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Arxiv: Imaging of I Zw 18 by JWST: I. Strategy and First Results of Dusty Stellar Populations Published: 3/11/2024 7:59:58 PM Updated: 3/11/2024 7:59:58 PM

Paper abstract: We present a James Webb Space Telescope (JWST) imaging survey of I Zw 18, thearchetypal extremely metal-poor, star-forming, blue compact dwarf galaxy. Withan oxygen abundance of only ~3% Z_{\odot}, it is among thelowest-metallicity systems known in the local universe, and is, therefore, anexcellent accessible analog for the galactic building blocks which existed atearly epochs of ionization and star formation. These JWST data provide acomprehensive infrared (IR) view of I Zw 18 with eight filters utilizing bothNIRCam (F115W, F200W, F356W, and F444W) and MIRI (F770W, F1000W, F1500W, andF1800W) photometry, which we have used to identify key stellar populations thatare bright in the near- and mid-IR. These data allow for a better understandingof the origins of dust and dust-production mechanisms in metal-poorenvironments by characterizing the population of massive, evolved stars in thered supergiant (RSG) and asymptotic giant branch (AGB) phases. In addition, itenables the identification of the brightest dust-enshrouded young stellarobjects (YSOs), which provide insight into the formation of massive stars atextremely low metallicities typical of the very early universe. This paperprovides an overview of the observational strategy and data processing, andpresents first science results, including identifications of dusty AGB star,RSG, and bright YSO candidates. These first results assess the scientificquality of JWST data and provide a guide for obtaining and interpreting futureobservations of the dusty and evolved stars inhabiting compact dwarfstar-forming galaxies in the local universe.