Title: Unveiling IZw18 age's mystery: Resolved Stellar Populations and Star Formation History Study with JWST/NIRCam
Speaker: Giacomo Bortolini
Affiliation: Stockholm University
Time: Thursday 13th June 2024, 14:00 to 15:00
Location: 90103 Å
Abstract: The blue compact dwarf galaxy IZw18 is among the most enigmatic system known in the local universe (D ~18Mpc). Since its discovery by Zwicky in 1966, the true nature of this system has sparked debates within the astronomical community. Indeed, with its blue color, high gas content, and extreme metal deficiency (Z ~1/30 Z_⊙), IZw18 resembles a young galaxy at high redshift forming its first generation of stars. However, according to Legrand (2000) IZw18 is an old system that has formed stars for a prolonged period of time at a rate too low to efficiently enrich its interstellar medium. The most reliable method for estimating the age of nearby galaxies involves analysing the color-magnitude diagram (CMD) of their resolved stellar populations. Given IZw18's distance, this analysis was only feasible with the Hubble Space Telescope (HST), albeit pushing the limits of the telescope resolution. Consequently, a definitive consensus on the age of IZw18 remained elusive until the advent of James Webb Space Telescope (JWST).
In this talk, I will present the first JWST/NIRcam 1.1 and 2.0 μm data of IZw18. We performed PSF-fitting photometry on these images to probe the galaxy's stellar populations with unprecedented sensitivity. Our analysis of its Near-infrared CMD reveals a very young stellar population, comprised of bright massive stars; but also a faint population of red low-mass stars, linked to the underlying halo of the galaxy. I will also present our state-of-the-art CMD fitting technique that we used to derive IZw18's star formation history. In conclusion, I will discuss how our study contributes to the ongoing effort of unraveling the underlying mechanisms responsible for the low metal abundance in IZw18, as well as shedding light on star formation processes within low metallicity environments.