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Berlin Brandenburg

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  • 1
    Language: English
    In: 2014 United States National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM), January 2014, pp.1-1
    Description: Summary form only given. Significant effort has recently been turned to the problem of detecting and characterizing intergalactic hydrogen prior to its complete ionization by stars, occurring sometime before t=950Ma (z=6). The distribution of HI, visible in redshifted 21cm radio emission, is one of the few observables into the onset of non-linear structure leading to the birth of the first stars and galaxies. Before it was ionized by stellar UV radiation, HI was found throughout the universe, roughly tracing out the underlying matter distribution and temperature. HI 21cm emission from this epoch (6 〈; z 〈; 12) is redshifted into the VHF radio band (100 〈; f 〈; 200 MHz) and with a observer frequency depending on redshift/distance provides a fully three dimensional view. The emission is expected to have surface brightness of ~25mK with a non-gaussian distribution and most power occurring on scales of 10cMpc. Here we describe how data from PAPER and MWA have significantly tightened our constraints on bright foregrounds, and through comparison, identified some of the most likely sources of error in foreground removal steps. In addition we present early results of an exploration of the redshift and spatial dependence of fainter foreground components identified in the deep PAPER data which has so far given the tightest constraints. Comparing with new MWA observations we seek to separate possible faint foreground contamination from equally likely systematic corruption.
    Keywords: Pollution Measurement ; Educational Institutions ; Contamination ; Jacobian Matrices ; Earth ; Space Exploration ; Hydrogen
    Source: IEEE Conference Publications
    Source: IEEE Xplore
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  • 2
    Language: English
    In: 2014 United States National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM), January 2014, pp.1-1
    Description: Recent interest in high redshift cosmology observations with the redshifted 21cm line has rekindled exploration of the VHF radio band (50-200MHz) for radio astronomy. Single antenna instruments like the ground-based EDGES and the proposed lunar orbiting DARE have the goal of characterizing the global HI signal and extracting astrophysical and cosmological information. One limitation over much of the band is strong man-made and naturally occurring interference, which DARE avoids by observing as it orbits the far side of the moon. Another advantage of space-based observing is avoidance of the ionosphere which becomes increasingly reflective at the lower end of the VHF band. Technical challenges to this type of mission include development of lower power wide-band spectrometers, better mapping of Earth originating interference, and incorporation of lessons learned from ongoing ground-based experiments. One of the main challenges faced by EDGES, observing the narrower but clean stretch of bandwidth found in Western Australia, is calibrating the spectral response of the antenna at the required 0.01dB level.
    Keywords: Space Vehicles ; Antennas ; Interference ; Bandwidth ; Educational Institutions ; Earth ; Propulsion
    Source: IEEE Conference Publications
    Source: IEEE Xplore
    Library Location Call Number Volume/Issue/Year Availability
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