A giant central red disk galaxy at redshift z = 0.76: Challenge to theories of galaxy formation

We report a giant red central disk galaxy in the XMM-LSS north region. The region is covered with a rich variety of multi-band photometric and spectroscopic observations. Using the photometric data of the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) and spectroscopic observation of the baryon oscillation spectroscopic survey (BOSS), we find that the galaxy has a stellar mass of ∼1011.6M⨀. The galaxy has a red color and has an old stellar population, and thus its star formation has stopped. With the photometric image data of the Hyper Suprime-Cam (HSC) Subaru Strategic Program, we demonstrate that its luminosity profile is perfectly described by a Sersic form with n=1.22 consistent with that of a disk. We also analyze its environment based on the VIMOS Public Extragalactic Redshift Survey (VIPERS) photometric catalog, and find that its close neighbors are all less massive, indicating that our observed galaxy is sitting at the center of its dark matter host halo. Existence of such a giant red central disk galaxy seriously challenges the current standard paradigm of galaxy formation, as there is no known physical mechanism to explain the quenching of its star formation. This conclusion is supported by state-of-the-art hydrodynamical simulations of galaxy formation.