Abstract

We present JWST/NIRSpec integral field data of the quasar PJ308-21 at z = 6.2342. As shown by previous ALMA and HST imaging, the quasar has two companion sources, interacting with the quasar host galaxy. The high-resolution G395H/290LP NIRSpec spectrum covers the 2.87 - 5.27 mu m wavelength range and shows the rest-frame optical emission of the quasar with exquisite quality (signal-to-noise ratio similar to 100 - 400 per spectral element). Based on the H beta line from the broad line region, we obtain an estimate of the black hole mass MBH, H beta similar to 2.7 x 10(9 )M circle dot. This value is within a factor less than or similar to 1.5 of the H alpha-based black hole mass from the same spectrum (M-BH,M- H alpha similar to 1.93 x 10(9) M-circle dot) and is consistent with a previous estimate relying on the Mg II lambda 2799 line (M-BH,M- MgII similar to 2.65 x 10(9) M-circle dot). All these MBH estimates are within the similar to 0.5 dex intrinsic scatter of the adopted mass calibrations. The high Eddington ratio of PJ308-21 lambda(Edd, H beta) similar to 0.67 (lambda(Edd, H alpha) similar to 0.96) is in line with the overall quasar population at z greater than or similar to 6. The relative strengths of the [O III], Fe II, and H beta lines are consistent with the empirical Eigenvector 1 correlations as observed for low redshift quasars. We find evidence for blueshifted [O III] lambda 5007 emission with a velocity offset Delta(v[O III] )= -1922 +/- 39 km s(-1) from the systemic velocity and a full width at half maximum (FWHM) FWHM([O III]) = 2776(-74)(+75) 2776( - 74) (+ 75) km s(-1). This may be the signature of outflowing gas from the nuclear region, despite the true values of Delta(v[O III]) and FWHM([O III]) likely being more uncertain due to the blending with H beta and Fe II lines. Our study demonstrates the unique capabilities of NIRSpec in capturing quasar spectra at cosmic dawn and studying their properties in unprecedented detail.