Prospects of constraining reionization model parameters using Minkowski tensors and Betti numbers

• Published in: Journal of cosmology and astroparticle physics 2021-05, Vol.2021 (5), p.26
• Main Authors: Kapahtia, Akanksha, Chingangbam, Pravabati, Ghara, Raghunath, Appleby, Stephen, Choudhury, Tirthankar Roy
• Format: Article
• Language: English
• Subjects: Bayesian analysis; Brightness temperature; Coefficient of variation; Constraining; Constraint modelling; Eigenvalues; first stars; Ionization; Ionizing radiation; Model accuracy; Parameters; Red shift; reionization; Tensors
• ISSN: 1475-7516; 1475-7516
• DOI: 10.1088/1475-7516/2021/05/026

We explore the possibility of constraining model parameters of the Epoch of Reionization (EoR) from 21cm brightness temperature maps, using a combination of morphological descriptors constructed from the eigenvalues of the Contour Minkowski Tensor (CMT), Betti numbers (count of connected regions n con and holes n hole ) and the area of structures in the excursion set of the field. We use a three parameter model of EoR simulated using 21cmFAST, namely the ionizing efficiency of sources ζ, the minimum virial temperature T vir required for collapse into a halo and the maximum radius for ionizing radiation described by R mfp . We performed a Bayesian analysis to recover model parameters for a mock 21cm image from SKA phase I at a redshift of z=7.4 corresponding to a mean neutral hydrogen fraction of x̅ HI ≃ 0.5. We find that in the absence of noise the average size of structures in the field with x HI ≲ 0.5 is smaller than regions with x HI ≳ 0.5 and the structures are equally isotropic when x̅ HI =0.5 . We also find that in order to recover the input model to within 1-σ accuracy for a mock noisy image at a single frequency channel of 1 MHz, for an observation time t_obs9.5 Mpc. Finally we show that the systematic behaviour of the statistic as ionization progresses, enables us to obtain stringent constraints on x̅ HI (with a coefficient of variation ∼ 0.05 as compared to ∼ 0.1–0.2 for model parameter constraints), thereby making these descriptors a promising statistic for constraining EoR model parameters and the ionization history of the universe.