A Stream Come True -- Connecting tidal tails, shells, streams, and planes with galaxy kinematics and formation history

Abstract

Context. The rapidly improving quality and resolution of both low surface brightness observations and cosmological simulations of galaxies enables an increasingly thorough investigation of the imprints of the formation history in the outer, unrelaxed regions of galaxies, and a direct comparison to another tracer of galaxy formation, the internal kinematics. Aims. Using the state-of-the-art hydrodynamical cosmological simulation Magneticum Pathfinder, we identify tidal tails, shells, streams, and satellite planes, and connect their existence to the amount of rotational support and the formation histories of the host galaxies. Methods. Tidal features are visually classified from a three-dimensional rendering of the simulated galaxies by several scientists independently. Only features that were identified by at least half of the participating individuals are considered as existing features. The results are compared to observations of the MATLAS survey. Results. Shells are preferentially found around kinematically slowly rotating galaxies in both simulations and observations, while streams can be found around all kind of galaxies with a slightly higher probability to be present around less rotationally supported galaxies. Tails and satellite planes, however, appear independently of the internal kinematics of the central galaxy, indicating that they are formed through processes that have not (yet) affected the internal kinematics. Conclusions. As shells are formed through radial merger events while streams are remnants of circular merger infall, this suggests that the orbital angular momentum of the merger event could play a more crucial role in transforming the host galaxy than previously anticipated. The existence of a shell around a given slow rotator can further be used to distinguish the radial merger formation scenario from other formation pathways of slow rotators.

Dark matter substructures affect dark matter-electron scattering in xenon-based direct detection experiments

“…However, for relatively recent mergers, there will not be sufficient time for virialization, resulting in plenty of substructures both in the stellar and in the DM component [85][86][87][88][89][90][91][92][93][94][95][96][97]. The presence of such additional stellar substructures (beyond the MW stars) have been detected by different sky-surveys like Gaia [83,90,[97][98][99][100], SDSS [90], LAMOST [101,102], etc., and have also been predicted in various N-body simulations [103][104][105][106][107][108][109][110][111].…”

Detection of Multiple Phase Space Overdensities of GSE Stars by Orbit Integration

“…In N-body simulations, tidal debris of nearly radial merger events can create patterns similar to shells or umbrellas both in the sky position (Amorisco 2015;Karademir et al 2019;Valenzuela & Remus 2022) and phase space (r − v r ; Seguin & Dupraz 1996;Sanderson & Helmi 2013;Dong-Páez et al 2022). Such tidal features are found in M31 (Fardal et al 2007) and some elliptical galaxies (Hendel & Johnston 2015;Bílek et al 2022) from the photometric images of their surface brightness.…”