Carbon and Iron Deficiencies in Quiescent Galaxies at z=1-3 from JWST-SUSPENSE: Implications for the Formation Histories of Massive Galaxies

We present the stellar metallicities and multi-element abundances (C, Mg, Si, Ca, Ti, Cr, and Fe) of 15 massive (log M/M_=10. 2-11. 2) quiescent galaxies at z=1-3, derived from ultradeep JWST-SUSPENSE spectra. Compared to quiescent galaxies at z~0, these galaxies exhibit a deficiency of 0. 25 dex in C/H, 0. 16 dex in Fe/H, and 0. 07 dex in Mg/H, implying rapid formation and quenching before significant enrichment from asymptotic giant branch stars and Type Ia supernovae. Additionally, we find that galaxies that form at higher redshift have higher Mg/Fe and lower Fe/H and Mg/H, irrespective of their observed redshift. The evolution in Fe/H and C/H is therefore primarily explained by lower redshift samples naturally including galaxies with longer star-formation timescales. On the other hand, the lower Mg/H can be explained by galaxies forming at earlier epochs expelling larger gas reservoirs during their quenching phase. Consequently, the mass-metallicity relation, primarily reflecting Mg/H, is also lower at z=1-3 compared to the lower redshift relation, though the slopes are similar. Finally, we compare our results to standard stellar population modeling approaches employing solar abundance patterns and non-parametric star-formation histories (using Prospector). Our SSP-equivalent ages agree with the mass-weighted ages from Prospector, while the metallicities disagree significantly. Nonetheless, the metallicities better reflect Fe/H than total Z/H. We also find that star-formation timescales inferred from elemental abundances are significantly shorter than those from Prospector, and we discuss the resulting implications for the early formation of massive galaxies.