MITの天文学者が古代のクェーサーを取り巻くとらえどころのない恒星の光を観測(MIT astronomers observe elusive stellar light surrounding ancient quasars)


2024-05-06 マサチューセッツ工科大学(MIT)

MITの天文学者たちは、宇宙の初期に存在したクエーサーを取り巻く星光を観測し、13億年以上前のものとされるこの光が、最初のブラックホールと銀河の進化に関する手がかりを提供しています。特に、クエーサーの母銀河の星からの光を観測することに成功し、これらのクエーサーの中心にある超大質量ブラックホールが、母銀河に比べて非常に大きいことが明らかになりました。これは、古代のブラックホールが短期間で巨大化する過程を理解するための重要な発見です。この研究成果は「Astrophysical Journal」に掲載されています。


アイガー V. z ≳ 6の高光度クェーサーの母銀河の特性決定 EIGER. V. Characterizing the Host Galaxies of Luminous Quasars at z ≳ 6

Minghao Yue, Anna-Christina Eilers, Robert A. Simcoe, Ruari Mackenzie, Jorryt Matthee, Daichi Kashino, Rongmon Bordoloi, Simon J. Lilly, and Rohan P. Naidu
The Astrophysical Journal  Published:2024 May 6

Figure 1.


We report JWST/NIRCam measurements of quasar host galaxy emissions and supermassive black hole (SMBH) masses for six quasars at 5.9 < z < 7.1 in the Emission-line galaxies and Intergalactic Gas in the Epoch of Reionization (EIGER) project. We obtain deep NIRCam imaging in the F115W, F200W, and F356W bands, as well as F356W grism spectroscopy of the quasars. We use bright unsaturated stars to construct models of the point-spread functions (PSFs) and estimate the errors of these PSFs. We then measure or constrain the fluxes and morphology of the quasar host galaxies by fitting the quasar images as a point source plus an exponential disk. We successfully detect the host galaxies of three quasars, which have host-to-quasar-flux ratios of ∼1%–5%. Spectral energy distribution fitting suggests that these quasar host galaxies have stellar masses of M* ≳ 1010M. For quasars with host galaxy nondetections, we estimate the upper limits of their stellar masses. We use the grism spectra to measure the Hβ line profile and the continuum luminosity, then estimate the SMBH masses for the quasars. Our results indicate that the positive relation between SMBH masses and host galaxy stellar masses already exists at redshift z ≳ 6. The quasars in our sample show a high BH-to-stellar-mass ratio of MBH/M* ∼ 0.15, which is about ∼2 dex higher than local relations. We find that selection effects only contribute partially to the high MBH/M* ratios of high-redshift quasars. This result hints at a possible redshift evolution of the MBHM* relation.