Planck intermediate results

XLVII. Planck constraints on reionization history

¹ APC, AstroParticule et Cosmologie, Université Paris Diderot, CNRS/IN2P3, CEA/lrfu, Observatoire de Paris, Sorbonne Paris Cité, 10 rue Alice Domon et Léonie Duquet, 75205 Paris Cedex 13, France
² Aalto University Metsähovi Radio Observatory and Dept of Radio Science and Engineering, PO Box 13000, 00076 Aalto, Finland
³ African Institute for Mathematical Sciences, 6−8 Melrose Road, 7945 Muizenberg, Cape Town, South Africa
⁴ Agenzia Spaziale Italiana Science Data Center, via del Politecnico snc, 00133 Roma, Italy
⁵ Aix-Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, 13388 Marseille, France
⁶ Aix-Marseille Université, Centre de Physique Théorique, 163 avenue de Luminy, 13288 Marseille, France
⁷ Astrophysics Group, Cavendish Laboratory, University of Cambridge, J J Thomson Avenue, Cambridge CB3 0HE, UK
⁸ Astrophysics & Cosmology Research Unit, School of Mathematics, Statistics & Computer Science, University of KwaZulu-Natal, Westville Campus, Private Bag X54001, 4000 Durban, South Africa
⁹ CITA, University of Toronto, 60 St. George St., Toronto, ON M5S 3H8, Canada
¹⁰ CNRS, IRAP, 9 Av. colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France
¹¹ California Institute of Technology, Pasadena, CA 91125, USA
¹² Computational Cosmology Center, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
¹³ DTU Space, National Space Institute, Technical University of Denmark, Elektrovej 327, 2800 Kgs. Lyngby, Denmark
¹⁴ Département de Physique Théorique, Université de Genève, 24 quai E. Ansermet, 1211 Genève 4, Switzerland
¹⁵ Departamento de Astrofísica, Universidad de La Laguna (ULL), 38206 La Laguna, Tenerife, Spain
¹⁶ Departamento de Física, Universidad de Oviedo, Avda. Calvo Sotelo s/n, 33003 Oviedo, Spain
¹⁷ Department of Astrophysics/IMAPP, Radboud University Nijmegen, PO Box 9010, 6500 GL Nijmegen, The Netherlands
¹⁸ Department of Physics & Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, British Columbia, Canada
¹⁹ Department of Physics and Astronomy, Dana and David Dornsife College of Letter, Arts and Sciences, University of Southern California, Los Angeles, CA 90089, USA
²⁰ Department of Physics and Astronomy, University College London, London WC1E 6BT, UK
²¹ Department of Physics and Astronomy, University of Sussex, Brighton BN1 9QH, UK
²² Department of Physics, Gustaf Hällströmin katu 2a, University of Helsinki, 00560 Helsinki, Finland
²³ Department of Physics, Princeton University, Princeton, NJ 08544, USA
²⁴ Department of Physics, University of California, Berkeley, CA 94720, USA
²⁵ Department of Physics, University of California, One Shields Avenue, Davis, CA 95064, USA
²⁶ Department of Physics, University of California, Santa Barbara, CA 93106, USA
²⁷ Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, IL 61801 USA
²⁸ Dipartimento di Fisica e Astronomia G. Galilei, Università degli Studi di Padova, via Marzolo 8, 35131 Padova, Italy
²⁹ Dipartimento di Fisica e Astronomia, Alma Mater Studiorum, Università degli Studi di Bologna, viale Berti Pichat 6/2, 40127 Bologna, Italy
³⁰ Dipartimento di Fisica e Scienze della Terra, Università di Ferrara, via Saragat 1, 44122 Ferrara, Italy
³¹ Dipartimento di Fisica, Università La Sapienza, P.le A. Moro 2, 00133 Roma, Italy
³² Dipartimento di Fisica, Università degli Studi di Milano, via Celoria, 16, 20133 Milano, Italy
³³ Dipartimento di Fisica, Università di Roma Tor Vergata, via della Ricerca Scientifica, 1, 00133 Roma, Italy
³⁴ Dipartimento di Matematica, Università di Roma Tor Vergata, via della Ricerca Scientifica, 1, 00133 Roma, Italy
³⁵ Discovery Center, Niels Bohr Institute, Copenhagen University, Blegdamsvej 17, 2100 Copenhagen, Denmark
³⁶ European Space Agency, ESAC, Planck Science Office, Camino bajo del Castillo, s/n, Urbanización Villafranca del Castillo, 28691 Villanueva de la Cañada, Madrid, Spain
³⁷ European Space Agency, ESTEC, Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands
³⁸ Gran Sasso Science Institute, INFN, viale F. Crispi 7, 67100 L’ Aquila, Italy
³⁹ HGSFP and University of Heidelberg, Theoretical Physics Department, Philosophenweg 16, 69120 Heidelberg, Germany
⁴⁰ Haverford College Astronomy Department, 370 Lancaster Avenue, Haverford, PA 19041, USA
