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		| Paper: | 
		Supermassive Black Holes of Quasars: At World’s End | 
	 
	
		| Volume: | 
		418, AKARI, a Light to Illuminate the Misty Universe | 
	 
	
		| Page: | 
		227 | 
	 
	
		| Authors: | 
		Im, M. | 
	 
	
	
		| Abstract: | 
		We outline our ongoing study of the rest-frame optical spectra of quasars at 4.5 < z < 6.5, based on an AKARI open time program HZQSO and a phase-3 mission program QSONG. Taking advantage of the AKARI’s unique spectroscopic capability at 2.5–5.0 μm, we are obtaining the rest-frame optical spectra of more than 150 quasars at high redshift, revealing the redshifted Hα lines at z > 4.5 for the first time. Using the well-calibrated mass-estimator based on the Hα line, we have measured the masses of Supermassive Black Holes (SMBHs) at the heart of a sample of 12 high redshift quasars in our preliminary study. We find that SMBHs as massive as a few ×109 Msun exist out to z ∼ 6, but at the same, the most massive SMBHs with M ∼ 1010 Msun seem to disappear at z > 5. This finding can be interpreted as we are witnessing the emergence of SMBHs with ∼ 1010 Msun in the history of the universe. | 
	 
	
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