Special Astrophysics Seminar

Foregrounds in 21 cm Cosmology: All-Sky Maps of the VHF Radio Sky from the Owens Valley Radio Observatory Long Wavelength Array (OVRO-LWA)

Michael Eastwood

Low-frequency radio telescopes are opening up a window into the epoch of reionization and the cosmic dawn of the universe -- where the first stars and galaxies bathed the universe in light. During this time, the hyperfine transition of neutral hydrogen is measurable as a 10-100 mK perturbation in the spectrum of the cosmic background radiation. Many low-frequency radio telescopes are attempting to detect this faint signature of highly redshifted neutral hydrogen (eg. HERA, MWA, LOFAR, SKA). However these measurements are primarily limited by the dynamic range they can achieve against low-redshift sources of low-frequency radio emission (ie. galactic synchrotron emission and AGN). Efforts to model the foreground contamination in these experiments are hampered by the availability of suitable foreground maps at frequencies below 408 MHz.

The OVRO-LWA is a low-frequency (25 to 82 MHz) interferometer located at the Owens Valley Radio Observatory (OVRO). It is composed of 288 antennas spanning 1.5 km, with 251 of those antennas located within a dense core that is 200 meters in diameter. This configuration ensures that the OVRO-LWA is sensitive to diffuse galactic emission and point sources. I will present full-sky multi-frequency maps of the VHF radio sky with 10 arcminute resolution, which can be used to characterize the foreground contamination in 21 cm cosmology experiments.