Publications
71 results found
Watkinson CA, Pritchard JR, Mesinger A, et al., 2015, The impact of small absorbers, galactic neutral hydrogen & X-rays on 1-point statistics of the 21-cm line., STATISTICAL CHALLENGES IN 21ST CENTURY COSMOLOGY, Vol: 10, Pages: 189-191, ISSN: 1743-9213
Koopmans LVE, Pritchard J, Mellema G, et al., 2015, The cosmic dawn and epoch of reionization with the square kilometre array, Proceedings of Sciencec
Concerted effort is currently ongoing to open up the Epoch of Reionization (EoR) (z∼15-6) for studies with IR and radio telescopes. Whereas IR detections have been made of sources (Lyman-α emitters, quasars and drop-outs) in this redshift regime in relatively small fields of view, no direct detection of neutral hydrogen, via the redshifted 21-cm line, has yet been established. Such a direct detection is expected in the coming years, with ongoing surveys, and could open up the entire universe from z∼6-200 for astrophysical and cosmological studies, opening not only the EoR, but also its preceding Cosmic Dawn (z∼30-15) and possibly even the later phases of the Dark Ages (z∼200-30). All currently ongoing experiments attempt statistical detections of the 21-cm signal during the EoR, with limited signal-to-noise. Direct imaging, except maybe on the largest (degree) scales at lower redshifts, as well as higher redshifts will remain out of reach. The Square Kilometre Array(SKA) will revolutionize the field, allowing direct imaging of neutral hydrogen from scales of arc-minutes to degrees over most of the redshift range z∼6-28 with SKA1-LOW, and possibly even higher redshifts with the SKA2-LOW. In this SKA will be unique, and in parallel provide enormous potential of synergy with other upcoming facilities (e.g. JWST). In this chapter we summarize the physics of 21-cm emission, the different phases the universe is thought to go through, and the observables that the SKA can probe, referring where needed to detailed chapters in this volume (Abridged).
Pritchard J, Masters K, Allen J, et al., 2014, Asking gender questions, Astronomy & Geophysics, Vol: 55, Pages: 8-12, ISSN: 1468-4004
Pritchard J, Masters K, Allen J, et al., 2014, Asking gender questions, Astronomy and Geophysics, Vol: 55, Pages: 6.8-6.12, ISSN: 1366-8781
Watkinson CA, Pritchard JR, 2014, Distinguishing models of reionization using future radio observations of 21-cm 1-point statistics, MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Vol: 443, Pages: 3090-3106, ISSN: 0035-8711
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- Citations: 47
Chang TC, Gong Y, Santos M, et al., 2014, Synergy of CO/[CII]/Lya line intensity mapping with the SKA, Proceedings of Science, Vol: 9-13-June-2014
This subchapter describes the science enabled by cross-correlations of the SKA1-LOW 21-cm EoR surveys with other line mapping programs. In particular, we identify and investigate potential synergies with planned programs, such as the line intensity mapping of redshifted CO rotational lines, [CII] and Ly-a emissions during reionization. We briefly describe how these tracers of the star-formation rate at z ∼ 8 can be modeled jointly before forecasting their autoand cross-power spectra measurements with the nominal 21cm EoR survey. After discussing the measurement prospect, we discuss how reionization parameters can be better constrained using these new measurements.
Mesinger A, Ferrara A, Greig B, et al., 2014, Constraining the astrophysics of the cosmic dawn and the epoch of reionization with the SKA, Proceedings of Science, Vol: 9-13-June-2014
The Square Kilometre Array (SKA) will offer an unprecedented view onto the early Universe, using interferometric observations of the redshifted 21cm line. The 21cm line probes the thermal and ionization state of the cosmic gas, which is governed by the birth and evolution of the first structures in our Universe. Here we show how the evolution of the 21cm signal will allow us to study when the first generations of galaxies appeared, what were their properties, and what was the structure of the intergalactic medium. We highlight qualitative trends which will offer robust insights into the early Universe. Advancing.
