A JWST/NIRSpec Integral Field Unit Survey of Luminous Quasars at z ~ 5-6 (Q-IFU): Rest-frame Optical Nuclear Properties and Extended Nebulae

TL;DR

This work investigates the rest-frame optical properties and surrounding gas of 27 luminous quasars at $z\sim5$--$6$ using JWST/NIRSpec IFU (Q-IFU). By modeling continua, Fe II, and multiple line components with PyQSOFit, the authors derive $H\beta$-based BH masses $\log(M_{\rm BH}/M_\odot) \sim 8.6$--$9.7$ and Eddington ratios $\lambda_{\rm Edd} \sim 0.1$--$2.6$, and they confirm H$\alpha$–based masses are broadly consistent. A composite spectrum shows overall similarity to lower-redshift, bolometrically matched quasars but with weaker and more blueshifted $[\mathrm{O\,III}]$, and stronger Fe II, indicating mature BLR/NLR accompanied by notable high-velocity outflows. Extended $[\mathrm{O\,III}]$ emission is detected in $\sim$22% of the sample, with morphologies and kinematics compatible with mergers or turbulent, clumpy ISM; in one case a merging companion (J1327_E) appears to be radiatively ionized by the quasar, suggesting possible quasar radiative feedback in early galaxy interactions. Overall, the results support rapid SMBH growth and complex gas environments at $z\sim5$--$6$, and they highlight the value of deep, spatially-resolved rest-frame optical spectroscopy for connecting quasar physics to host galaxy evolution in the early universe.

Abstract

It remains debatable how billion-solar-mass supermassive black holes (SMBHs) form and evolve within the first billion years. We report results from a James Webb Space Telescope (JWST)/NIRSpec integral field unit (IFU) survey of 27 luminous quasars at $z \sim 5$-$6$, enabling a systematic investigation of their key physical properties and the associated, extended line emission. Our sample hosts SMBHs with $\log(M_{\mathrm{BH}}/M_\odot) \sim 8.6$-$9.7$ and Eddington ratios of $\sim 0.1$-$2.6$ based on H$β$, and the H$β$-based and H$α$-based BH mass are broadly consistent with each other. Our sample may have a slightly smaller median BH mass and larger median Eddington ratio than lower-redshift quasars within the same luminosity range, although the difference could still be explained by statistical uncertainties. They generally follow the empirical correlations between [O III] $λ$5007 equivalent width and bolometric luminosities or Eddington ratios formed by lower-redshift quasars. The majority of them fall within the Eigenvector~1 planes formed by lower-redshift quasars. Nevertheless, a subset of the sample shows enhanced, blueshifted [O III] emission associated with fast outflows. Spatially extended [O III] line emission is detected in 6 objects and shows morphologies and kinematics consistent with merging activities and/or turbulent and clumpy interstellar media (ISM). Tentative evidence of quasar radiative feedback shaping the ISM of a merging companion galaxy is seen in the object with the most extended [O III] emission. Our results provide crucial insight into the rapid growth of SMBHs and the gaseous environments they reside in at z$\sim$5-6.

Figures (15)

• Figure 1: M$_{1450}$ (absolute magnitude at 1450 Å) versus redshift for our objects (red) and all other spectrally-confirmed luminous quasars within the same redshift ranges from the literature (black) in Table \ref{['tab:redshift']}.
• Figure 2: Difference of the systemic redshifts between those determined from our data ($z_{sys}$) and those from the literature which are based on rest-frame UV emission lines including C$\,$ IV, C$\,$ III] and/or Si$\,$ IV] ($z_{ref}$).
• Figure 3: Composite spectra of our z $\sim$ 5--6 sample (red) and the z $\sim$ 1.5--3.5 Shen quasars matched in the same luminosity range. The two spectra are further normalized at 5100 Å. The locations of the major quasar emission lines are indicated by the dotted lines. The horizontal gray bars indicate the locations of the major blended Fe emission.
• Figure 4: Bolometric luminosity versus BH mass for our objects (red), Shen quasars (blue), ASPIRE quasars at z $\sim$ 6.5--6.8 (orange) and all z $>$ 5.9 quasars from Fan2023. The green contours represent the distributions of 99.998%, 90% and 50% of all z $<$ 1 SDSS quasars from wu_spectroscopic_2023. The dashed lines show the locations of constant accretion rates at 0.1, 1 and 10 times the Eddington luminosity. All BH masses are based on H$\beta$, except for those of quasars from Fan2023 which are based on Mg$\,$ II. The typical statistical uncertainties for the bolometric luminosity and H$\beta$ BH mass are indicated by the blue cross. The top and right panels show the fraction histograms for our objects, Shen quasars and all z$>$5.9 quasars.
• Figure 5: Left: H$\alpha$ FWHM versus H$\beta$ FWHM. The blue line indicates the 1-to-1 equality. The black solid and dotted lines indicate the best-fit relation of z$<$0.35 SDSS quasars and the associated 0.1 dex rms from GreeneHo2005. Middle: H$\alpha$ luminosity versus H$\beta$ luminosity. The solid line indicates the theoretical expectation of 3.1 and the dotted line indicates the mean value of our sample (3.8). Right: BH mass based on H$\alpha$ and H$\beta$. The errorbars only reflect the measurement errors. The solid and dotted lines indicate the 1-to-1 equality and the $\pm{0.4}$ dex ranges, respectively. Overall, the relative H$\alpha$ and H$\beta$ properties of our sample are consistent with those observed in low-z quasars.