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

TL;DR

This study investigates the broad line region of NGC 1275, revealing persistent broad emission lines, a low luminosity continuum, and a correlation between BEL luminosity and jet power, suggesting accretion rate influences jet activity.

Contribution

It provides detailed spectroscopic analysis of NGC 1275's broad emission lines and links BEL luminosity to jet power, offering insights into the AGN's accretion and jet mechanisms.

Findings

Persistent broad emission lines over 35 years.

Low luminosity, thermal accretion flow with low Eddington ratio.

Correlation between BEL luminosity and jet mm wave luminosity.

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 $\sim 10$ Jy at $\sim 1$ mm wavelengths, down from the historic high of $\sim 65$ 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$\beta$ BEL over the last 35 years with a full width half maximum (FWHM) of 4150 - 6000 km/s. We also find a prominent P$\alpha$ BEL (FWHM $\approx 4770 $ km/s) and a weak CIV BEL (FWHM $\approx 4000 $ km/s), H$\beta$/CIV $\approx 2$. A far UV HST observation during suppressed jet activity reveals a low luminosity continuum. The H$\beta$ BEL luminosity is typical of broad line Seyfert galaxies with similar far UV luminosity. X-ray observations indicate a softer ionizing continuum than expected for a broad line Seyfert galaxy with similar far UV luminosity. This is 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, $\sim 0.0001$. The soft, weak ionizing continuum is consistent with the relatively weak CIV BEL. Evidence that the BEL luminosity is correlated with the jet mm wave luminosity is presented. Apparently, the accretion rate regulates jet power.