2002/05/23 by E. Le Floc'h, V. Charmandaris, O. Laurent +6 · 1 citation
Physics and Astronomy · #Active galactic nucleus #Astronomy and Astrophysical Research #Galaxies: Formation, Evolution, Phenomena #Galaxy #Gamma-ray bursts and supernovae #Infrared #Luminous infrared galaxy #Radio galaxy #Spectral energy distribution #Star formation #Stars #astro-ph
paper · pdf · doi:10.1051/0004-6361:20020784
14 pages, 5 figures, accepted for publication in A&A
arxiv created 2002/05/23 · openalex publication_date 2002/08/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We present our 5–16 μm spectro-imaging observations of VV 114, an infrared luminous early-stage merger of two galaxies VV 114E and VV 114W, taken with the ISOCAM camera on-board the Infrared Space Observatory. We find that only 40% of the mid-infrared (MIR) flux is associated with a compact nuclear region of VV 114E, while the rest of the emission originates from a rather diffuse component extended over several kpc in the regions between VV 114E and VV 114W. This is in stark contrast with the very compact MIR starbursts usually seen in luminous and ultraluminous infrared galaxies. A secondary peak of MIR emission is associated with an extra-nuclear star forming region of VV 114W which displays the largest Hα equivalent width in the whole system. Comparing our data with the distribution of the molecular gas and cold dust, as well as with radio observations, it becomes evident that the conversion of molecular gas into stars can be triggered over large areas at the very first stages of an interaction. This extended star formation along with the extreme nuclear starburst observed in VV 114E can easily lead to the heating of dust grains found in the tidally disturbed disks of the progenitor galaxies and subsequently traced via their MIR emission. The presence of a very strong continuum at the 5–6.5 μm range in the spectrum of VV 114E indicates that an enshrouded active galactic nucleus (AGN) may contribute to ~40% of its MIR flux. We finally note that the relative variations in the UV to radio spectral properties between VV 114E and VV 114W provide evidence that the extinction-corrected star formation rate of similar objects at high z, such as those detected in optical deep surveys, cannot be accurately derived from their rest-frame UV properties.