부산대학교 도서관

In the early universe, the formation process of supermassive blackholes in quasars is still in debate. Our group focuses on the light variation of quasars and discuss this problem. We continuously observe high-z quasars in J, H, and Ks bands with Nayuta/NIC since 2019. Here we report 2022 data for three quasars, PSO338+29 (redshift z = 6.66), ULAS J1120+0641 (redshift z = 7.09) and ULAS J1342+0928 (redshift z = 7.54). We also report J, Ks bands magnitude of ULAS J1342+0928 observed with Subaru/SWIMS in 2022. PSO338+29 shows a ∼ 2 σ level light variation in the J band. ULAS J1342+0928 shows a sign of ∼ 102 days periodic variation in the J band. At redshift z ∼ 7, the C IV emission line comes into the J band. Hence, we discuss the relation between periodic motion of BLR (Broad Line Region) to this variability period. The orbital period of BLR is ∼ 104 days. We conclude that the BLR motion is not responsible to this periodic variability. It is important to reduce the magnitude uncertainty for the variability research. We have examined the magnitude uncertainties when adopting different numbers of dithering points and ubercalibration. However, any significant reduction of the uncertainties was not observed.