A1 Refereed original research article in a scientific journal
Adaptive optics imaging and optical spectroscopy of a multiple merger in a luminous infrared galaxy
Authors: Vaisanen P, Mattila S, Kniazev A, Adamo A, Efstathiou A, Farrah D, Johansson PH, Ostlin G, Buckley DAH, Burgh EB, Crause L, Hashimoto Y, Lira P, Loaring N, Nordsieck K, Romero-Colmenero E, Ryder S, Still M, Zijlstra A
Publisher: BLACKWELL PUBLISHING
Publication year: 2008
Journal:Monthly Notices of the Royal Astronomical Society
Journal name in sourceMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Journal acronym: MON NOT R ASTRON SOC
Volume: 384
Issue: 3
First page : 886
Last page: 906
Number of pages: 21
ISSN: 0035-8711
DOI: https://doi.org/10.1111/j.1365-2966.2007.12703.x
Abstract
One nucleus is a regular barred spiral with significant rotation, while another is highly disturbed with a surface brightness distribution intermediate to that of disc and bulge systems, and hints of remaining arm/bar structure. We derive dynamical masses in the range 3-7 x 10(10) M-circle dot for both. The third component appears to be a 1-2 x 10(10) M-circle dot mass irregular galaxy. The total system exhibits H ii galaxy-like optical line ratios and strengths, and no evidence for active galactic nucleus (AGN) activity is found from optical or mid-IR data. The star formation rate is estimated to be similar to 190 M-circle dot yr(-1). We also report a search for supernovae from NIR images separated by five months and search for superstar cluster candidates. We detect outflowing gas from the Bird mostly in the range 100-300 km s(-1) using Na i D absorption features. Overall, the Bird shows kinematic, dynamical and emission-line properties typical for cool ultraluminous IR galaxies (ULIRGs). However, the interesting features setting it apart for future studies are its triple merger nature, and the location of its star formation peak - the strongest star formation, as revealed by Spitzer imaging, does not come from the two major K-band nuclei, but from the third irregular component. This is in contrast to the conventional view that the (U)LIRG phases are powered by infalling gas to the major nuclei of the merging spiral galaxies. Aided by simulations, we discuss scenarios where the irregular component is on its first high-speed encounter with the more massive components.
One nucleus is a regular barred spiral with significant rotation, while another is highly disturbed with a surface brightness distribution intermediate to that of disc and bulge systems, and hints of remaining arm/bar structure. We derive dynamical masses in the range 3-7 x 10(10) M-circle dot for both. The third component appears to be a 1-2 x 10(10) M-circle dot mass irregular galaxy. The total system exhibits H ii galaxy-like optical line ratios and strengths, and no evidence for active galactic nucleus (AGN) activity is found from optical or mid-IR data. The star formation rate is estimated to be similar to 190 M-circle dot yr(-1). We also report a search for supernovae from NIR images separated by five months and search for superstar cluster candidates. We detect outflowing gas from the Bird mostly in the range 100-300 km s(-1) using Na i D absorption features. Overall, the Bird shows kinematic, dynamical and emission-line properties typical for cool ultraluminous IR galaxies (ULIRGs). However, the interesting features setting it apart for future studies are its triple merger nature, and the location of its star formation peak - the strongest star formation, as revealed by Spitzer imaging, does not come from the two major K-band nuclei, but from the third irregular component. This is in contrast to the conventional view that the (U)LIRG phases are powered by infalling gas to the major nuclei of the merging spiral galaxies. Aided by simulations, we discuss scenarios where the irregular component is on its first high-speed encounter with the more massive components.
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