Detection of Iron Emission in the z = 5.74 QSO SDSSp J104433.04 $-$ 012502.2

• Published in: Publications of the Astronomical Society of Japan Vol. 54; no. 3; pp. 353 - 358
• Main Authors: Aoki, Kentaro, Murayama, Takashi, Denda, Kiyomi
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford University Press 25.06.2002
• Subjects: galaxies: active; quasars: individual (SDSSp J104433.04-012502.2); quasars: emission lines
• ISSN: 0004-6264; 2053-051X
• DOI: 10.1093/pasj/54.3.353

We obtained near-infrared spectroscopy of the $z = 5.74$ QSO, SDSSp J104433.04 $-$ 012502.2, with the Infrared Camera and Spectrograph of the Subaru Telescope. The redshift of 5.74 corresponds to a cosmological age of 1.0 Gyr for the current $\Lambda$ -dominated cosmology. We found a similar strength of the Fe ii (3000–3500 Å) emission lines in SDSSp J104433.04 $-$ 012502.2 as in low-redshift QSOs. This is the highest redshift detection of iron. We subtracted a power-law continuum from the spectrum and fitted model Fe ii emission and the Balmer continuum. The rest equivalent width of Fe ii (3000–3500 Å) is $\sim 30 \,$  Å, which is similar to those of low-redshift QSOs measured in the same manner. The chemical-enrichment models that assume the lifetime of the progenitor of SNe Ia is longer than 1 Gyr predict that weaker Fe ii emission in high-redshift ( $z \gt 3$ ) QSOs than low-redshift ones. However, none of the observed high redshift QSOs show a systematic decrease of Fe ii emission compared with low-redshift QSOs. This may be due to a shorter lifetime of SNe Ia in QSO nuclei than in the solar neighborhood. Another reason for the strong Fe ii emission at $z = 5.74$ may be a longer cosmological age due to a smaller $\Omega _\mathrm{M}$ .