SWS spectra the ultraluminous infrared galaxy Arp 220 that reveal the presence of emission lines indicating vigorous star formation.
This image has been taken from the MPG Press Release, "Europe's space telescope ISO reveals the energy source of luminous galaxies".
More information on this source can be found in;
"ISO-SWS spectroscopy of ARP 220 - A highly obscured Starburst Galaxy", Sturm, E. et al.
"What powers luminous infrared galaxies?", Lutz, D et al.