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Eight new luminous z ≥ 6 quasars discovered via SED model fitting of VISTA, WISE and Dark Energy Survey Year 1 observations

Eight new luminous z ≥ 6 quasars discovered via SED model fitting of VISTA, WISE and Dark Energy Survey Year 1 observations
Eight new luminous z ≥ 6 quasars discovered via SED model fitting of VISTA, WISE and Dark Energy Survey Year 1 observations

We present the discovery and spectroscopic confirmation with the European Southern Observatory New Technology Telescope (NTT) and Gemini South telescopes of eight new, and the rediscovery of two previously known, 6.0 < z < 6.5 quasars with zAB < 21.0. These quasars were photometrically selected without any morphological criteria from 1533 deg2 using spectral energy distribution (SED) model fitting to photometric data from Dark Energy Survey (g, r, i, z, Y), VISTA Hemisphere Survey (J, H, K) and Wide-field Infrared Survey Explorer (W1, W2). The photometric data were fitted with a grid of quasar model SEDs with redshift-dependent Ly α forest absorption and a range of intrinsic reddening as well as a series of low-mass cool star models. Candidates were ranked using an SED-model-based χ2-statistic, which is extendable to other future imaging surveys (e.g. LSST and Euclid). Our spectral confirmation success rate is 100 per cent without the need for follow-up photometric observations as used in other studies of this type. Combined with automatic removal of the main types of non-astrophysical contaminants, the method allows large data sets to be processed without human intervention and without being overrun by spurious false candidates. We also present a robust parametric redshift estimator that gives comparable accuracy to Mg ii and CO-based redshift estimators. We find two z ∼ 6.2 quasars with H ii near zone sizes ≤3 proper Mpc that could indicate that these quasars may be young with ages ≲ 106-107 years or lie in over dense regions of the IGM. The z = 6.5 quasar VDES J0224−4711 has JAB = 19.75 and is the second most luminous quasar known with z ≥ 6.5.

astro-ph.GA, astro-ph.CO
0035-8711
4702-4718
Reed, S. L.
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McMahon, R. G.
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Auger, M.
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Hewett, P. C.
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Koposov, S. E.
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Gibbons, S. L. J.
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Banerji, M.
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Auger, M.
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Hewett, P. C.
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Koposov, S. E.
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Gibbons, S. L. J.
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Gonzalez-Solares, E.
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Ostrovski, F.
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Tie, S. S.
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Costa, L. N. da
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DePoy, D. L.
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Flaugher, B.
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Reed, S. L., McMahon, R. G., Martini, P., Banerji, M., Auger, M., Hewett, P. C., Koposov, S. E., Gibbons, S. L. J., Gonzalez-Solares, E., Ostrovski, F., Tie, S. S., Abdalla, F. B., Allam, S., Benoit-Levy, A., Bertin, E., Brooks, D., Buckley-Geer, E., Burke, D. L., Rosell, A. Carnero, Kind, M. Carrasco, Carretero, J., Costa, L. N. da, DePoy, D. L., Desai, S., Diehl, H. T., Doel, P., Evrard, A. E., Finley, D. A., Flaugher, B., Fosalba, P., Frieman, J., Garcıa-Bellido, J., Gaztanaga, E., Goldstein, D. A., Gruen, D., Gruendl, R. A., Gutierrez, G., James, D. J., Kuehn, K., Kuropatkin, N., Lahav, O., Lima, M., Maia, M. A. G., Marshall, J. L., Melchior, P., Miller, C. J., Miquel, R., Nord, B., Ogando, R., Plazas, A. A., Romer, A. K., Sanchez, E., Scarpine, V., Schubnell, M., Sevilla-Noarbe, I., Smith, R. C., Sobreira, F., Suchyta, E., Swanson, M. E. C., Tarle, G., Tucker, D. L., Walker, A. R. and Wester, W. (2017) Eight new luminous z ≥ 6 quasars discovered via SED model fitting of VISTA, WISE and Dark Energy Survey Year 1 observations. Monthly Notices of the Royal Astronomical Society, 468 (4), 4702-4718. (doi:10.1093/mnras/stx728).

