The Misdirected Central Engine of the Hyperluminous Infrared Galaxy and Type 2 QSO IRAS P09104+4109

Abstract

Hubble Space T elescope Wide-Field Planetary Camera 2 imaging polarimetry of the hyperluminous infrared galaxy (and misdirected QSO) IRAS P09104)4109 reveals a highly polarized (p B 20%) giant (D5 kpc) bipolar re—ection nebula centered on the nucleus. This, together with our previous detection of broad, polarized Mg II and newly detected broad, polarized Balmer emission lines in our ground-based spectropolarimetry, con—rms that the lobes of the nebula are dominated by scattered light from the mis- directed QSO and that the object would be indistinguishable from typical luminous QSOs if viewed from either pole. Comparison with previously published narrowband images in the light of (O III) jj4959, 5007 and (O II) j3727 shows that the northern lobe of the nebula is coincident with the ioniza- tion cone, thus the same light that impinges on the scattering material also ionizes the narrow-line gas. The biconical structure and high polarization suggest that the central UV continuum source is sur- rounded by a dusty torus of half-opening angle D23i inclined D37i with respect to our line of sight. The radio structure of this radio-intermediate object also indicates a long-lived axisymmetry to the central power source, but with a diUerent axis relative to the scattering bicone. We propose that this diUerence in axes betrays the history of a cataclysmic event that altered the fundamental orientation of the central enginethe bicone de—nes the current axis of the system. Radio-emitting plasma is beginning to move outward along this new axis, depriving the old radio lobes of power. IRAS P09104)4109 is the —rst radio-quiet/intermediate object of QSO luminosity and hidden broad lines to show direct evidence that the axisymmetric torus inferred to exist in many Seyfert nuclei is also present in objects of high luminosity.