Infrared emission regions in the interacting galaxy system ARP 299

Abstract

We present infrared imagery and photometry of the interacting galaxy system Arp 299 (also called Markarian 171, or NGC 3690/IC 694). In the central region of NGC 3690 we see two 2.2 μm sources; one of these (component B2) coincides with the apparent visible nucleus, while the other (component B1) coincides with the 6 cm and 10 μm sources. We see no evidence at 2.2 μm for a compact AGN in IC 694 (component A). Approximately 75% of the 12-25 μm power from Arp 299 comes from three regions each smaller than 600 pc in diameter centered on components A, B 1, and C, making the distribution of mid-infrared emission more concentrated than the distribution of starlight. We remain ambivalent as to whether or not source C marks the position of a further galaxy nucleus. It is more luminous than any known nonnuclear astronomical object and has physical conditions even more extreme than those in well established starburst nuclei. The main arguments against its being a nucleus are based on the implausibility of multiple simultaneous mergers.