The origin of the LMC stellar bar: clues from the SFH of the bar and inner disc

L. Monteagudo , C. Gallart , M. Monelli , E. J. Bernard (1) , P. B. Stetson

1 OCA - Observatoire de la Côte d'Azur

We discuss the origin of the Large Magellanic Cloud (LMC) stellar bar by comparing the star formation histories (SFHs) obtained from deep colour-magnitude diagrams (CMDs) in the bar and in a number of fields in different directions within the inner disc. The CMDs, reaching the oldest main-sequence turn-offs in these very crowded fields, have been obtained with VIMOS on the Very Large Telescope in the service mode, under very good seeing conditions. We show that the SFHs of all fields share the same patterns, with consistent variations of the star formation rate as a function of time in all of them. We therefore conclude that no specific event of star formation can be identified with the formation of the LMC bar, which instead likely formed from a redistribution of disc material which occurred when the LMC disc became bar unstable, and shared a common SFH with the inner disc thereafter. The strong similarity between the SFH of the centre and edge of the bar rules out the expected significant spatial variations of the SFH across the bar.

Mots clés: Hertzsprung-Russell and colour-magnitude diagrams; galaxies: evolution; Magellanic Clouds; galaxies: stellar content; galaxies: structure; Astrophysics - Astrophysics of Galaxies

Domaines: Planète et Univers [physics]; Astrophysique [astro-ph]

L. Monteagudo, C. Gallart, M. Monelli, E. J. Bernard, P. B. Stetson. The origin of the LMC stellar bar: clues from the SFH of the bar and inner disc. Monthly Notices of the Royal Astronomical Society: Letters, 2018, 473, pp.L16-L20. ⟨10.1093/mnrasl/slx158⟩. ⟨insu-03689242⟩