Towards a higher mass for NGC 1052-DF2: an analysis based on full distribution functions

It is demonstrated that the kinematics of the 10 star clusters in NGC 1052-DF2 is compatible with a high dynamical mass close to those implied by the standard stellar-to-halo-mass ratio (SHMR). The analysis relies on a convenient form for the distribution function of projected phase space data, capturing non-Gaussian features in the spread of true velocities of the mass tracers. A key ingredient is tidal stripping by the gravity of the apparently nearby larger galaxy, NGC 1052. Tidal stripping decreases the range of velocities of mass tracers, while only mildly lowering the total mass inside the trimming radius r(tr). The analysis is performed assuming halo profiles consistent with simulations of the Lambda CDM model. For the fiducial value r(tr) = 10 kpc, we find that the virial mass of the pre-trimmed halo is M < 1.6 x 10(10) M-circle dot at 2 sigma (95 per cent) and M < 8.6 x 10(9) M-circle dot at 1.64 sigma (90 per cent). For the mass within 10 kpc we obtain, M-10kpc < 3.9 x 10(9) M-circle dot and < 2.9 x 10(9) M-circle dot at 2 sigma and 1.64 sigma, respectively. The 2 sigma upper limit on the virial mass is roughly a factor of 3-5 below the mean SHMR relation: faking r(tr) = 20 kpc lowers the 2 sigma virial mass limits by a factor of similar to 4, bringing our results closer to those of Wasserman et al. (2018) without their SHMR prior.