Shedding New Light on Weak Emission-line Quasars in the C iv–Hβ Parameter Space

Ha, T.; Dix, Cooper; Matthews, Brandon M.; Shemmer, Ohad; Brotherton, Michael S.; Myers, Adam D.; Richards, Gordon T.; Maithil, Jaya; Anderson, Scott F.; Brandt, W. N.; Diamond‐Stanic, Aleksandar M.; Fan, Xiaohui; Gallagher, S. C.; Green, Richard F.; Lira, P.; Netzer, H.; Plotkin, Richard M.; Runnoe, Jessie C.; Schneider, Donald P.; Strauss, Michael A.; Trakhtenbrot, Benny; Wu, Jianfeng

doi:10.3847/1538-4357/acd04d

Cited by 4 publications

(2 citation statements)

References 86 publications

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“…Based on the continuum fitting method, Marculewicz & Nikolajuk (2020) found that most of the WLQs have a BH mass larger than 10 9 M e and pointed out that the BH mass estimated from FWHM(Hβ) is underestimated. However, Ha et al (2023) proposed that the BH mass estimated from the traditional method of the broad-emission-line region sizeluminosity relation may be overestimated by up to an order of magnitude, where the corrections based on the strength of the optical Fe II emission and possible blueshift of C IV lines are applied. It should be noted that the larger value of R Fe II = Fe II (4434-4684 Å)/Hβ in WLQs may not be an indicator of high Eddington ratios, as found in narrow-line Seyferts, but caused by the weaker Hβ emission, since both low-ionization and high-ionization lines can become weaker in WLQs (see Figure 3 and Shemmer et al 2010).…”

Section: Conclusion and Discussionmentioning

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: Conclusion and Discussionmentioning

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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“…A primary interest going forward would be bolstering the sample with supplementary observations of quasars, primarily at z ∼ 3, in order to obtain statistically meaningful results on a potential redshift dependence, and further improve UV-based redshift determinations. It will also be interesting to test our prescriptions at the highest accessible redshifts, where considerably larger C IV blueshifts have been observed in sources at z  6, perhaps due to higher accretion rates (e.g., Meyer et al 2019;Schindler et al 2020;Ha et al 2023). Another avenue of further investigation includes increasing the sample size of quasars with significantly higher spectral resolution, e.g., using Gemini's Spectrograph and Camera for Observations of Rapid Phenomena in the Infrared and Optical (Robberto et al 2020), in order to further improve the UV-based redshift corrections by obtaining more accurate line peaks of spectral features.…”

Section: Discussionmentioning

confidence: 99%

Gemini Near Infrared Spectrograph–Distant Quasar Survey: Augmented Spectroscopic Catalog and a Prescription for Correcting UV-based Quasar Redshifts

Matthews

Dix

Shemmer

et al. 2023

ApJ

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Quasars at z ≳ 1 most often have redshifts measured from rest-frame ultraviolet emission lines. One of the most common such lines, C iv λ1549, shows blueshifts up to ≈5000 km s−1 and in rare cases even higher. This blueshifting results in highly uncertain redshifts when compared to redshift determinations from rest-frame optical emission lines, e.g., from the narrow [O iii] λ5007 feature. We present spectroscopic measurements for 260 sources at 1.55 ≲ z ≲ 3.50 having −28.0 ≲ M i ≲ − 30.0 mag from the Gemini Near Infrared Spectrograph–Distant Quasar Survey (GNIRS-DQS) catalog, augmenting the previous iteration, which contained 226 of the 260 sources whose measurements are improved upon in this work. We obtain reliable systemic redshifts based on [O iii] λ5007 for a subset of 121 sources, which we use to calibrate prescriptions for correcting UV-based redshifts. These prescriptions are based on a regression analysis involving C iv full-width-at-half-maximum intensity and equivalent width, along with the UV continuum luminosity at a rest-frame wavelength of 1350 Å. Applying these corrections can improve the accuracy and the precision in the C iv-based redshift by up to ∼850 km s−1 and ∼150 km s−1, respectively, which correspond to ∼8.5 and ∼1.5 Mpc in comoving distance at z = 2.5. Our prescriptions also improve the accuracy of the best available multifeature redshift determination algorithm by ∼100 km s−1, indicating that the spectroscopic properties of the C iv emission line can provide robust redshift estimates for high-redshift quasars. We discuss the prospects of our prescriptions for cosmological and quasar studies utilizing upcoming large spectroscopic surveys.

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X-ray properties of reverberation-mapped AGNs with super-Eddington accreting massive black holes

Maithil,

Brotherton,

Shemmer

et al. 2024

Monthly Notices of the Royal Astronomical Society

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The X-ray properties of Active Galactic Nuclei (AGNs) depend on their underlying physical parameters, particularly the accretion rate. We identified eight reverberation-mapped AGNs with some of the largest known accretion rates without high-quality X-ray data. We obtained new Chandra ACIS-S X-ray observations and nearly simultaneous optical spectrophotometry to investigate the properties of these AGNs with extreme super-Eddington accreting black holes (SEAMBHs). We combined our new X-ray measurements with those of other reverberation-mapped AGNs, which have the best-determined masses and accretion rates. The trend of the steepening of the spectral slope between X-ray and optical-UV, αox, with increasing optical-UV luminosity, L2500Å, holds true for even the most extreme SEAMBHs. One of our new SEAMBHs appears X-ray weak for its luminosity, perhaps due to absorption associated with orientation effects involving a slim disk thought to be present in highly accreting systems. The correlation of the $\rm 2-8~ keV$ X-ray photon index with the accretion rate also holds for the extreme SEAMBHs, which show some of the largest photon indices reported for AGNs.

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Shedding New Light on Weak Emission-line Quasars in the C iv–Hβ Parameter Space

Cited by 4 publications

References 86 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

Gemini Near Infrared Spectrograph–Distant Quasar Survey: Augmented Spectroscopic Catalog and a Prescription for Correcting UV-based Quasar Redshifts

X-ray properties of reverberation-mapped AGNs with super-Eddington accreting massive black holes

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