J/A+A/689/A190 Photometry of stars around SGR A* (Gallego-Cano+, 2024)
Photometric classification of stars around the Milky Way's central black hole.
I. Central parsec.
Gallego-Cano E., Fritz T., Schoedel R., Feldmeier-Krause A., Do T.,
Nishiyama S.
<Astron. Astrophys. 689, A190 (2024)>
=2024A&A...689A.190G 2024A&A...689A.190G (SIMBAD/NED BibCode)
ADC_Keywords: Galactic center ; Photometry, infrared ; Stars, nearby ;
Stars, early-type ; Infrared sources ; Photometry, infrared
Keywords: Galaxy: center - Galaxy: kinematics and dynamics -
Galaxy: stellar content
Abstract:
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. We aim to improve
our knowledge about the distribution and the IMF of young, massive,
stars in the vicinity of Sgr A*. 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. 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. 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*.
Description:
This table provides the coordinates, and the corrected intermediate
band (IB) magnitudes and their errors obtained in the paper for the
sample of 6590 stars. The table also includes the CO band depth (CBD)
values and their errors obtained after all the corrections, used
spectroscopic classification, extinction flag, and a flag indicating
if a star is located in a corner of the image, where data completeness
may be lower. Additionally, the table includes the probabilities of
being early-type star obtained for the three methods: XGBoost and MLP,
as well as likelihood, prior, and posterior for Bayesian analysis.
Metallicity and temperature predictions are provided for stars within
the validity of their prediction. the table is described in
Appendix G.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table.dat 452 6590 Photometric classification of stars
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See also:
J/A+A/499/483 : NIR observations of sources in galactic center
(Buchholz+, 2009)
J/A+A/511/A18 : NIR observations of stars near SgrA* (Schoedel+ 2010)
J/ApJ/764/154 : Stellar populations in the central 0.5pc of the GC. I
(Do+, 2013)
J/A+A/549/A57 : Young, massive star candidates in Sgr A* (Nishiyama+, 2013)
J/A+A/584/A2 : KMOS view of the Galactic centre. I. (Feldmeier-Krause+, 2015)
J/A+A/609/A26 : Galactic Center old stars distribution (Gallego-Cano+, 2018)
Byte-by-byte Description of file: table.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Id [0/6589] Sequential number
7- 20 F14.10 deg RAdeg Right ascension (J2000.0)
23- 36 F14.10 deg DEdeg Declination (J2000.0)
40- 52 F13.10 mag IB200 Magnitude in NACO IB200 filter
57- 68 F12.10 mag e_IB200 Uncertainty in IB200
72- 84 F13.10 mag IB206 Magnitude in NACO IB206 filter
89-100 F12.10 mag e_IB206 Uncertainty in IB206
104-116 F13.10 mag IB224 Magnitude in NACO IB224 filter
121-132 F12.10 mag e_IB224 Uncertainty in IB224
136-148 F13.10 mag IB227 Magnitude in NACO IB227 filter
153-164 F12.10 mag e_IB227 Uncertainty in IB227
168-180 F13.10 mag IB230 Magnitude in NACO IB230 filter
185-196 F12.10 mag e_IB230 Uncertainty in IB230
200-212 F13.10 mag IB233 Magnitude in NACO IB233 filter
217-228 F12.10 mag e_IB233 Uncertainty in IB233
232-244 F13.10 mag IB236 Magnitude in NACO IB236 filter
249-260 F12.10 mag e_IB236 Uncertainty in IB236
264-276 F13.10 mag CBD CO band depth (CBD) value
281-292 F12.10 mag e_CBD Uncertainty in CBD
308 I1 --- flagA [0/1] Flag foreground/background (1)
324 I1 --- flagCorner [0/1] Flag location corner (2)
326-328 F3.1 --- SpType [0/1]? Spectroscopic classified star (3)
345-356 F12.10 --- MLPeprob MLP probability
361-372 F12.10 --- XGBeprob XGB probability
377-388 F12.10 --- PosTeprob Posterior Bayesian
393-404 F12.10 --- Prioreprob Prior Bayesian
409-420 F12.10 --- Likeeprob Likelihood Bayesian
422-436 F15.10 K Tepred ? Temperature predicted
440-452 F13.10 [-] [M/H]pred ? Metallicity predicted
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Note (1): The value of the flag 1 indicate that the star is a
foreground/background star
Note (2): The value of the flag 1 indicate that the star is located
in the corner
Note (3): Spectroscopic classified star in previous studies:
1.0 = early-type star
0.0 = late-type star
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Acknowledgements:
Laly Gallego-Cano, lgc(at)iaa.es
References:
Buchholz et al., 2009A&A...499..483B 2009A&A...499..483B, Cat. J/A+A/499/483
Bartko et al., 2010ApJ...708..834B 2010ApJ...708..834B
Schoedel, 2010A&A...509A..58S 2010A&A...509A..58S
Schoedel et al., 2010A&A...511A..18S 2010A&A...511A..18S, Cat. J/A+A/511/A18
Do et al., 2013ApJ...764..154D 2013ApJ...764..154D, Cat. J/ApJ/764/154
Lu et al., 2013ApJ...764..155L 2013ApJ...764..155L
Nishiyama & Schoedel, 2013A&A...549A..57N 2013A&A...549A..57N, Cat. J/A+A/549/A57
Feldmeier-Krause et al., 2015A&A...584A...2F 2015A&A...584A...2F, Cat. J/A+A/584/A2
Gallego-Cano et al., 2018A&A...609A..26G 2018A&A...609A..26G, Cat. J/A+A/609/A26
Plewa, 2018MNRAS.476.3974P 2018MNRAS.476.3974P
von Fellenberg et al., 2022ApJ...932L...6V 2022ApJ...932L...6V
(End) Patricia Vannier [CDS] 12-Jun-2024