Simulations for Gravitational Lensing of 21 cm Radiation at EoR and Post-EoR Redshifts

Romeo, Alessandro (2015) Simulations for Gravitational Lensing of 21 cm Radiation at EoR and Post-EoR Redshifts, [Dissertation thesis], Alma Mater Studiorum Università di Bologna. Dottorato di ricerca in Astronomia, 27 Ciclo. DOI 10.6092/unibo/amsdottorato/7239.
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Abstract

21 cm cosmology opens an observational window to previously unexplored cosmological epochs such as the Epoch of Reionization (EoR), the Cosmic Dawn and the Dark Ages using powerful radio interferometers such as the planned Square Kilometer Array (SKA). Among all the other applications which can potentially improve the understanding of standard cosmology, we study the promising opportunity given by measuring the weak gravitational lensing sourced by 21 cm radiation. We performed this study in two different cosmological epochs, at a typical EoR redshift and successively at a post-EoR redshift. We will show how the lensing signal can be reconstructed using a three dimensional optimal quadratic lensing estimator in Fourier space, using single frequency band or combining multiple frequency band measurements. To this purpose, we implemented a simulation pipeline capable of dealing with issues that can not be treated analytically. Considering the current SKA plans, we studied the performance of the quadratic estimator at typical EoR redshifts, for different survey strategies and comparing two thermal noise models for the SKA-Low array. The simulation we performed takes into account the beam of the telescope and the discreteness of visibility measurements. We found that an SKA-Low interferometer should obtain high-fidelity images of the underlying mass distribution in its phase 1 only if several bands are stacked together, covering a redshift range that goes from z=7 to z=11.5. The SKA-Low phase 2, modeled in order to improve the sensitivity of the instrument by almost an order of magnitude, should be capable of providing images with good quality even when the signal is detected within a single frequency band. Considering also the serious effect that foregrounds could have on this detections, we discussed the limits of these results and also the possibility provided by these models of measuring an accurate lensing power spectrum.

Abstract
Tipologia del documento
Tesi di dottorato
Autore
Romeo, Alessandro
Supervisore
Co-supervisore
Dottorato di ricerca
Scuola di dottorato
Scienze matematiche, fisiche ed astronomiche
Ciclo
27
Coordinatore
Settore disciplinare
Settore concorsuale
Parole chiave
21 cm cosmology, theory, Cosmology, Dark Ages, Epoch of Reionization, Weak Gravitational Lensing, Dark Matter, Dark Energy, Large Scale Structures of the Universe, SKA
URN:NBN
DOI
10.6092/unibo/amsdottorato/7239
Data di discussione
21 Dicembre 2015
URI

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