Aether-SHELLQs: JWST integral-field spectroscopy of candidate obscured quasars at z ~ 6

Abstract

We present James Webb Space Telescope (JWST) NIRSpec integral field unit (IFU) observations of six galaxies at $z\sim 6$, obtained as part of the Aether project (General Observers program 5645). The targets were originally identified by the Subaru High-$z$ Exploration of Low-Luminosity Quasars (SHELLQs) survey, as candidate obscured quasars with luminous ($\gtrsim 10^{43}$ erg s${}^{-1}$) but narrow ($\lesssim 500$ km s${}^{-1}$) Ly$\hat{I}\pm$ emission. Two objects exhibit a broad component in their Balmer lines (FWHM $>3000$ km s${}^{-1}$), indicating the presence of active galactic nuclei (AGNs), while the remaining four show similar profiles in permitted and forbidden lines. Combining these data with similar SHELLQs objects reported previously, we find that the presence of broad lines is strongly correlated with Ly$\hat{I}\pm$ luminosity ($L_{\mathrm{Ly}\hat{\mathrm{I}}\pm }$); the inferred AGN fraction is $>$77 % and $<$15 % above and below $L_{\mathrm{Ly}\hat{\mathrm{I}}\pm }=10^{44}$ erg s${}^{-1}$, respectively. Dust-extinction corrections inferred from the Balmer decrement would imply unrealistically high Ly$\hat{I}\pm$ luminosities, suggesting that the line-emitting gas consists of multiple zones. The IFU data reveal diverse spatial structures. The AGN hosts are compact, whereas the other galaxies show extended ionized gas on scales up to 10 kpc and star formation rates of 60 - 600 $M_{\odot }$ yr${}^{-1}$. One of the extended objects exhibits a signature of rotation, while most of the others show little ordered kinematics, with velocity widths (FWHM) up to 200 - 300 km s${}^{-1}$. These objects populate the intermediate luminosity regime between classical luminous quasars and the low-luminosity AGNs discovered by JWST, including Little Red Dots, potentially linking the two populations.

Accepted for publication in ApJ