Improving IGM temperature constraints using wavelet analysis on high-redshift quasars

Wolfson, Molly; Davies, Frederick B.; Oñorbe, José; Hiss, Hector; Lukić, Zarija

doi:10.1093/mnras/stab2920

Cited by 8 publications

(3 citation statements)

References 76 publications

(116 reference statements)

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“…where σ obs is the reported observational uncertainty in the flux power spectrum or helium opacity, respectively. In their study, Wolfson et al (2021) showed the importance of using the covariance matrix when inferring the temperature of the IGM from measurements of the Lyα power spectrum and wavelet statistics. For our MCMC analysis we use the covariance matrices of P(k) in the likelihood calculation (see Section 2.9).…”

Section: Systematic Uncertaintiesmentioning

confidence: 99%

Inferring the Thermal History of the Intergalactic Medium from the Properties of the Hydrogen and Helium Lyα Forest

Villasenor

Robertson

Madau

et al. 2022

ApJ

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The filamentary network of intergalactic medium (IGM) gas that gives origin to the Lyα forest in the spectra of distant quasars encodes information on the physics of structure formation and the early thermodynamics of diffuse baryonic material. Here we use a massive suite of more than 400 high-resolution cosmological hydrodynamical simulations run with the Graphics Processing Unit–accelerated code Cholla to study the IGM at high spatial resolution maintained over the entire computational volume. The simulations capture a wide range of possible IGM thermal histories by varying the photoheating and photoionizing background produced by star-forming galaxies and active galactic nuclei. A statistical comparison of synthetic spectra with the observed 1D flux power spectra of hydrogen at redshifts 2.2 ≤ z ≤ 5.0 and with the helium Lyα opacity at redshifts 2.4 < z < 2.9 tightly constrains the photoionization and photoheating history of the IGM. By leveraging the constraining power of the available Lyα forest data to break model degeneracies, we find that the IGM experienced two main reheating events over 1.2 Gyr of cosmic time. For our best-fit model, hydrogen reionization completes by z R ≈ 6.0 with a first IGM temperature peak of T 0 ≃ 1.3 × 104 K and is followed by the reionization of He ii that completes by z R ≈ 3.0 and yields a second temperature peak of T 0 ≃ 1.4 × 104 K. We discuss how our results can be used to obtain information on the timing and the sources of hydrogen and helium reionization.

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Section: Systematic Uncertaintiesmentioning

confidence: 99%

Inferring the Thermal History of the Intergalactic Medium from the Properties of the Hydrogen and Helium Lyα Forest

Villasenor

Robertson

Madau

et al. 2022

ApJ

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“…So the accuracy of their numerical CWTs can be verified by the corresponding analytical results. Finally, it should be noted that the CWT for 1D signals is not trivial in astrophysics and cosmology, as it is also applicable to a wide range of scenarios, such as analyzing the light curves of astronomical sources (e.g., Tarnopolski et al 2020;Ren et al 2022), subtracting the foreground emission from the 21 cm signal (e.g., Gu et al 2013;Li et al 2019), measuring the smallscale structure in the Lyman-α forest (e.g., Lidz et al 2010;Garzilli et al 2012;Wolfson et al 2021), investigating the time-frequency properties of the gravitational waves (e.g., Tary et al 2018), characterizing the 1D density fields (e.g., da Cunha et al 2018;Wang & He 2021;, and so on. We publicly release the Fortran 95 implementation of the fast CWT algorithms described in this manuscript 1 , in the hope that the community will use them to perform wavelet analysis of 1D signals.…”

Section: Introductionmentioning

confidence: 99%

Comparisons between fast algorithms for the continuous wavelet transform and applications in cosmology: the one-dimensional case

