The LMC geometry and outer stellar populations from early DES data

The Dark Energy Camera has captured a large set of images as part of Science Verifi- cation (SV) for the Dark Energy Survey. The SV footprint covers a large portion of the outer Large Magellanic Cloud (LMC), providing photometry 1.5 magnitudes fainter than the main sequence turn-off of the oldest LMC stellar population. We derive geo- metrical and structural parameters for various stellar populations in the LMC disk. For the distribution of all LMC stars, we find an inclination of $i = −38.14^{\circ} \pm 0.08^{\circ}$ (near side in the North) and a position angle for the line of nodes of $\theta_0 = 129.51^{\circ} \pm 0.17^{\circ}$. We find that stars younger than ∼4 Gyr are more centrally concentrated than older stars. Fitting a projected exponential disk shows that the scale radius of the old populations is $R_{>4Gyr} = 1.41 \pm 0.01$ kpc, while the younger population has $R_{<4Gyr} = 0.72 \pm 0.01$ kpc. However, the spatial distribution of the younger population deviates significantly from the projected exponential disk model. The distribution of old stars suggests a large truncation radius of $R_t = 13.5 \pm 0.8$ kpc. If this truncation is dominated by the tidal field of the Galaxy, we find that the LMC is $\simeq 24^{+9}_{−6}$ times less massive than the encircled Galactic mass. By measuring the Red Clump peak magnitude and comparing with the best-fit LMC disk model, we find that the LMC disk is warped and thicker in the outer regions north of the LMC centre. Our findings may either be interpreted as a warped and flared disk in the LMC outskirts, or as evidence of a spheroidal halo component.