High‐redshift active galactic nuclei and the next decade of Chandra and <scp>XMM</scp>‐Newton

Brandt, W. N.; Vito, F.

doi:10.1002/asna.201713337

Cited by 11 publications

(9 citation statements)

References 49 publications

(63 reference statements)

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“…Euclid, eROSITA, LSST, SUMIRE-HSC, and WFIRST) are expected to push the QSO redshift frontier far into the reionization era, detecting hundreds of accreting SMBHs at z ≈ 7 − 10 (e.g. Brandt & Vito 2017). Studying QSO properties in the first few 10 8 years of the Universe will be extremely important to understand some of the major open issues in modern astrophysics, such as the formation and early growth of SMBHs, their interplay with proto-galaxies, the formation of the first structures, and the mechanisms responsible for the reionization of the Universe.…”

Section: Discussionmentioning

confidence: 99%

The X-ray properties of z > 6 quasars: no evident evolution of accretion physics in the first Gyr of the Universe

Vito

Brandt

Bauer

et al. 2019

A&A

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Context. X-ray emission from quasars (QSOs) has been used to assess supermassive black hole (SMBH) accretion properties up to z ≈ 6. However, at z > 6 only ≈ 15 QSOs are covered by sensitive X-ray observations, preventing a statistically significant investigation of the X-ray properties of the QSO population in the first Gyr of the Universe. Aims. We present new Chandra observations of a sample of 10 z > 6 QSOs, selected to have virial black-hole mass estimates from Mg II line spectroscopy (log M BH M = 8.5 − 9.6). Adding archival X-ray data for an additional 15 z > 6 QSOs, we investigate the X-ray properties of the QSO population in the first Gyr of the Universe, focusing in particular on the L UV − L X relation, which is traced by the α ox parameter, and the shape of their X-ray spectra. Methods. We performed photometric analyses to derive estimates of the X-ray luminosities of our z > 6 QSOs, and thus their α ox values and bolometric corrections (K bol = L bol /L X ). We compared the resulting α ox and K bol distributions with the results found for QSO samples at lower redshift, and ran several statistical tests to check for a possible evolution of the L UV − L X relation. Finally, we performed a basic X-ray spectral analysis of the brightest z > 6 QSOs to derive their individual photon indices, and joint spectral analysis of the whole sample to estimate the average photon index. Results. We detected seven of the new Chandra targets in at least one standard energy band, while two more are detected discarding energies E > 5 keV, where background dominates. We confirm a lack of significant evolution of α ox with redshift, extending the results from previous works up to z > 6 with a statistically significant QSO sample, and the trend of an increasing bolometric correction with increasing luminosity found for QSOs at lower redshifts. The average power-law photon index of our sample ( Γ = 2.20 +0.39 −0.34 and Γ = 2.13 +0.13 −0.13 for sources with < 30 and > 30 net counts, respectively) is slightly steeper than, but still consistent with, typical QSOs at z = 1 − 6. Conclusions. All these results point toward a lack of substantial evolution of the inner accretion-disk/hot-corona structure in QSOs from low redshift to z > 6. Our data hint at generally high Eddington ratios at z > 6.

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Section: Discussionmentioning

confidence: 99%

The X-ray properties of z > 6 quasars: no evident evolution of accretion physics in the first Gyr of the Universe

Vito

Brandt

Bauer

et al. 2019

A&A

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106

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“…For example, SDSS detected only one-third of all 20 cm FIRST sources (Becker et al 1995) because it was too shallow by ∼4 mag for a complete optical identification. Similarly, deep optical data are required for identification of faint X-ray sources (Brandt & Hasinger 2005;Brandt & Vito 2017).…”

