The evolution of chemical abundance in quasar broad line region

Fei Xu, Fuyan Bian, Yue Shen, Wenwen Zuo, Xiaohui Fan, Zonghong Zhu

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

We study the relation between the metallicity of quasar broad line region (BLR) and black hole (BH) mass (107.5-1010M) and quasar bolometric luminosity (1044.6-1048 erg s-1) using a sample of ~130 000 quasars at 2.25 ≤ z ≤ 5.25 from Sloan Digital Sky Survey Data Release 12 (DR12). We generate composite spectra by stacking individual spectra in the same BH mass (bolometric luminosity) and redshift bins and then estimate the metallicity of quasar BLR using metallicity-sensitive broad emission-line flux ratios based on the photoionization models. We find a significant correlation between quasar BLR metallicity and BH mass (bolometric luminosity) but no correlation between quasar BLR metallicity and redshift. We also compare the metallicity of quasar BLR and that of host galaxies inferred from the mass- metallicity relation of star-forming galaxy at z ~ 2.3 and 3.5. We find quasar BLR metallicity is 0.3 ~ 1.0 dex higher than their host galaxies. This discrepancy cannot be interpreted by the uncertainty due to different metallicity diagnostic methods, mass-metallicity relation of galaxy, metallicity gradient in quasar host galaxies, BH mass estimation, the effect of different spectral energy distribution models, and a few other potential sources of uncertainties. We propose a possibility that the high metallicity in quasar BLR might be caused by metal enrichment from massive star formation in the nucleus region of quasars or even the accretion disc.

Original languageEnglish (US)
Pages (from-to)345-357
Number of pages13
JournalMonthly Notices of the Royal Astronomical Society
Volume480
Issue number1
DOIs
StatePublished - Oct 11 2018

Fingerprint

quasars
metallicity
galaxies
luminosity
chemical
stacking
erg
accretion
spectral energy distribution
massive stars
accretion disks
photoionization
star formation
metal
energy
stars
gradients
nuclei
composite materials

Keywords

  • Galaxies: abundances
  • Galaxies: active
  • Galaxies: high redshift
  • Quasars: emission lines

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

The evolution of chemical abundance in quasar broad line region. / Xu, Fei; Bian, Fuyan; Shen, Yue; Zuo, Wenwen; Fan, Xiaohui; Zhu, Zonghong.

In: Monthly Notices of the Royal Astronomical Society, Vol. 480, No. 1, 11.10.2018, p. 345-357.

Research output: Contribution to journalArticle

Xu, Fei ; Bian, Fuyan ; Shen, Yue ; Zuo, Wenwen ; Fan, Xiaohui ; Zhu, Zonghong. / The evolution of chemical abundance in quasar broad line region. In: Monthly Notices of the Royal Astronomical Society. 2018 ; Vol. 480, No. 1. pp. 345-357.
@article{08b710d2754b48e7b2e0446e97158da2,
title = "The evolution of chemical abundance in quasar broad line region",
abstract = "We study the relation between the metallicity of quasar broad line region (BLR) and black hole (BH) mass (107.5-1010M⊙) and quasar bolometric luminosity (1044.6-1048 erg s-1) using a sample of ~130 000 quasars at 2.25 ≤ z ≤ 5.25 from Sloan Digital Sky Survey Data Release 12 (DR12). We generate composite spectra by stacking individual spectra in the same BH mass (bolometric luminosity) and redshift bins and then estimate the metallicity of quasar BLR using metallicity-sensitive broad emission-line flux ratios based on the photoionization models. We find a significant correlation between quasar BLR metallicity and BH mass (bolometric luminosity) but no correlation between quasar BLR metallicity and redshift. We also compare the metallicity of quasar BLR and that of host galaxies inferred from the mass- metallicity relation of star-forming galaxy at z ~ 2.3 and 3.5. We find quasar BLR metallicity is 0.3 ~ 1.0 dex higher than their host galaxies. This discrepancy cannot be interpreted by the uncertainty due to different metallicity diagnostic methods, mass-metallicity relation of galaxy, metallicity gradient in quasar host galaxies, BH mass estimation, the effect of different spectral energy distribution models, and a few other potential sources of uncertainties. We propose a possibility that the high metallicity in quasar BLR might be caused by metal enrichment from massive star formation in the nucleus region of quasars or even the accretion disc.",
keywords = "Galaxies: abundances, Galaxies: active, Galaxies: high redshift, Quasars: emission lines",
author = "Fei Xu and Fuyan Bian and Yue Shen and Wenwen Zuo and Xiaohui Fan and Zonghong Zhu",
year = "2018",
month = "10",
day = "11",
doi = "10.1093/mnras/sty1763",
language = "English (US)",
volume = "480",
pages = "345--357",
journal = "Monthly Notices of the Royal Astronomical Society",
issn = "0035-8711",
publisher = "Oxford University Press",
number = "1",

