Abstract
We present for the first time extended stellar density and/or surface brightness radial profiles for almost all the known Large Magellanic Cloud (LMC) old globular clusters (GCs). These were built from DECam images and reach out to ~ 4 times the GCs' tidal radii. The background subtracted radial profiles reveal that the GCs located closer than ~ 5 kpc from the LMC centre contain an excess of stars in their outermost regions with respect to the stellar density expected from a King profile. Such a residual amount of stars - not seen in GCs located farther than ~ 5 kpc from the LMC centre-, as well as the GCs' dimensions, show a clear dependence with the GCs' positions in the galaxy, in the sense that, the farther the GC from the centre of the LMC, the larger both the excess of stars in its outskirts and size. Although the masses of GCs located inside and outside ~ 5 kpc are commensurate, the outermost regions of GCs located closer than ~ 5 kpc from the LMC centre appear to have dynamically evolved more quickly. These outcomes can be fully interpreted in the light of the known GC radial velocity disc-like kinematics, from which GCs have been somehow mostly experiencing the influence of the LMC gravitational field at their respective mean distances from the LMC centre.
Highlights
Wagner-Kaiser et al (2017, hereafter WK17) used HST data to show that metal-poor old globular clusters (GCs) in the inner halo of the Milky Way (MW) and in the Large Magellanic Cloud (LMC) are highly synchronized, in the sense that they seem to be coeval to 0.2 ± 0.4 Gyr
By searching the National Optical Astronomy Observatory (NOAO) Science Data Management (SDM) Archives1 we found DECam images taken in the field of NGC 1841, 2210 and Hodge 11 by the Survey of the Magellanic Stellar History (SMASH; Nidever et al 2017), and in the field of Reticulum by the Dark Energy Survey (DES; Abbott et al 2016)
A first glance, results contrary to the expected higher tidal filling in more massive GCs. We found that such an apparent opposite behaviour could be due to the differential LMC gravitational field, i.e, GCs located in the galaxy outskirts have been allowed to expand more than those in inner regions, provided that they were placed in disc-like orbits during their lifetimes (Miholics et al 2014)
Summary
Wagner-Kaiser et al (2017, hereafter WK17) used HST data to show that metal-poor old globular clusters (GCs) in the inner halo of the Milky Way (MW) and in the Large Magellanic Cloud (LMC) are highly synchronized, in the sense that they seem to be coeval to 0.2 ± 0.4 Gyr. It presents estimates of a wide variety of dynamical and structural parameters from the constructed profiles that results in an homogeneous compilation for almost all ancient GCs in the LMC. We performed extensive artificial star tests around the cluster regions in order to accurately map the completeness of our photometry in terms of photometric depth and spatial dependence with the distance from the cluster centre In doing this we repeated the PSF photometry recipes referred above – including the three passes to measure fainter stars – on a thousand created images per cluster with nearly 5 per cent added stars distributed appropriately according to the cluster stellar density profile and covered magnitude range
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
