LMCa: the LMC analog
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LMCa was chosen because it is a fairly massive subhalo with a pericentric distance ($\sim 50$ kpc ) and velocity ($\sim 400$ km/s) in good agreement with that of the LMC [@Kallivayalil2006 hereafter K06]. Identified before infall, at $z_{id}=0.9$, LMCa has a virial mass of $M_{200}=3.6 \times 10^{10} \; M_\odot$, which corresponds to a circular velocity of $\sim 65$ km/s.

LMCa first crosses the virial boundary of the main Aquarius halo (Aq-A) at $z = 0.51$ ($t = 8.6$ Gyr), reaches first pericenter at $t_{\rm
  1p}=9.6$ Gyr, and is able to complete a second pericentric passage at $t_{\rm 2p}=13.3$ Gyr. The host halo has a virial mass of $M_{200}=1.8\times 10^{12}\, M_\odot$ at $z=0$. (These times are actually slightly past actual pericenter, thus chosen so as to best accommodate the fact that the LMC has a slight positive radial velocity and is itself just past pericenter at present.)

At $t_{1p}$ and $t_{2p}$, the distances, radial velocities, and tangential velocities are, respectively, $r_{1p}=65$ kpc, $r_{2p}=69$ kpc, $V_{r,1p} = 78$ km/s, $V_{r,2p}=89$ km/s; $V_{t,1p} = 345$ km/s; and $V_{t,2p}=302$ km/s. These values are in reasonable agreement with the K06 LMC measurements (see Fig. 1 in S11), although the 