ALMA unveils a triple merger and gas exchange in a hyper-luminous radio galaxy at z=2: the Dragonfly Galaxy (II)

摘要: The Dragonfly Galaxy (MRC0152-209), at redshift z~2, is one of the most vigorously star-forming radio galaxies in Universe. What triggered its activity? We present ALMA Cycle 2 observations cold molecular CO(6-5) gas and dust, which reveal that this likely a gas-rich triple merger. It consists close double nucleus (separation ~4 kpc) weak CO-emitter ~10 kpc distance, all have counterparts HST/NICMOS imagery. hyper-luminous starburst powerful radio-AGN were precoalescent stage traces dense central region, complements existing CO(1-0) data, revealed more widespread tidal debris gas. also find ~10$^{10}$ M(sun) with enhanced excitation highest velocities. At least 20-50% high-excitation, high-velocity shows kinematics suggests it being displaced redistributed within merger, although line-of-sight velocities |v| < 500 km/s, will probably not escape system. processes drive redistribution are related to either gravitational interaction between two kpc-scale discs, or starburst/AGN-driven outflows. estimate rate ~1200 +- M(sun)/yr, could perhaps even approach star formation ~3000 800 M(sun)/yr. fact depletion timescales similar implies dynamical can be important evolution massive high-z galaxies.