Abstact: Baryon cycle — the inflow of gas into galaxies, its conversion into stars, and its ejection by feedback — sets the pace of galaxy growth, yet it has long been difficult to observe directly in the early Universe. JWST has changed that. In this talk I will review recent progress using two complementary capabilities: wide-field slitless spectroscopy (WFSS) with NIRISS and NIRCam, and multi-object and slit-stepping spectroscopy with NIRSpec. These open a new window onto unbiased, spatially resolved studies of star formation, feedback, and ISM conditions from the epoch of reionization (EoR) to cosmic noon.
With JWST WFSS, we have carried out the first spatially resolved emission-line analysis of galaxies in the early Universe and assembled the largest sample of sub-kpc metallicity gradients to date, extending into the EoR and uncovering evidence for a rapid transition in mass assembly and chemical enrichment. We have also developed a new 3D spectroscopic technique — stepping NIRSpec/MSA slits across galaxy surfaces — to build chemical and dynamical maps of high-redshift galaxies, with an efficiency an order of magnitude higher than that of the NIRSpec IFU. These data reveal that galaxies with negative metallicity gradients are strongly rotationally supported, consistent with predictions from the FIRE-2 simulations. I will further discuss Gz9p3, a galaxy seen just 500 Myr after the Big Bang, in which metal-enriched outflows driven by delayed feedback remain bound to the system — arguably the earliest emerging baryon cycle yet observed.
Together, these results suggest a unified picture in which chemical enrichment is governed by localized star formation during the EoR and by feedback-regulated starbursts at cosmic noon. They highlight the multifaceted processes that regulate the baryon cycle, from external drivers such as cosmological accretion and mergers to internal ones such as feedback-regulated star formation and gas mixing.
Short bio: Xin Wang is currently an Associate Professor in the School of Astronomy and Space Science, University of Chinese Academy of Sciences (UCAS) and NAOC. Before professorship, Xin was a postdoctoral research associate at Caltech/IPAC, and earned his Ph.D. in Astronomy & Astrophysics from UCLA in 2019. Xin has been the PI of one JWST NIRSpec/IFU program (GO-9692) and two medium HST programs, awarded 45 orbits of deep near-infrared slitless spectroscopy and 38 orbits of ultra-deep near-ultraviolet imaging in cycles 28 and 30, respectively. Xin is also a core member of several large JWST observing programs, including the GLASS ERS program, and two NIRSpec slit-stepping programs. Xin is selected by NASA as one of the participants in the inaugural JWST master class, and has hosted several JWST proposal planning workshops for the community. Xin has great expertise in the reduction and analysis of space-based wide-field slitless spectroscopy, multi-band imaging and photometry, and has been responsible for producing the science-enabling data products for the GLASS and UVCANDELS HST treasury programs.