Record type: Article

Abstract

We present the discovery and spectroscopic confirmation with the European Southern Observatory New Technology Telescope (NTT) and Gemini South telescopes of eight new, and the rediscovery of two previously known, 6.0 < z < 6.5 quasars with zAB < 21.0. These quasars were photometrically selected without any morphological criteria from 1533 deg2 using spectral energy distribution (SED) model fitting to photometric data from Dark Energy Survey (g, r, i, z, Y), VISTA Hemisphere Survey (J, H, K) and Wide-field Infrared Survey Explorer (W1, W2). The photometric data were fitted with a grid of quasar model SEDs with redshift-dependent Ly α forest absorption and a range of intrinsic reddening as well as a series of low-mass cool star models. Candidates were ranked using an SED-model-based χ2-statistic, which is extendable to other future imaging surveys (e.g. LSST and Euclid). Our spectral confirmation success rate is 100 per cent without the need for follow-up photometric observations as used in other studies of this type. Combined with automatic removal of the main types of non-astrophysical contaminants, the method allows large data sets to be processed without human intervention and without being overrun by spurious false candidates. We also present a robust parametric redshift estimator that gives comparable accuracy to Mg ii and CO-based redshift estimators. We find two z ∼ 6.2 quasars with H ii near zone sizes ≤3 proper Mpc that could indicate that these quasars may be young with ages ≲ 106-107 years or lie in over dense regions of the IGM. The z = 6.5 quasar VDES J0224−4711 has JAB = 19.75 and is the second most luminous quasar known with z ≥ 6.5.

Text
Eight new luminous z 6 quasars selected via SED model fitting of VISTA, WISE and Dark Energy Survey Year 1 Observations - Accepted Manuscript
Available under License Creative Commons Attribution.
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Accepted/In Press date: 22 March 2017
e-pub ahead of print date: 24 March 2017
Published date: 1 July 2017
Additional Information: 19 pages, 15 figures ARXIV IS AM
Keywords: astro-ph.GA, astro-ph.CO

Identifiers

Local EPrints ID: 443899
URI: http://eprints.soton.ac.uk/id/eprint/443899
ISSN: 0035-8711
PURE UUID: 7a4222e3-4a6b-4ee2-a2e6-59a64b670102

Catalogue record

Date deposited: 16 Sep 2020 16:34
Last modified: 25 Nov 2021 17:44

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Contributors

Author: S. L. Reed
Author: R. G. McMahon
Author: P. Martini
Author: M. Banerji
Author: M. Auger
Author: P. C. Hewett
Author: S. E. Koposov
Author: S. L. J. Gibbons
Author: E. Gonzalez-Solares
Author: F. Ostrovski
Author: S. S. Tie
Author: F. B. Abdalla
Author: S. Allam
Author: A. Benoit-Levy
Author: E. Bertin
Author: D. Brooks
Author: E. Buckley-Geer
Author: D. L. Burke
Author: A. Carnero Rosell
Author: M. Carrasco Kind
Author: J. Carretero
Author: L. N. da Costa
Author: D. L. DePoy
Author: S. Desai
Author: H. T. Diehl
Author: P. Doel
Author: A. E. Evrard
Author: D. A. Finley
Author: B. Flaugher
Author: P. Fosalba
Author: J. Frieman
Author: J. Garcıa-Bellido
Author: E. Gaztanaga
Author: D. A. Goldstein
Author: D. Gruen
Author: R. A. Gruendl
Author: G. Gutierrez
Author: D. J. James
Author: K. Kuehn
Author: N. Kuropatkin
Author: O. Lahav
Author: M. Lima
Author: M. A. G. Maia
Author: J. L. Marshall
Author: P. Melchior
Author: C. J. Miller
Author: R. Miquel
Author: B. Nord
Author: R. Ogando
Author: A. A. Plazas
Author: A. K. Romer
Author: E. Sanchez
Author: V. Scarpine
Author: M. Schubnell
Author: I. Sevilla-Noarbe
Author: R. C. Smith
Author: F. Sobreira
Author: E. Suchyta
Author: M. E. C. Swanson
Author: G. Tarle
Author: D. L. Tucker
Author: A. R. Walker
Author: W. Wester

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