⁴¹ Helsinki Institute of Physics, Gustaf Hällströmin katu 2, University of Helsinki, 00560 Helsinki, Finland
⁴² INAF–Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35131 Padova, Italy
⁴³ INAF–Osservatorio Astronomico di Roma, via di Frascati 33, 00040 Monte Porzio Catone, Italy
⁴⁴ INAF–Osservatorio Astronomico di Trieste, via G. B. Tiepolo 11, 34127 Trieste, Italy
⁴⁵ INAF/IASF Bologna, via Gobetti 101, 40127 Bologna, Italy
⁴⁶ INAF/IASF Milano, via E. Bassini 15, 20133 Milano, Italy
⁴⁷ INFN-CNAF, viale Berti Pichat 6/2, 40127 Bologna, Italy
⁴⁸ INFN, Sezione di Bologna, viale Berti Pichat 6/2, 40127 Bologna, Italy
⁴⁹ INFN, Sezione di Ferrara, via Saragat 1, 44122 Ferrara, Italy
⁵⁰ INFN, Sezione di Roma 1, Università di Roma Sapienza, P.le Aldo Moro 2, 00185 Roma, Italy
⁵¹ INFN, Sezione di Roma 2, Università di Roma Tor Vergata, via della Ricerca Scientifica, 1, 00185 Roma, Italy
⁵² Imperial College London, Astrophysics group, Blackett Laboratory, Prince Consort Road, London, SW7 2AZ, UK
⁵³ Institut d’Astrophysique Spatiale, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Bât. 121, 91405 Orsay Cedex, France
⁵⁴ Institut d’Astrophysique de Paris, CNRS (UMR 7095), 98bis boulevard Arago, 75014 Paris, France
⁵⁵ Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
⁵⁶ Institute of Theoretical Astrophysics, University of Oslo, Blindern, 0371 Oslo, Norway
⁵⁷ Instituto de Astrofísica de Canarias, C/Vía Láctea s/n, La Laguna, 38205 Tenerife, Spain
⁵⁸ Instituto de Física de Cantabria (CSIC-Universidad de Cantabria), Avda. de los Castros s/n, 39005 Santander, Spain
⁵⁹ Istituto Nazionale di Fisica Nucleare, Sezione di Padova, via Marzolo 8, 35131 Padova, Italy
⁶⁰ Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA
⁶¹ Jodrell Bank Centre for Astrophysics, Alan Turing Building, School of Physics and Astronomy, TheUniversity of Manchester, Oxford Road, Manchester, M13 9PL, UK
⁶² Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL 60637, USA
⁶³ Kavli Institute for Cosmology Cambridge, Madingley Road, Cambridge, CB3 0HA, UK
⁶⁴ LAL, Université Paris-Sud, CNRS/IN2P3, 91405 Orsay, France
⁶⁵ LERMA, CNRS, Observatoire de Paris, 61 avenue de l’Observatoire, 75000 Paris, France
⁶⁶ Laboratoire Traitement et Communication de l’Information, CNRS (UMR 5141) and Télécom ParisTech, 46 rue Barrault, 75634 Paris Cedex 13, France
⁶⁷ Laboratoire de Physique Subatomique et Cosmologie, Université Grenoble-Alpes, CNRS/IN2P3, 53 rue des Martyrs, 38026 Grenoble Cedex, France
⁶⁸ Laboratoire de Physique Théorique, Université Paris-Sud 11 & CNRS, Bâtiment 210, 91405 Orsay, France
⁶⁹ Lawrence Berkeley National Laboratory, Berkeley, California, USA
⁷⁰ Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85741 Garching, Germany
⁷¹ Mullard Space Science Laboratory, University College London, Surrey RH5 6NT, UK
⁷² Nicolaus Copernicus Astronomical Center, Bartycka 18, 00-716 Warsaw, Poland
⁷³ Niels Bohr Institute, Copenhagen University, Blegdamsvej 17, 1165 Copenhagen, Denmark
⁷⁴ Nordita (Nordic Institute for Theoretical Physics), Roslagstullsbacken 23, 106 91 Stockholm, Sweden
⁷⁵ SISSA, Astrophysics Sector, via Bonomea 265, 34136 Trieste, Italy
⁷⁶ School of Chemistry and Physics, University of KwaZulu-Natal, Westville Campus, Private Bag X54001, 4000 Durban, South Africa
⁷⁷ School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, UK
⁷⁸ Simon Fraser University, Department of Physics, 8888 University Drive, Burnaby BC, Canada
⁷⁹ Sorbonne Université-UPMC, UMR 7095, Institut d’Astrophysique de Paris, 98bis boulevard Arago, 75014 Paris, France
⁸⁰ Space Research Institute (IKI), Russian Academy of Sciences, Profsoyuznaya Str, 84/32, 117997 Moscow, Russia
⁸¹ Space Sciences Laboratory, University of California, Berkeley, CA 94720, USA
⁸² Sub-Department of Astrophysics, University of Oxford, Keble Road, Oxford OX1 3RH, UK
⁸³ The Oskar Klein Centre for Cosmoparticle Physics, Department of Physics, Stockholm University, AlbaNova, 106 91 Stockholm, Sweden
⁸⁴ UPMC Univ. Paris 06, UMR 7095, 98bis boulevard Arago, 75014 Paris, France
⁸⁵ Université de Toulouse, UPS-OMP, IRAP, 31028 Toulouse Cedex 4, France
⁸⁶ University of Granada, Departamento de Física Teórica y del Cosmos, Facultad de Ciencias, 18010 Granada, Spain
⁸⁷ Warsaw University Observatory, Aleje Ujazdowskie 4, 00-478 Warszawa, Poland

