Narrow-Line Seyfert 1 Galaxies

TL;DR

Narrow-line Seyfert 1 galaxies exhibit extreme Seyfert activity across the electromagnetic spectrum, offering insights into accretion physics, black hole growth, metal formation, and radio loudness in active galactic nuclei.

Contribution

This review synthesizes current knowledge of NLS1 galaxies, highlighting their unique properties and implications for understanding AGN physics and evolution.

Findings

High accretion rates near Eddington limit provide new insights into accretion physics.

Low black hole masses and young ages inform black hole growth models.

Strong FeII emission constrains metal formation and emission-line cloud conditions.

Abstract

I provide a short review of the properties of Narrow-line Seyfert 1 (NLS1) galaxies across the electromagnetic spectrum and of the models to explain them. Their continuum and emission-line properties manifest one extreme form of Seyfert activity. As such, NLS1 galaxies may hold important clues to the key parameters that drive nuclear activity. Their high accretion rates close to the Eddington rate provide new insight into accretion physics, their low black hole masses and perhaps young ages allow us to address issues of black hole growth, their strong optical FeII emission places strong constraints on FeII and perhaps metal formation models and physical conditions in these emission-line clouds, and their enhanced radio quiteness permits a fresh look at causes of radio loudness and the radio-loud radio-quiet bimodality in AGN.