The effect of Galactic foreground subtraction on redshifted 21-cm observations of quasar HII regions

Abstract

We assess the impact of Galactic synchrotron foreground removal on the observation of high-redshift quasar HII regions in redshifted 21-cm emission. We consider the case where a quasar is observed in an intergalactic medium (IGM) whose ionisation structure evolves slowly relative to the light crossing time of the HII region, as well as the case where the evolution is rapid. The latter case is expected towards the end of the reionisation era where the highest redshift luminous quasars will be observed. In the absence of foregrounds the fraction of neutral hydrogen in the IGM could be measured directly from the contrast between the HII region and surrounding IGM. However, we find that foreground removal lowers the observed contrast between the HII region and the IGM. This indicates that measurement of the neutral fraction would require modelling to correct for this systematic effect. On the other hand, foreground removal does not modify the most prominent features of the 21-cm maps. Using a simple algorithm we demonstrate that measurements of the size and shape of observed HII regions will not be affected by continuum foreground removal. Moreover, measurements of these quantities will not be adversely affected by the presence of a rapidly evolving IGM.

9 pages, 3 figures

References in corpus (15)

• Wilkinson Microwave Anisotropy Probe (WMAP) Three Year Results: Implications for Cosmology
• Constraining the Evolution of the Ionizing Background and the Epoch of Reionization with z ~ 6 Quasars II: A Sample of 19 Quasars
• Cosmological Parameter Estimation Using 21 cm Radiation from the Epoch of Reionization
• Efficient Simulations of Early Structure Formation and Reionization
• Simulating Cosmic Reionization at Large Scales I: the Geometry of Reionization
• Simulations and Analytic Calculations of Bubble Growth During Hydrogen Reionization
• The Global 21 Centimeter Background from High Redshifts
• Foreground simulations for the LOFAR - Epoch of Reionization Experiment
• On using visibility correlations to probe the HI distribution from the dark ages to the present epoch I: Formalism and the expected signal
• Cosmic Reionization Redux
• The Impact of a Percolating IGM on Redshifted 21 cm Observations of Quasar HII Regions
• Biased Reionisation and Non-Gaussianity in Redshifted 21cm Intensity Maps of the Reionisation Epoch
• Detecting ionized bubbles in redshifted 21 cm maps
• The correlation between the distribution of galaxies and 21cm emission at high redshifts
• Radio views of cosmic reionization

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