Spatial distributions of young Large Magellanic Cloud clusters and tracers of a bar pertubation

Abstract

The spatial distributions of SWB I [10<~t(Myr)30]<~ and SWB II [30<~t(Myr)<~70] LMC clusters are analyzed using the enlarged sample of integrated V BV photometry of star clusters and associations published by Bica et ai. in 1996. The differences in the clusters' spatial distributions are interpreted as dating back from their formation epoch and as being caused by a perturbation in the gaseous disk generated by the LMC stellar bar. The two SWB distributions present noncoincident bar or barlike struc­ tures with a position angle difference of ≈22° ± 2°, which, together with the age difference between the groups, leads to a perturbation propagation velocity of 13.7 ± 2 km s-ˡ kpc-ˡ, which suggests bar­ induced star formation effects bn the disk. Differences are also observed in the outer parts of the SWB I and SWB II spatial distributions. A spatial Fourier analysis reveals the predominance of m = 1 and m = 2 components in both cases. The spatial distribution of clusters younger than 10 Myr (SWB O) is also studied. The patterns measured by the Fourier analysis for the SWB O clusters resemble the gas distribution in the potential of disk models with an off-center bar. The H I kinematics is also evidence of the presence of the perturbation in the LMC disk. Although some evidence of locally induced star formation effects is found, our analysis indicates that globally triggered star formation effects induced by the potential play an important role in organizing the overall patterns and the toei of Shapley's Constellations.