Periodic Reporting for period 4 - MSTAR (Massive Star Formation through the Universe)
Berichtszeitraum: 2023-03-01 bis 2025-02-28
This project aims to understand how massive stars and star clusters form, including implications for the origin of supermassive black holes. It has societal importance, since it helps humanity understand the origins of cosmic structures, including galaxies, stars and planets. The overall objectives are to develop new theoretical models and simulations of massive star and star cluster formation and then to test them observationally.
Work on this project has involved a combination of theoretical and observational studies of massive star and star cluster formation. Most effort has focused on how these processes occur in the local universe (WP1-WP4). However, significant progress has also been made in WP5 on an application of massive star formation in the very early universe with relevance to the origin of supermassive black holes (SMBHs). WP1 concerned development of new theoretical models of how individual massive stars form, including semi-analytic radiative transfer models and magneto-hydrodynamic (MHD) numerical simulations. WP2 focused on observational studies of individual massive protostars with the main goal of testing the WP1 theoretical models. This main occurred in the context of the SOFIA Massive (SOMA) Star Formation Survey, led by the PI, using SOFIA-FORCAST, but also with follow-up observations with ALMA, HST, JWST and other telescopes. WP3 involved developing new theoretical models of star cluster formation, including MHD simulations and pure N-Body simulations. WP4 has encompassed our observational studies of young star clusters with a variety of telescope facilities, including ALMA, HST and JWST. WP5 has led to development of a new theoretical paradigm for the formation of all SMBHs from "Population III.1 Seeds", which predicted that all SMBHs form very early in the universe. This prediction appears to be in alignment with the exciting new results from JWST. We have also initiated an observational program to test the Pop III.1 model via a search for high redshift SMBHs via photometric variability in the Hubble Ultra Deep Field (HUDF). This program has yielded the most stringent observational constraints to date on the abundance of SMBHs in the early universe.
The most significant achievements that have made progress beyond the state of the art are: 1) Development of the new Pop III.1 paradigm of supermassive black hole (SMBH) formation, which has been presented in a series of papers (Banik, Tan & Monaco 2019; Singh, Monaco & Tan 2023; Cammelli et al. 2025a) and a review article (Tan et al. 2024). 2) Testing of the Pop III.1 scenario via new observations of the Hubble Ultra Deep Field to find SMBHs that appear as variable active galactic nuclei (AGN) (Hayes, Tan et al. 2024; Cammelli, Tan et al. 2025, ApJ, submitted), with these studies find evidence for a very high abundance of SMBHs in the early universe. 3) Completion of the SOFIA Massive (SOMA) Star Formation Survey (e.g. Liu et al. 2020; Fedriani et al. 2023; Telkamp et al. 2025), with important new constraints on theoretical models of massive star formation. 4) Presentation of some of the first JWST results on massive star formation, including both the extremes of our Galaxy: the Galactic Center region Sgr C (Crowe et al. 2025) and the far outer Galaxy region S284 (Cheng, Tan et al. 2025, ApJ, submitted). The Sgr C study was accompanied by a major NASA/JWST press release that had worldwide impact. 5) The development of novel diffusion-based machine learning methods for inferring astrophysical properties, such as density (Xu et al. 2023) and magnetic field strength (Xu et al. 2025), has also been a very significant achievement.