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

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 ($M_{\mathrm{UV}}=-27.42$) 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 arcsec ($\sim$10 proper kpc). J1133c exhibits unusually bright and broad [C II] emission ($L_{[\mathrm{CII}]}>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 AGN activity. The inferred star formation rate from [C II] is approximately $10^3$ M${}_{\odot }$ 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.

RNAAS; 4 pages, 1 figure