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dc.contributor.authorEmonts, B.
dc.contributor.authorDe Breuck, C.
dc.contributor.authorLehnert, M.
dc.contributor.authorVernet, J.
dc.contributor.authorGullberg, B.
dc.contributor.authorVillar-Martin, M.
dc.contributor.authorNesvadba, N.
dc.contributor.authorDrouart, G.
dc.contributor.authorIvison, R.
dc.contributor.authorSeymour, Nick
dc.contributor.authorWylezalek, D.
dc.contributor.authorBarthel, P.
dc.identifier.citationEmonts, B. and De Breuck, C. and Lehnert, M. and Vernet, J. and Gullberg, B. and Villar-Martin, M. and Nesvadba, N. et al. 2015. The Dragonfly Galaxy: II. ALMA unveils a triple merger and gas exchange in a hyper-luminous radio galaxy at z = 2. Astronomy and Astrophysics. 584.

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.

dc.titleThe Dragonfly Galaxy: II. ALMA unveils a triple merger and gas exchange in a hyper-luminous radio galaxy at z = 2
dc.typeJournal Article
dcterms.source.titleAstronomy and Astrophysics

Reproduced with permission from Astronomy & Astrophysics, © ESO

curtin.departmentDepartment of Physics and Astronomy
curtin.accessStatusOpen access

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