Hercules A

Hercules A
Radio-Optical View of the Galaxy Hercules A - Many thanks to: NASA, ESA, S. Baum and C. O'Dea (RIT), R. Perley and W. Cotton (NRAO/AUI/NSF), and the Hubble Heritage Team (STScI/AURA)

Tuesday, May 6, 2014

The Owens Valley Long Wavelength Array - Dark Ages - Gregg Hallinan

I note this presentation at the Exascale Radio Astronomy Conference held March-April 2014 in Monterey, California:




Abstract: "The Owens Valley LWA is a new array of 256 dual polarization antennas at Caltech's Owens Valley Radio Observatory (OVRO). It hosts the LEDA correlator, which provides full cross-correlation capability and enables instantaneous snapshot imaging of most of the viewable sky, as well as a dedicated back-end for transient searching. Developed in collaboration between Caltech, JPL and the LEDA and LWA consortia, the array targets the 28-88 MHz band with primary focus on high redshift HI (Dark Ages), radio transients (particularly radio exoplanets), solar dynamic imaging spectroscopy and measurement of coronal magnetic fields, and production of a full-Stokes, low frequency, all-sky catalog. The array comprises a 230m diameter dense core and outriggers at 365m capable of imaging with a resolution of 1 degree. Over the next 12 months, 32 additional antennas will be installed, powered by solar panels and serviced by optical fiber, with the goal of delivering instantaneous all-sky images with ~10' resolution. The associated data rate for the latter array will be extremely large, at 1.5 GB per integration, corresponding to 45,000 baselines x 4 polarizations x 2000 channels (60 MHz). Our collaboration is also working towards a much larger next generation array for study of HI and transients, sited at or near the Owens Valley observatory. I will briefly discuss some of the related ongoing technical development and data processing challenges."

"...Before decoupling occurred, most of the photons in the universe were interacting with electrons and protons in the photon–baryon fluid. The universe was opaque or "foggy" as a result. There was light but not light we can now observe through telescopes. The baryonic matter in the universe consisted of ionized plasma, and it only became neutral when it gained free electrons during "recombination", thereby releasing the photons creating the CMB. When the photons were released (or decoupled) the universe became transparent. At this point the only radiation emitted was the 21 cm spin line of neutral hydrogen. There is currently an observational effort underway to detect this faint radiation, as it is in principle an even more powerful tool than the cosmic microwave background for studying the early universe. The Dark Ages are currently thought to have lasted between 150 million to 800 million years after the Big Bang. The October 2010 discovery of UDFy-38135539, the first observed galaxy to have existed during the following reionization epoch, gives us a window into these times. The galaxy earliest in this period observed and thus also the most distant galaxy ever observed is currently on the record of Leiden University's Richard J. Bouwens and Garth D. Illingsworth from UC Observatories/Lick Observatory. They found the galaxy UDFj-39546284 to be at a time some 480 million years after the Big Bang or about halfway through the Cosmic Dark Ages at a distance of about 13.2 billion light-years. More recently, the UDFj-39546284 galaxy was found to be around "380 million years" after the Big Bang and at a distance of 13.37 billion light-years.[14]..."