SHELLQs-JWST: Revealing the Spectra of Extended Emission in 12 z > 6 Quasar Host Galaxies using the JWST NIRSpec Fixed Slit

TL;DR

This study uses JWST NIRSpec spectra to analyze extended emission in 12 high-redshift quasar host galaxies, revealing star formation, ionized outflows, and the impact of low-luminosity AGNs at z > 6.

Contribution

First detailed spectral analysis of extended emission in z > 6 quasar hosts using JWST, showing AGN activity has minimal impact on galaxy properties at this epoch.

Findings

Most hosts show extended line emission and some show stellar continuum.

Detected ionized outflows and rotation in host galaxies.

Star formation rates are consistent with the main sequence at z ~ 6.

Abstract

We present an analysis of the rest frame optical JWST NIRSpec Fixed Slit spectra of extended host galaxy emission in 12 quasars from the Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs) sample at redshifts 6.0 < z < 6.4. The spatial point spread function is modeled primarily by a sum of two Gaussians as a function of wavelength and is used to fit and subtract the quasar from the 2D spectra, leaving only extended galaxy emission which we analyze. Ten of 12 systems show spatially extended line emission and five of 12 systems show an extended stellar continuum. From the extended [OIII]5008 emission line, we measure a 132 ${\pm}$ 19 km/s ionized outflow in one system and 52 ${\pm}$ 12 km/s rotation, suggesting a coherent disk, in another. From the extended narrow H${\alpha}$ emission, which we hypothesize is ionized by star-forming regions rather than the quasar, we measure star formation rates ranging from ${\sim}$ 7 to 111 M${_\odot}$/yr, the majority of which are consistent with the star-forming main sequence at z ${\approx}$ 6. The positions of our host galaxies on the log10[OIII]5008/H${\beta}$ vs. log10[NII]6584/H${\alpha}$ (R3N2) Baldwin-Phillips-Terlevich (BPT) diagram indicate ionization rates typical of AGN activity in the low-redshift universe, but are consistent with the placement of similar z ${\approx}$ 6 quasar host galaxies, suggesting that the R3N2 line ratios cannot distinguish AGN and star-formation powered line emission at high redshifts. We conclude from the consistency between our quasar host sample with z ${\sim}$ 6 galaxies that the presence of a low-luminosity AGN causes little significant change in the properties of galaxies at z ${\approx}$ 6 on 10 Myr timescales.