Title: Testing the Compton Downscatter Model: NGC 4418

Title: Testing the Compton Downscatter Model: NGC 4418

Proposal ID: 0120169
Subject category: Extragalactic Object
Principal investigator: Dudley
Institute: Naval Research Laboratory (NRL)

Abstract

The aim of this proposal is to search for the signature of Compton downscattering in the soft gamma-ray continuum of the protostar-like AGN NGC 4418. There are presently two competing explanations for the absence of 2--10 keV emission from protostar-like AGN. The first is that they are Compton thick and that their intrinsic hard X--soft gamma radiation is similar to that of other AGNs but supressed through radiative transfer in the surrounding medium. The second is that when galaxy collisions are involved, the intrinsic spectrum is supressed at the source. NGC 4418 provides the best case for a protostar-like AGN in a non-merging system to unambiguously examine the first of these models, and thus provide a control for related studies of merging systems. We request a 250 ks INTEGRAL observation to conduct this experiment.