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تسجيل مستخدم جديدMetal Deficiency in Two Massive Dead Galaxies at $zsim2$
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Local massive early-type galaxies are believed to have completed most of their star formation $sim10$Gyr ago and evolved without having substantial star formation since. If so, their progenitors should have roughly solar stellar metallicities ($Z_*$), comparable to their values today. We report the discovery of two lensed massive ($log M_*/M_odotsim11$), $zsim2.2$ dead galaxies, that appear markedly metal deficient given this scenario. Using 17-band $HST$+$K_{s}$+$Spitzer$ photometry and deep $HST$ grism spectra from the GLASS and SN Refsdal follow-up campaigns covering features near $lambda_{rm rest}sim4000$AA, we find these systems to be dominated by A-type stars with $log Z_*/Z_odot=-0.40pm0.02$ and $-0.49pm0.03$ ($30$-$40%$ solar) under standard assumptions. The second systems lower metallicity is robust to isochrone changes, though this choice can drive the first systems from $log Z_*/Z_odot=-0.6$ to 0.1. If these two galaxies are representative of larger samples, this finding suggests that evolutionary paths other than dry minor-merging are required for these massive galaxies. Future analyses with direct metallicity measurements-e.g., by the $James Webb Space Telescope$-will provide critical insight into the nature of such phenomena.
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