The Dragonfly Galaxy: II. ALMA unveils a triple merger and gas exchange in a hyper-luminous radio galaxy at z = 2
MetadataShow full item record
Reproduced with permission from Astronomy & Astrophysics, © ESO
The Dragonfly Galaxy (MRC 0152-209), at redshift z ~ 2, is one of the most vigorously star-forming radio galaxies in the Universe. What triggered its activity? We present ALMA Cycle 2 observations of cold molecular CO(6−5) gas and dust, which reveal that this is likely a gas-rich triple merger. It consists of a close double nucleus (separation ~4 kpc) and a weak CO-emitter at ~10 kpc distance, all of which have counterparts in HST/NICMOS imagery. The hyper-luminous starburst and powerful radio-AGN were triggered at this precoalescent stage of the merger. The CO(6−5) traces dense molecular gas in the central region, and complements existing CO(1−0) data, which reveal more widespread tidal debris of cold gas. We also find ~1010 M☉ of molecular gas with enhanced excitation at the highest velocities. At least 20−50% of this high-excitation, high-velocity gas shows kinematics that suggests it is being displaced and redistributed within the merger, although with line-of-sight velocities of |v| < 500 km s-1, this gas will probably not escape the system. The processes that drive the redistribution of cold gas are likely related to either the gravitational interaction between two kpc-scale discs, or starburst/AGN-driven outflows. We estimate that the rate at which the molecular gas is redistributed is at least [Ṁentity!#x2009!]~ 1200 ± 500 M☉ yr-1, and could perhaps even approach the star formation rate of ~3000 ± 800 M☉ yr-1. The fact that the gas depletion and gas redistribution timescales are similar implies that dynamical processes can be important in the evolution of massive high-z galaxies.
Showing items related by title, author, creator and subject.
A CO-rich merger shaping a powerful and hyperluminous infrared radio galaxy at z = 2: The Dragonfly GalaxyEmonts, B.; Mao, M.; Stroe, A.; Pentericci, L.; Villar-Martín, M.; Norris, R.; Miley, G.; De Breuck, C.; Van Moorsel, G.; Lehnert, M.; Carilli, C.; Röttgering, H.; Seymour, Nick; Sadler, E.; Ekers, R.; Drouart, G.; Feain, I.; Colina, L.; Stevens, J.; Holt, J. (2015)In the low-redshift Universe, the most powerful radio sources are often associated with gas-rich galaxy mergers or interactions. We here present evidence for an advanced, gas-rich (‘wet’) merger associated with a powerful ...
SDSS J002531.46-104022.2 at z = 0.30: A candidate for the (ultra)luminous infrared galaxy to optical quasar transitionVillar-Martín, M.; Emonts, B.; Rodríguez, M.; Pérez Torres, M.; Drouart, Guillaume (2013)Using data obtained with the Australia Telescope Compact Array (ATCA), we have characterized the amount, spatial distribution and kinematics of the molecular gas in the merging, double-nucleus type 2 quasar (QSO) SDSS ...
An ALMA survey of submillimetre galaxies in the COSMOS field: Physical properties derived from energy balance spectral energy distribution modellingMiettinen, O.; Delvecchio, I.; Smolcic, V.; Aravena, M.; Brisbin, D.; Karim, A.; Magnelli, B.; Novak, M.; Schinnerer, E.; Albrecht, M.; Aussel, H.; Bertoldi, F.; Capak, P.; Casey, C.; Hayward, C.; Ilbert, O.; Intema, Hubertus; Jiang, C.; Le Fèvre, O.; McCracken, H.; Munõz Arancibia, A.; Navarrete, F.; Padilla, N.; Riechers, D.; Salvato, M.; Scott, K.; Sheth, K.; Tasca, L. (2017)Context. Submillimetre galaxies (SMGs) represent an important source population in the origin and cosmic evolution of the most massive galaxies. Hence, it is imperative to place firm constraints on the fundamental physical ...