Subaru High-z Exploration of Low-luminosity Quasars (SHELLQs). VI. Black Hole Mass Measurements of Six Quasars at 6.1 ≤ z ≤ 6.7

Onoue, Masafusa; Kashikawa, Nobunari; Matsuoka, Yoshiki; Kato, Nanako; Izumi, Teruo; Strauss, Michael A.; Harikane, Yuichi; Imanishi, Masatoshi; Ito, K.; Iwasawa, K.; Kawaguchi, Toshihiro; Lee, Chien‐Hsiu; Noboriguchi, Akatoki; Suh, Hyewon; Tanaka, Masayuki; Toba, Yoshiki

doi:10.3847/1538-4357/ab29e9

Cited by 138 publications

(157 citation statements)

References 95 publications

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“…Fig. 7 in Onoue et al 2019). Estimating the bolometric luminosity of SDSSJ08 from M 1450 Å (Runnoe et al 2012), we find that it accretes at ∼0.1 L Edd .…”

Section: Origin Of the X-ray Emissionmentioning

confidence: 74%

First constraints on the AGN X-ray luminosity function atz~ 6 from an eROSITA-detected quasar

Wolf

Nandra

Salvato

et al. 2021

A&A

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Context. High-redshift quasars signpost the early accretion history of the Universe. The penetrating nature of X-rays enables a less absorption-biased census of the population of these luminous and persistent sources compared to optical/near-infrared colour selection. The ongoing SRG/eROSITA X-ray all-sky survey offers a unique opportunity to uncover the bright end of the high-z quasar population and probe new regions of colour parameter space. Aims. We searched for high-z quasars within the X-ray source population detected in the contiguous ~140 deg2 field observed by eROSITA during the performance verification phase. With the purpose of demonstrating the unique survey science capabilities of eROSITA, this field was observed at the depth of the final all-sky survey. The blind X-ray selection of high-redshift sources in a large contiguous, near-uniform survey with a well-understood selection function can be directly translated into constraints on the X-ray luminosity function (XLF), which encodes the luminosity-dependent evolution of accretion through cosmic time. Methods. We collected the available spectroscopic information in the eFEDS field, including the sample of all currently known optically selected z > 5.5 quasars and cross-matched secure Legacy DR8 counterparts of eROSITA-detected X-ray point-like sources with this spectroscopic sample. Results. We report the X-ray detection of eFEDSU J083644.0+005459, an eROSITA source securely matched to the well-known quasar SDSS J083643.85+005453.3 (z = 5.81). The soft X-ray flux of the source derived from eROSITA is consistent with previous Chandra observations. The detection of SDSS J083643.85+005453.3 allows us to place the first constraints on the XLF at z > 5.5 based on a secure spectroscopic redshift. Compared to extrapolations from lower-redshift observations, this favours a relatively flat slope for the XLF at z ~ 6 beyond L*, the knee in the luminosity function. In addition, we report the detection of the quasar with LOFAR at 145 MHz and ASKAP at 888 MHz. The reported flux densities confirm a spectral flattening at lower frequencies in the emission of the radio core, indicating that SDSS J083643.85+005453.3 could be a (sub-) gigahertz peaked spectrum source. The inferred spectral shape and the parsec-scale radio morphology of SDSS J083643.85+005453.3 indicate that it is in an early stage of its evolution into a large-scale radio source or confined in a dense environment. We find no indications for a strong jet contribution to the X-ray emission of the quasar, which is therefore likely to be linked to accretion processes. Conclusions. Our results indicate that the population of X-ray luminous AGNs at high redshift may be larger than previously thought. From our XLF constraints, we make the conservative prediction that eROSITA will detect ~90 X-ray luminous AGNs at redshifts 5.7 < z < 6.4 in the full-sky survey (De+RU). While subject to different jet physics, both high-redshift quasars detected by eROSITA so far are radio-loud; a hint at the great potential of combined X-ray and radio surveys for the search of luminous high-redshift quasars.

