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

According to the Lambda cold dark matter (Lambda CDM) cosmology, present-day galaxies with stellar masses M-star > 10(11) M-circle dot should contain a sizable fraction of dark matter within their stellar body. Models indicate that in massive early-type galaxies (ETGs) with M-star approximate to 1.5 x 10(11) M-circle dot, dark matter should account for similar to 15% of the dynamical mass within one effective radius (1 R-e) and for similar to 60% within 5 Re. Most massive ETGs have been shaped through a two-phase process: the rapid growth of a compact core was followed by the accretion of an extended envelope through mergers. The exceedingly rare galaxies that have avoided the second phase, the so-called relic galaxies, are thought to be the frozen remains of the massive ETG population at z greater than or similar to 2. The best relic galaxy candidate discovered to date is NGC1277, in the Perseus cluster. We used deep integral field George and Cynthia Mitchel Spectrograph (GCMS) data to revisit NGC1277 out to an unprecedented radius of 6 kpc (corresponding to 5 R-e). By using Jeans anisotropic modelling, we find a negligible dark matter fraction within 5 R-e (f(DM)(5 R-e) < 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 NGC1277 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, NGC1277 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 approximate to 2000 km s(-1) required for the latter process to happen were possible in the progenitors of the present-day rich galaxy clusters.