Lyα emission-line reconstruction for high-<i>z</i>QSOs

Greig, Bradley; Mesinger, Andrei; McGreer, Ian D.; Gallerani, S.; Haiman, Zoltán

doi:10.1093/mnras/stw3210

Cited by 85 publications

(103 citation statements)

References 100 publications

(118 reference statements)

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“…All quasars in our sample show significant blueshifts, from ∼730 to ∼5900 km s −1 . For the previously studied case of ULAS 1120, the value found here is consistent with the ones reported in the literature (De Rosa et al 2014;Greig et al 2017). We neglect the following here: PSO 167-13 and HSC 1205, due to the low S/N; PSO 183+05, for which we do not have a measurement of the Mg II redshift (see Section 5.5); and PSO 011+09, PSO 006+39, and PSO 261+19, since we do not have NIR spectral coverage (see Section 3 and Figure 3); also, we still consider VIK2348, but with the caveat that this object was flagged as a possible broad absorption line (BAL) quasar (De Rosa et al 2014).…”

Section: IV Blueshiftssupporting

confidence: 92%

Physical Properties of 15 Quasars at z ≳ 6.5

Mazzucchelli

Bañados

Venemans

et al. 2017

ApJ

310

444

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Quasars are galaxies hosting accreting supermassive black holes; due to their brightness, they are unique probes of the early universe. To date, only a few quasars have been reported at (<800 Myr after the big bang). In this work, we present six additional quasars discovered using the Pan-STARRS1 survey. We use a sample of 15 quasars to perform a homogeneous and comprehensive analysis of this highest-redshift quasar population. We report four main results: (1) the majority of quasars show large blueshifts of the broad C iv λ1549 emission line compared to the systemic redshift of the quasars, with a median value ∼3× higher than a quasar sample at ; (2) we estimate the quasars’ black hole masses ( (0.3–5) × 109 M ⊙) via modeling of the Mg ii λ2798 emission line and rest-frame UV continuum and find that quasars at high redshift accrete their material (with ) at a rate comparable to a luminosity-matched sample at lower redshift, albeit with significant scatter (0.4 dex); (3) we recover no evolution of the Fe ii/Mg ii abundance ratio with cosmic time; and (4) we derive near-zone sizes and, together with measurements for quasars from recent work, confirm a shallow evolution of the decreasing quasar near-zone sizes with redshift. Finally, we present new millimeter observations of the [C ii] 158 μm emission line and underlying dust continuum from NOEMA for four quasars and provide new accurate redshifts and [C ii]/infrared luminosity estimates. The analysis presented here shows the large range of properties of the most distant quasars.

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Section: IV Blueshiftssupporting

confidence: 92%

Physical Properties of 15 Quasars at z ≳ 6.5

Mazzucchelli

Bañados

Venemans

et al. 2017

ApJ

310

444

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“…Second, a damping wing signature redward of rest-frame Lyα will be present, arising from the Lorentzian wings of the Lyα resonant absorption cross-section (Miralda-Escudé 1998). The two highest redshift quasars known, ULAS J1120+0641 (Mortlock et al 2011) (henceforth J1120+0641) at z = 7.09, and ULAS J1342+0928 (Bañados et al 2018) (henceforth J1342+0928) at z = 7.54, both exhibit truncated proximity zones (Bolton et al 2011;Davies et al 2018b) (compared to similarly-luminous quasars at z ∼ 6-6.5, Eilers et al 2017) and show strong evidence for damping wing absorption (Mortlock et al 2011;Bolton et al 2011;Greig et al 2017;Bañados et al 2018;Davies et al 2018b). As we show below, an extension of the Soltan argument to individual quasars is uniquely possible at z 7 due to the presence of neutral hydrogen in the IGM along our line of sight to the quasar.…”