Section: Synergy With Other Projectsmentioning

confidence: 99%

LSST: From Science Drivers to Reference Design and Anticipated Data Products

Ivezić

Kahn

Tyson

et al. 2019

ApJ

2,585

1,494

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We describe here the most ambitious survey currently planned in the optical, the Large Synoptic Survey Telescope (LSST). The LSST design is driven by four main science themes: probing dark energy and dark matter, taking an inventory of the solar system, exploring the transient optical sky, and mapping the Milky Way. LSST will be a large, wide-field ground-based system designed to obtain repeated images covering the sky visible from Cerro Pachón in northern Chile. The telescope will have an 8.4 m (6.5 m effective) primary mirror, a 9.6 deg 2 field of view, a 3.2-gigapixel camera, and six filters (ugrizy) covering the wavelength range 320-1050 nm. The project is in the construction phase and will begin regular survey operations by 2022. About 90% of the observing time will be devoted to a deep-wide-fast survey mode that will uniformly observe a 18,000 deg 2 region about 800 times (summed over all six bands) during the anticipated 10 yr of operations and will yield a co-added map to r∼27.5. These data will result in databases including about 32 trillion observations of 20 billion galaxies and a similar number of stars, and they will serve the majority of the primary science programs. The remaining 10% of the observing time will be allocated to special projects such as Very Deep and Very Fast time domain surveys, whose details are currently under discussion. We illustrate how the LSST science drivers led to these choices of system parameters, and we describe the expected data products and their characteristics.

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“…The understanding of the SMBH formation and growth mechanisms in the early universe requires the collection of much larger samples of X-ray selected AGN and galaxies at higher redshifts and lower luminosities than those probed by current X-ray surveys. Moreover, while Chandra and XMM-Newton, jointly with large-area optical/IR surveys, are successfully improving our knowledge of the bright quasar population up to z ≈ 7 (e.g., Brandt & Vito 2017), the bulk of the AGN population, constituted by low-luminosity and possibly obscured systems, are currently completely missed beyond z ≈ 5 − 6 even by the deepest X-ray surveys available, and Chandra observations substantially deeper than the 7 Ms CDF-S are not foreseeable. The Athena X-ray Observatory (Nandra et al 2013) 17 , which will be launched in ∼ 2028, is expected to detect hundreds of L * AGN at z > 6 (Aird et al 2013), thanks to its survey power a factor of ∼ 100 faster than Chandra or XMM-Newton, boosting our knowledge of the high-rate accretion phases, which likely dominate SMBH growth at high redshift (Vito et al 2016).…”

Section: The Case For Athena and Lynxmentioning

confidence: 99%

High-redshift AGN in the Chandra Deep Fields: the obscured fraction and space density of the sub-L* population

Vito

Brandt

Yang

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We investigate the population of high-redshift (3 z < 6) AGN selected in the two deepest X-ray surveys, the 7 Ms Chandra Deep Field-South and 2 Ms Chandra Deep Field-North. Their outstanding sensitivity and spectral characterization of faint sources allow us to focus on the sub-L * regime (logL X 44), poorly sampled by previous works using shallower data, and the obscured population. Taking fully into account the individual photometric-redshift probability distribution functions, the final sample consists of ≈ 102 X-ray selected AGN at 3 z < 6. The fraction of AGN obscured by column densities logN H > 23 is ∼ 0.6 − 0.8, once incompleteness effects are taken into account, with no strong dependence on redshift or luminosity. We derived the high-redshift AGN number counts down to F 0.5−2 keV = 7 × 10 −18 erg cm −2 s −1 , extending previous results to fainter fluxes, especially at z > 4. We put the tightest constraints to date on the low-luminosity end of AGN luminosity function at high redshift. The space-density, in particular, declines at z > 3 at all luminosities, with only a marginally steeper slope for low-luminosity AGN. By comparing the evolution of the AGN and galaxy densities, we suggest that such a decline at high luminosities is mainly driven by the underlying galaxy population, while at low luminosities there are hints of an intrinsic evolution of the parameters driving nuclear activity. Also, the black-hole accretion rate density and star-formation rate density, which are usually found to evolve similarly at z 3, appear to diverge at higher redshifts.

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High‐redshift active galactic nuclei and the next decade of Chandra and XMM‐Newton

Cited by 11 publications

References 49 publications

The X-ray properties of z > 6 quasars: no evident evolution of accretion physics in the first Gyr of the Universe

The X-ray properties of z > 6 quasars: no evident evolution of accretion physics in the first Gyr of the Universe

LSST: From Science Drivers to Reference Design and Anticipated Data Products

High-redshift AGN in the Chandra Deep Fields: the obscured fraction and space density of the sub-L* population

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