecular ions done in C4 are critical to fully exploit a suite of new key tracers of massive star-forming environments in the Early Universe, as targeted in C1.
Image credits: C3/C6 from Karoumpis et al. 2022; C4 from Töpfer et al. 2020; C7 provided by N. Honingh; C8 from Klein et al. 2012; Galaxy composite for C1, C2 and C5 is a composite image of NGC 628 with ALMA (orange) and Hubble (blue) data provided by NRAO/AUI/NSF, B. Saxton: ALMA (ESO/NAOJ/NRAO), NASA/Hubble; for the connection to project areas A and B we show Orion.
