Paul M. Geil

Baryonic acoustic oscillations in 21-cm emission: a probe of dark energy out to high redshifts

Low-frequency observatories are currently being constructed with the goal of detecting red-shifted 21-cm emission from the epoch of reionization. These observatories will also be able to detect intensity fluctuations in the cumulative 21-cm emission after reionization, from hydrogen in unresolved damped Lya absorbers (such as gas-rich galaxies) down to a redshift z ∼ 3.5. The inferred power spectrum of 21-cm fluctuations at all redshifts will show acoustic oscillations, whose comoving scale can be used as a standard ruler to infer the evolution of the equation of state for the dark energy. We find that the first generation of low-frequency experiments (such as MWA or LOFAR) will be able to constrain the acoustic scale to within a few per cent in a redshift window just prior to the end of the reionization era, provided that foregrounds can be removed over frequency bandpasses of ≥ 8 MHz. This sensitivity to the acoustic scale is comparable to the best current measurements from galaxy redshift surveys, but at much higher redshifts. Future extensions of the first-generation experiments (involving an order of magnitude increase in the antennae number of the MWA) could reach sensitivities below 1 per cent in several redshift windows and could be used to study the dark energy in the unexplored redshift regime of 3.5 ≤ z ≤ 12. Moreover, new experiments with antennae designed to operate at higher frequencies would allow precision measurements (≤1 per cent) of the acoustic peak to be made at more moderate redshifts (1.5 ≤ z ≤ 3.5), where they would be competitive with ambitious spectroscopic galaxy surveys covering more than 1000 deg 2 . Together with other data sets, observations of 21-cm fluctuations will allow full coverage of the acoustic scale from the present time out to z ∼ 12.

Polarized foreground removal at low radio frequencies using rotation measure synthesis: uncovering the signature of hydrogen reionization

Measurement of redshifted 21-cm emission from neutral hydrogen promises to be the most effective method for studying the reionization history of hydrogen and, indirectly, the first galaxies. These studies will be limited not by raw sensitivity to the signal, but rather, by bright foreground radiation from Galactic and extragalactic radio sources and the Galactic continuum. In addition, leakage due to gain errors and non-ideal feeds conspire to further contaminate low-frequency radio observations. This leakage leads to a portion of the complex linear polarization signal finding its way into Stokes I, and inhibits the detection of the non-polarized cosmological signal from the epoch of reionization. In this work, we show that rotation measure synthesis can be used to recover the signature of cosmic hydrogen reionization in the presence of contamination by polarized foregrounds. To achieve this, we apply the rotation measure synthesis technique to the Stokes I component of a synthetic data cube containing Galactic foreground emission, the effect of instrumental polarization leakage and redshifted 21-cm emission by neutral hydrogen from the epoch of reionization. This produces an effective Stokes I Faraday dispersion function for each line of sight, from which instrumental polarization leakage can be fitted and subtracted. Our results show that it is possible to recover the signature of reionization in its late stages (z≈ 7) by way of the 21-cm power spectrum, as well as through tomographic imaging of ionized cavities in the intergalactic medium.

Dark-ages reionization and galaxy formation simulation – IV. UV luminosity functions of high-redshift galaxies

In this paper we present calculations of the UV luminosity function from the Dark-ages Reionization And Galaxy-formation Observables from Numerical Simulations (DRAGONS) project, which combines N-body, semi-analytic and semi-numerical modelling designed to study galaxy formation during the Epoch of Reionization. Using galaxy formation physics including supernova feedback, the model naturally reproduces the UV LFs for high-redshift star-forming galaxies from

Dark-ages Reionization and Galaxy Formation Simulation II: Spin and concentration parameters for dark matter haloes during the Epoch of Reionization

z{\sim}5

Dark-ages reionization and galaxy formation simulation – X. The small contribution of quasars to reionization

through to

Dark-ages reionization and galaxy formation simulation V: morphology and statistical signatures of reionization

z{\sim}10

Modification of the 21‐cm power spectrum by quasars during the epoch of reionization

. We investigate the luminosity--star formation rate (SFR) relation, finding that variable SFR histories of galaxies result in a scatter around the median relation of

Dark-ages reionization and galaxy-formation simulation – VII. The sizes of high-redshift galaxies

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Dark-ages reionization and galaxy-formation simulation– VI. The origins and fate of the highest known redshift galaxy

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Dark-ages reionization and galaxy formation simulation–XI. Clustering and halo masses of high redshift galaxies

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