Subrahmanyan R, Shankar NU, Pritchard J, et al., 2014, All-sky signals from recombination to reionization with the SKA, Proceedings of Science, Vol: 9-13-June-2014
Cosmic evolution in the hydrogen content of the Universe through recombination and up to the end of reionization is expected to be revealed as subtle spectral features in the uniform extragalactic cosmic radio background. The redshift evolution in the excitation temperature of the 21-cm spin flip transition of neutral hydrogen appears as redshifted emission and absorption against the cosmic microwave background. The precise signature of the spectral trace from cosmic dawn and the epoch of reionization are dependent on the spectral radiance, abundance and distribution of the first bound systems of stars and early galaxies, which govern the evolution in the spin-flip level populations. Redshifted 21 cm from these epochs when the spin temperature deviates from the temperature of the ambient relic cosmic microwave background results in an all-sky spectral structure in the 40-200 MHz range, almost wholly within the band of SKA-Low. Another spectral structure from gas evolution is redshifted recombination lines from epoch of recombination of hydrogen and helium; the weak all-sky spectral structure arising from this event is best detected at the upper end of the 350-3050 MHz band of SKA-mid. Total power spectra of SKA interferometer elements form the measurement set for these faint signals from recombination and reionization; the inter-element interferometer visibilities form a calibration set. The challenge is in precision polarimetric calibration of the element spectral response and solving for additives and unwanted confusing leakages of sky angular structure modes into spectral modes. Herein we discuss observing methods and design requirements that make possible these all-sky SKA measurements of the cosmic evolution of hydrogen.
Glover SCO, Chluba J, Furlanetto SR, et al., 2014, Atomic, Molecular, and Optical Physics in the Early Universe: From Recombination to Reionization, ADVANCES IN ATOMIC, MOLECULAR, AND OPTICAL PHYSICS, VOL 63, Editors: Arimondo, Berman, Lin, Publisher: ELSEVIER ACADEMIC PRESS INC, Pages: 135-270, ISBN: 978-0-12-800129-5
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- Citations: 17
Pritchard JR, Loeb A, 2013, Evolution of the 21cm signal throughout cosmic history, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 78, ISSN: 1089-4918
The potential use of the redshifted 21 cm line from neutral hydrogen for probing the epoch of reionization is motivating the construction of several low-frequency interferometers. There is also much interest in the possibility of constraining the initial conditions from inflation and the nature of the dark matter and dark energy by probing the power spectrum of density perturbations in three dimensions and on smaller scales than probed by the microwave background anisotropies. Theoretical understanding of the 21 cm signal has been fragmented into different regimes of physical interest. In this paper, we make the first attempt to describe the full redshift evolution of the 21 cm signal between 0<z<300. We include contributions to the 21 cm signal from fluctuations in the gas density, temperature, and neutral fraction, as well as the Lyα flux, and allow for a post-reionization signal from damped Lyα systems. Our comprehensive analysis provides a useful foundation for optimizing the design of future arrays whose goal is to separate the particle physics from the astrophysics, either by probing the peculiar velocity distortion of the 21 cm power spectrum, or by extending the 21 cm horizon to z≳25 before the first galaxies had formed, or to z≲6 when the residual pockets of hydrogen trace large-scale structure.
Mellema G, Koopmans LVE, Abdalla FA, et al., 2013, Reionization and the Cosmic Dawn with the Square Kilometre Array, EXPERIMENTAL ASTRONOMY, Vol: 36, Pages: 235-318, ISSN: 0922-6435
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- Citations: 252
Liu A, Pritchard JR, Tegmark M, et al., 2013, Global 21 cm signal experiments: A designer's guide, PHYSICAL REVIEW D, Vol: 87, ISSN: 1550-7998
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- Citations: 54
Loeb A, Pritchard J, 2012, The missing reel, NEW SCIENTIST, Vol: 216, Pages: 30-33, ISSN: 0262-4079
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- Citations: 1
Pritchard JR, Loeb A, 2012, 21 cm cosmology in the 21st century, REPORTS ON PROGRESS IN PHYSICS, Vol: 75, ISSN: 0034-4885
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- Citations: 581
Burns JO, Lazio J, Bale S, et al., 2012, Probing the first stars and black holes in the early Universe with the Dark Ages Radio Explorer (DARE), Advances in Space Research, Vol: 49, Pages: 433-450-433-450
Silva MB, Santos MG, Pritchard JR, et al., 2012, Probing the very first galaxies with the SKA, Pages: 101-116, ISSN: 1570-6591
We describe the use of the high redshift 21 cm signal to probe the very first galaxies to appear in the Universe. Using fast large volume simulations of the pre-Reionization epoch we have shown that the Lyman alpha radiation emitted from these young galaxies makes a strong contribution to the 21cm signal on large scales at z∼20. With the current setup the Square Kilometre Array (SKA) should be able to measure this signal, therefore making it probably the only telescope capable of giving us detailed information about the radiation emitted by the first stars and characterizing their host galaxies. SKA-pathfinders with ∼10%of the full collecting area should be capable of making a statistical detection of the 21cm power spectrum at redshifts z<20.We then discuss the use of the redshift space distortions as a way to further constrain the Lyman alpha signal and demonstrate that they can be used as a model independent way to extract this signature with the SKA. © Springer-Verlag Berlin Heidelberg 2012.
