Recovering the H II region size statistics from 21-cm tomography

Kakiichi, K., Majumdar, S., Mellema, G., Ciardi, B., Dixon, K. L., Iliev, I. T., Jelić, V., Koopmans, L. V. E., Zaroubi, S. & Busch, P., Oct-2017, In : Monthly Notices of the Royal Astronomical Society. 471, 2, p. 1936-1954 19 p.

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We introduce a novel technique, called 'granulometry', to characterize and recover the mean size and the size distribution of H II regions from 21-cm tomography. The technique is easy to implement, but places the previously not very well-defined concept of morphology on a firm mathematical foundation. The size distribution of the cold spots in 21-cm tomography can be used as a direct tracer of the underlying probability distribution of H II region sizes. We explore the capability of the method using large-scale reionization simulations and mock observational data cubes while considering capabilities of Square Kilometre Array 1 (SKA1) low and a future extension to SKA2. We show that the technique allows the recovery of the H II region size distribution with a moderate signal-to-noise ratio from wide-field imaging (SNR ≲ 3), for which the statistical uncertainty is sample variance dominated. We address the observational requirements on the angular resolution, the field of view, and the thermal noise limit for a successful measurement. To achieve a full scientific return from 21-cm tomography and to exploit a synergy with 21-cm power spectra, we suggest an observing strategy using wide-field imaging (several tens of square degrees) by an interferometric mosaicking/multibeam observation with additional intermediate baselines ( ∼ 2-4 km) in an SKA phase 2.
Original languageEnglish
Pages (from-to)1936-1954
Number of pages19
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
Publication statusPublished - Oct-2017


  • radiative transfer, methods: data analysis, techniques: image processing, intergalactic medium, dark ages, reionization, first stars, cosmology: theory, NEUTRAL HYDROGEN, HIGH-REDSHIFT, SIMULATING COSMIC REIONIZATION, DETECTING IONIZED BUBBLES, 21 CENTIMETER TOMOGRAPHY, POWER-SPECTRUM, LARGE SCALES, COSMOLOGICAL REIONIZATION, HYDROGEN REIONIZATION, INTERGALACTIC MEDIUM

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