Subaru High-z Exploration of Low-luminosity Quasars (SHELLQs). XVII. Black Hole Mass Distribution at z ～ 6 Estimated via Spectral Comparison with Low-z Quasars

作者：Takahashi, Ayumi^*; Matsuoka, Yoshiki; Onoue, Masafusa; Strauss, Michael A.; Kashikawa, Nobunari; Toba, Yoshiki; Iwasawa, Kazushi; Imanishi, Masatoshi; Akiyama, Masayuki; Kawaguchi, Toshihiro; Noboriguchi, Akatoki; Lee, Chien-Hsiu

来源：Astrophysical Journal, 2024, 960(2): 112.

DOI：10.3847/1538-4357/ad045e

• DIGITAL SKY SURVEY
• NEAR-INFRARED SPECTROSCOPY
• Z-GREATER-THAN-5.7 QUASARS
• DATA RELEASE
• INTERGALACTIC MEDIUM
• STAR-FORMATION
• IV. DISCOVERY
• II. DISCOVERY
• REDSHIFT
• GALAXIES

We report the distribution of black hole (BH) masses and Eddingont ratios estimated for a sample of 131 low luminosity quasars in the early cosmic epoch (5.6 < z < 7.0). Our work is based on the Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs) project, which has constructed a low luminosity quasar sample down to M- 1450 similar to - 21 mag, exploiting the survey data of Hyper Suprime-Cam installed on Subaru Telescope. The discovery spectra of these quasars are limited to the rest-frame wavelengths of similar to 1200-1400 angstrom, which contain no emission lines that can be used as BH mass estimators. In order to overcome this problem, we made use of low-z counterpart spectra from the Sloan Digital Sky Survey, which are spectrally matched to the high-z spectra in overlapping wavelengths. We then combined the C iv emission line widths of the counterparts with the continuum luminosity from the SHELLQs data to estimate BH masses. The resulting BH mass distribution has a range of similar to 10(7-10) M (circle dot,) with most of the quasars having BH masses similar to 10(8) M (circle dot) with sub-Eddington accretion. The present study provides not only a new insight into normal quasars in the reionization epoch, but also a new promising way to estimate BH masses of high-z quasars without near-infrared spectroscopy.

• 单位
  北京大学; 中国科学院; 中国科学院国家天文台