Monday, December 10, 2012

The Theoretical Astrophysical Observatory

This post is not going to be about CANDELS directly, but about work that, in the long run, could play an enormous part in helping CANDELS astronomers analyse and interpret their data.

ASwinburne University in Australia, myself and my group are developing a new tool, called the Theory Astrophysical Observatory (TAO), which will make access to cutting edge supercomputer simulations of galaxy formation almost trivial. TAO will put the latest theory data in to the "cloud" for use by the international astronomy community, plus add a number of science enhancing eResearch tools. It is part of a larger project funded by the Australian Government called the All Sky Virtual Observatory (ASVO).

TAO boasts a clean and intuitive web interface. It avoids the need to know a database query language (like SQL) by providing a custom point-and-click web-form to select virtual galaxies and their properties, which auto-generates the query code in the background. Query results can then be funneled through additional "modules" and sent to a local supercomputer for further processing and manipulation. These include the ability to:

  • Construct observer light-cones (i.e. with the geometry of the sky) from simulated data cubes (the default format of the models and which assume a cartesian geometry);
  • Generate complete spectral energy distributions for model galaxies to provide true multi-wavelength galaxy luminosities;
  • Produce custom mock images of the sky in each simulated universe;
  • Add a virtual telescope simulator, through which the theory data can be "observed" by current or future telescopes.

TAO is already making it easy for the scientific community to apply the latest theoretical models. With an early TAO prototype, a group of Australian astronomers constructed a representation of the deep night sky that will be seen by the newly commissioned Australian Square Kilometer Array Pathfinder (ASKAP) radio telescope, which is based in the outback of Western Australia.

To do this, the TAO prototype was used to build a light-cone of many hundreds of thousands of simulated galaxies. These galaxies were selected from the much larger millions contained in the TAO database. The selection was based on the neutral hydrogen properties of each galaxy, as predicted by one of my galaxy formation models (Croton et al. 2006). After fine tuning to match the sensitivity of the ASKAP telescope, the researchers were able to reproduce the ASKAP night sky even before a single photon in the radio part of the electromagnetic spectrum had ever been collected by the telescope.

The night sky, as seen by the ASKAP radio telescope, and generated by a new eResearch tool, the Theoretical Astrophysical Observatory (TAO). Similar representations of the CANDELS fields are currently under development.

In the visualisation shown above one can see the light-cone of galaxies produced by TAO. Two surveys were constructed from the simulated data. The first replicates the shallower and wider WALLABY galaxy survey and is expected to find approximately 600,000 galaxies. The second is the much deeper and  narrower DINGO galaxy survey, and will find approximately 100,000 galaxies according to TAO. More information on these surveys can be found at the ASKAP science page.

The work has recently been published in the prestigious UK journal The Monthly Notices of the Royal Astronomical Society. Don't forget to check out the amazing movie here!

These tools are being applied to the CANDELS survey to do similarly exciting science. Watch this space!

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