NGC1277 + NGC1278 spectra + kinematic information

By using Jeans anisotropic modelling, we find a negligible dark matter fraction within 5Re (fDM(5Re)<0.05; two-sigma confidence level), which is in tension with the Lambda-CDM expectation. Since the lack of an extended envelope would reduce dynamical friction and prevent the accretion of an envelope, we propose that NGC 1277 lost its dark matter very early or that it was dark matter deficient ab initio. We discuss our discovery in the framework of recent proposals, suggesting that some relic galaxies may result from dark matter stripping as they fell in and interacted within galaxy clusters.

Alternatively, NGC 1277 might have been born in a high-velocity collision of gas-rich proto-galactic fragments, where dark matter left behind a disc of dissipative baryons. We speculate that the relative velocities of ~2000km/s required for the latter process to happen were possible in the progenitors of the present-day rich galaxy clusters.