Early Results From GLASS-JWST XVII: Building the First Galaxies -- Chapter 1 Star Formation Histories at 5<z < 7

Early Results From GLASS-JWST XVII: Building the First Galaxies -- Chapter 1 Star Formation Histories at 5<z < 7 by A. Dressler et al. on Sunday 27 November 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 7 wide bands covering 1-5 mu 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. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2208.04292v3