Photometric classification of stars around the Milky Way’s central black hole
- Author(s)
- E. Gallego-Cano, T. Fritz, R. Schödel, A. Feldmeier-Krause, T. Do, S. Nishiyama
- Abstract
Context. The presence of young massive stars in the Galactic Centre (GC) raises questions about how such stars could form near the
massive black hole Sagittarius A* (Sgr A*). Furthermore, the shape of the initial mass function (IMF) in this region seems to differ
from its standard Salpeter/Kroupa law. Due to observational challenges such as extreme extinction and crowding, our understanding
of the stellar population in this region remains limited, with spectroscopic data available only for selected small and comparably bright
sources.
Aims. We aim to improve our knowledge about the distribution and the IMF of young, massive, stars in the vicinity of Sgr A*.
Methods. We used intermediate band (IB) photometry to identify candidates for massive young stars. To ensure robust classification,
we applied three different, but complementary methods: Bayesian inference, a basic neural network, and a fast gradient-boosted trees
algorithm.
Results. We obtain spectral energy distributions for 6590 stars, 1181 of which have been previously classified spectroscopically.
We identify 351 stars that are classified as early types by all three classification methods, with 155 of them being newly identified
candidates. The radial density profiles for late and early-type stars fit well with broken power laws, revealing a break radius of
9.2 ± 0.6′′ for early-type stars. The late-type stars show a core-like distribution around Sgr A* while the density of the early-type stars
increases steeply towards the black hole, consistent with previous work. We infer a top-heavy IMF of the young stars near Sgr A*
(R < 9′′), with a power-law of 1.6 ± 0.1. At greater distances from Sgr A* a standard Salpeter/Kroupa IMF can explain the data.
Additionally, we demonstrate that IB photometry can also constrain the metallicities of late-type stars, estimating metallicities for
over 600 late-type stars.
Conclusions. The variation of the IMF with radial distance from Sgr A* suggests that different mechanisms of star formation may
have been at work in this region. The top-heavy IMF in the innermost region is consistent with star formation in a disc around Sgr A*.- Organisation(s)
- Department of Astrophysics
- External organisation(s)
- Instituto de Astrofísica de Andalucía (CSIC), University of Virginia, University of California, Los Angeles, Tohoku University
- Journal
- Astronomy & Astrophysics
- Volume
- 689
- No. of pages
- 34
- ISSN
- 0004-6361
- DOI
- https://doi.org/10.1051/0004-6361/202449881
- Publication date
- 09-2024
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 103004 Astrophysics
- Portal url
- https://ucrisportal.univie.ac.at/en/publications/445aac26-1d1d-4145-8719-7bee932ddd89