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“…Fig. 7 in Onoue et al 2019). Estimating the bolometric luminosity of SDSSJ08 from M 1450 Å (Runnoe et al 2012), we find that it accretes at ∼0.1 L Edd .…”

Section: Origin Of the X-ray Emissionmentioning

confidence: 74%

First constraints on the AGN X-ray luminosity function atz~ 6 from an eROSITA-detected quasar

Wolf

Nandra

Salvato

et al. 2021

A&A

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“…The total number of the quasars compiled here is 40. The M BH measurements of our HSC quasars, which are also based on the single-epoch method with MgII line, are described in Onoue et al (2019).…”

Section: Resultsmentioning

confidence: 99%

“…Overview of the HSC quasars observed by ALMA. M1450 and MBH are quoted fromMatsuoka et al (2016Matsuoka et al ( , 2018a andOnoue et al 2019. For J1202−0057 and J2228+0152, we assumed the Eddington-limited accretion to compute the lower-limit of their MBH.…”

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confidence: 99%

Rapid evolution and transformation into quiescence?: ALMA view on z > 6 low-luminosity quasars

et al. 2019

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We present ALMA [CII] line and far-infrared (FIR) continuum observations of seven z > 6 low-luminosity quasars (M1450 > −25 mag) discovered by our on-going Subaru Hyper Suprime-Cam survey. The [CII] line was detected in all targets with luminosities of ∼(2−10) × 108 L⊙, about one order of magnitude smaller than optically luminous quasars. Also found was a wide scatter of FIR continuum luminosity, ranging from LFIR < 1011L⊙ to ∼2 × 1012L⊙. With the [CII]-based dynamical mass, we suggest that a significant fraction of low-luminosity quasars are located on or even below the local Magorrian relation, particularly at the massive end of the galaxy mass distribution. This is a clear contrast to the previous finding that luminous quasars tend to have overmassive black holes relative to the relation. Our result is expected to show a less-biased nature of the early co-evolution of black holes and their host galaxies.

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“…More accurate estimates of M BH were obtained by using dedicated, intensive near-IR spectroscopy, which probes the rest-frame UV broad Mg ii emission line, and by relying on so-called "virial" (or "single-epoch") M BH prescriptions (e.g., Shen 2013). These reveal that the highest redshift quasars are indeed powered by SMBHs with M BH ∼ 10 8−10 M , accreting at rates L/L Edd ∼ 0.1 − 1 (e.g., Willott et al 2010b;Trakhtenbrot et al 2011;De Rosa et al 2014;Onoue et al 2019;Shen et al 2019; see Wang et al 2015, Wu et al 2015, and 2018 for examples of "extreme" values). Here, too, the number of sources with reliable determinations of M BH and L/L Edd is steadily growing.…”

Section: Mass and Accretion Ratesmentioning

confidence: 96%

What do observations tell us about the highest-redshift supermassive black holes?

Trakhtenbrot

2019

Proc. IAU

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I review the current understanding of some key properties of the earliest growing supermassive black holes (SMBHs), as determined from the most up-to-date observations of z ≲ 5 quasars. This includes their accretion rates and growth history, their host galaxies, and the large-scale environments that enabled their emergence less than a billion years after the Big Bang. The available multi-wavelength data show that these SMBHs are consistent with Eddington-limited, radiatively efficient accretion that had to proceed almost continuously since very early epochs. ALMA observations of the hosts’ ISM reveal gas-rich, well developed galaxies, with a wide range of SFRs that may exceed ∼1000 Mȯyr−1. Moreover, ALMA uncovers a high fraction of companion, interacting galaxies, separated by < 100 kpc (projected). This supports the idea that the first generation of high-mass, luminous SMBHs grew in over-dense environments, and that major mergers may be important drivers for rapid SMBH and host galaxy growth. Current X-ray surveys cannot access the lower-mass, supposedly more abundant counterparts of these rare z ≳ 5 massive quasars, which should be able to elucidate the earliest stages of BH formation and growth. Such lower-mass nuclear BHs will be the prime targets of the deepest surveys planned for the next generation of facilities, such as the upcoming Athena mission and the future Lynx mission concept.

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Subaru High-z Exploration of Low-luminosity Quasars (SHELLQs). VI. Black Hole Mass Measurements of Six Quasars at 6.1 ≤ z ≤ 6.7

Cited by 138 publications

References 95 publications

First constraints on the AGN X-ray luminosity function atz~ 6 from an eROSITA-detected quasar

First constraints on the AGN X-ray luminosity function atz~ 6 from an eROSITA-detected quasar

Rapid evolution and transformation into quiescence?: ALMA view on z > 6 low-luminosity quasars

What do observations tell us about the highest-redshift supermassive black holes?

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