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arXiv · 1811.06429

Discovery of Tidal RR LYRAE stars in the Bulge Globular Cluster M 62

Dante Minniti·José G. Fernández-Trincado·Vincenzo Ripepi·Javier Alonso-García·Rodrigo Contreras Ramos·Marcella Marconi
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Abstract

The RR Lyrae (RRL) rich globular cluster M 62 (NGC 6266) is one of the most massive globular clusters in the Milky Way, located in the dense region of the Galactic bulge, where dynamical processes that affect the survival of globular clusters are maximised. Using Gaia DR2 data we have found clear evidence for an excess of RRLs beyond the cluster tidal radius of M 62, associated partly with stars stripped into the Galaxy field. This is confirmed with new VVVX survey observations, that discard any differential reddening effect as the possible cause of the observed RRL density excess. We also determined the orbit of M 62 using accurate new measurements of its distance, radial velocity and proper motions (PMs), finding that its orbit is prograde respect to the direction of the Galactic rotation. Orbits are integrated in the non-axisymmetric galactic model \texttt{GravPot16}, which includes the perturbations due to the central Galactic bar. M 62 shows a particular orbital behaviour, having a dynamical signature of the bar-bulge region. The small extra-tidal RRLs extensions observed are roughly aligned towards the galactic center and the direction almost perpendicular to the galactic plane and not with its motion along its orbit, which may be a clear sign of bulge-crossing shocks, during the last passage close of the cluster towards its perigalacticon. M 62 would be the first clear observed case of bulge shocking in the inner Galaxy acting on a globular cluster.

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Dante Minniti, José G. Fernández-Trincado, Vincenzo Ripepi, Javier Alonso-García, Rodrigo Contreras Ramos, Marcella Marconi. 2018-11-15. Discovery of Tidal RR LYRAE stars in the Bulge Globular Cluster M 62. https://doi.org/10.3847/2041-8213%2Faaf1cd

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