Asymmetries in the LMC velocity maps
arXiv:2508.01434 · doi:10.1051/0004-6361/202556309
Abstract
The analysis of precise Gaia DR3 astrometry in the LMC region has revealed asymmetric patterns in the bar quadrupole and the disc outskirts of the LMC in-plane velocity maps. We aim to quantify the asymmetries detected in the LMC radial and residual tangential velocity maps, and determine whether they are generated naturally due to the LMC's interaction with the SMC. We analyse the velocity maps of different simulations from the KRATOS suite of N-body simulations of the LMC-SMC-MW system, proposing a new methodology to quantify the kinematic asymmetry in the bar and the outskirts of the disc. We also transform the KRATOS simulations into Gaia mock catalogues to confirm that the asymmetric signature in the LMC is not an effect of observational uncertainties. In addition, we investigate the possibility of a classification bias in the neural network classifier of the Gaia optimal sample. In the KRATOS simulations of the LMC and SMC interaction, the dynamical effect of the SMC passages produces a displacement of the bar and asymmetries in the LMC velocity maps. By comparing the velocity maps of mock catalogues of the future Gaia data releases DR4, DR5 and GaiaNIR, we find that the asymmetric signature in the bar quadrupole is independent of observational errors. We thereby confirm that it is a consequence of the interaction of the LMC with the SMC. We also find a classification bias in the neural network classifier, indicating that the outer disc asymmetry observed in the optimal sample is artificial. The analysis of the KRATOS simulations reveals that the interaction of the LMC with the SMC can generate asymmetric patterns in the velocity field. In the case of the Gaia DR3 LMC velocity maps we conclude that the bar quadrupole asymmetry is directly correlated with the SMC interaction, while the outer disc asymmetry is an artefact of the classifier for the optimal sample.
11 pages, 13 figures, accepted for publication in A&A on 31/07/2025. Tool for mock catalogues available at https://github.com/mschoelch24/MockCatalogue
References in corpus (29)
- Gaia Data Release 3: Summary of the content and survey properties
- Modelling the Galactic Interstellar Extinction Distribution in Three Dimensions
- A distance to the Large Magellanic Cloud that is precise to one per cent
- New Understanding of Large Magellanic Cloud Structure, Dynamics and Orbit from Carbon Star Kinematics
- The Role of Dwarf Galaxy Interactions in Shaping the Magellanic System and Implications for Magellanic Irregulars
- The Araucaria Project. The distance to the Small Magellanic Cloud from late-type eclipsing binaries
- Hunting for the Dark Matter Wake Induced by the Large Magellanic Cloud
- Updated Gaia-2MASS 3D maps of Galactic interstellar dust
- Magellanic Cloud Structure from Near-IR Surveys II: Star Count Maps and the Intrinsic Elongation of the LMC
- SMASH - Survey of the MAgellanic Stellar History
- Measuring the Mass of the Large Magellanic Cloud with Stellar Streams Observed by
- Empirical photometric calibration of the Gaia Red Clump: colours, effective temperature and absolute magnitude
- An empirical model of the Gaia DR3 selection function
- The effect of the LMC on the Milky Way system
- The Proper Motion Field Along the Magellanic Bridge: a New Probe of the LMC-SMC Interaction
- The recent LMC-SMC collision: Timing and impact parameter constraints from comparison of Gaia LMC disk kinematics and N-body simulations
- Overview and stellar statistics of the expected Gaia Catalogue using the Gaia Object Generator
- OGLE-ing the Magellanic System: Stellar populations in the Magellanic Bridge
- SMASHing THE LMC: Mapping a Ring-like Stellar Overdensity in the LMC Disk
- The Magellanic Inter-Cloud Project (MAGIC) III: First spectroscopic evidence of a dwarf stripping a dwarf
- Kinematic analysis of the Large Magellanic Cloud using Gaia DR3
- The Case of the Off-Center, Levitating Bar in the Large Magellanic Cloud
- Estimating the selection function of Gaia DR3 sub-samples
- The Magellanic Bridge as a DLA System: Physical Properties of Cold Gas toward PKS0312-770
- Vertical structure and kinematics of the LMC disc from SDSS/Gaia
- Application of a Neural Network classifier for the generation of clean Small Magellanic Cloud stellar samples
- Precise Measurements of the LMC Bar's Geometry With Gaia DR3 and a Novel Solution to Crowding Induced Incompleteness in Star Counting
- Tidal interaction can stop galactic bars: on the LMC non-rotating bar
- The VMC survey -- LIV. The internal kinematics of the LMC with new VISTA observations