Harker GJA, Pritchard JR, Burns JO, et al., 2012, An MCMC approach to extracting the global 21-cm signal during the cosmic dawn from sky-averaged radio observations, Monthly Notices of the Royal Astronomical Society, Vol: 419, Pages: 1070-1084-1070-1084
Silva MB, Santos MG, Pritchard JR, et al., 2012, Probing the Very First Galaxies with the SKA, Joint European and National Astronomy Meeting (JENAM)/18th Annual Meeting of the European-Astronomical-Society/20th Annual Portuguese Meeting of Astronomy and Astrophysics/Symposium 7 - Square Kilometre Array (SKA), Publisher: SPRINGER, Pages: 101-116, ISSN: 1570-6591
Lidz A, Furlanetto SR, Oh SP, et al., 2011, Intensity Mapping with Carbon Monoxide Emission Lines and the Redshifted 21 cm Line, The Astrophysical Journal: an international review of astronomy and astronomical physics, Vol: 741, Pages: 70-70
Abazajian KN, Calabrese E, Cooray A, et al., 2011, Cosmological and astrophysical neutrino mass measurements, ASTROPARTICLE PHYSICS, Vol: 35, Pages: 177-184, ISSN: 0927-6505
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- Citations: 107
Mirabel IF, Dijkstra M, Laurent P, et al., 2011, Stellar black holes at the dawn of the universe, Astronomy and Astrophysics, Vol: 528, Pages: A149-A149
Santos MG, Silva MB, Pritchard JR, et al., 2011, Probing the first galaxies with the Square Kilometer Array, Astronomy and Astrophysics, Vol: 527, Pages: A93-A93
Adshead P, Easther R, Pritchard J, et al., 2011, Inflation and the scale dependent spectral index: prospects and strategies, Journal of Cosmology and Astroparticle Physics, Vol: 2, Pages: 21-21
Pritchard J, Loeb A, 2010, Cosmology: Hydrogen was not ionized abruptly, Nature, Vol: 468, Pages: 772-773-772-773
Pritchard JR, Loeb A, Wyithe JSB, 2010, Constraining reionization using 21-cm observations in combination with CMB and Lyα forest data, Monthly Notices of the Royal Astronomical Society, Vol: 408, Pages: 57-70-57-70
Pritchard JR, Loeb A, 2010, Constraining the unexplored period between the dark ages and reionization with observations of the global 21 cm signal, Physical Review D (Particles, Fields, Gravitation and Cosmology), Vol: 82, Pages: 023006-+-023006-+
Colombo LPL, Pierpaoli E, Pritchard JR, 2009, Cosmological parameters after WMAP5: forecasts for Planck and future galaxy surveys, Monthly Notices of the Royal Astronomical Society, Vol: 398, Pages: 1621-1637-1621-1637
Gordon C, Pritchard JR, 2009, Forecasted 21cm constraints on compensated isocurvature perturbations, Physical Review D (Particles, Fields, Gravitation and Cosmology), Vol: 80, Pages: 063535-+-063535-+
Pritchard JR, Pierpaoli E, 2009, Neutrino mass from cosmological 21 cm observations, Neutrino Oscillation Workshop, Publisher: ELSEVIER SCIENCE BV, Pages: 31-33, ISSN: 0920-5632
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- Citations: 5
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