2020ApJ...905..100C

The complicated story of the Cetus Stream (CS) is recently revealed by its newly discovered ∼150 members with 6D kinematics from the cross-matched catalog of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) DR5 K giants and Gaia DR2. It exhibits a very diffuse structure at heliocentric distances between 20 and 50 kpc, extending over at least 100°, and crossing the Galactic plane. Interestingly, The CS is dynamically linked to a massive globular cluster, NGC 5824. A suggestive scenario is that NGC 5824 was the nuclear star cluster of the dwarf progenitor of the CS. We explore this scenario by modeling the disruption process of a dwarf galaxy in the Milky Way potential, on the orbit of NGC 5824, using a suite of N-body simulations. Our results show that the simulated stream can marginally recover the main component of the CS, which is the densest part of the observed stream. Inspired by this mismatch, we use a dwarf progenitor following the representative orbit of the main component members, and find it can reproduce the general morphology of the CS. This gives us a more favorable scenario of the CS progenitor, in which NGC 5824 was not the core, but located off-center. Our fiducial model also predicts a vast extension of the CS in the South, surprisingly coincident with a newly discovered wide southern stream "Palca." Another more diffuse substructure, the Eridanus-Phoenix overdensity is also likely to be related to the CS progenitor.