Dusty origin of the Broad Line Region in active galaxies

TL;DR

This paper proposes that dust located closer to the black hole than previously thought is responsible for the formation of the Broad Line Region in active galaxies, offering new insights into their structure and potential cosmological applications.

Contribution

It introduces the novel idea that dust near the black hole, at temperatures around 1000 K, forms the Broad Line Region, challenging previous models that placed dust further out.

Findings

Dust temperature near 1000 K is consistent across different black hole masses.

The proposed dust-based formation mechanism explains the complexity of active galactic nuclei.

This understanding enables the use of BLR as standard candles in cosmology.

Abstract

The most characteristic property of active galaxies, including quasars, are prominent broad emission lines. I will discuss an interesting possibility that dust is responsible for this phenomenon. The dust is known to be present in quasars in the form of a dusty/molecular torus which results in complexity of the appearance of active galaxies. However, this dust is located further from the black hole than the Broad Line Region. We propose that the dust is present also closer in and it is actually responsible for formation of the broad emission lines. The argument is based on determination of the temperature of the disk atmosphere underlying the Broad Line Region: it is close to 1000 K, independently from the black hole mass and accretion rate of the object. The mechanism is simple and universal but leads to a considerable complexity of the active nucleus surrounding. The understanding the formation of BLR opens a way to use it reliably - in combination with reverberation measurement of its size - as standard candles in cosmology.