Line of sight depth of the Large and Small Magellanic Clouds

TL;DR

This study estimates the line of sight depth of the Large and Small Magellanic Clouds using red clump stars, revealing their structural features, halo presence, and possible merger history.

Contribution

It provides new measurements of the depth profiles and halo structures of the Magellanic Clouds using optical survey data.

Findings

LMC has a flared bar with an average depth of 4.0±1.4 kpc.

SMC shows similar depth in its bar and disk regions.

Evidence suggests the SMC may have a bulge and the LMC experienced minor mergers.

Abstract

We used the red clump stars from the Optical Gravitational Lensing Experiment (OGLE II) survey and the the Magellanic Cloud Photometric Survey (MCPS), to estimate the line of sight depth. The observed dispersion in the magnitude and colour distribution of red clump stars is used to estimate the line of sight depth, after correcting for the contribution due to other effects. This dispersion due to depth, has a range from minimum dispersion that can be estimated, to 0.46 mag (a depth of 500 pc to 10.44 Kpc), in the LMC. In the case of SMC, the dispersion ranges from minimum dispersion to 0.35 magnitude (a depth of 665 pc to 9.53 Kpc). The thickness profile of LMC bar indicates that it is flared. The average depth in the bar region is 4.0$\pm$1.4 kpc. The halo of the LMC (using RR Lyrea stars) is found to have larger depth compared to the disk/bar, which supports the presence of inner halo for the LMC. The large depth estimated for the LMC bar and the disk suggests that the LMC might have had minor mergers. In the case of SMC, the bar depth (4.90$\pm$1.23 Kpc) and the disk depth (4.23$\pm$1.48 Kpc) are found to be within the standard deviations. We find evidence for increase in depth near the optical center (up to 9 kpc). On the other hand, the estimated depth for the halo (RR Lyrea stars) and disk (RC stars) for the bar region of the SMC is found to be similar. Thus, increased depth and enhanced stellar as well as HI density near the optical center suggests that the SMC may have a bulge.