Eddington Ratios of Dust-Obscured Quasars at z ∼ 2

• Published in: Journal of the Korean Astronomical Society, 57(1) Vol. 57; no. 1; pp. 95 - 103
• Main Authors: Dohyeong Kim, Myungshin Im, Gu Lim, Yongjung Kim
• Format: Journal Article
• Language: English
• Published: 한국천문학회 01.01.2024
• Subjects: 천문학; galaxies; supermassive black holes; general — galaxies; interactions — galaxies; quasars: emission lines — galaxies; evolution — galaxies; quasars
• ISSN: 1225-4614; 2288-890X
• DOI: 10.5303/JKAS.2024.57.1.95

In the merger-driven galaxy evolution scenario, dust-obscured quasars are considered to be an intermediate population between merger-driven star-forming galaxies and unobscured quasars; however, this scenario is still controversial. To verify this, it is necessary to investigate whether dust-obscured quasars have higher Eddington ratio (λEdd) values than those of unobscured quasars, as expected in the merger-driven galaxy evolution scenario. In this study, we derive black hole (BH) masses of 10 dust-obscured quasars at z ∼ 2, during the peak period of star-formation and BH growth in the Universe, using a newly derived mid-infrared (MIR) continuum luminosity (LMIR)-based estimator that is highly resistant to dust extinction. Then, we compare the λEdd values of these dust-obscured quasars to those of unobscured type-1 quasars at similar redshifts. We find that the measured log (λEdd) values of the dust-obscured quasars, −0.06 ± 0.10, are significantly higher than those of the unobscured quasars, −0.86 ± 0.01. This result remains consistent across the redshift range from 1.5 to 2.5. Our results show that the dust-obscured quasars are at their maximal growth, consistent with the expectation from the merger-driven galaxy evolution scenario at the epoch quasar activities were most prominent in the cosmic history.