# An observational link between AGN Eddington ratio and [NII]{\lambda}6583/Ha at 0.6<z<1.7

## TL;DR

This study finds a consistent anti-correlation between Eddington ratio and [N II]{}6583/Hb1 at redshifts 0.6 to 1.7, extending the relationship observed locally to earlier cosmic times.

## Contribution

It demonstrates a persistent relationship between Eddington ratio and emission-line ratio in AGN up to z , using new near-infrared spectra and literature data.

## Key findings

- Eddington ratio and [N II]{}6583/Hb1 ratio are anti-correlated at 0.6<z<1.7.
- The anti-correlation observed locally also exists at higher redshifts.
- Further research needed for low Eddington ratio AGN at high redshift.

## Abstract

We present an observed relationship between Eddington ratio ({\lambda}Edd) and optical narrow-emission-line ratio ([N II]{\lambda}6583/H{\alpha}) of X-ray-selected broad-line active galactic nuclei (AGN) at 0.6 < z < 1.7. We use 27 near-infrared spectra from the Fiber Multi-Object Spectrograph along with 26 sources from the literature. We show that the {\lambda}Edd and [N II]{\lambda}6583/H{\alpha} ratio at 0.6 < z < 1.7 exhibits a similar anti-correlation distribution of {\lambda}Edd-[N II]{\lambda}6583/H{\alpha} as has been found for local (<z> = 0.036), ultra-hard X-ray selected AGN. The observed distribution implies that there is a consistent relationship from local to z \sim 1.7 which corresponds from the present time to 4 Gyr old. Further study of high redshift low Eddington ratio AGN (log{\lambda}Edd < -2) is necessary to determine fully whether the {\lambda}Edd-[N II]{\lambda}6583/H{\alpha} anti-correlation still holds in high-redshift AGN at low Eddington ratios.