Volume 549, January 2013
|Number of page(s)||8|
|Published online||18 December 2012|
IRAM – Institut de RadioAstronomie Millimétrique, 300 rue de la Piscine,
Saint Martin d’Hères,
2 INAF – Osservatorio astronomico di Roma, via Frascati 33, 00040 Monteporzio Catone, Italy
3 Cavendish Laboratory, University of Cambridge, 19 J. J. Thomson Ave., Cambridge CB3 0HE, UK
4 XMM-Newton Science Operations Centre, ESAC, PO Box 78, 28691 Villanueva de la Canãda, Madrid, Spain
5 Laboratoire AIM-Paris-Saclay, CEA/DSM/Irfu, CNRS, Université Paris Diderot, Saclay, pt courrier 131, 91191 Gif-sur-Yvette, France
6 Max-Planck-Institut fur Extraterrestrische Physik (MPE), Giessenbachstr. 1, 85748 Garching, Germany
Received: 4 June 2012
Accepted: 5 November 2012
We present deep CO(1–0) observations of NGC 6240 performed with the IRAM Plateau de Bure Interferometer (PdBI). NGC 6240 is the prototypical example of a major galaxy merger in progress, caught at an early stage, with an extended, strongly-disturbed butterfly-like morphology and a heavily obscured active nucleus in the core of each progenitor galaxy. The CO line shows a skewed profile with very broad and asymmetric wings detected out to velocities of −600 km s-1 and +800 km s-1 with respect to the systemic velocity. The PdBI maps reveal two prominent structures of blueshifted CO emission. One extends eastward, i.e. approximately perpendicular to the line connecting the galactic nuclei, on scales of ~7 kpc, and it shows velocities up to −400 km s-1. The other extends southwestward out to ~7 kpc from the nuclear region, and has a velocity of −100 km s-1 with respect to the systemic one. Interestingly, redshifted emission with velocities 400 to 800 km s-1 is detected around the two nuclei, extending in the east-west direction, and partly overlapping with the eastern blueshifted structure, although tracing a more compact region of size ~1.7 kpc. The overlap between the southwestern CO blob and the dust lanes seen in HST images, which are interpreted as tidal tails, indicates that the molecular gas is deeply affected by galaxy interactions. The eastern blueshifted CO emission is cospatial with an Hα filament that is associated with strong H2 and soft X-ray emission. The analysis of Chandra X-ray data provides strong evidence of shocked gas at the position of the Hα emission. Its association with outflowing molecular gas supports a scenario where the molecular gas is compressed into a shock wave that propagates eastward from the nuclei. If this is an outflow, the active galactic nuclei are very likely the driving force.
Key words: galaxies: active / galaxies: interactions / galaxies: evolution / galaxies: ISM / quasars: general
© ESO, 2012
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.