In:
The Astrophysical Journal, American Astronomical Society, Vol. 944, No. 1 ( 2023-02-01), p. 79-
Abstract:
We report the first star formation history study of the Milky Ways nuclear star cluster (NSC), which includes observational constraints from a large sample of stellar metallicity measurements. These metallicity measurements were obtained from recent surveys from Gemini and the Very Large Telescope of 770 late-type stars within the central 1.5 pc. These metallicity measurements, along with photometry and spectroscopically derived temperatures, are forward modeled with a Bayesian inference approach. Including metallicity measurements improves the overall fit quality, as the low-temperature red giants that were previously difficult to constrain are now accounted for, and the best fit favors a two-component model. The dominant component contains 93% ± 3% of the mass, is metal-rich ( [ M / H ] ¯ ∼ 0.45 ), and has an age of 5 − 2 + 3 Gyr, which is ∼3 Gyr younger than earlier studies with fixed (solar) metallicity; this younger age challenges coevolutionary models in which the NSC and supermassive black holes formed simultaneously at early times. The minor population component has low metallicity ( [ M / H ] ¯ ∼ − 1.1 ) and contains ∼7% of the stellar mass. The age of the minor component is uncertain (0.1–5 Gyr old). Using the estimated parameters, we infer the following NSC stellar remnant population (with ∼18% uncertainty): 1.5 × 10 5 neutron stars, 2.5 × 10 5 stellar-mass black holes (BHs), and 2.2 × 10 4 BH–BH binaries. These predictions result in 2–4 times fewer neutron stars compared to earlier predictions that assume solar metallicity, introducing a possible new path to understand the so-called “missing-pulsar problem”. Finally, we present updated predictions for the BH–BH merger rates (0.01–3 Gpc −3 yr −1 ).
Type of Medium:
Online Resource
ISSN:
0004-637X
,
1538-4357
DOI:
10.3847/1538-4357/aca8ad
Language:
Unknown
Publisher:
American Astronomical Society
Publication Date:
2023
detail.hit.zdb_id:
2207648-7
detail.hit.zdb_id:
1473835-1
SSG:
16,12
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