Detection of H3+ in the interstellar medium of IRAS 08572+3915

The first detection of the molecular ion H3+ in an extragalactic object has been made toward the highly obscured ultraluminous galaxy, IRAS 08572+3915. Two absorption features near 3.9 microns in its spectrum are identified as the redshifted 3.668 microns doublet and 3.716 microns singlet lines of H3+, both previously detected in a number of galactic molecular and diffuse clouds. We discuss the probable location of the H3+ in this galaxy.