Scientific Seminars

A new and unexpected view of the high-redshift universe with JWST

Marco Castellano

2023-02-13    14:30    - Aula Caldirola

JWST is transforming our understanding of the high-redshift universe and of the epoch of cosmic dawn. In this talk, I will present the capabilities of JWST instruments for investigating the high-redshift universe and an overview of the most recent results obtained from cycle 1 programs and public surveys. In particular, I will focus on the results from the GLASS-JWST survey that has provided the deepest NIRCam images collected by the ERS programs. The first set of GLASS-JWST NIRCam observations led to the discovery of two robust photometric candidates at z~10.5 and z~12.2, that have been both found to have a possible counterpart in ALMA follow-up observations. The discovery of these two objects in a relatively small volume, together with independent analysis from other surveys, points to a number density of bright galaxies at z>9 which is significantly larger than predicted by theoretical models, and could possibly even be in tension with the standard cosmological scenario. A subsequent analysis of NIRCam observations including GLASS and other programs targeting the foreground cluster Abell 2744 led to the discovery of 7 bright objects at z>9 providing further evidence of an unexpected high density of bright galaxies 300-500 Myr after the Big Bang, and hinting at the presence of an overdensity in the field.