| 11. |
- Jelic, Vibor, et al.
(författare)
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A cross-correlation study between the cosmological 21 cm signal and the kinetic Sunyaev-Zel'dovich effect
- 2010
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 402:4, s. 2279-2290
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Tidskriftsartikel (refereegranskat)abstract
- The Universe's Epoch of Reionization can be studied using a number of observational probes that provide complementary or corroborating information. Each of these probes suffers from its own systematic and statistical uncertainties. It is therefore useful to consider the mutual information that these data sets contain. In this paper, we present a cross-correlation study between the kinetic Sunyaev-Zel'dovich effect - produced by the scattering of cosmic microwave background (CMB) photons off free electrons produced during the reionization process - and the cosmological 21 cm signal - which reflects the neutral hydrogen content of the Universe, as a function of redshift. The study is carried out using a simulated reionization history in 100 h(-1) Mpc scale N-body simulations with radiative transfer. In essence, we find that the two probes anticorrelate. The significance of the anticorrelation signal depends on the extent of the reionization process, wherein extended histories result in a much stronger signal compared to instantaneous cases. Unfortunately, however, once the primary CMB fluctuations are included into our simulation they serve as a source of large correlated noise that renders the cross-correlation signal insignificant, regardless of the reionization scenario.
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| 12. |
- Thomas, Rajat M., et al.
(författare)
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Fast Large-Scale Reionization Simulations
- 2008
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We present an efficient method to generate large simulations of the Epoch of Reionization (EoR) without the need for a full 3-dimensional radiative transfer code. Large dark-matter-only simulations are post-processed to produce maps of the redshifted 21cm emission from neutral hydrogen. Dark matter haloes are embedded with sources of radiation whose properties are either based on semi-analytical prescriptions or derived from hydrodynamical simulations. These sources could either be stars or power-law sources with varying spectral indices. Assuming spherical symmetry, ionized bubbles are created around these sources, whose radial ionized fraction and temperature profiles are derived from a catalogue of 1-D radiative transfer experiments. In case of overlap of these spheres, photons are conserved by redistributing them around the connected ionized regions corresponding to the spheres. The efficiency with which these maps are created allows us to span the large parameter space typically encountered in reionization simulations. We compare our results with other, more accurate, 3-D radiative transfer simulations and find excellent agreement for the redshifts and the spatial scales of interest to upcoming 21cm experiments. We generate a contiguous observational cube spanning redshift 6 to 12 and use these simulations to study the differences in the reionization histories between stars and quasars. Finally, the signal is convolved with the LOFAR beam response and its effects are analyzed and quantified. Statistics performed on this mock data set shed light on possible observational strategies for LOFAR.
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| 13. |
- Thomas, Rajat M., et al.
(författare)
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Fast large-scale reionization simulations
- 2009
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 393, s. 32-48
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Tidskriftsartikel (refereegranskat)abstract
- We present an efficient method to generate large simulations of the epoch of reionization without the need for a full three-dimensional radiative transfer code. Large dark-matter-only simulations are post-processed to produce maps of the redshifted 21-cm emission from neutral hydrogen. Dark matter haloes are embedded with sources of radiation whose properties are either based on semi-analytical prescriptions or derived from hydrodynamical simulations. These sources could either be stars or power-law sources with varying spectral indices. Assuming spherical symmetry, ionized bubbles are created around these sources, whose radial ionized fraction and temperature profiles are derived from a catalogue of one-dimensional radiative transfer experiments. In case of overlap of these spheres, photons are conserved by redistributing them around the connected ionized regions corresponding to the spheres. The efficiency with which these maps are created allows us to span the large parameter space typically encountered in reionization simulations. We compare our results with other, more accurate, three-dimensional radiative transfer simulations and find excellent agreement for the redshifts and the spatial scales of interest to upcoming 21-cm experiments. We generate a contiguous observational cube spanning redshift 6 to 12 and use these simulations to study the differences in the reionization histories between stars and quasars. Finally, the signal is convolved with the Low Frequency Array (LOFAR) beam response and its effects are analysed and quantified. Statistics performed on this mock data set shed light on possible observational strategies for LOFAR.
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