Subaru High-z Exploration of Low-luminosity Quasars (SHELLQs). V. Quasar Luminosity Function and Contribution to Cosmic Reionization at z = 6

Matsuoka, Yoshiki; Strauss, Michael A.; Kashikawa, Nobunari; Onoue, Masafusa; Iwasawa, K.; Tang, Ji-Jia; Lee, Chien‐Hsiu; Imanishi, Masatoshi; Akiyama, Masayuki; Asami, Naoko; Bosch, James; Furusawa, Hisanori; Goto, Tomotsugu; Gunn, James E.; Harikane, Yuichi; Ikeda, Hiroyuki; Izumi, Teruo; Kawaguchi, Toshihiro; Kato, Nanako; Kikuta, Satoshi; Kohno, Kotaro; Komiyama, Yutaka; Lupton, Robert H.; Minezaki, Takeo; Miyazaki, Satoshi; Murayama, Hitoshi; Niida, Mana; Nishizawa, Atsushi J.; Noboriguchi, Akatoki; Oguri, Masamune; Ono, Yoshiyasu; Ouchi, Masami; Price, P. A.; Sameshima, Hiroaki; Schulze, Andreas; Shirakata, Hikari; Silverman, John D.; Sugiyama, Naoshi; Tait, Philip J.; Takada, Masahiro; Takata, Tadafumi; Tanaka, Masayuki; Toba, Yoshiki; Utsumi, Yousuke; Wang, Shiang‐Yu; Yamashita, Takuji

doi:10.3847/1538-4357/aaee7a

Cited by 207 publications

(275 citation statements)

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“…Madau & Haardt 2015). However they have recently been reported to contribute less than ≈ 10% of the ionizing photons needed to keep the IGM ionized (over a UV magnitude range of −18 to −30 mag; Matsuoka et al 2018, see also Parsa et al 2018). Pre-Article number, page 1 of 25 arXiv:2003.12083v1 [astro-ph.GA] 26 Mar 2020 A&A proofs: manuscript no.…”

Section: Introductionmentioning

confidence: 99%

The MUSE Hubble Ultra Deep Field Survey

Kusakabe

Blaizot

Garel

et al. 2020

A&A

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Context. The Lyα emitter (LAE) fraction, X LAE , is a potentially powerful probe of the evolution of the intergalactic neutral hydrogen gas fraction. However, uncertainties in the measurement of X LAE are still debated. Aims. Thanks to deep data obtained with the integral field spectrograph MUSE (Multi-Unit Spectroscopic Explorer), we can measure the evolution of the LAE fraction homogeneously over a wide redshift range of z ≈ 3-6 for UV-faint galaxies (down to UV magnitudes of M 1500 ≈ −17.75). This is significantly fainter than in former studies (M 1500 ≤ −18.75), and allows us to probe the bulk of the population of high-redshift star-forming galaxies. Methods. We construct a UV-complete photometric-redshift sample following UV luminosity functions and measure the Lyα emission with MUSE using the latest (second) data release from the MUSE Hubble Ultra Deep Field Survey. Results. We derive the redshift evolution of X LAE for M 1500 ∈ [−21.75; −17.75] for the first time with a equivalent width range EW(Lyα) ≥ 65 Å and find low values of X LAE 30% at z 6. The best fit linear relation is X LAE = 0.07 +0.06 −0.03 z − 0.22 +0.12 −0.24 . For M 1500 ∈ [−20.25; −18.75] and EW(Lyα) ≥ 25 Å, our X LAE values are consistent with those in the literature within 1σ at z 5, but our median values are systematically lower than reported values over the whole redshift range. In addition, we do not find a significant dependence of X LAE on M 1500 for EW(Lyα) ≥ 50 Å at z ≈ 3-4, in contrast with previous work. The differences in X LAE mainly arise from selection biases for Lyman Break Galaxies (LBGs) in the literature: UV-faint LBGs are more easily selected if they have strong Lyα emission, hence X LAE is biased towards higher values when those samples are used. Conclusions. Our results suggest either a lower increase of X LAE towards z ≈ 6 than previously suggested, or even a turnover of X LAE at z ≈ 5.5, which may be the signature of a late or patchy reionization process. We compared our results with predictions from a cosmological galaxy evolution model. We find that a model with a bursty star formation (SF) can reproduce our observed LAE fractions much better than models where SF is a smooth function of time.