Wang¹,

He²

2023

Preprint

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The continuous wavelet transform (CWT) is very useful for processing signals with intricate and irregular structures in astrophysics and cosmology. It is crucial to propose precise and fast algorithms for the CWT. In this work, we review and compare four different fast CWT algorithms for the 1D signals, including the FFTCWT, the V97CWT, the M02CWT, and the A19CWT. The FFTCWT algorithm implements the CWT using the Fast Fourier Transform (FFT) with a computational complexity of O(N log 2 N ) per scale. The rest algorithms achieve the complexity of O(N ) per scale by simplifying the CWT into some smaller convolutions. We illustrate explicitly how to set the parameters as well as the boundary conditions for them. To examine the actual performance of these algorithms, we use them to perform the CWT of signals with different wavelets. From the aspect of accuracy, we find that the FFTCWT is the most accurate algorithm, though its accuracy degrades a lot when processing the non-periodic signal with zero boundaries. The accuracy of O(N ) algorithms is robust to signals with different boundaries, and the M02CWT is more accurate than the V97CWT and A19CWT. From the aspect of speed, the O(N ) algorithms do not show an overall speed superiority over the FFTCWT at sampling numbers of N 10 6 , which is due to their large leading constants. Only the speed of the V97CWT with real wavelets is comparable to that of the FFTCWT. However, both the FFTCWT and V97CWT are substantially less efficient in processing the non-periodic signal because of zero padding. Finally, we conduct wavelet analysis of the 1D density fields, which demonstrate the convenience and power of techniques based on the CWT. We publicly release our CWT codes as resources for the community.

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“…The Ly𝛼 forest is thus used as the premier probe of the IGM thermal history. Various statistical properties of the Ly𝛼 forest are used to measure the IGM thermal state, including the power spectrum Zaldarriaga et al 2001;McDonald et al 2001;Walther et al 2017;Walther et al 2018;Khaire et al 2019;Gaikwad et al 2021), the flux probability density function (PDF) (Bolton et al 2008;Viel et al 2009;Lee et al 2015), the transmission curvature (Becker et al 2011;Boera et al 2014), the wavelet decomposition of the forest (Theuns & Zaroubi 2000;Theuns et al 2002;Lidz et al 2010;Garzilli et al 2012;Wolfson et al 2021), and the quasar pair phase angle distribution (Rorai et al 2013(Rorai et al , 2017. These measurements are typically performed using Ly𝛼 forest spectra from groundbased telescopes at 𝑧 > 1.6, where the Ly𝛼 transition lies above the atmospheric cutoff (𝜆 ∼ 3300Å), explaining why there are currently very few measurements of the IGM thermal state at redshift below such limit (i.e.…”

Section: Introductionmentioning

confidence: 99%

Measuring the thermal and ionization state of the low-z IGM using likelihood free inference

Teng

Khaire

Walther

et al. 2022

Monthly Notices of the Royal Astronomical Society

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We present a new approach to measure the power-law temperature density relationship $T=T_0 (\rho \ / \bar{\rho })^{\gamma -1}$ and the UV background photoionization rate $\Gamma _{{{{\rm H\, {\small i}}}}{}}$ of the intergalactic medium(IGM) based on the Voigt profile decomposition of the Lyα forest into a set of discrete absorption lines with Doppler parameter b and the neutral hydrogen column density $N_{\rm H\, {\small i}}$. Previous work demonstrated that the shape of the $b-N_{{{{\rm H\, {\small i}}}}{}}$ distribution is sensitive to the IGM thermal parameters T0 and γ, whereas our new inference algorithm also takes into account the normalization of the distribution, i.e. the line-density dN/dz, and we demonstrate that precise constraints can also be obtained on $\Gamma _{{{{\rm H\, {\small i}}}}{}}$. We use density-estimation likelihood-free inference (DELFI) to emulate the dependence of the $b-N_{{{{\rm H\, {\small i}}}}{}}$ distribution on IGM parameters trained on an ensemble of 624 Nyx hydrodynamical simulations at z = 0.1, which we combine with a Gaussian process emulator of the normalization. To demonstrate the efficacy of this approach, we generate hundreds of realizations of realistic mock HST/COS datasets, each comprising 34 quasar sightlines, and forward model the noise and resolution to match the real data. We use this large ensemble of mocks to extensively test our inference and empirically demonstrate that our posterior distributions are robust. Our analysis shows that by applying our new approach to existing Lyα forest spectra at z ≃ 0.1, one can measure the thermal and ionization state of the intergalactic medium(IGM) with very high precision ($\sigma _{\log T_0} \sim 0.08$ dex, σγ ∼ 0.06, and $\sigma _{\log \Gamma _{{{{\rm H\, {\small i}}}}{}}} \sim 0.07$ dex).

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Improving IGM temperature constraints using wavelet analysis on high-redshift quasars

Cited by 8 publications

References 76 publications

Inferring the Thermal History of the Intergalactic Medium from the Properties of the Hydrogen and Helium Lyα Forest

Inferring the Thermal History of the Intergalactic Medium from the Properties of the Hydrogen and Helium Lyα Forest

Comparisons between fast algorithms for the continuous wavelet transform and applications in cosmology: the one-dimensional case

Measuring the thermal and ionization state of the low-z IGM using likelihood free inference

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