JWST Spectroscopic View of a Rapidly Growing, Dust-obscured Quasar at <i>z</i> ∼ 4: Effect of Dust Extinction Correction on Black Hole Mass and Eddington Ratio Estimation

Abstract In the merger-driven galaxy evolution scenario, the central supermassive black holes (SMBHs) in dust-obscured galaxies grow rapidly. Interestingly, a recent work on a dust-obscured galaxy, LID-568 at z = 3.965, has shown that its SMBH is growing extremely fast at about 40 times the Eddington-limited accretion rate (i.e., super-Eddington accretion). However, the heavy dust extinction of the host galaxy could affect the result if not corrected properly. Here, we analyze James Webb Space Telescope (JWST) NIRSpec integral field unit (IFU) and MIRI spectra of LID-568. By measuring its bolometric luminosity ( L bol ) and black hole (BH) mass ( M BH ) using an extinction-free estimator based on mid-infrared spectra, we obtain L bol = 10 46.83±0.07 erg s −1 and M BH = 10 8.43±0.15 M ⊙ . The measured Eddington ratio ( λ Edd ) is 1.97 ± 0.88, consistent with the accretion rate at the Eddington limit; in other words, it is not super-Eddington in a significant manner. This result underscores challenges and the importance of carefully considering dust extinction when analyzing the BH growth in dust-obscured quasars.