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Section: Introductionmentioning

confidence: 99%

The MUSE Hubble Ultra Deep Field Survey

Kusakabe

Blaizot

Garel

et al. 2020

A&A

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“…Bouwens et al 2017;Livermore et al 2017;Ishigaki et al 2018, but see also Atek et al 2018 for a detailed analysis of the model uncertainties), and therefore that the number of faint galaxies able to produce ionizing radiation is large In the recent years, a lot of work has been dedicated to identify faint active galactic nuclei (AGN) in the highredshift Universe and determine their contribution to the reionization of the Universe (e.g. Giallongo et al 2015;Ricci et al 2017;Boutsia et al 2018;Parsa et al 2018;Matsuoka et al 2018;Stevans et al 2018). These AGN, while less luminous than bright quasars, could in principle be far more numerous.…”

Section: Introductionmentioning

confidence: 99%

Modelling a bright z = 6 galaxy at the faint end of the AGN luminosity function

Trebitsch

Volonteri

Dubois

2020

Monthly Notices of the Royal Astronomical Society

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Recent deep surveys have unravelled a population of faint active galactic nuclei (AGN) in the high redshift Universe, leading to various discussions on their nature and their role during the Epoch of Reionization. We use cosmological radiation-hydrodynamics simulations of a bright galaxy at z ∼ 6 (M 10 10 M ) hosting an actively growing super-massive black hole to study the properties of these objects. In particular, we study how the black hole and the galaxy co-evolve and what is the relative contribution of the AGN and of the stellar populations to the luminosity budget of the system. We find that the feedback from the AGN has no strong effect on the properties of the galaxy, and does not increase the total ionizing luminosity of the host. The average escape fraction of our galaxy is around f esc ∼ 5%. While our galaxy would be selected as an AGN in deep X-ray surveys, most of the UV luminosity is originating from stellar populations. This confirms that there is a transition in the galaxy population from star forming galaxies to quasar hosts, with bright Lyman-Break Galaxies (LBGs) with M UV around -22 falling in the overlap region. Our results also suggest that faint AGN do not contribute significantly to reionizing the Universe.

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“…Considering 13.6 eV per H-ionizing photon, this translates to photon densities ofṅ CO/DO = 3.2 × 10 49 , 6.8 × 10 49 s −1 Mpc −3 (in the best-case scenario, χ = ξ = = 1). Matsuoka et al (2018) estimate the contribution of AGN accretion disks to reionization without correcting their Φ for the presence of obscured sources, as they assume no ionizing radiation can escape them. However, in a jetted source, a small fraction of ionizing radiation can escape in the direction of the jets (which must be unobscured) and contribute to the ionization of the surrounding medium.…”

Section: Contribution Of Agn Jets To Reionizationmentioning

confidence: 99%

“…This would increase the contribution of disks in a factor (1−f obsc ) −1 f esc , where f esc is the escape fraction caused by the drilling of the jets and f obsc the fraction of obscured sources (set to 0.8 in this work). Considering f esc = 1 for unobscured sources and f esc = 0.1 for obscured ones, and using = 1 as is done for jets, AGN disks may contribute a 50% more toṅ ion than accounted for by Matsuoka et al (2018). Using this corrected LF, the resulting ionizing photon density produced by the accretion disks of AGN isṅ disk = 6.3 × 10 48 s −1 Mpc −3 .…”

Section: Contribution Of Agn Jets To Reionizationmentioning

confidence: 99%

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AGN jets versus accretion as reionization sources

Torres-Albà

Bosch‐Ramon

Iwasawa

2020

A&A

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Context. Cosmic reionization put an end to the dark ages that came after the recombination era. Observations seem to favor the scenario where massive stars generating photons in low-mass galaxies were responsible for the bulk of reionization. Even though a possible contribution from accretion disks of active galactic nuclei (AGN) has been widely considered, they are currently thought to have had a minor role in reionization. Aims. Our aim is to study the possibility that AGN contributed to reionization not only through their accretion disks, but also through ionizing photons coming from the AGN jets interacting with the IGM. Methods. We adopt an empirically derived AGN luminosity function at z 6, use X-ray observations to correct it for the presence of obscured sources, and estimate the density of jetted AGN. We then use analytical calculations to derive the fraction of jet energy that goes into ionizing photons. Finally, we compute the contribution of AGN jets to the H II volume filling factor at redshifts z 15 − 5.Results. We show that the contribution of the AGN jet lobes to the reionization of the Universe at z ∼ 6 might have been as high as 10% of that of star-forming galaxies, under the most favorable conditions of jetted and obscuration fraction.Conclusions. The contribution of AGN to the reionization, while most likely not dominant, could have been higher than previously assumed, thanks to the radiation originated in the jet lobes.

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Subaru High-z Exploration of Low-luminosity Quasars (SHELLQs). V. Quasar Luminosity Function and Contribution to Cosmic Reionization at z = 6

Cited by 207 publications

References 80 publications

The MUSE Hubble Ultra Deep Field Survey

The MUSE Hubble Ultra Deep Field Survey

Modelling a bright z = 6 galaxy at the faint end of the AGN luminosity function

AGN jets versus accretion as reionization sources

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