2017/01/04 by P. Väisänen, J. Reunanen, J. Kotilainen +8
Physics and Astronomy · #Active galactic nucleus #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Galaxies: Formation, Evolution, Phenomena #Galaxy #Galaxy formation and evolution #Luminous infrared galaxy #Physics #Population #Redshift #Star formation #Stellar population #Stellar, planetary, and galactic studies #astro-ph.GA
paper · pdf · doi:10.1093/mnras/stx1685
Submitted to MNRAS. 17 pages, 7 tables, 15 figures
arxiv created 2017/01/04 · openalex created_date 2017/01/13 · openalex publication_date 2017/07/04 · arxiv updated 2017/08/23 · openalex updated_date 2026/08/05
We present new SINFONI near-infrared (NIR) integral field unit (IFU) spectroscopy and Southern African Large Telescope (SALT) optical long-slit spectroscopy characterizing the history of a nearby merging luminous infrared galaxy, dubbed the Bird (IRAS19115−2124). The NIR line-ratio maps of the IFU data cubes and stellar population fitting of the SALT spectra now allow dating of the star formation (SF) over the triple system uncovered from our previous adaptive optics data. The distinct components separate clearly in line-ratio diagnostic diagrams, both thermal and non-thermal excitation is present. An off-nuclear starburst dominates the current SF of the Bird with 60–70 per cent of the total, with a 4–7 Myr age. The most massive nucleus, in contrast, is quenched with a starburst age of >40 Myr and shows hints of budding active galactic nucleus (AGN) activity. The secondary massive nucleus is at an intermediate stage. The two major components have signs of an older stellar population, consistent with a starburst triggered 1 Gyr ago in a first encounter. The simplest explanation of the history is that of a triple merger, where the strongly star-forming component has joined later. We detect multiple gas flows. The Bird offers an opportunity to witness multiple stages of galaxy evolution in the same system; triggering as well as very recent quenching of SF, and, perhaps, an early appearance of AGN activity. It also serves as a cautionary note on interpretations of observations with lower spatial resolution and/or without infrared data. At high redshift the system would look like a clumpy starburst with crucial pieces of its puzzle hidden in danger of misinterpretations.