J/A+A/711/A55 MW-MC Bridge young stellar members (Schoelch+, 2026)
Characterisation of the Clouds' young stellar Bridge using Gaia DR3.
Schoelch M., Jimenez-Arranz O., Romero-Gomez M., Luri X.
<Astron. Astrophys. 711, A55 (2026)>
=2026A&A...711A..55S 2026A&A...711A..55S (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Magellanic Clouds ; Optical
Keywords: galaxies: interactions - galaxies: kinematics and dynamics -
Magellanic Clouds - galaxies: structure
Abstract:
The interaction between the LMC and SMC (the Clouds) has resulted in
prominent tidal features, including an extended bridge of gas and
stars connecting the two galaxies. This Bridge has likely formed
during the most recent interaction between the Clouds, about
150-250Myr ago. While some young stars observed in the Bridge have
formed in-situ from the tidally stripped gas, stellar populations may
also have been drawn out of the SMC during the tidal interaction. We
aim to identify a clean sample of likely Bridge stars in the region
between the LMC and SMC using Gaia DR3 astrometric and photometric
data combined with machine-learning techniques. We use the
dimensionality-reduction algorithm UMAP to construct a training sample
of young stars in the outskirts of the SMC and LMC. A neural network
trained on this sample is then applied to Gaia sources in the
inter-Cloud region to classify the stars and identify candidate Bridge
members. We present and characterise a new sample of young candidate
Bridge stars, selected from Gaia DR3. We investigate its spatial
distribution, kinematic properties and colour-magnitude diagram and
validate it using existing Bridge samples. The young stellar Bridge
aligns well with HI gas, clusters, and Cepheid samples, apart from a
small offset near the LMC outer disc. We measure a Bridge length of
∼15kpc and the stars are travelling from the SMC to the LMC at a
median tangential velocity of ∼114km/s. This implies a crossing time
of ∼125Myr, which is within the timeframe of the last interaction of
the Clouds and therefore supports tidal stripping as a possible
formation scenario of the Bridge.
Description:
We provide a table of neural network classification scores for Gaia
DR3 inter-Cloud sources. A value close to 1 indicates Bridge
membership. The third column, 'bridge', is 'True' for stars classified
as Bridge members in the paper.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
class.dat 48 2487652 MW/Bridge classification
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See also:
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
Byte-by-byte Description of file: class.dat
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Bytes Format Units Label Explanations
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1- 19 I19 --- GaiaDR3 Gaia DR3 source identifier, source_id
21- 43 E23.17 --- score NN Bridge classification score
44- 48 A5 --- Bridge [False/True ] Bridge membership, this paper (1)
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Note (1): Bridge membership is defined by applying a threshold of score ≥0.8
and a positional cut excluding the LMC disc. Users may adopt alternative
thresholds on the classification score to construct customised Bridge samples.
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Acknowledgements:
Marie Schoelch, marie.schoelch(at)fqa.ub.edu
License: CC0-1.0
(End) Patricia Vannier [CDS] 05-May-2026