Reply to Kampougeris et al

Vedantham, Vasumathy; Lalitha, Prajna; Velpandian, Thirumurthy; Ghose, Supriyo; Mahalakhsmi, R; Ramasamy, Kim

doi:10.1038/sj.eye.6702916

Cited by 2 publications

(2 citation statements)

References 4 publications

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“…While 21 cm cosmology faces formidable observational challenges, recent years have seen significant advances toward resolving issues of optimal array design (Beardsley et al 2012;Parsons et al 2012b;Dillon & Parsons 2016), internal systematics (Ewall-Wice et al 2016c; Barry et al 2016;Patil et al 2016;Ewall-Wice et al 2016a), and astrophysical foreground mitigation (Datta et al 2010;Morales et al 2012;Vedantham et al 2012;Parsons et al 2012b;Trott et al 2012;Chapman et al 2012Chapman et al , 2013Thyagarajan et al 2013;Pober et al 2013a;Liu et al 2014a,b;Switzer & Liu 2014;Wolz et al 2013;Moore et al 2015;Thyagarajan et al 2015a,b;Asad et al 2015;Chapman et al 2016;Kohn et al 2016;. Increasingly competitive upper limits have been placed on the red-shifted 21 cm signal, using instruments such as the Donald C. Backer Precision Array for Probing the Epoch of Reionization (PAPER; Parsons et al 2014;Jacobs et al 2015;Ali et al 2015), the Giant Metrewave Radio Telescope (GMRT; Paciga et al 2013), the Murchison Widefield Array (MWA; Dillon et al 2014Dillon et al , 2015Ewall-Wice et al 2016c;Beardsley et al 2016), and the Low Frequency Array (LOFAR; Vedantham et al 2015;Patil et al 2017). Many of these upper limits are stringent enough to be scientifically interesting, and have typically ruled out extremely cold reionization scenarios…”

Section: Introductionmentioning

confidence: 99%

Emulating Simulations of Cosmic Dawn for 21 cm Power Spectrum Constraints on Cosmology, Reionization, and X-Ray Heating

Kern

Liu

Parsons

et al. 2017

ApJ

138

107

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Current and upcoming radio interferometric experiments are aiming to make a statistical characterization of the high-redshift 21 cm fluctuation signal spanning the hydrogen reionization and X-ray heating epochs of the universe. However, connecting 21 cm statistics to underlying physical parameters is complicated by the theoretical challenge of modeling the relevant physics at computational speeds quick enough to enable exploration of the high dimensional and weakly constrained parameter space. In this work, we use machine learning algorithms to build a fast emulator that can accurately mimic an expensive simulation of the 21 cm signal across a wide parameter space. We embed our emulator within a Markov-Chain Monte Carlo framework in order to perform Bayesian parameter constraints over a large number of model parameters, including those that govern the Epoch of Reionization, the Epoch of X-ray Heating, and cosmology. As a worked example, we use our emulator to present an updated parameter constraint forecast for the Hydrogen Epoch of Reionization Array experiment, showing that its characterization of a fiducial 21 cm power spectrum will considerably narrow the allowed parameter space of reionization and heating parameters, and could help strengthen Planck 's constraints on σ 8 . We provide both our generalized emulator code and its implementation specifically for 21 cm parameter constraints as publicly available software.

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Section: Introductionmentioning

confidence: 99%

Emulating Simulations of Cosmic Dawn for 21 cm Power Spectrum Constraints on Cosmology, Reionization, and X-Ray Heating

Kern

Liu

Parsons

et al. 2017

ApJ

138

107

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show abstract

“…; EDGES, SCI-HI, LEDA, BIGHORNS; Bowman & Rogers 2010;Voytek et al 2014;Greenhill & Bernardi 2012;Sokolowski et al 2015), though space-based observatories will be required to probe the cosmic dawn at z 30 (e.g., the Dark Ages Radio Explorer, (DARE); Burns et al 2012), as the Earth's ionosphere reflects and refracts radio signals at low frequencies (Vedantham et al 2013;Datta et al 2014). Interferometers are in principle capable of measuring the global 21-cm signal, so long as they are compact (Presley et al 2015;Singh et al 2015) or can overcome challenges in lunar occultation techniques (Vedantham et al 2014).…”

Section: Introductionmentioning

confidence: 99%

INTERPRETING THE GLOBAL 21-cm SIGNAL FROM HIGH REDSHIFTS. II. PARAMETER ESTIMATION FOR MODELS OF GALAXY FORMATION

Mirocha

Harker

Burns

2015

ApJ

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Following our previous work, which related generic features in the sky-averaged (global) 21-cm signal to properties of the intergalactic medium, we now investigate the prospects for constraining a simple galaxy formation model with current and near-future experiments. Markov-Chain Monte Carlo fits to our synthetic dataset, which includes a realistic galactic foreground, a plausible model for the signal, and noise consistent with 100 hours of integration by an ideal instrument, suggest that a simple four-parameter model that links the production rate of Lyman-α, Lyman-continuum, and X-ray photons to the growth rate of dark matter halos can be well-constrained (to ∼ 0.1 dex in each dimension) so long as all three spectral features expected to occur between 40 ν/MHz 120 are detected. Several important conclusions follow naturally from this basic numerical result, namely that measurements of the global 21-cm signal can in principle (i) identify the characteristic halo mass threshold for star formation at all redshifts z 15, (ii) extend z 4 upper limits on the normalization of the X-ray luminosity star-formation rate (L X -SFR) relation out to z ∼ 20, and (iii) provide joint constraints on stellar spectra and the escape fraction of ionizing radiation at z ∼ 12. Though our approach is general, the importance of a broad-band measurement renders our findings most relevant to the proposed Dark Ages Radio Explorer, which will have a clean view of the global 21-cm signal from ∼ 40 − 120 MHz from its vantage point above the radio-quiet, ionosphere-free lunar far-side.

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Reply to Kampougeris et al

Cited by 2 publications

References 4 publications

Emulating Simulations of Cosmic Dawn for 21 cm Power Spectrum Constraints on Cosmology, Reionization, and X-Ray Heating

Emulating Simulations of Cosmic Dawn for 21 cm Power Spectrum Constraints on Cosmology, Reionization, and X-Ray Heating

INTERPRETING THE GLOBAL 21-cm SIGNAL FROM HIGH REDSHIFTS. II. PARAMETER ESTIMATION FOR MODELS OF GALAXY FORMATION

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