21SSD: a public data base of simulated 21-cm signals from the epoch of reionization

Semelin, B.; Eames, Evan; Bolgar, Florian; Caillat, Michel

doi:10.1093/mnras/stx2274

Cited by 37 publications

(43 citation statements)

References 40 publications

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“…These two cases follow a similar evolution to the results found in Mesinger et al (2013) with X-ray efficiency fx = 1, although significant reionization begins earlier in their model. On the other hand Semelin et al (2017) find that, in all models, their signals transition to emission much later and is much more patchy than our model due to their rarer sources.…”

Section: Evolution Of the Signalcontrasting

confidence: 59%

“…Consequently, the mean value from S4 begins to increase markedly earlier and follows a patern more similar to that seen in Mesinger et al (2013). Our models predict that the value of δT b rises significantly earlier than all models shown in Semelin et al (2017), again due to the relative rarity of their X-ray sources.…”

Section: Evolution Of the Signalsupporting

confidence: 48%

“…Santos et al (2008) find comparable results to our own. Due to the different timings of the models, it is difficult to compare to the results of Semelin et al (2017). We compare this redshift to their power spectra from z≈10 (where their heating has just begun and Lyman-α is not yet fully coupled).…”

Section: Power Spectramentioning

confidence: 99%

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Evaluating the QSO contribution to the 21-cm signal from the Cosmic Dawn

Ross

Dixon

Ghara

et al. 2019

Monthly Notices of the Royal Astronomical Society

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The upcoming radio interferometer Square Kilometre Array (SKA) is expected to directly detect the redshifted 21-cm signal from the neutral hydrogen present during the Cosmic Dawn. Temperature fluctuations from X-ray heating of the neutral intergalactic medium can dominate the fluctuations in the 21-cm signal from this time. This heating depends on the abundance, clustering, and properties of the X-ray sources present, which remain highly uncertain. We present a suite of three new large-volume, 349 Mpc a side, fully numerical radiative transfer simulations including QSO-like sources, extending the work previously presented in Ross et al. (2017). The results show that our QSOs have a modest contribution to the heating budget, yet significantly impact the 21-cm signal. Initially, the power spectrum is boosted on large scales by heating from the biased QSO-like sources, before decreasing on all scales. Fluctuations from images of the 21-cm signal with resolutions corresponding to SKA1-Low at the appropriate redshifts are well above the expected noise for deep integrations, indicating that imaging could be feasible for all the X-ray source models considered. The most notable contribution of the QSOs is a dramatic increase in non-Gaussianity of the signal, as measured by the skewness and kurtosis of the 21-cm probability distribution functions. However, in the case of late Lyman-α saturation, this non-Gaussianity could be dramatically decreased particularly when heating occurs earlier. We conclude that increased non-Gaussianity is a promising signature of rare X-ray sources at this time, provided that Lyman-α saturation occurs before heating dominates the 21-cm signal.

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Section: Evolution Of the Signalcontrasting

confidence: 59%

Section: Evolution Of the Signalsupporting

confidence: 48%

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Evaluating the QSO contribution to the 21-cm signal from the Cosmic Dawn

Ross

Dixon

Ghara

et al. 2019

Monthly Notices of the Royal Astronomical Society

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“…We chose the power spectra P (k, z) as our observable. We define the distance between two observables to be the same as in Semelin et al (2017), based on the L2 norm:…”

Section: Simulation Configurationmentioning

confidence: 99%

Working towards an optimal sampling of the 21 cm signal parameter space

Eames

Doussot

Semelin

2019

Monthly Notices of the Royal Astronomical Society

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With a statistical detection of the 21 cm signal fluctuations from the Epoch of Reionization (EoR) expected in the next few years, there is an interest in developing robust and precise techniques to constrain the underlying astrophysical parameters. Bayesian inference with Markov Chain Monte Carlo, or different types of supervised learning for backward modelling (from signal to parameters) are examples of such techniques. They usually require many instances of forward modelling (from parameters to signal) in sampling the parameters space, either when performing the steps of the Markov Chain or when building a training sample for supervised learning. As forward modelling can be costly (if performed with numerical simulations for example), we should attempt to perform an optimal sampling according to some principle. With this goal in mind, we present an approach based on defining a metric on the space of observables, induced by the manner through which the modelling creates a mapping from the parameter space onto the space of observables. This metric bears a close connection to Jeffreys' prior from information theory. It is used to generate a homogeneous and isotropic sampling of the signal space with two different methods. We show that when the resulting optimized samplings, created with 21cmFAST, are used to train a neural network we obtain a modest reduction of the error on parameter reconstruction of ∼10% (compared to a naïve sampling of the same size). Excluding the borders of the parameter space region, the improvement is more substantial, on the order of 30-40%.

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“…[61,62]) and radiative transfer simulations (e.g. [63,64]). 3 Bounds on primordial power spectrum from EDGES 21cm global signal Now in this section, we study the bound on the running parameters α s and β s of primordial power spectrum by demanding that the absorption line should appear in the redshift range of 14 < z < 22 indicated by the EDGES result.…”

Section: CM Global Signal and Primordial Power Spectrummentioning

confidence: 99%

Impact of EDGES 21-cm global signal on the primordial power spectrum

Yoshiura

Takahashi

2018

Phys. Rev. D

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We investigate the impact of the recent observation of the 21cm global signal by EDGES on primordial power spectrum, particularly focusing on the running parameters α s and β s which characterize the detailed scale dependence of the primordial spectrum. When primordial power spectrum is enhanced/suppressed on small scales, the structure formation proceeds faster/slower and changes the abundance of small size halos, which affects the sources of Lyman α radiation at high redshifts to alter the position of the absorption line. Recent observation of EDGES detected the 21cm absorption line at z = 17.2 and this result also indicates that the brightness temperature is consistent with zero for z 14 and z 22, which can exclude a scenario giving the absorption line at such redshifts. We argue that the bound on the running parameters can be obtained by requiring that the absorption line should not exceed observational bounds at such redshift ranges and found that some parameter space of α s and β s allowed by Planck may be disfavored for some values of astrophysical parameters.

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21SSD: a public data base of simulated 21-cm signals from the epoch of reionization

Cited by 37 publications

References 40 publications

Evaluating the QSO contribution to the 21-cm signal from the Cosmic Dawn

Evaluating the QSO contribution to the 21-cm signal from the Cosmic Dawn

Working towards an optimal sampling of the 21 cm signal parameter space

Impact of EDGES 21-cm global signal on the primordial power spectrum

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