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According to the $\Lambda$CDM cosmology, present-day galaxies with stellarmasses $M_\star>10^{11} {\rm M}_\odot$ should contain a sizable fraction ofdark matter within their stellar body. Models indicate that in massiveearly-type galaxies (ETGs) dark matter should account for $\sim60\%$ of thedynamical mass within five effective radii ($5 R_{\rm e}$). Most massive ETGshave been shaped through a two-phase process: the rapid growth of a compactcore was followed by the accretion of an extended envelope through mergers. Theexceedingly rare galaxies that have avoided the second phase, the so-calledrelic galaxies, are thought to be the frozen remains of the massive ETGpopulation at $z\gtrsim2$. The best relic galaxy candidate discovered to dateis NGC 1277, in the Perseus cluster. We used deep integral field GCMS data torevisit NGC 1277 out to an unprecedented radius of 6 kpc (corresponding to $5R_{\rm e}$). By using Jeans anisotropic modelling we find a negligible darkmatter fraction within $5 R_{\rm e}$ ($f_{\rm DM}(5 R_{\rm e})<0.05$; two-sigmaconfidence level), which is in tension with the expectation. Since the lack ofan extended envelope would reduce dynamical friction and prevent the accretionof an envelope, we propose that NGC 1277 lost its dark matter very early orthat it was dark matter deficient ab initio. We discuss our discovery in theframework of recent proposals suggesting that some relic galaxies may resultfrom dark matter stripping as they fell in and interacted within galaxyclusters. Alternatively, NGC 1277 might have been born in a high-velocitycollision of gas-rich proto-galactic fragments, where dark matter left behind adisc of dissipative baryons. We speculate that the relative velocities of$\approx2000 {\rm km/s}$ required for the latter process to happen werepossible in the progenitors of the present-day rich galaxy clusters.

The massive relic galaxy NGC 1277 is dark matter deficient. From dynamical models of integral-field stellar kinematics out to five effective radii