Author

S. Zhai

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Preprint Sep 2026

Nitrogen-Loud Quasars from the Dark Energy Spectroscopic Instrument. II. Broad-Line Region Metallicity and Relative Nitrogen Enrichment

Whether the unusually strong nitrogen emission in nitrogen-loud (N-loud) quasars reflects high overall metallicity, enhanced nitrogen abundance relative to other elements, or both has long been debated. We analyze the broad-line region (BLR) abundances of 121 N-loud quasars at $2.13 \leq z \leq 3.90$ selected from the...

S. Zhai, Wei-Ji Guo, Yong-Jie Chen et al. · 0 citations

Preprint Oct 2026

The Population of Type~1 Active Galactic Nuclei in Dark Energy Spectroscopic Instrument. I. Profile-dependent Measurements of the Low-redshift Sample

We present a spectral analysis of a large sample of low-redshift type 1 active galactic nuclei (AGNs) selected from the first data release of the Dark Energy Spectroscopic Instrument (DESI DR1). For objects at $z\le0.9$, we perform spectral fitting and ML-assisted refinement, yielding 114,754 type 1 AGNs. We use two fi...

Zhu-Heng Yao, Wei-Ji Guo, S. Zhai et al. · 0 citations

Preprint Sep 2026

Nitrogen-Loud Quasars from the Dark Energy Spectroscopic Instrument. I. Sample Selection and Basic Properties

We present the largest sample to date of nitrogen-loud (N-loud) quasars with strong broad N IV] $\lambda1486$ and/or N III] $\lambda1750$ emission lines over the redshift range $1.6<z<4.3$, selected from the Dark Energy Spectroscopic Instrument (DESI) Data Release 1. The final sample contains 1,993 N-loud quasars, corr...

S. Zhai, Wei-Ji Guo, Yong-Jie Chen et al. · 0 citations