Discovery of a Unique Close Quasar–DSFG Pair Linked by a [C II] Bridge at z = 5.63

Abstract

Abstract We report the discovery of a unique quasar-dusty star-forming galaxy (DSFG) system at z = 5.63, consisting of the bright quasar J1133+1603 ( M UV = − 27.42) and its compact, dust-obscured companion, J1133c. ALMA observations reveal a prominent [C II ] bridge connecting the quasar and DSFG, indicating ongoing interaction at a projected separation of 1 . ″ 8 (∼10 proper kpc). J1133c exhibits unusually bright and broad [C II ] emission ( L [C II ] > 10 43 erg s −1 , FWHM > 500 km s −1 ), with a [C II ] luminosity five times that of the quasar, suggesting intense star formation or potential active galactic nucleus activity. The inferred star formation rate from [C II ] is approximately 10 3 M ⊙ yr −1 . The remarkable properties of this pair strongly suggest that galaxy interactions may simultaneously trigger both starburst and quasar activity, driving rapid evolution in the early universe.