Gaia view of a stellar sub-structure in front of the Small Magellanic Cloud

Abstract

Recent observational studies identified a foreground stellar sub-structure traced by red clump (RC) stars (~ 12 kpc in front of the main body) in the eastern regions of the Small Magellanic Cloud (SMC) and suggested that it formed during the formation of the Magellanic Bridge (MB), due to the tidal interaction of the Magellanic Clouds. Previous studies investigated this feature only up to 4.0 deg from the centre of the SMC due to the limited spatial coverage of the data and hence could not find a physical connection with the MB. To determine the spatial extent and properties of this foreground population, we analysed data from the Gaia data release 2 (DR2) of a ~ 314 sq. deg region centred on the SMC, which cover the entire SMC and a significant portion of the MB. We find that the foreground population is present only between 2.5 deg to ~ 5-6 deg from the centre of the SMC in the eastern regions, towards the MB and hence does not fully overlap with the MB in the plane of the sky. The foreground stellar population is found to be kinematically distinct from the stellar population of the main body with ~ 35 km/s slower tangential velocity and moving to the North-West relative to the main body. Though the observed properties are not fully consistent with the simulations, a comparison indicates that the foreground stellar structure is most likely a tidally stripped counterpart of the gaseous MB and might have formed from the inner disc (dominated by stars) of the SMC. A chemical and 3D kinematic study of the RC stars along with improved simulations, including both tidal and hydro-dynamical effects, are required to understand the offset between the foreground structure and MB.

Accepted for publication in MNRAS

References in corpus (18)

• The NumPy array: a structure for efficient numerical computation
• Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties
• The Origin of the Magellanic Stream and Its Leading Arm
• Clustering of Local Group distances: publication bias or correlated measurements? I. The Large Magellanic Cloud
• The VISTA ZYJHKs Photometric System: Calibration from 2MASS
• Clustering of Local Group distances: publication bias or correlated measurements? III. The Small Magellanic Cloud
• The VMC Survey. XXV. The 3D structure of the Small Magellanic Cloud from Classical Cepheids
• Clouds, Streams and Bridges. Redrawing the blueprint of the Magellanic System with Gaia DR1
• The Magellanic Bridge: The Nearest Purely Tidal Stellar Population
• Empirical photometric calibration of the Gaia Red Clump: colours, effective temperature and absolute magnitude
• Toward a Complete Understanding of the Magellanic Stream Formation
• OGLE-ing the Magellanic System: Stellar populations in the Magellanic Bridge
• The Magellanic Inter-Cloud Project (MAGIC) III: First spectroscopic evidence of a dwarf stripping a dwarf
• Disk of the Small Magellanic Cloud as traced by Cepheids
• The Magellanic System: the puzzle of the leading gas stream
• The VMC survey -- XXXVIII. Proper motion of the Magellanic Bridge
• Spectroscopy of the Young Stellar Association Price-Whelan 1: Origin in the Magellanic Leading Arm and Constraints on the Milky Way Hot Halo
• Spitzer View of Massive Star Formation in the Tidally Stripped Magellanic Bridge

Cited by in corpus (18)

• The VMC survey -- XLI. Stellar proper motions within the Small Magellanic Cloud
• Magellanic Mayhem: Metallicities and Motions
• Stellar substructures in the periphery of the Magellanic Clouds with the VISTA Hemisphere Survey from the red clump and other tracers
• The VISCACHA survey -- III. Star clusters counterpart of the Magellanic Bridge and Counter-Bridge in 8D
• Ca II Triplet Spectroscopy of Small Magellanic Cloud Red Giants. V. Abundances and Velocities for 12 Massive Clusters
• Presence of red giant population in the foreground stellar sub-structure of the Small Magellanic Cloud
• The Magellanic Edges Survey IV. Complex tidal debris in the SMC outskirts
• Lessons from the Magellanic System and its modeling
• UVIT Study of the MAgellanic Clouds (U-SMAC) II. A Far-UV catalog of the Small Magellanic Cloud: Morphology and Kinematics of young stellar population
• Kinematic complexity around NGC419: resolving the proper motion of the cluster, the Small Magellanic Cloud and the Magellanic Bridge
• Kinematics of stellar substructures in the Small Magellanic Cloud
• The red giant branch tip in the SDSS, PS1, JWST, NGRST and Euclid photometric systems. Calibration in optical passbands using Gaia DR3 synthetic photometry
• Residual velocities of Small Magellanic Cloud star clusters
• Discovery of NES, an extended tidal structure in the North-East of the Large Magellanic Cloud
• The YMCA (Yes, Magellanic Clouds Again) survey: probing the outer regions of the Magellanic system with VST
• Dwarf-Dwarf interactions and their influence on star formation : Insights from post-merger galaxies
• Strömgren photometric metallicity map of the Magellanic Cloud stars using Gaia DR3--XP spectra
• Probing the farthest star clusters to the Small Magellanic Cloud