UV spectral diagnostics for low redshift quasars: estimating physical conditions and radius of the broad line region

Marziani, Paola; Sulentic, J. W.; Negrete, C. A.; Dultzin, D.; Olmo, A. del; Martínez-Carballo, M. A.; Zwitter, T.; Bachev, R.

doi:10.1007/s10509-014-2136-z

Cited by 16 publications

(14 citation statements)

References 57 publications

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“…Many studies have suggested that the broad emission-line flux ratios of quasars at the rest-frame ultraviolet and optical wavelength can provide accurate chemical abundance measurements in quasar BLRs (Hamann et al 2002;Warner et al 2003;Dietrich et al 2003;Nagao et al 2006;Matsuoka et al 2011;Marziani et al 2015;Sameshima et al 2017). The theoretical accuracy of any broad emission-line flux ratios as metallicity indicators depends on a variety of factors such as the central radiation field, temperature sensitivity of the emission-line ratio, the similarity of the ionization potentials and critical densities, the extent to which the line-emitting regions overlap spatially (Hamann et al 2002).…”

Section: Metallicity Measurementsmentioning

confidence: 99%

“…The BLRs contain gas clouds close to the SMBHs, which are photoionized by the radiation field from the accretion disk of the SMBH. The ultraviolet and optical emission lines from BLRs are widely ⋆ E-mail: astroxf@163.com † E-mail: fbian@eso.org used to estimate the SMBH mass (Vestergaard & Peterson 2006;Shen 2013;Zuo et al 2015) and the chemical abundance close to the SMBH (Hamann et al 2002;Nagao et al 2006;Jiang et al 2007;Juarez et al 2009;Matsuoka et al 2011;Marziani et al 2015).…”

Section: Introductionmentioning

confidence: 99%

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The evolution of chemical abundance in quasar broad line region

Bian

Shen

et al. 2018

Monthly Notices of the Royal Astronomical Society

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We study the relation between the metallicity of quasar broad line region (BLR) and black hole (BH) mass (10 7.5 M ⊙ ∼ 10 10 M ⊙ ) and quasar bolometric luminosity (10 44.6 erg/s ∼ 10 48 erg/s) using a sample of ∼130,000 quasars at 2.25 ≤ z ≤ 5.25 from Sloan Digital Sky Survey (SDSS) 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 metallicitysensitive 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 z ∼ 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 (SED) 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 disk.

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Section: Metallicity Measurementsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The evolution of chemical abundance in quasar broad line region

Bian

Shen

et al. 2018

Monthly Notices of the Royal Astronomical Society

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“…The issue of the intensity ratios of the doublet components is relevant to the spectral analysis of high-z quasars or low-z type-1 AGNs observed from spaceborne observatories [51]. As the lines originate from the transition between the same spectroscopic terms, we would expect that, in the case of optically thin line emission, the ratio is equal to the ratio of the statistical weight of each level, i.e., g j /g i = (2J j + 1)/(2J i + 1), implying a maximum ratio of two for the ratio between the J = 3 2 and the J = 1 2 components of the doublet, I( 2 P o 3 2…”

Section: Applications To Empirical Line Profile Modeling: Intensity Rmentioning

confidence: 99%

Broad UV Emission Lines in Type-1 Active Galactic Nuclei: A Note on Spectral Diagnostics and the Excitation Mechanism

Marziani

Olmo

Perea

et al. 2020

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This paper reviews several basic emission properties of the UV emission lines observed in the spectra of quasars and type-1 active galactic nuclei, mainly as a function of the ionization parameter, metallicity, and density of the emitting gas. The analysis exploits a general-purpose 4D array of the photoionization simulations computed using the code CLOUDY, covering ionization parameter in the range 10−4.5–10+1.0, hydrogen density nH∼107–1014 cm−3, metallicity Z between 0.01 and 100 Z⊙, and column density in the range 1021–1023 cm−2. The focus is on the most prominent UV emission lines observed in quasar spectra, namely Nvλ1240, Siivλ1397, Oiv]λ1402, Civλ1549, Heiiλ1640, Aliiiλ1860, Siiii]λ1892, and Ciii]λ1909, and on the physical conditions under which electron-ion impact excitation is predicted to be the dominant line producer. Photoionization simulations help constrain the physical interpretation and the domain of applicability of spectral diagnostics derived from measurements of emission line ratios, reputed to be important for estimating the ionization degree, density, and metallicity of the broad line emitting gas, as well as the relative intensity ratios of the doublet or multiplet components relevant for empirical spectral modeling.

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“…The subsquent tasks will be to check the R FeII dependence on other parameters (see Sulentic et al, 2000;Mao et al, 2009;Marziani et al, 2015) which are used (L bol , α uv , α ox , n H , N H , cos(i), a and others). We intend to incorporate the microturbulence as suggested in Bruhweiler and Verner (2008).…”

Section: Futurementioning

confidence: 99%

The Physical Driver of the Optical Eigenvector 1 in Quasar Main Sequence

Panda

Wildy

2017

Front. Astron. Space Sci.

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Quasars are complex sources, characterized by broad band spectra from radio through optical to X-ray band, with numerous emission and absorption features. This complexity leads to rich diagnostics. However, Boroson and Green (1992) used Principal Component Analysis (PCA), and with this analysis they were able to show significant correlations between the measured parameters. The leading component, related to Eigenvector 1 (EV1) was dominated by the anticorrelation between the FeII optical emission and [OIII] line and EV1 alone contained 30% of the total variance. It opened a way in defining a quasar main sequence, in close analogy to the stellar main sequence on the Hertzsprung-Russel (HR) diagram (Sulentic et al., 2001). The question still remains which of the basic theoretically motivated parameters of an active nucleus (Eddington ratio, black hole mass, accretion rate, spin, and viewing angle) is the main driver behind the EV1. Here we limit ourselves to the optical waveband, and concentrate on theoretical modeling the FeII to Hβ ratio, and we test the hypothesis that the physical driver of EV1 is the maximum of the accretion disk temperature, reflected in the shape of the spectral energy distribution (SED). We performed computations of the Hβ and optical FeII for a broad range of SED peak position using CLOUDY photoionisation code. We assumed that both Hβ and FeII emission come from the Broad Line Region represented as a constant density cloud in a plane-parallel geometry. We expected that a hotter disk continuum will lead to more efficient production of FeII but our computations show that the FeII to Hβ ratio actually drops with the rise of the disk temperature. Thus either hypothesis is incorrect, or approximations used in our paper for the description of the line emissivity is inadequate.

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UV spectral diagnostics for low redshift quasars: estimating physical conditions and radius of the broad line region

Cited by 16 publications

References 57 publications

The evolution of chemical abundance in quasar broad line region

The evolution of chemical abundance in quasar broad line region

Broad UV Emission Lines in Type-1 Active Galactic Nuclei: A Note on Spectral Diagnostics and the Excitation Mechanism

The Physical Driver of the Optical Eigenvector 1 in Quasar Main Sequence

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