Early Results from GLASS-JWST. XVII. Building the First Galaxies—Chapter 1. Star Formation Histories for 5 < z < 7 Galaxies
Alan Dressler, Benedetta Vulcani, Tommaso Treu, Marcia Rieke, C. R. Burns, Antonello Calabrò, Andrea Bonchi, M. Castellano, A. Fontana, Nicha Leethochawalit, Charlotte Mason, E. Merlin, Takahiro Morishita, D. Paris, Maruša Bradač, A. Mercurio, Themiya Nanayakkara, Bianca M. Poggianti, P. Santini, Xin Wang, K. A. Misselt, Daniel P. Stark, Christopher N. A. Willmer
Abstract
Abstract The JWST observations of high-redshift galaxies are used to measure their star formation histories—the buildup of stellar mass in the earliest galaxies. Here we use a novel analysis program, SEDz*, to compare near-IR spectral energy distributions for galaxies with redshifts 5 < z < 7 to combinations of stellar population templates evolved from z = 12. We exploit NIRCam imaging in seven wide bands covering 1–5 μ m taken in the context of the GLASS-JWST-ERS program and use SEDz* to solve for well-constrained star formation histories for 24 exemplary galaxies. In this first look, we find a variety of histories, from long, continuous star formation over 5 < z < 12 to short but intense starbursts, sometimes repeating, and, most commonly, contiguous mass buildup lasting ∼0.5 Myr, possibly the seeds of today’s typical M * galaxies.