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




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Abstract: We assess the impact of Galactic synchrotron foreground removal on theobservation of high-redshift quasar HII regions in redshifted 21-cm emission.We consider the case where a quasar is observed in an intergalactic mediumIGM whose ionisation structure evolves slowly relative to the light crossingtime of the HII region, as well as the case where the evolution is rapid. Thelatter case is expected towards the end of the reionisation era where thehighest redshift luminous quasars will be observed. In the absence offoregrounds the fraction of neutral hydrogen in the IGM could be measureddirectly from the contrast between the HII region and surrounding IGM. However,we find that foreground removal lowers the observed contrast between the HIIregion and the IGM. This indicates that measurement of the neutral fractionwould require modelling to correct for this systematic effect. On the otherhand, foreground removal does not modify the most prominent features of the21-cm maps. Using a simple algorithm we demonstrate that measurements of thesize and shape of observed HII regions will not be affected by continuumforeground removal. Moreover, measurements of these quantities will not beadversely affected by the presence of a rapidly evolving IGM.



Autor: Paul. M. Geil, Stuart Wyithe, Nada Petrovic, Peng Oh

Fuente: https://arxiv.org/







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