Received: 11 May 2016
Accepted: 23 July 2016

Abstract

We investigate constraints on cosmic reionization extracted from the Planck cosmic microwave background (CMB) data. We combine the Planck CMB anisotropy data in temperature with the low-multipole polarization data to fit ΛCDM models with various parameterizations of the reionization history. We obtain a Thomson optical depth τ = 0.058 ± 0.012 for the commonly adopted instantaneous reionization model. This confirms, with data solely from CMB anisotropies, the low value suggested by combining Planck 2015 results with other data sets, and also reduces the uncertainties. We reconstruct the history of the ionization fraction using either a symmetric or an asymmetric model for the transition between the neutral and ionized phases. To determine better constraints on the duration of the reionization process, we also make use of measurements of the amplitude of the kinetic Sunyaev-Zeldovich (kSZ) effect using additional information from the high-resolution Atacama Cosmology Telescope and South Pole Telescope experiments. The average redshift at which reionization occurs is found to lie between z = 7.8 and 8.8, depending on the model of reionization adopted. Using kSZ constraints and a redshift-symmetric reionization model, we find an upper limit to the width of the reionization period of Δz < 2.8. In all cases, we find that the Universe is ionized at less than the 10% level at redshifts above z ≃ 10. This suggests that an early onset of reionization is strongly disfavoured by the Planck data. We show that this result also reduces the tension between CMB-based analyses and constraints from other astrophysical sources.