The Dragonfly Galaxy: II. ALMA unveils a triple merger and gas exchange in a hyper-luminous radio galaxy at z = 2
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...
| Main Authors: | , , , , , , , , , , , |
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| Format: | Journal Article |
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2015
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| Online Access: | http://hdl.handle.net/20.500.11937/7309 |
| _version_ | 1848745331972374528 |
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| author | Emonts, B. De Breuck, C. Lehnert, M. Vernet, J. Gullberg, B. Villar-Martin, M. Nesvadba, N. Drouart, G. Ivison, R. Seymour, Nick Wylezalek, D. Barthel, P. |
| author_facet | Emonts, B. De Breuck, C. Lehnert, M. Vernet, J. Gullberg, B. Villar-Martin, M. Nesvadba, N. Drouart, G. Ivison, R. Seymour, Nick Wylezalek, D. Barthel, P. |
| author_sort | Emonts, B. |
| building | Curtin Institutional Repository |
| collection | Online Access |
| description | 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. |
| first_indexed | 2025-11-14T06:15:40Z |
| format | Journal Article |
| id | curtin-20.500.11937-7309 |
| institution | Curtin University Malaysia |
| institution_category | Local University |
| last_indexed | 2025-11-14T06:15:40Z |
| publishDate | 2015 |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | curtin-20.500.11937-73092017-09-13T14:37:01Z The Dragonfly Galaxy: II. ALMA unveils a triple merger and gas exchange in a hyper-luminous radio galaxy at z = 2 Emonts, B. De Breuck, C. Lehnert, M. Vernet, J. Gullberg, B. Villar-Martin, M. Nesvadba, N. Drouart, G. Ivison, R. Seymour, Nick Wylezalek, D. Barthel, P. 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. 2015 Journal Article http://hdl.handle.net/20.500.11937/7309 10.1051/0004-6361/201526090 fulltext |
| spellingShingle | Emonts, B. De Breuck, C. Lehnert, M. Vernet, J. Gullberg, B. Villar-Martin, M. Nesvadba, N. Drouart, G. Ivison, R. Seymour, Nick Wylezalek, D. Barthel, P. The Dragonfly Galaxy: II. ALMA unveils a triple merger and gas exchange in a hyper-luminous radio galaxy at z = 2 |
| title | The Dragonfly Galaxy: II. ALMA unveils a triple merger and gas exchange in a hyper-luminous radio galaxy at z = 2 |
| title_full | The Dragonfly Galaxy: II. ALMA unveils a triple merger and gas exchange in a hyper-luminous radio galaxy at z = 2 |
| title_fullStr | The Dragonfly Galaxy: II. ALMA unveils a triple merger and gas exchange in a hyper-luminous radio galaxy at z = 2 |
| title_full_unstemmed | The Dragonfly Galaxy: II. ALMA unveils a triple merger and gas exchange in a hyper-luminous radio galaxy at z = 2 |
| title_short | The Dragonfly Galaxy: II. ALMA unveils a triple merger and gas exchange in a hyper-luminous radio galaxy at z = 2 |
| title_sort | dragonfly galaxy: ii. alma unveils a triple merger and gas exchange in a hyper-luminous radio galaxy at z = 2 |
| url | http://hdl.handle.net/20.500.11937/7309 |