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ZOMG III and beyond!

As promised some time ago, the third paper of the ZOMG series is out! We have some very intriguing results here. First off, the dynamics of satellites is similar to the dark matter one, with the obvious advantage of being (potentially) observable. This means that, in old haloes the trajectories (of both dark matter and satellites) are bent by the strong gravitational potential in which the host resides. On the other hand, young haloes dominates the gravitational potential of their environment and therefore experience radial accretion. As a consequence, the radial velocity of satellites has very different distributions in these two categories of haloes. This is, in principle, already observable but requires a lot of proper motion measurements in order to sample this distribution. Therefore, we condense this distribution into a single number, the anisotropy parameter of the satellites. We find that it is consistently negative (tangential-dominated) in old haloes and positive (radial-dominated) in young ones. Comparing this finding with the anisotropy parameter measured using the Milky Way classical satellites, we can tentatively classify the latter as hosted by an old halo. Finally, we also give a look into the satellite plane in our simulation. We interestingly find a possible hint linking the plane and galactic disc formation, but this requires more work.

Figure 1 (from Garaldi et al. 2018): Trajectories of satellites, with some of them colored for visual clarity. In accreting haloes (left), satellites follow radial trajectories, while in stalled objects (right) they first fall onto the filament (here oriented along the x axis) and then on to the halo, therefore entering the host with very tangential motion.

And now? Now it is time to think about the future of ZOMG. We plan to extend our simulation suite, both in mass range and collapse time explored. So, stay tuned for news!

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