J/A+A/704/A167 Tidal tails in open clusters (Sharma+, 2025)
Tidal tails in open clusters.
Morphology, binary fraction, dynamics, and rotation
Sharma I., Jadhav V., Subramaniam A., Wirth H.
<Astron. Astrophys. 704, A167 (2025)>
=2025A&A...704A.167S 2025A&A...704A.167S (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Surveys ; Clusters, open ; Positional data
Keywords: methods: data analysis - methods: observational -
methods: statistical - astrometry - Galaxy: kinematics and dynamics -
open clusters and associations: general
Abstract:
This research presents unsupervised machine learning and statistical
methods to identify and analyze tidal tails in open star clusters
using data from the Gaia DR3 catalog.
We aim to identify member stars, detect and analyze tidal tails in
five open clusters, BH 164, Alessi 2, NGC 2281, NGC 2354, and M67, of
ages between 60Myr and 4Gyr. These clusters were selected based on the
previous evidence of extended tidal structures.
We utilized machine learning algorithms such as Density-based Spatial
Clustering of Applications with Noise (DBSCAN) and Principal Component
Analysis (PCA), along with statistical methods to analyze the
kinematic, photometric, and astrometric properties of stars. Key
characteristics of tidal tails, including radial velocity,
color-magnitude diagram, and spatial projections in the tangent plane
beyond the cluster's Jacobi radius, were used to detect them. We used
N-body simulations to visualize and compare the observables with real
data. Further analysis was done on the detected cluster and tail stars
to study their internal dynamics and populations, including binary
fraction. We also applied the residual velocity method to detect
rotational patterns in the clusters and their tails.
We identified tidal tails in all five clusters, with detected tails
extending farther in some clusters and containing significantly more
stars than previously reported (tails ranging from 40 to 100pc, one
to four times the Jacobi radius, with 100-200 tail stars). The
luminosity functions of the tails and their parent clusters were
generally consistent, and tails lacked massive stars. In general, the
binary fraction was found to be higher in the tidal tails. Significant
rotation was detected in M67 and NGC 2281 for the first time.
Description:
This catalog lists the astrometric and photometric properties of stars
identified as members of the five open clusters and their tidal tails.
Objects:
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RA (2000) DE Designation(s)
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04 46 32.16 +55 11 05.6 Alessi 2 = Cl Alessi 2
13 20 19.36 -70 11 33.6 BH 164 = BH 164
08 51 23.51 +11 48 54.0 M67 = NGC 2682
06 48 19.68 +41 02 34.7 NGC 2281 = NGC 2281
07 13 59.23 -25 43 40.4 NGC 2354 = [KPS2012] MWSC 1148
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
members.dat 125 2786 *Cluster and tidal tail members of five open
clusters
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Note on members.dat: All quantities are derived from Gaia DR3 unless stated
otherwise.
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See also:
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
J/A+A/686/A42 : Improving the open cluster census. III. (Hunt+, 2024)
J/A+A/659/A59 : Structural parameters of 389 local open clusters
(Tarricq+, 2022)
J/A+A/694/A258 : Tidal tails of nearby open clusters (Risbud+, 2025)
Byte-by-byte Description of file: members.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Cluster Cluster name (Cluster)
10- 28 I19 --- GaiaDR3 Gaia DR3 source id (source_id)
30- 40 F11.6 deg RAdeg Right ascension (ICRS) at Ep=2016.0 (ra)
42- 52 F11.6 deg DEdeg Declination (ICRS) at Ep=2016.0 (dec)
54- 61 F8.6 mas plx Absolute stellar parallax (parallax)
63- 72 F10.6 mas/yr pmRA Proper motion in right ascension (pmra)
74- 83 F10.6 mas/yr pmDE Proper motion in declination (pmdec)
85- 90 F6.3 mag BP-RP ? Gaia DR3 BP minus RP colour (bp_rp)
92- 99 F8.3 mag Gmag Gaia DR3 mean G magnitude
(photgmean_mag)
101-108 F8.3 mag GMAG Absolute G magnitude (derived) (abs_mag)
110-117 F8.3 km/s RV ? Radial velocity (radial_velocity)
119 I1 --- flagCluster [0/1] Flag indicating the star is a
cluster member (flag_cluster)
121 I1 --- flagTidalTail [0/1] Flag indicating the star in the
tidal tail (flagtidaltail)
123 I1 --- flagLeadingTail [0/1] Flag indicating the star in the
leading tail (flagleadingtail)
125 I1 --- flagTrailingTail [0/1] Flag indicating the star in the
trailing tail (flagtrailingtail)
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Acknowledgements:
Ira Sharma, irasharma2208(at)gmail.com
(End) Patricia Vannier [CDS] 08-Oct-2025