Ikki Mitsuhashi (University of Colorado) - Towards a Comprehensive Understanding of the UV-Bright Galaxies at Cosmic Dawn

JWST has discovered a surprisingly large number of bright galaxies at z>10, which challenges theoretical expectations. Several possible explanations were proposed from theoretical/analytical models to account for their existence, such as the bursty star formation, nebular continuum contribution, AGN contribution, and dusty outflow. We introduce our observational demonstration, mainly about the bursty star formation and AGN contribution. For the bursty star formation at high redshift, we investigated the star formation histories (SFH) and their evolution across z ~ 3-9 by measuring the line-to-UV ratio (R(line)) or equivalent width (EW) with a spectro-photometric dataset taken by the UNCOVER/MegaScience survey. The mass-complete sample allows us to compare observed R(line) and EW distributions and those from FSPS models in the population. For the AGN contribution, we investigated the AGN activity in GHZ2, one of the brightest galaxies at z>12. With high spectral resolution MIRI spectral observations, we successfully detected spectrally resolved Ha emission and constrained the significance of the broad line component. We will further introduce our recent studies about the dust-obscured star formation at high redshift.

Special guest talk Monday, June 15 from 12:00-1:00 PM in LGRT 533. All members of the FCAD community are welcome to attend.