Four Quasars above Redshift 6 Discovered by the Canada-France High-<i>z</i>Quasar Survey

Willott, Chris J.; Delorme, P.; Omont, A.; Bergeron, J.; Delfosse, X.; Forveille, T.; Li, Albert; Reylé, C.; Hill, Gary J.; Gully-Santiago, Michael; Vinten, Phillip; Crampton, D.; Hutchings, J. B.; Schade, David; Simard, Luc; Sawicki, Marcin; Beelen, A.; Cox, P.

doi:10.1086/522962

Cited by 269 publications

(290 citation statements)

References 83 publications

(133 reference statements)

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“…All of them are identified in this work, with the same criteria of i ′ − z ′ >1.3, and z ′ − zR >0.3, as shown with purple squares Table 1. Target information adopted from Willott et al (2007); Goto et al (2009Goto et al ( , 2011 …”

Section: Lae Selectionmentioning

confidence: 99%

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No Ly α emitters detected around a QSO at z = 6.4: Suppressed by the QSO?

Goto

Utsumi

Kikuta

et al. 2017

Monthly Notices of the Royal Astronomical Society: Letters

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Understanding how QSO's UV radiation affects galaxy formation is vital to our understanding of reionization era. Using a custom made narrow-band filter, N B906, on Subaru/SuprimeCam, we investigated the number density of Lyα emitters (LAE) around a QSO at z=6.4. To date, this is the highest redshift narrow-band observation, where LAEs around a luminous QSO are investigated. Due to the large field-of-view of Suprime-Cam, our survey area is ∼5400 cMpc 2 , much larger than previously studies at z=5.7 (∼200 cMpc 2 ).In this field, we previously found a factor of 7 overdensity of Lyman break galaxies (LBGs). Based on this, we expected to detect ∼100 LAEs down to N B906=25 ABmag. However, our 6.4 hour exposure found none. The obtained upper limit on the number density of LAEs is more than an order lower than the blank fields. Furthermore, this lower density of LAEs spans a large scale of 10 pMpc across. A simple argument suggests a strong UV radiation from the QSO can suppress star-formation in halos with M vir < 10 10 M ⊙ within a pMpc from the QSO, but the deficit at the edge of the field (5 pMpc) remains to be explained.

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Section: Lae Selectionmentioning

confidence: 99%

“…In this paper, we report our N B906 observation of the QSO field centred on CFHQS J2329−0301 (Table 1; Willott et al 2007) at z=6.417 (Willott et al 2010). Unless otherwise stated, we adopt the following cosmology: (h, Ωm, ΩL) = (0.7, 0.3, 0.7).…”

Section: Introductionmentioning

confidence: 99%

No Ly α emitters detected around a QSO at z = 6.4: Suppressed by the QSO?

Goto

Utsumi

Kikuta

et al. 2017

Monthly Notices of the Royal Astronomical Society: Letters

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“…Finally, we also include the NIR spectrum of CFHQS J1509-1749 (z = 6.12) obtained by Willott et al (2007) at GEMINI South by using GNIRS and the NIR spectrum of ULAS J0203+0012 (z = 5.72) by Mortlock et al (2009) at GEMINI North with GNIRS.…”

