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Register a new userSignatures of tidal disruption in the Milky Way globular cluster NGC 6981 (M72)
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Added by
Andr\\'es E. Piatti
Publication date
2021
fields
Physics
and research's language is
English
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We study the outer regions of the Milky Way globular cluster NGC6981 from publicly available $BV$ photometry and new Dark Energy Camera (DECam) observations, both reaching nearly 4 mag below the cluster main sequence (MS) turnoff. While the $BV$ data sets reveal the present of extra-tidal features around the cluster, the much larger field of view of DECam observations allowed us to identify some other tidal features, which extend from the cluster toward the opposite direction to the Milky Way center. These cluster structural features arise from stellar density maps built using MS stars, once the cluster color-magnitude diagram was cleaned from the contamination of field stars. We also performed $N$-body simulations in order to help us to understand the spatial distribution of the extra-tidal debris. The outcomes reveal the presenceof long trailing and leading tails mostly parallel to the direction of the cluster velocity vector. We found that the cluster has lost most of its mass by tidal disruption during its perigalactic passages, that lasted nearly 20 Myr each. Hence, a decrease in the density of escaping stars near the cluster is expected from our $N$-body simulations, which in turn means that stronger extra-tidal features could be found out by exploring much larger areas around NGC6891.
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We present results on the extra-tidal features of the Milky Way globular cluster NGC 7099, using deep gr photometry obtained with the Dark Energy Camera (DECam). We reached nearly 6 mag below the cluster Main Sequence (MS) turnoff, so that we dealt with the most suitable candidates to trace any stellar structure located beyond the cluster tidal radius. From star-by-star reddening corrected color-magnitude diagrams (CMDs) we defined four adjacent strips along the MS, for which we built the respective stellar density maps, once the contamination by field stars was properly removed. The resulting field star cleaned stellar density maps show a short tidal tail and some scattered debris. Such extra-tidal features are hardly detected when much shallower Gaia DR2 data sets are used and the same CMD field star cleaning procedure is applied. Indeed, by using 2.5 magnitudes below the cluster MS turnoff as the faintest limit (G < 20.5 mag), cluster members turned out to be distributed within the clusters tidal radius, and some hints for field star density variations are found across a circle of radius 3.5deg centered on the cluster and with similar CMD features as cluster stars. The proper motion distribution of these stars is distinguishable from that of the cluster, with some superposition, which resembles that of stars located beyond 3.5deg from the cluster center.
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