Title：Dissecting the Baryon Cycle at Cosmic Noon with Space-based Slitless Spectroscopy  

　　Speaker：Dr. Xin Wang 王鑫（IPAC/Caltech）

　　Abstract：To understand quantitatively the baryon cycle at the peak of cosmic star formation, I developed a highly efficient method for sub-kiloparsec scale spatially resolved analysis of strongly lensed galaxies using space-based wide-field slitless spectroscopy. Applying this method to the deep Hubble Space Telescope (HST) near-infrared grism observations, I obtained precise gas-phase metallicity maps for an unprecedentedly large sample of 79 star-forming galaxies in the redshift range of 1.2 ？ z ？ 2.3. Over half of my galaxies reside in the dwarf mass regime (Mstar ？ 10^9 Msun), making my sample the first statistically representative sample of high-redshift dwarf galaxies with their chemical profiles mapped at sufficient resolution. The metallicity maps obtained in my work reveal a variety of baryonic physics, such as efficient radial mixing from tidal torques, rapid accretion of low-metallicity gas, and various feedback processes which can significantly influence the chemo-structural properties of star-forming galaxies. For the first time, I discovered two dwarf galaxies at z~2 displaying strongly inverted radial metallicity gradients, suggesting that powerful galactic winds triggered by central starbursts carry the bulk of stellar nucleosynthesis yields to the outskirts. I also measure a negative correlation between stellar mass and metallicity gradient, which strongly suggests that strong feedback, not secular processes, is the primary governor of the chemo-structural evolution of star-forming galaxies at cosmic noon. Furthermore, I find that the intrinsic scatter of metallicity gradients increases with decreasing stellar mass and increasing specific star-formation rate. This increase in the intrinsic scatter is likely caused by the combined effect of cold-mode gas accretion and merger-induced starbursts, with the latter more predominant in the dwarf mass regime. My method can be readily applied to the slitless spectroscopic data from future space missions employing grism instruments, e.g., JWST, Euclid, WFIRST, and the Chinese Space Station Telescope. Combined with the continuous input of HST resources, these data will revolutionize our understanding of the chemo-structural evolution of galaxies throughout vast cosmic time.  

　　Time：10:30-11:30am, December 27 (Friday), 2019  

　　Place：PMO 3-402 room  

欢迎大家参加！

紫金山天文台学术委员会