Speaker
Description
Rest-frame UV spectra play a key role in the understanding of massive stellar populations, chemical evolution, feedback processes, and reionization. In particular, in the current JWST era, the UV spectroscopic frontier has been pushed to higher redshifts than ever before, to finally reveal the first galaxies in the distant Universe. It is thus fundamental to understand the diagnostic power of UV spectral features. To this end, I will discuss how HST UV spectra of local high-z analogues from CLASSY (COS Legacy Archive Spectroscopic SurveY) can represent a powerful ideal laboratory, thanks to the level of data quality and spatial resolution the local Universe can offer. The sample is representative of SFGs across all redshifts, including extremely metal-poor objects similar to reionization-era systems. As such, we can tailor a complete UV diagnostic toolkit to explore the interstellar medium (ISM) properties (i.e., density, temperature, gas-phase metallicity, ionization parameter, source of ionization, star formation rate). In this talk I will present such a toolkit, obtained from the analysis of the main emission lines of CLASSY spectra and the comparison with well-known optical diagnostics, and discuss both benfits and challenges in using UV ISM diagnostics at high-z. Moreover, using UV ISM absorption lines, I will showcase how comparing abundances in the neutral vs ionized gas can provide us with essential insight into enrichment scenarios and mixing timescales in high-z systems. Overall, this talk demonstrates how powerful local analogues can be in understanding the ISM conditions of the earliest galaxies.
