Revealing the Broad Line Region of NGC 1275: The Relationship to Jet Power

Abstract

NGC 1275 is one of the most conspicuous active galactic nuclei (AGN) in the local universe. The radio jet currently emits a flux density of ∼10 Jy at ∼1 mm wavelengths, down from the historic high of ∼65 Jy in 1980. Yet, the nature of the AGN in NGC 1275 is still controversial. It has been debated whether this is a broad emission line (BEL) Seyfert galaxy, an obscured Seyfert galaxy, a narrow line radio galaxy, or a BL Lac object. We clearly demonstrate a persistent H β BEL over the last 35 yr with a full width at half maximum (FWHM) of 4150–6000 km s −1 . We also find a prominent P α BEL (FWHM ≈ 4770 km s −1 ) and a weak C iv BEL (FWHM ≈ 4000 km s −1 ), H β /C iv  ≈ 2. A far-UV Hubble Space Telescope observation during suppressed jet activity reveals a low luminosity continuum. The H β BEL luminosity is typical of broad line Seyfert galaxies with similar far-UV luminosity. X-ray observations indicate a softer ionizing continuum than what would be expected for a broad line Seyfert galaxy with similar far-UV luminosity. This is the opposite of the expectation of advection-dominated accretion. The AGN continuum appears to be thermal emission from a low luminosity, optically thick, accretion flow with a low Eddington ratio, ∼0.0001. The soft, weak, ionizing continuum is consistent with the relatively weak C iv BEL. Evidence that the BEL luminosity is correlated with the jet millimeter-wave luminosity is presented. It appears that the accretion rate regulates jet power.