Hunting young stars in the Galactic centre. Hundreds of thousands of solar masses of young stars in the Sagittarius C region
arxiv(2024)
摘要
The Galactic centre stands out as the most prolific star-forming environment
of the Galaxy when averaged over volume. In the last 30 million years, it has
witnessed the formation of ∼10^6 M_⊙ of stars. However, crowding and
high extinction hamper their detection and, up to now, only a small fraction of
the expected mass of young stars has been identified. We aim to detect hidden
young stars at the Galactic centre by analysing the stellar population in
Sagittarius (Sgr) C. This is a region at the western edge of the nuclear
stellar disc whose HII emission makes it a perfect candidate to host young
stars. We built dereddened luminosity functions for Sgr C and a control field
in the central region of the nuclear stellar disc, and fitted them with a
linear combination of theoretical models to analyse their stellar population.
We find that Sgr C hosts several 10^5 M_⊙ of young stars. We compared our
results with the recently discovered young stellar population in Sgr B1, which
is situated at the opposite edge of the nuclear stellar disc. We estimated that
the Sgr C young stars are ∼20 Myr old, and likely show the next
evolutionary step of the slightly younger stars in Sgr B1. Our findings
contribute to addressing the discrepancy between the expected and the detected
number of young stars in the Galactic centre, and shed light on their evolution
in this extreme environment. As a secondary result, we find an intermediate-age
stellar population in Sgr C (∼50
between 2 and 7 Gyr), which is not present in the innermost regions of the
nuclear stellar disc (dominated by stars >7 Gyr). This supports the existence
of an age gradient and favours an inside-out formation of the nuclear stellar
disc.
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