The Role of Nuclear Starbursts in Luminous Infrared Seyfert 2 Galaxies

We present HST (WFPC2 and FOC) images and UV GHRS spectra plus ground-based optical spectra of four Luminous Infrared Galaxies (LIRGs) that have Seyfert 2 nuclei (Mrk 477, NGC 7130, NGC 5135 and IC 3639). The data provide direct evidence of the existence of a central nuclear starburst that dominates the UV and optical light and are dusty and compact. The bolometric luminosity (∼ 1010 L⊙) of these starbursts is similar to the estimated bolometric luminosities of their obscured Seyfert 1 nuclei, and thus they contribute in the same amount to the overall energetics of these galaxies. An extended work based on ground-based optical spectra of the 20 brightest nuclei known indicate that at least 40% of the Seyfert 2 galaxies harbor a nuclear starburst. The eight Seyfert 2 nuclei that harbor a starburst are strong IR emitters. This suggests that nuclear starbursts can make a significant contribution or even dominate the UV and optical light of LIRGs.