Daily Image
31-03-2022
Colloquium: How Bright is the Radio Sky? We Don't Know…yet
| Submitter: | Jack Singal |
| Description: | The actual level of diffuse radio emission on our sky is surprisingly uncertain. Almost all investigations that depend on understanding the radio sky, including cosmic microwave background and 21 cm cosmology foregrounds, ultimately rely on just one measurement - the 408 MHz Haslam map from the 1980s, which traces its absolute calibration to highly uncertain, low resolution blocked aperture measurements from the 1960s and earlier. The question of the absolute level of diffuse radio emission has taken on additional urgency given the claimed high radio synchrotron background level from the ARCADE instrument and other recent measurements. Such a high level of background radio emission would require a new population of incredibly numerous, faint radio sources in the universe, or for our Galaxy to be highly anomalous. This talk will discuss the present situation and the project to make the first-ever reliably absolutely calibrated large-scale radio map, using the unique features of the Green Bank Telescope combined with custom instrumentation. This polarization-sensitive map of the whole sky North of -47 degrees declination with all Galactic latitudes observed will provide an important new resource for understanding and constraining almost all Galactic and extragalactic phenomena that manifest in, or depend on the understanding of, diffuse radio emission. The image here shows a photograph of the Green Bank telescope, taken from two miles away to appreciate the scale. It is the world’s largest clear aperture telescope and has been a crucial resource in radio astronomy. It also has the unique capabilities to make the first-ever reliably absolutely calibrated large-scale radio map if outfitted with the appropriate custom instrumentation. |
| Copyright: | CC-BY-SA-NC (Credit: Jack Singal) |
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