Section: Spectroscopic Data and Samplementioning

confidence: 99%

The extinction law at high redshift and its implications

Gallerani

Maiolino

Juárez

et al. 2010

A&A

152

171

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We analyze the optical-near infrared spectra of 33 quasars with redshifts 3.9 ≤ z ≤ 6.4 to investigate the properties of dust extinction at these cosmic epochs. The SMC extinction curve has been shown to reproduce the dust reddening of most quasars at z < 2.2; we investigate whether this curve also provides a good description of dust extinction at higher redshifts. We fit the observed spectra with synthetic absorbed quasar templates obtained by varying the intrinsic slope (α λ ), the absolute extinction (A 3000 ), and by using a grid of empirical and theoretical extinction curves. We find that seven quasars in our sample are affected by substantial extinction (A 3000 ≥ 0.8), and characterized by very steep intrinsic slopes (α λ ≤ −2.3). All of the individual quasars require extinction curve deviating from that of the SMC, with a tendency to flatten at λ ≤ 2000 Å (in the rest frame of the source). However, due to the uncertainties in the individual extinction curves the SMC is still (marginally) consistent with the data in most cases. We obtain a mean extinction curve at z > 4, both by performing a simultaneous fit of all quasars and by averaging the extinction curves inferred for individual quasars. In the case of broad absorption line quasars (which are generally more absorbed by dust and possibly in a younger evolutionary stage), the mean extinction curve deviates from the SMC at a confidence level ≥95%. The difference between extinction curves in quasars at z > 4 and in quasars at lower redshift is indicative of either a different dust production mechanism at high redshift, or a different mechanism for processing dust into the ISM. We suggest that the same transitions may also apply to normal, star-forming galaxies at z > 4. In particular, the observed change in the average spectral slope of galaxies at z > 4 may be partially ascribed to a variation in the extinction curve, rather than a lower dust content at high redshift. In this scenario, the extinction curve inferred at z > 4 would imply a cosmic star-formation corrected for dust attenuation a factor of ∼2 higher than estimated in the past.

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“…Attempts have also been made to measure the ionization state of the IGM directly. Reionization is relatively wellconstrained to be completed at z 6 by analysis of the Gunn-Peterson effect (Gunn & Peterson 1965) in the spectra of high-redshift QSOs (e.g., Fan et al 2006;Willott et al 2007;Bolton et al 2011;McGreer et al 2015) and gammaray bursts (GRBs, e.g., Chornock et al 2013). Preliminary measurements of the IGM neutral fraction at z ∼ 7-8 have been made using the Lyα emission fraction of star-forming galaxies (e.g., Stark et al 2010;Treu et al 2013;Pentericci et al 2014;Tilvi et al 2014;Faisst et al 2014;Schenker et al 2014).…”

Section: Introductionmentioning

confidence: 99%

Constraints on the star formation efficiency of galaxies during the epoch of reionization

Sun

Furlanetto

2016

Mon. Not. R. Astron. Soc.

173

157

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Reionization is thought to have occurred in the redshift range of 6 < z < 9, which is now being probed by both deep galaxy surveys and CMB observations. Using halo abundance matching over the redshift range 5 < z < 8 and assuming smooth, continuous gas accretion, we develop a model for the star formation efficiency f of dark matter halos at z > 6 that matches the measured galaxy luminosity functions at these redshifts. We find that f peaks at ∼ 30% at halo masses M ∼ 10 11 -10 12 M , in qualitative agreement with its behavior at lower redshifts. We then investigate the cosmic star formation histories and the corresponding models of reionization for a range of extrapolations to small halo masses. We use a variety of observations to further constrain the characteristics of the galaxy populations, including the escape fraction of UV photons. Our approach provides an empirically-calibrated, physically-motivated model for the properties of star-forming galaxies sourcing the epoch of reionization. In the case where star formation in low-mass halos is maximally efficient, an average escape fraction ∼ 0.1 can reproduce the optical depth reported by Planck, whereas inefficient star formation in these halos requires either about twice as many UV photons to escape, or an escape fraction that increases towards higher redshifts. Our models also predict how future observations with JWST can improve our understanding of these galaxy populations.

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Four Quasars above Redshift 6 Discovered by the Canada-France High-zQuasar Survey

Cited by 269 publications

References 83 publications

No Ly α emitters detected around a QSO at z = 6.4: Suppressed by the QSO?

No Ly α emitters detected around a QSO at z = 6.4: Suppressed by the QSO?

The extinction law at high redshift and its implications

Constraints on the star formation efficiency of galaxies during the epoch of reionization

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