Formed too Fast? Massive Galaxies at Cosmic Dawn

Abstract: A growing number of surprisingly massive galaxies are now being found in the first ~billion years after the Big Bang that push the limits of theoretical predictions within Lambda-CDM. Unusually bright high-redshift galaxies discovered by JWST challenge our most fundamental models of how fast stars form. Some of them contain overly massive black holes whose formation is uncharted. Massive dusty starbursts found with ALMA are requiring new explanations about early dust production. I will present recent results from the COSMOS-Web survey and related efforts to find the rarest galaxies at early times (UV-luminous, dust-obscured, and little red dots) that help place constraints on our interpretation of their growth and buildup at early times.