A Super-Eddington, Lensing-Magnified Quasar at $z=5.07$ observed with JWST

TL;DR

This study tests whether the $z=5.07$ quasar J0025--0145 is singly or multiply imaged by a foreground lens and quantifies the magnification to recover the intrinsic accretion properties. Using JWST NIRCam imaging in F070W and F480M, the authors perform PSF-based image fitting and demonstrate a single quasar image with no detectable host, while constraining the lensing galaxy’s properties with SED fitting. They derive a lens redshift of $z_{\text{phot}}=3.62^{+0.06}_{-0.04}$, a stellar mass of $\log(M_*/M_\odot)=11.15\pm0.16$, and an Einstein radius of $\theta_E=0.27^{+0.10}_{-0.08}$ arcsec, implying a maximum magnification of $\mu_{\text{max}}=3.2$. Consequently, the intrinsic Eddington ratio is $\lambda_{\text{Edd}}^{\text{intrinsic}} > 4.9$, making J0025--0145 one of the most extreme high-$z$ SMBHs known and supporting the viability of super-Eddington accretion in the early universe.

Abstract

We present JWST/NIRCam F070W and F480M imaging for a quasar at $z = 5.07$, J0025-0145, which is magnified by a foreground lensing galaxy. Existing Hubble Space Telescope (HST) imaging does not have sufficient spatial resolution to determine whether the background quasar is multiply imaged. Exploiting the sharp PSF of the F070W band, we confirm that the background quasar can be well-described by a single point spread function (PSF), essentially ruling out the existence of multiple lensed images. We do not detect the quasar host galaxy in either the F070W or the F480M band. Using the HST and JWST photometry, we fit the Spectral Energy Distribution (SED) of the foreground galaxy. The estimated mass ($\log(M_{*} / M_{\odot}) = 11.15 \pm 0.16$) and redshift ($z_{\text{phot}} = 3.62_{-0.04}^{+0.06}$) of the foreground galaxy are consistent with a single-image lensing model. We estimate the maximum possible magnification of the quasar to be $μ_{\text{max}} = 3.2$, which implies that the intrinsic Eddington ratio of the quasar is at least $λ_{\text{Edd}}^{\text{intrinsic}} > 4.9$. Therefore, J0025-0145 has one of the highest Eddington ratios among $z>5$ supermassive black holes known so far, suggesting the viability of super-Eddington growth for supermassive black holes in the early universe.

Figures (4)

• Figure 1: Images of J0025--0145. Top, from left to right: HST ACS/WFC F435W and HST ACS/WFC F606W. Bottom, from left to right: JWST NIRCam F070W and JWST NIRCam F480M. Both the quasar and the foreground galaxy are visible in the HST F606W, JWST F070W, and JWST F480M filters. Only the foreground galaxy is visible in the HST F435W filter.
• Figure 2: Best Galfit models and residuals for JWST NIRCam F070W (top) and F480M (bottom) filters. The left column shows a cutout of the quasar and lensing galaxy, the middle column shows the Galfit model, with the quasar modeled as a PSF and the lensing galaxy modeled with a Sérsic profile, and the right column shows the residuals after subtracting the model. The quasar and galaxy locations are labeled in the model with a cross. For both filters, a single PSF image fits the quasar best.
• Figure 3: Galfit best fit parameters
• Figure 4: The Prospector model for the foreground lensing galaxy. The red dots are the HST and JWST photometric points. The black line gives the median of the posterior model spectrum, and the gray shaded area represents the 16th and 84th percentiles.