Title: The LMC structure from early Dark Energy Survey data

Authors: Eduardo Balbinot (University of Surrey, UK)

Talk abstract:
We use new Dark Energy Survey (DES) Science Verification (SV) data to study the outskirts of 
the Large Magellanic Cloud (LMC). This novel dataset provides photometry up to 1.5 
magnitudes fainter than the LMC oldest main sequence turn-off in an area of $\sim 300$ deg
$^2$ north of the LMC. We derive geometrical and structural parameters for age-selected stellar 
populations by fitting a circular projected exponential disk model. We find an inclination of ~38 
deg (North side near) and a position angle of the line of nodes of ~130 deg, both which are 
in agreement with previous determinations. Our main finding is that stars older than 4 Gyr are 
more centrally concentrated (scale radius of $R_s = 1.41\pm0.01$ kpc) than younger stars 
($R_s = 0.72\pm0.01$ kpc); favouring the outside-in formation scenario. In addition to that, we 
find that the oldest LMC stars are indistinguishable - in number - to Milky Way (MW) stars at a 
radius of $13.5\pm0.8$ kpc. If the truncation in the LMC luminous component is due to the tidal 
field of the MW, we estimate an upper limit in the LMC-MW$_{encircled}$ mass ratio of 
​$​23^{+9}_{-6}​$​, which is in agreement with recent dynamical mass determinations. However, it 
is not clear if LMC stars are not "shielded" from the tidal field by a larger dark matter halo, 
making our initial assumption invalid. Using Red Clump stars we find signs of thickening (flare) 
of the LMC disk outer parts, as well as evidence of warping in the north edge of the disk. Both 
the warp and flare detections agree with what is expected from simulations and other 
observations. We hope the findings reported here will be useful to constrain the interaction 
history of the LMC and SMC, as well as to shed light on their orbit around the MW. We also 
briefly discuss future works that will greatly benefit from upcoming DES data, such as the 
search for a stellar component in the Magellanic Stream and other MW halo substructures.