Evolutionary Map of the Universe

""Evolutionary Map of the Universe"", or EMU, is a large project which will use the new ASKAP telescope to make a census of radio sources in the sky. EMU is expected to detect about 70 million radio sources .[1] compared to the 2.5 million radio sources currently known, most of which were detected by the NRAO VLA Sky Survey. Most of these radio sources will be galaxies millions of light years away, many containing massive black hole, and some of the signals detected will have been sent less than half a billion years after the Big Bang, which created the Universe 13.7 billion years ago. Unlike the NVSS, which mainly detected Active Galactic Nuclei, the greater sensitivity of EMU means that about half the galaxies detected will be star-forming galaxies.

EMU's primary science driver is to try to understand how the stars and galaxies were first formed, and how they evolved to their present state. The census of 70 million galaxies detected by EMU will represent galaxies in all their different stages of evolution, so that they can be placed in sequence, enabling the study of how their properties change as they evolve. EMU will be able to probe star forming galaxies up to a redshift of about 1, Active Galactic Nuclei to the edge of the Observable Universe, and will undoubtedly uncover new classes of object.

EMU was chosen (with WALLABY) as one of the two highest-ranked proposals for ASKAP from an initial field of 39 expressions of interest .[2] EMU is an international project, and the EMU team consists of about 300 astronomers in 21 countries.

In addition to planning and conducting the radio survey itself, the EMU project also includes

Technical Overview

EMU is a radio sky survey project which will use the new ASKAP telescope to make a deep (~10 microJy rms) radio continuum survey covering the entire Southern Sky as far north as declination +30°. It will have about 40 times the sensitivity, and six times the resolution, of the NVSS”, and will also be more sensitive to extended diffuse emission, because of the short baselines built into the ASKAP array.

EMU will survey the entire sky visible from the ASKAP telescope in 30 square degree fields. Each field will be surveyed over the 300 MHz band from about 1110 to 1410 MHz, in 1 MHz channels, delivering both spectral shapes and, through the POSSUM [7] project, all four Stokes parameters and rotation measures. The data will be processed in near-real-time by the ASKAP pipeline processor. After the processed data have been approved for quality control by the EMU team, they will be placed in the public domain. The radio components will then be grouped into radio sources, and where possible cross-matched with other multiwavelength data. They will then be placed into the EMU value-added catalogue (EVACAT) which will be available only to members of the EMU team for some proprietary period before being released into the public domain.

Timeline

The EMU project has five phases (dates are notional, and depend on construction and commissioning progress):

References

  1. Norris, R.P., et al., EMU: Evolutionary Map of the Universe, PASA (2015), Volume 28, Issue 2, pp. 215-248. http://adsabs.harvard.edu/abs/2011PASA...28..215N
  2. Johnston, S, et al., Science with ASKAP. The Australian square-kilometre-array pathfinder, Experimental Astronomy (2008), Volume 22, p. 151. http://adsabs.harvard.edu/abs/2008ExA....22..151J
  3. Umana, G. et al., SCORPIO: a deep survey of radio emission from the stellar life-cycle, MNRAS (2015), Volume 454, p. 902. http://adsabs.harvard.edu/abs/2015MNRAS.454..902U
  4. Hopkins, A. et al., The ASKAP/EMU Source Finding Data Challenge, PASA (2015), in press. http://adsabs.harvard.edu/abs/2015arXiv150903931H
  5. Fan, D. et al., Matching radio catalogues with realistic geometry: application to SWIRE and ATLAS, MNRAS (2015), 451, 1299. http://adsabs.harvard.edu/abs/2015MNRAS.451.1299F
  6. Banfield, J. et al., Radio Galaxy Zoo: host galaxies and radio morphologies derived from visual inspection, MNRAS (2015), 453, 2326. http://adsabs.harvard.edu/abs/2015MNRAS.453.2326B
  7. Gaensler, B. et al., Survey Science with ASKAP: Polarization Sky Survey of the Universe's Magnetism (POSSUM), Bulletin of the American Astronomical Society (2010), Vol. 42, p.515. http://adsabs.harvard.edu/abs/2010AAS...21547013G

External links

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