In section 1. Letters to the Editor
Sub-arcsecond imaging of Arp299-A at 150 MHz with LOFAR: Evidence for a starburst-driven outflow
Starbursts in merging galaxies can provide spectacular outflows, due to supernovae feedback. The starburst in the Arp 299 pair of colliding galaxies is here shown to provide a huge outflow, of about 5kpc in length, perpendicular to one of the disks. The outflow is remarkable in the high-resolution (0.4 arcsec) image at 150 MHz obtained with the International Low Frequency Array (LOFAR) Telescope. The filamentary outflowing structure accounts for almost 40% of the extended emission of the entire galaxy system. The structure coincides with the ionized gas outflow imaged with HST/NICMOS in the [FeII] and H2 2 mumicron lines. The outflow is also confirmed through Na I D spectra. The low-luminosity AGN in this galaxy would be insufficient to drive this outflow, contrary to the powerful and compact nuclear starburst. The outflow corresponds to 10-60 Mo/yr at a velocity 400-800km/s. This work shows that subarcsecond imaging with LOFAR might be an excellent new tool with which to unveil outflows in the central regions of local luminous infrared galaxies.