The Covering Factor of Warm Dust in Weak Emission-Line Active Galactic Nuclei

Zhang, Xudong; Liu, Yuan

doi:10.3847/0004-637x/830/2/69

Cited by 2 publications

(1 citation statement)

References 53 publications

(79 reference statements)

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“…The physical mechanism for the weak or absent emission lines is still quite unclear so far. One possible physical reason is the underdeveloped broad-line region (BLR) in these AGNs with a lower covering factor (CF) of BLR clouds, where WLQs may belong to an early stage in AGN evolution and the BLR was not yet fully formed (e.g., Hryniewicz et al 2010;Shemmer et al 2010;Zhang & Liu 2016;Kumar et al 2023). If this is the case, most emission lines, including the lowionization lines, in WLQs should be weaker than those of normal quasars.…”

Section: Introductionmentioning

confidence: 99%

The Weakness of Soft X-Ray Intensity: Possible Physical Reason for Weak-line Quasars

Wu,

Jin

et al. 2024

ApJ

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Weak-line quasars (WLQs) are a notable group of active galactic nuclei (AGNs) that show unusually weak UV lines even though their optical-UV continuum shapes are similar to those of typical quasars. The physical mechanism for WLQs is an unsolved puzzle in the AGN unified model. We explore the properties of UV emission lines by performing extensive photoionization calculations based on Cloudy simulations with different spectral energy distributions (SEDs) of AGNs. The AGN continua are built from several observational empirical correlations, where the blackbody emission from the cold disk, the power-law emission from the hot corona, and a soft X-ray excess component are considered. We find that the equivalent width (EW) of C iv from our models is systematically lower than observational values if the component of soft X-ray excess is neglected. The EW will increase several times and is roughly consistent with the observations after considering the soft X-ray excess component as constrained from normal type I AGNs. We find that the UV lines are weak for QSOs with quite large black hole mass (e.g., M BH > 109 M ⊙) and weak soft X-ray emission due to the deficit of ionizing photons. As an example, we present the strength of C iv based on the multiband SEDs for three nearby weak-line AGNs, where the weaker soft X-ray emission normally predicts the weaker lines.

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Section: Introductionmentioning

confidence: 99%

The Weakness of Soft X-Ray Intensity: Possible Physical Reason for Weak-line Quasars

Wu,

Jin

et al. 2024

ApJ

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Evidence of underdeveloped torus and broad-line region of weak emission line quasars based on their spectral energy distribution

Kumar

Chand

Joshi

2022

Monthly Notices of the Royal Astronomical Society

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To unravel the dominant cause of the weak emission line in a subset of optically selected radio-quiet ‘weak emission line quasars’ (WLQs), we have investigated the possibility of an underdeveloped broad line region (BLR). For this, we have modeled spectral energy distributions (SED) of 61 WLQs by using their optical and infrared (IR) photometric observations from SDSS and WISE respectively. SED fit consists of various emission components, including the luminosity from the dusty torus (Ltor). For comparison with the normal quasar, we have used a control sample of 55 QSOs for each WLQs matching in emission redshift and SDSS r-band. Based on our measurement of Ltor, we found a decrement of 42 ± 2% in IR-luminosity in WLQs w.r.t the control sample of normal QSOs. Using Ltor/Lbol as the measure of torus covering factor (CFtor) we found a similar decrement in WLQs covering factor, with their CFtor distribution being significantly different w.r.t. the normal QSOs with a KS-test Pnull of 4.27 × 10−14. As dusty torus and BLR covering factors are expected to be of a similar order in AGN, our results suggest that the BLR in the WLQs is underdeveloped and could be a dominant cause of the weakness of their emission line. As a result, our analysis gives support to the models of WLQs based on the evolution scenario being in an early stage of AGNs.

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The Covering Factor of Warm Dust in Weak Emission-Line Active Galactic Nuclei

Cited by 2 publications

References 53 publications

The Weakness of Soft X-Ray Intensity: Possible Physical Reason for Weak-line Quasars

The Weakness of Soft X-Ray Intensity: Possible Physical Reason for Weak-line Quasars

Evidence of underdeveloped torus and broad-line region of weak emission line quasars based on their spectral energy distribution

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