Early reionization by the first galaxies
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In this article, the authors studied the reionization process using supercomputer simulations of a large and representative region of a universe which has cosmological parameters consistent with the WMAP results.Abstract:
Large-scale polarization of the cosmic microwave background measured by the WMAP satellite requires a mean optical depth to Thomson scattering, τ e ∼ 0.17. The reionization of the Universe must therefore have begun at relatively high redshift. We have studied the reionization process using supercomputer simulations of a large and representative region of a universe which has cosmological parameters consistent with the WMAP results (Ω m = 0.3, Ω Λ = 0.7, h = 0.7, Ω b = 0.04, n = 1 and σ 8 = 0.9). Our simulations follow both the radiative transfer of ionizing photons and the formation and evolution of the galaxy population which produces them. A previously published model with ionizing photon production as expected for zero-metallicity stars distributed according to a standard stellar initial mass function (IMF) (10 6 1 photons per unit solar mass of formed stars) and with a moderate photon escape fraction from galaxies (5 per cent), produces τ e = 0.104, which is within 1.0 to 1.5σ of the 'best' WMAP value. Values of up to 0.16 can be produced by taking larger escape fractions or a top-heavy IMF. The data do not require a separate populations of 'miniquasars' or of stars forming in objects with total masses below 10 9 M O .. Reconciling such early reionization with the observed Gunn-Peterson troughs in z > 6 quasars may be challenging. Possible resolutions of this problem are discussed.read more
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Journal ArticleDOI
Wilkinson Microwave Anisotropy Probe (WMAP) three year results: implications for cosmology
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LOFAR: The LOw-Frequency ARray
M. P. van Haarlem,Michael W. Wise,Michael W. Wise,A. W. Gunst,George Heald,John McKean,Jason W. T. Hessels,Jason W. T. Hessels,de Antonius Bruyn,de Antonius Bruyn,R. Nijboer,John D. Swinbank,Richard Fallows,Michiel A. Brentjens,A. Nelles,Rainer Beck,Heino Falcke,Heino Falcke,Rob Fender,Jörg R. Hörandel,Luitje Koopmans,G. Mann,George K. Miley,Huub Röttgering,B. W. Stappers,Ralph A. M. J. Wijers,Saleem Zaroubi,M. van den Akker,A. Alexov,J. M. Anderson,Kenneth C. Anderson,A. van Ardenne,A. van Ardenne,Michel Arts,Ashish Asgekar,I. M. Avruch,I. M. Avruch,F. Batejat,L. Bähren,Martin Bell,Michael R. Bell,I. van Bemmel,P. Bennema,Mark J. Bentum,Gianni Bernardi,Philip Best,Laura Birzan,Annalisa Bonafede,Albert-Jan Boonstra,Robert Braun,Joel N. Bregman,F. Breitling,R. H. van de Brink,J. W. Broderick,P. C. Broekema,W. N. Brouw,W. N. Brouw,Marcus Brüggen,Harvey Butcher,Harvey Butcher,W. A. van Cappellen,B. Ciardi,T. Coenen,John Conway,A. H. W. M. Coolen,Arthur Corstanje,S. Damstra,O. Davies,Adam Deller,R. J. Dettmar,G. van Diepen,K. Dijkstra,P. Donker,A. Doorduin,J. Dromer,M. Drost,A. van Duin,Jochen Eislöffel,J. van Enst,Chiara Ferrari,Wilfred Frieswijk,H. Gankema,M. A. Garrett,M. A. Garrett,F. de Gasperin,M. Gerbers,E. de Geus,J.-M. Grießmeier,J.-M. Grießmeier,T. Grit,P. Gruppen,J. P. Hamaker,Tim Hassall,Matthias Hoeft,H. A. Holties,A. Horneffer,A. Horneffer,A. J. van der Horst,A. van Houwelingen,A. Huijgen,Marco Iacobelli,Hubertus Intema,Hubertus Intema,N. J. Jackson,Vibor Jelić,A. de Jong,E. Juette,D. Kant,Aris Karastergiou,A. Koers,H. Kollen,V. I. Kondratiev,E. Kooistra,Y. Koopman,A. Koster,M. Kuniyoshi,Michael Kramer,Michael Kramer,G. Kuper,P. Lambropoulos,Casey J. Law,Casey J. Law,J. van Leeuwen,J. van Leeuwen,J. Lemaitre,M. Loose,P. Maat,Giulia Macario,Sera Markoff,J. Masters,J. Masters,Rebecca McFadden,D. McKay-Bukowski,H. Meijering,H. Meulman,M. Mevius,Enno Middelberg,R. Millenaar,James Miller-Jones,James Miller-Jones,R. N. Mohan,J. D. Mol,J. Morawietz,Raffaella Morganti,Raffaella Morganti,D. D. Mulcahy,E. Mulder,H. Munk,Lambert J.M. Nieuwenhuis,R. van Nieuwpoort,J. E. Noordam,M. J. Norden,A. Noutsos,A. R. Offringa,Hans Olofsson,Amitesh Omar,Emanuela Orrú,Emanuela Orrú,R. Overeem,H. Paas,M. Pandey-Pommier,Vishambhar Pandey,Roberto Pizzo,A. G. Polatidis,D. A. Rafferty,Steve Rawlings,W. Reich,J.-P. de Reijer,J. Reitsma,G.A. Renting,P. Riemers,E. Rol,J. W. Romein,J. Roosjen,M. Ruiter,Anna M. M. Scaife,K. van der Schaaf,Bart Scheers,Bart Scheers,Pim Schellart,A. P. Schoenmakers,G. Schoonderbeek,M. Serylak,M. Serylak,Aleksandar Shulevski,J. Sluman,Oleg Smirnov,Charlotte Sobey,H. Spreeuw,Matthias Steinmetz,C. G. M. Sterks,H.-J. Stiepel,K. Stuurwold,Michel Tagger,Y. Tang,C. Tasse,I. Thomas,Satyendra Thoudam,M. C. Toribio,B. van der Tol,O. Usov,M. van Veelen,A.-J. van der Veen,S. ter Veen,Joris P. W. Verbiest,R. Vermeulen,N. J. Vermaas,C. Vocks,C. Vogt,M. de Vos,E. van der Wal,R. J. van Weeren,R. J. van Weeren,H. Weggemans,Patrick Weltevrede,Simon D. M. White,Stefan J. Wijnholds,T. Wilhelmsson,Olaf Wucknitz,Sarod Yatawatta,Philippe Zarka,Anton Zensus,J. E. van Zwieten +222 more
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