J/MNRAS/518/4249 Study of extra-tidal M3 stars with APOGEE/Gaia (Grondin+, 2023)
Searching for the extra-tidal stars of globular clusters using high-dimensional
analysis and a core particle spray code.
Grondin S.M., Webb J.J., Leigh N.W.C., Speagle J.S., Khalifeh R.J.
<Mon. Not. R. Astron. Soc. 518, 4249-4264 (2023)>
=2023MNRAS.518.4249G 2023MNRAS.518.4249G (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Milky Way ; Positional data ; Spectroscopy ;
Stars, distances ; Proper motions ; Radial velocities ; Infrared ;
Photometry ; Optical
Keywords: stars: kinematics and dynamics - globular clusters: individual -
galaxies: star clusters - software: simulations
Abstract:
Three-body interactions can eject stars from the core of a globular
cluster, causing them to enter the Galactic halo as extra-tidal stars.
While finding extra-tidal stars is imperative for understanding
cluster evolution, connecting isolated extra-tidal field stars back to
their birth cluster is extremely difficult. In this work, we present a
new methodology consisting of high- dimensional data analysis and a
particle spray code to identify extra-tidal stars of any Galactic
globular cluster using M3 as a case study. Using the t-Stochastic
Neighbour Embedding and Uniform Manifold Approximation and Projection
machine learning dimensionality reduction algorithms, we first
identify a set of 103 extra-tidal candidates in the APOGEE DR17 data
catalogue with chemical abundances similar to M3 stars. To confirm
each candidate's extra- tidal nature, we introduce corespray - a new
python-based three-body particle spray code that simulates extra-tidal
stars for any Galactic globular cluster. Using Gaia EDR3 proper
motions and APOGEE DR17 radial velocities, we apply multivariate
Gaussian modelling and an extreme deconvolution to identify the
extra-tidal candidates that are more likely to be associated with a
distribution of corespray-simulated M3 extra-tidal stars than the
field. Through these methods, we identify 10 new high-probability
extra-tidal stars produced via three-body interactions in M3. We also
explore whether any of our extra-tidal candidates are consistent with
being ejected from M3 through different dynamical processes. Future
applications of corespray will yield better understandings of core
dynamics, star formation histories, and binary fractions in globular
clusters.
Description:
Increasing the known sample of extra-tidal stars in our Galaxy will
allow us to better constrain the underlying Galactic gravitational
potential, possible overdensities and binary fractions, ultimately
allowing for advancements in our understanding of the evolution of
both Galactic GCs and the Milky Way itself. Thus, in this study, we
present a new methodology for identifying extra-tidal stars in and
around any Galactic GC, using M3 as a case study.
To identify extra-tidal candidates, we search the DR17 catalogue from
the APOGEE survey which is a high-resolution (R ∼22500), high
signal-to-noise ratio (SNR >100), infrared (1.51-1.70µm)
spectroscopic survey.As our observational extra-tidal identification
scheme centres around chemical abundances, we utilize the high-quality
astroNN abundances. AstroNN abundances are determined through a neural
network using APOGEE data, providing us with 19 chemical abundances
and stellar parameters for an initial sample of 694932 stars. To
examine the kinematics of extra-tidal star candidates throughout our
analyses, we use GaiaEDR3 proper motions and APOGEE barycentric radial
velocities. Of our initial sample, 685 978 stars have GaiaEDR3 proper
motions (i.e section 2).
As explained in section 3 methodology, we use high-order dimensional
analysis to identify 103 extra-tidal candidates that are both
spatially and chemically similar to a control group of M3 stars. We
develop corespray to further constrain the origin of our
observationally identified extra-tidal candidates. However,
quantifying the probability that each extra-tidal candidate is an
extra-tidal star of M3 requires us to infer two distributions: one
distribution of extra-tidal stars of M3 (corespray) and another
distribution of field stars surrounding M3. Results are presented in
tablea1.dat for the 103 stars.
Objects:
----------------------------------------------------------------------------
RA (2000) DE Designation(s)
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13 42 11.62 +28 22 38.2 M3 = BD+29
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File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tablea1.dat 84 103 Spatial, kinematic and probability parameters of
identified extra-tidal star sample around M3
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See also:
J/MNRAS/494/2268 : Solar siblings search with APOGEE and Gaia DR2 (Webb+, 2020)
J/MNRAS/492/1641 : APOGEE southern GCs with the BACCHUS code (Meszaros+, 2020)
J/MNRAS/489/2079 : Calibration of distances with deep learning (Leung+, 2019)
J/MNRAS/484/2832 : Proper motions of Milky Way globular clusters
(Vasiliev, 2019)
J/MNRAS/478/1520 : Milky Way globular clusters data (Baumgardt+, 2018)
J/ApJ/900/146 : Abundances in 2 metal-poor GCs, M53 & NGC5053 (Chun+, 2020)
III/286 : APOGEE-2 DR17 final allStar catalog (Abdurro'uf+, 2022)
III/284 : APOGEE-2 data from DR16 (Johnsson+, 2020)
I/352 : Distances to 1.47 billion stars in Gaia EDR3
(Bailer-Jones+, 2021)
I/350 : Gaia EDR3 (Gaia Collaboration, 2020)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 A18 --- APOGEE APOGEE identifier 2MASS-style object name
from Abdurro'uf et al.
(2022ApJS..259...35A 2022ApJS..259...35A, Cat. III/286)
(APOGEE_ID) (1)
20 A1 --- f_APOGEE Indicating high-probability extra-tidal
stars
22- 28 F7.3 deg RAdeg Right ascension (J2000) (α)
30- 35 F6.3 deg DEdeg Declination (J2000) (δ)
37- 45 F9.3 pc D Star distance (d) (2)
47- 54 F8.3 mas/yr pmRA Proper motion in right ascension
pmRA*cosDE of the source in ICRS at
Ep=2016.0 from Gaia EDR3 (µα)
56- 63 F8.3 mas/yr pmDE Proper motion in declination direction
from Gaia EDR3 (µδ)
65- 72 F8.3 km/s RV Radial velocity from Abdurro'uf et al.
(2022ApJS..259...35A 2022ApJS..259...35A, Cat. III/286) (vr)
74- 84 F11.3 --- log(Pc/Pf) Individual extra-tidal candidate corespray
probability to the probability of each
candidate star belonging to the field P(f)
arithmetic ratio (log (Pc/Pf)
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Note (1): Some of these stars had lower probabilities of belonging to the
corespray extra-tidal star distribution, they are chemically similar
to a control group of cluster members of M3.
Note (2): Parameters obtained from astroNN by
Leung & Bovy (2019MNRAS.483.3255L 2019MNRAS.483.3255L), Leung & Bovy (2019MNRAS.489.2079L 2019MNRAS.489.2079L,
Cat. J/MNRAS/489/2079) and Bovy et al. (2019MNRAS.490.4740B 2019MNRAS.490.4740B).
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History:
From electronic version of the journal
(End) Luc Trabelsi [CDS] 13-Jan-2026