Nitrogen-Loud Quasars from the Dark Energy Spectroscopic Instrument. I. Sample Selection and Basic Properties
Abstract
We present the largest sample to date of nitrogen-loud (N-loud) quasars with strong broad N IV] λ1486 and/or N III] λ1750 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, corresponding to about 1.2% of the parent quasar sample. The L1450 distribution of the N-loud quasars is broadly similar to that of the DESI parent sample, but their redshift distribution is distinct, with a stronger concentration around z ∼ 2.5--3. Their composite spectrum displays a broadly similar UV continuum shape to that of the parent quasars, while showing significantly enhanced broad nitrogen emission features, including N V, N IV], and N III]. Other metal emission features also show a moderate enhancement. Relative to a control sample matched in redshift and UV continuum luminosity, the N-loud quasars show systematically narrower broad C IV and Mg II emission lines, lower single-epoch virial black hole masses, and higher Eddington ratios, suggesting that N-loud quasars may preferentially appear during a relatively rapid black hole accretion phase. The radio-loud fraction is 10.1%, with the highest fraction among objects exhibiting both N III] and N IV] emission. The catalog provides a statistical baseline for future studies of nitrogen enhancement and its physical origin.
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BibTeX
@misc{zhai2026nitrogenloud,
title = {{Nitrogen-Loud Quasars from the Dark Energy Spectroscopic Instrument. I. Sample Selection and Basic Properties}},
author = {Shuo Zhai and Wei-Jian Guo and Yong-Jie Chen and Zhi-Qiang Chen and Haining Li and Jian-Min Wang and Gang Zhao},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.11104},
eprint = {2609.11104},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.11104},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Nitrogen-Loud Quasars from the Dark Energy Spectroscopic Instrument. I. Sample Selection and Basic Properties
AU - Shuo Zhai
AU - Wei-Jian Guo
AU - Yong-Jie Chen
AU - Zhi-Qiang Chen
AU - Haining Li
AU - Jian-Min Wang
AU - Gang Zhao
PY - 2026
DA - 2026/09/10
PB - arXiv
DO - 10.48550/arxiv.2609.11104
UR - https://arxiv.org/abs/2609.11104
AB - We present the largest sample to date of nitrogen-loud (N-loud) quasars with strong broad N IV] λ1486 and/or N III] λ1750 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, corresponding to about 1.2% of the parent quasar sample. The L_1450 distribution of the N-loud quasars is broadly similar to that of the DESI parent sample, but their redshift distribution is distinct, with a stronger concentration around z ∼ 2.5--3. Their composite spectrum displays a broadly similar UV continuum shape to that of the parent quasars, while showing significantly enhanced broad nitrogen emission features, including N V, N IV], and N III]. Other metal emission features also show a moderate enhancement. Relative to a control sample matched in redshift and UV continuum luminosity, the N-loud quasars show systematically narrower broad C IV and Mg II emission lines, lower single-epoch virial black hole masses, and higher Eddington ratios, suggesting that N-loud quasars may preferentially appear during a relatively rapid black hole accretion phase. The radio-loud fraction is 10.1%, with the highest fraction among objects exhibiting both N III] and N IV] emission. The catalog provides a statistical baseline for future studies of nitrogen enhancement and its physical origin.
ER -