JWST NIRCam simulations and observations of AGN ionization cones in cosmic noon galaxies

TL;DR

This study demonstrates JWST NIRCam's capability to resolve and analyze the morphology of AGN ionization cones in galaxies at cosmic noon, providing new insights into the AGN-host galaxy relationship at high redshift.

Contribution

The paper introduces simulations and observations showing JWST NIRCam can effectively detect and characterize AGN narrow line regions at $z=2-3$, revealing their sizes and morphologies.

Findings

NIRCam can resolve NLR morphologies at $z=2-3$.

Six galaxies show AGN ionization cones with NLR sizes of 1-2.5 kpc.

Surface brightness dimming biases NLR size-luminosity trends at high redshift.

Abstract

The extended narrow line region (NLR) of Active Galactic Nuclei (AGN) provides a valuable laboratory for exploring the relationship between AGN and their host galaxies, often appearing as an "ionization cone" that can extend out to the very edge of the galaxy. We use new James Webb Space Telescope (JWST) NIRCam imaging to study the morphologies and sizes of NLRs traced by [O III] at cosmic noon ($z\sim2-3$). To determine NIRCam's ability to probe the properties of the NLR in cosmic noon galaxies, we present simulated images of AGN at $z=2-3$ created with archival data cubes from the Multi Unit Spectroscopic Explorer (MUSE) of nine nearby ($z<0.05$) AGN host galaxies with previously confirmed extended NLRs. Our simulated images show that NIRCam is able to resolve the morphologies of NLRs at $z=2-3$ with narrow- and medium-band observations. We then search for extended NLRs with NIRCam medium-band observations targeting the [O III]$+\mathrm{H}\beta$ emission in twenty-seven previously identified AGN at $z=2.4-3.4$ in the Great Observatories Origins Deep Survey South (GOODS-S) field. We detect six galaxies in our observed sample with [O III]$+\mathrm{H}\beta$ morphologies consistent with AGN ionization cones with characteristic NLR sizes of $1-2.5$ kpc. Thanks to our simulated data, we can predict the effects of cosmological surface brightness dimming and instrument noise on the NLR size measurements at high redshift, which has the biasing effect of lowering the NLR size-AGN luminosity trend that is observed at low redshift by a factor of $\sim 2$.