Optical spectrum of eFEDSJ0828-0139 taken by KOOLS-IFU. Credit: Toba et al, 2024
An international team of astronomers has announced the discovery of a new, hyperluminous quasar. The new quasar, which has been designated eFEDSJ0828–0139, has a high star formation rate and its black hole is accreting mass at a super-Eddington rate. The discovery was detailed in a research paper published August 16 on the preprint server arXiv.
Quasars, or quasi-stellar objects (QSOs), are extremely high-luminosity active galactic nuclei (AGNs) powered by supermassive black holes (SMBHs), emitting electromagnetic radiation observable in radio, infrared, visible, ultraviolet, and X-ray wavelengths. They are among the brightest and most distant objects in the known universe, and serve as fundamental tools for many studies in astrophysics as well as cosmology.
A group of astronomers led by Yoshiki Toba of the National Astronomical Observatory of Japan (NAOJ) has detected a new quasar with a bolometric luminosity of over 290 quattuordecillion erg/s. The quasar was first identified by the eROSITA instrument on board the Spektr-RG spacecraft and its nature was confirmed by Toba’s team using the Seimei Telescope and the James Clerk Maxwell Telescope (JCMT).
“We performed the optical spectroscopic observations with KOOLS-IFU on the Seimei telescope (…) To measure the precise infrared luminosity (LIR), we obtain submillimeter data taken by SCUBA-2 on JCMT and perform the spectral energy distribution analysis with submillimeter X-ray data,” the researchers explained.
According to the study, the newly discovered hyperluminous quasar eFEDSJ0828–0139 has a spectroscopic redshift of 1.62. The mass of the SMBH of this quasar is about 620 million solar masses.
The study revealed that eFEDSJ0828–0139 has a very high infrared luminosity, on the order of 68 trillion solar luminosities, and its Eddington ratio is 3.6. This confirms that eFEDSJ0828–0139 is a hyperluminous quasar with a very high black hole mass accretion rate.
The results indicate that eFEDSJ0828–0139 also exhibits an extremely high star formation rate. Astronomers have calculated that the star formation rate of this quasar is at least 1,000 solar masses per year.
Summarizing the results, the authors of the paper noted that eFEDSJ0828−0139 is likely in a particular phase in which SMBH and its host galaxy are actively expanding as part of galaxy-SMBH coevolution.
“We may be witnessing the growth phase of the SMBH and its host galaxy during galaxy-SMBH coevolution, as predicted by the numerical simulation,” the researchers concluded.
The astronomers added that their discovery proves that many more hyperluminous quasars could be detected through eROSITA’s all-sky survey and follow-up observations using next-generation multi-object spectrographs, such as the Subaru Prime Focus Spectrograph (PFS).
More information:
Yoshiki Toba et al, Discovery of a hyperluminous quasar at z = 1.62 with an Eddington ratio > 3 in the eFEDS field confirmed by KOOLS-IFU on the Seimei telescope, arXiv (2024). DOI: 10.48550/arxiv.2408.08498
Journal information:
arXiv
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