| Type |
Journal Article |
| Names |
P. Väisänen, S. Mattila, A. Kniazev, A. Adamo, A. Efstathiou, D. Farrah, P. H. Johansson, G. Östlin, D. A. H. Buckley, E. B. Burgh, L. Crause, Y. Hashimoto, P. Lira, N. Loaring, K. Nordsieck, E. Romero-Colmenero, S. Ryder, M. Still, A. Zijlstra |
| Publication |
Monthly Notices of the Royal Astronomical Society |
| Volume |
384 |
| Issue |
3 |
| Pages |
886-906 |
| Date |
March 1, 2008 |
| URL |
http://adsabs.harvard.edu/abs/2008MNRAS.384..886V |
| Library Catalog |
NASA ADS |
| Abstract |
We present near-infrared (NIR) adaptive optics imaging obtained with
VLT/NACO and optical spectroscopy from the Southern African Large
Telescope of a luminous IR galaxy (LIRG) IRAS 19115-2124. These data are
combined with archival Hubble Space Telescope imaging and Spitzer
imaging and spectroscopy, allowing us to study this disturbed
interacting/merging galaxy, dubbed the Bird, in extraordinary detail. In
particular, the data reveal a triple system where the LIRG phenomenon is
dominated by the smallest of the 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 ×
1010Msolarfor both. The third component appears to
be a 1-2 × 1010Msolar mass irregular galaxy.
The total system exhibits HII 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 ~190Msolaryr-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 NaI 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.
Based on observations made with ESO Telescopes at the Paranal
Observatory under programme 073.D-0406A, and with the Southern African
Large Telescope (SALT).
E-mail: petri@saao.ac.za |
| Tags |
GALAXIES: EVOLUTION, GALAXIES: INTERACTIONS, galaxies: individual: IRAS 19115-2124, galaxies: kinematics and dynamics, galaxies: starburst, infrared: galaxies |