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Arxiv: The JWST-SUSPENSE Ultradeep Spectroscopic Program: Survey Overview and Star-Formation Histories of Quiescent Galaxies at 1 < z < 3 Published: 4/18/2024 9:00:02 PM Updated: 4/18/2024 9:00:02 PM

Paper abstract: We present an overview and first results from the Spectroscopic UltradeepSurvey Probing Extragalactic Near-infrared Stellar Emission (SUSPENSE),executed with NIRSpec on JWST. The primary goal of the SUSPENSE program is tocharacterize the stellar, chemical, and kinematic properties of massivequiescent galaxies at cosmic noon. In a single deep NIRSpec/MSA configuration,we target 20 distant quiescent galaxy candidates (z=1-3, H_{AB}<23), aswell as 53 star-forming galaxies at z=1-4. With 16hr of integration and theG140M-F100LP dispersion-filter combination, we observe numerous Balmer andmetal absorption lines for all quiescent candidates. We derive stellar masses(logM_*/M_{\odot}~10.3-11.5) and detailed star-formation histories (SFHs)and show that all 20 candidate quiescent galaxies indeed have quenched stellarpopulations. These galaxies show a variety of mass-weighted ages (0.8-3.0Gyr)and star formation timescales (~0.5-4Gyr), and four out of 20 galaxieswere already quiescent by z=3. On average, the z>1.75 [z<1.75] galaxiesformed 50% of their stellar mass before z=4 [z=3]. Furthermore, the typicalSFHs of galaxies in these two redshift bins (z_{\text{mean}}=2.2 andz_{\text{mean}}=1.3) indicate that galaxies at higher redshift formed earlierand over shorter star-formation timescales compared to lower redshifts.Although this evolution is naturally explained by the growth of the quiescentgalaxy population over cosmic time, we cannot rule out that mergers andlate-time star formation also contribute to the evolution. In future work, wewill further unravel the early formation, quenching, and late-time evolution ofthese galaxies by extending this work with studies on their chemicalabundances,