Presentation Abstract

Presentation Number 104.03
Presentation Time: Monday, Jun 11, 2012, 10:30 AM -10:45 AM
Title HI at z ~ 20: The Large Aperture Experiment to Detect the Dark Ages
Author Block Lincoln J. Greenhill1, D. Werthimer2, G. Taylor3, S. Ellingson4, LEDA Collaboration
1Harvard-Smithsonian, CfA, 2University of California, Berkeley, 3University of New Mexico, 4Virginia Tech.
Abstract When did the first stars form? Did supermassive black holes form at the same time, earlier, or later? One of the great challenges of cosmology today is the study of these first generation objects. The Large Aperture Experiment to Detect the Dark Ages (LEDA) project seeks to detect, in total-power, emission from neutral Hydrogen (21 cm rest wavelength) in the intergalactic medium about 100 million years after the Big Bang (redshifts ~ 20). Detection would deliver the first observational constraints on models of structure formation and the first pockets of star and black holes formation in the Universe.
LEDA will develop and integrate by 2013 signal processing instrumentation into the new first station of the Long Wavelength Array (LWA). This comprises a large-N correlator serving all 512 dipole antennas of the LWA1, leveraging a packetized CASPER architecture and combining FPGAs and GPUs for the F and X stages. Iterative calibration and imaging will rely on warped snapshot imaging and be drawn from a GPU-enabled library (cuWARP) that is designed specifically to support wide-field full polarization imaging with fixed dipole arrays. Calibration techniques will include peeling, correction for ionospheric refraction, direction dependent dipole gains, deconvolution via forward modeling, and exploration of pulsar data analysis to improve performance. Accurate calibration and imaging will be crucial requirements for LEDA, necessary to subtract the bright foreground sky and detect the faint neutral Hydrogen signal. From the computational standpoint, LEDA is a O(100) TeraFlop per second challenge that enables a scalable architecture looking toward development of radio arrays requiring power efficient 10 PetaFlop per second performance. Stage two of the Hydrogen Epoch of Reionization Array (HERA2) is one example.