}

TY - JOUR

T1 - The evolution of chemical abundance in quasar broad line region

AU - Xu, Fei

AU - Bian, Fuyan

AU - Shen, Yue

AU - Zuo, Wenwen

AU - Fan, Xiaohui

AU - Zhu, Zonghong

PY - 2018/10/11

Y1 - 2018/10/11

N2 - We study the relation between the metallicity of quasar broad line region (BLR) and black hole (BH) mass (107.5-1010M⊙) and quasar bolometric luminosity (1044.6-1048 erg s-1) using a sample of ~130 000 quasars at 2.25 ≤ z ≤ 5.25 from Sloan Digital Sky Survey Data Release 12 (DR12). We generate composite spectra by stacking individual spectra in the same BH mass (bolometric luminosity) and redshift bins and then estimate the metallicity of quasar BLR using metallicity-sensitive broad emission-line flux ratios based on the photoionization models. We find a significant correlation between quasar BLR metallicity and BH mass (bolometric luminosity) but no correlation between quasar BLR metallicity and redshift. We also compare the metallicity of quasar BLR and that of host galaxies inferred from the mass- metallicity relation of star-forming galaxy at z ~ 2.3 and 3.5. We find quasar BLR metallicity is 0.3 ~ 1.0 dex higher than their host galaxies. This discrepancy cannot be interpreted by the uncertainty due to different metallicity diagnostic methods, mass-metallicity relation of galaxy, metallicity gradient in quasar host galaxies, BH mass estimation, the effect of different spectral energy distribution models, and a few other potential sources of uncertainties. We propose a possibility that the high metallicity in quasar BLR might be caused by metal enrichment from massive star formation in the nucleus region of quasars or even the accretion disc.

AB - We study the relation between the metallicity of quasar broad line region (BLR) and black hole (BH) mass (107.5-1010M⊙) and quasar bolometric luminosity (1044.6-1048 erg s-1) using a sample of ~130 000 quasars at 2.25 ≤ z ≤ 5.25 from Sloan Digital Sky Survey Data Release 12 (DR12). We generate composite spectra by stacking individual spectra in the same BH mass (bolometric luminosity) and redshift bins and then estimate the metallicity of quasar BLR using metallicity-sensitive broad emission-line flux ratios based on the photoionization models. We find a significant correlation between quasar BLR metallicity and BH mass (bolometric luminosity) but no correlation between quasar BLR metallicity and redshift. We also compare the metallicity of quasar BLR and that of host galaxies inferred from the mass- metallicity relation of star-forming galaxy at z ~ 2.3 and 3.5. We find quasar BLR metallicity is 0.3 ~ 1.0 dex higher than their host galaxies. This discrepancy cannot be interpreted by the uncertainty due to different metallicity diagnostic methods, mass-metallicity relation of galaxy, metallicity gradient in quasar host galaxies, BH mass estimation, the effect of different spectral energy distribution models, and a few other potential sources of uncertainties. We propose a possibility that the high metallicity in quasar BLR might be caused by metal enrichment from massive star formation in the nucleus region of quasars or even the accretion disc.

KW - Galaxies: abundances

KW - Galaxies: active

KW - Galaxies: high redshift

KW - Quasars: emission lines

UR - http://www.scopus.com/inward/record.url?scp=85052554128&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85052554128&partnerID=8YFLogxK

U2 - 10.1093/mnras/sty1763

DO - 10.1093/mnras/sty1763

M3 - Article

VL - 480

SP - 345

EP - 357

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

SN - 0035-8711

IS - 1

ER -