ISO Status Report - February 2006
ISO continues to have a significant presence in the refereed literature, with about 1300 papers published to date, embracing all areas of astronomy. Recent highlights include the detection of dust obscured star formation in the colliding galaxies system Markarian 297. The result, published in A&A by Metcalfe et al., is derived from observations with the ISOCAM, ISOPHOT and LWS instruments on board ISO. The ISOCAM observations reveal that the strongest emission, seen in four bands, is at a location completely unremarkable at visible and near infrared wavelengths, and does not coincide with the nuclear region of either colliding galaxy.
This striking characteristic has also been observed in the overlap region of the colliding galaxies in the Antennae, the intragroup region of Stephan's Quintet, and in IC 694 in the interacting system Arp 299, and again underlines the importance of infrared observations in understanding star formation in colliding/merging systems. At 15 micron, the hidden source in Mkn 297 is, respectively, 14.6 and 3.8 times more luminous than the hidden sources in the Antennae and Stephan's Quintet. The total infrared luminosity is approximately 1011 solar luminosities, which (marginally) classifies the system as a luminous infrared galaxy (LIRG). A supernova that exploded in 1979 (SN 1982aa) gave rise to one of the most powerful known radio remnants, which falls close to the strongest mid-infrared source.