A sample of quasars with strong nitrogen emission lines from the sloan digital sky survey

Linhua Jiang, Xiaohui Fan, M. Vestergaard

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

We report on 293 quasars with strong N IV] λ1486 or N III λ1750 emission lines (rest-frame equivalent width >3 Å) at 1.7 < z < 4.0 selected from the Sloan Digital Sky Survey (SDSS) Fifth Data Release. These nitrogen-rich (N-rich) objects comprise ∼ 1.1 % of the SDSS quasars. The comparison between the N-rich quasars and other quasars shows that the two quasar subsets share many common properties. We also confirm previous results that N-rich quasars have much stronger Lya and N v λ1240 emission lines. Strong nitrogen emission in all ionization states indicates high overall nitrogen abundances in these objects. We find evidence that the nitrogen abundance is closely related to quasar radio properties. The radio-loud fraction in the N m]-rich quasars is 26% and in the N IV]-rich quasars is 69%, significantly higher than ∼8% measured in other quasars with similar redshift and luminosity. Therefore, the high nitrogen abundance in N-rich quasars could be an indicator of a special quasar evolution stage, in which the radio activity is also strong.

Original languageEnglish (US)
Pages (from-to)962-966
Number of pages5
JournalAstrophysical Journal
Volume679
Issue number2
DOIs
StatePublished - Jun 1 2008

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quasars
nitrogen
radio
common property resource
radioactivity
ionization
set theory
luminosity

Keywords

  • Galaxies: active
  • Quasars: emission lines
  • Quasars: general

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

A sample of quasars with strong nitrogen emission lines from the sloan digital sky survey. / Jiang, Linhua; Fan, Xiaohui; Vestergaard, M.

In: Astrophysical Journal, Vol. 679, No. 2, 01.06.2008, p. 962-966.

Research output: Contribution to journalArticle

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abstract = "We report on 293 quasars with strong N IV] λ1486 or N III λ1750 emission lines (rest-frame equivalent width >3 {\AA}) at 1.7 < z < 4.0 selected from the Sloan Digital Sky Survey (SDSS) Fifth Data Release. These nitrogen-rich (N-rich) objects comprise ∼ 1.1 {\%} of the SDSS quasars. The comparison between the N-rich quasars and other quasars shows that the two quasar subsets share many common properties. We also confirm previous results that N-rich quasars have much stronger Lya and N v λ1240 emission lines. Strong nitrogen emission in all ionization states indicates high overall nitrogen abundances in these objects. We find evidence that the nitrogen abundance is closely related to quasar radio properties. The radio-loud fraction in the N m]-rich quasars is 26{\%} and in the N IV]-rich quasars is 69{\%}, significantly higher than ∼8{\%} measured in other quasars with similar redshift and luminosity. Therefore, the high nitrogen abundance in N-rich quasars could be an indicator of a special quasar evolution stage, in which the radio activity is also strong.",
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AU - Fan, Xiaohui

AU - Vestergaard, M.

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N2 - We report on 293 quasars with strong N IV] λ1486 or N III λ1750 emission lines (rest-frame equivalent width >3 Å) at 1.7 < z < 4.0 selected from the Sloan Digital Sky Survey (SDSS) Fifth Data Release. These nitrogen-rich (N-rich) objects comprise ∼ 1.1 % of the SDSS quasars. The comparison between the N-rich quasars and other quasars shows that the two quasar subsets share many common properties. We also confirm previous results that N-rich quasars have much stronger Lya and N v λ1240 emission lines. Strong nitrogen emission in all ionization states indicates high overall nitrogen abundances in these objects. We find evidence that the nitrogen abundance is closely related to quasar radio properties. The radio-loud fraction in the N m]-rich quasars is 26% and in the N IV]-rich quasars is 69%, significantly higher than ∼8% measured in other quasars with similar redshift and luminosity. Therefore, the high nitrogen abundance in N-rich quasars could be an indicator of a special quasar evolution stage, in which the radio activity is also strong.

AB - We report on 293 quasars with strong N IV] λ1486 or N III λ1750 emission lines (rest-frame equivalent width >3 Å) at 1.7 < z < 4.0 selected from the Sloan Digital Sky Survey (SDSS) Fifth Data Release. These nitrogen-rich (N-rich) objects comprise ∼ 1.1 % of the SDSS quasars. The comparison between the N-rich quasars and other quasars shows that the two quasar subsets share many common properties. We also confirm previous results that N-rich quasars have much stronger Lya and N v λ1240 emission lines. Strong nitrogen emission in all ionization states indicates high overall nitrogen abundances in these objects. We find evidence that the nitrogen abundance is closely related to quasar radio properties. The radio-loud fraction in the N m]-rich quasars is 26% and in the N IV]-rich quasars is 69%, significantly higher than ∼8% measured in other quasars with similar redshift and luminosity. Therefore, the high nitrogen abundance in N-rich quasars could be an indicator of a special quasar evolution stage, in which the radio activity is also strong.

KW - Galaxies: active

KW - Quasars: emission lines

KW - Quasars: general

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