Flare-like variability of the Mg II\lambda 2800\AA\ emission line in the gamma-ray blazar 3C 454.3

TL;DR

This study detects a flare-like event in the Mg II emission line of blazar 3C 454.3, linking broad-line region fluctuations to jet activity and suggesting broad-line material may exist outside the inner parsec.

Contribution

It provides evidence of broad-line region material interacting with jet activity at parsec scales, challenging traditional models of the broad-line region location.

Findings

Correlation between Mg II line flux and jet component passage.

Broad-line region material may exist several parsecs from the black hole.

Implications for black hole mass estimates and gamma-ray production.

Abstract

We report the detection of a statistically significant flare-like event in the Mg II\lambda 2800\AA\ emission line of 3C 454.3 during the outburst of autumn 2010. The highest levels of emission line flux recorded over the monitoring period (2008 - 2011) coincide with a superluminal jet component traversing through the radio core. This finding crucially links the broad-emission line fluctuations to the non-thermal continuum emission produced by relativistically moving material in the jet and hence to the presence of broad-line region clouds surrounding the radio core. If the radio core were located at several parsecs from the central black hole then our results would suggest the presence of broad-line region material outside the inner parsec where the canonical broad-line region is envisaged to be located. We briefly discuss the implications of broad-emission line material ionized by non-thermal continuum on the context of virial black hole mass estimates and gamma-ray production mechanisms.