Section: Introductionmentioning

confidence: 99%

Evidence for Low Radiative Efficiency or Highly Obscured Growth of z > 7 Quasars

Davies

Hennawi

Eilers

2019

ApJL

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The supermassive black holes (SMBHs) observed at the centers of all massive galaxies are believed to have grown via luminous accretion during quasar phases in the distant past. The fraction of inflowing rest mass energy emitted as light, the radiative efficiency, has been inferred to be 10%, in agreement with expectations from thin disk accretion models. But the existence of billion solar-mass SMBHs powering quasars at z > 7 challenges this picture: provided they respect the Eddington limit, there is not enough time to grow z > 7 SMBHs from stellar remnant seeds unless the radiative efficiency is below 10%. Here we show that one can constrain the radiative efficiencies of the most distant quasars known using foreground neutral intergalactic gas as a cosmological-scale ionizing photon counter. From the Lyα absorption profiles of ULAS J1120+0641 (z = 7.09) and ULAS J1342+0928 (z = 7.54), we determine posterior median radiative efficiencies of 0.08% and 0.1%, respectively, and the combination of the two measurements rule out the canonical 10% efficiency at 99.8% credibility after marginalizing over the unknown obscured fraction. This low radiative efficiency implies rapid mass accretion for the earliest SMBHs, greatly easing the tension between the age of the Universe and the SMBH masses. However, our measured efficiency may instead reflect nearly complete obscuration by dusty gas in the quasar host galaxies over the vast majority of their SMBH growth. Assuming 10% efficiency during unobscured phases, we find that the obscured fraction would be > 82% at 95% credibility, and imply a 25.7 +49.6 −16.5 times larger obscured than unobscured luminous quasar population at z > 7.

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“…As noted earlier, we have predictions from 100 individual NNs that go into our ensemble. None of these 100 NNs predict a Lyα peak that is nearly as strong as that from Greig et al (2017a). In contrast, some of the individual NNs do predict Lyα as strong as that seen in the SDSS composite and the PCA method.…”

Section: Reconstructing High-redshift Quasar Spectramentioning

confidence: 89%

“…Mortlock et al (2011) and Bañados et al (2018) used composite spectra of the most similar low-redshift SDSS quasars to reconstruct the intrinsic spectra of two z > 7 QSOs. Greig et al (2017aGreig et al ( , 2019 constructed a covariance matrix to capture the relationships between the Lyα, SiIV+OIV], CIV and CIII] emission lines and used these features to reconstruct the intrinsic spectra of the same QSOs. Davies et al (2018a) used a principal component analysis technique to extract the mapping from the spectral features redward of Lyα to the blueward features, and once again applied this to the two z > 7 QSOs.…”

Section: Introductionmentioning

confidence: 99%

Reionization history constraints from neural network based predictions of high-redshift quasar continua

Ďurovčíková

Katz

Davies

et al. 2020

Monthly Notices of the Royal Astronomical Society

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Observations of the early Universe suggest that reionization was complete by z ∼ 6, however, the exact history of this process is still unknown. One method for measuring the evolution of the neutral fraction throughout this epoch is via observing the Lyα damping wings of high-redshift quasars. In order to constrain the neutral fraction from quasar observations, one needs an accurate model of the quasar spectrum around Lyα, after the spectrum has been processed by its host galaxy but before it is altered by absorption and damping in the intervening IGM. In this paper, we present a novel machine learning approach, using artificial neural networks, to reconstruct quasar continua around Lyα. Our QSANNdRA algorithm improves the error in this reconstruction compared to the state-of-the-art PCA-based model in the literature by 14.2% on average, and provides an improvement of 6.1% on average when compared to an extension thereof. In comparison with the extended PCA model, QSANNdRA further achieves an improvement of 22.1% and 16.8% when evaluated on low-redshift quasars most similar to the two high-redshift quasars under consideration, ULAS J1120+0641 at z = 7.0851 and ULAS J1342+0928 at z = 7.5413, respectively. Using our more accurate reconstructions of these two z > 7 quasars, we estimate the neutral fraction of the IGM using a homogeneous reionization model and findx HI = 0.25 +0.05 −0.05 at z = 7.0851 andx HI = 0.60 +0.11 −0.11 at z = 7.5413. Our results are consistent with the literature and favour a rapid end to reionization.

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Lyα emission-line reconstruction for high-zQSOs

Cited by 85 publications

References 100 publications

Physical Properties of 15 Quasars at z ≳ 6.5

Physical Properties of 15 Quasars at z ≳ 6.5

Evidence for Low Radiative Efficiency or Highly Obscured Growth of z > 7 Quasars

Reionization history constraints from neural network based predictions of high-redshift quasar continua

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