Strong asymptotic giant branch stars' spectral features in distant quiescent galaxies: Impact on galaxy evolution
arxiv(2024)
摘要
Age-dating and weighting stellar populations in galaxies at various cosmic
epochs are essential steps to study galaxy formation through cosmic times.
Evolutionary population synthesis models with different input physics are used
towards this aim. In particular, the contribution from the thermally pulsing
asymptotic-giant-branch (TP-AGB) stellar phase, which peaks for
intermediate-age 0.6-2 Gyr systems, has been debated upon for decades. Here we
report the detection of strong cool star signatures in the rest-frame
near-infrared spectra of three young ( 1 Gyr), massive ( 10^10 Msun) quiescent
galaxies at large look-back time, z=1-2, using JWST/NIRSpec. The co-existence
of oxygen- and carbon-type absorption features, spectral edges and features
from rare species such as Vanadium, and possibly Zirconium, reveal a strong
contribution from TP-AGB stars. Population synthesis models with significant
TP-AGB contribution reproduce the observations considerably better than those
with weak TP-AGB, which are those commonly used. These findings call for
revisions of published stellar population fitting results, pointing to lower
masses and younger ages, with additional implications on cosmic dust production
and chemical enrichment. These results will stimulate new generations of
improved models informed by these and future observations.
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