Infrared spectral energy distributions of the interacting galaxies ARP 244, NGC 6240, and ARP 220.

Abstract

For the luminous galaxies Arp 244, NGC 6240 and Arp 220 detailed infrared spectral energy distributions between 3 and 200μm obtained with ISOPHOT are presented. The maximum of the infrared energy distribution can now clearly be determined. The SEDs can be well represented by cold dust emission with temperatures of 30-50K which by far dominates the luminosity. In addition, a second warm dust component is present with temperatures of 120-160K. The infrared luminosities derived from the ISOPHOT data agree, within the errors, with the extrapolated IRAS 8-1000μm luminosities. The cold component of Arp 244 shows similarities to HII regions in normal galaxies, while NGC 6240 and Arp 220 have huge dust masses heated up to considerably higher temperatures. We discuss the observations in the context of heating by starbursts and conversion of mechanical energy from collision or outflow.