The VISTA VIDEO survey

(Stevens, Bonfield, Smith)

The VIDEO survey is a 12 sq.degree, Z,Y,J,H,K survey specifically designed to enable galaxy and cluster/structure evolution to be traced as a function of both epoch and environment from the present day out to z=4, and AGN and the most massive galaxies up to and into the epoch of reionization. With its depth and area, VIDEO will be able to fully probe the epoch of activity in the Universe, where AGN and starburst activity were at their peak and the first galaxy clusters were beginning to virialise. VIDEO therefore offers a unique data set with which to investigate the interplay between AGN, starbursts and environment, and the role of feedback at a time when it is most crucial. The multi-band nature of the survey ensures many key science drivers can be tackled using the survey alone, without recourse to data from other wavebands. However, the survey fields have been carefully selected to ensure a good RA spread and mix of fields with existing multi-band data thereby enhancing the usefulness of the survey to the whole of the astronomical community, and with an eye to future use of other ESO facilities such as APEX and ALMA. The area and depth means that VIDEO fits naturally between the VIKING and Ultra-VISTA surveys, and has been allocated >200 nights over the next five years.

The VIDEO dataset also acts as a useful testbed for future large surveys. The EUCLID mission, for example, will obtain near-infrared imaging to a similar depth over tens of thousands of square degrees. To be able to use EUCLID data to constrain dark energy via weak lensing (one of its primary probes), we will need to estimate redshifts using only broad-band photometry for hundreds of millions of galaxies with exquisite precision, and are using VIDEO to test the accuracy of algorithms which might achieve this.

This YJKs image shows a small portion of the data already obtained for VIDEO. This 18 square arcminute cutout contains around 1000 galaxies; the full survey will be 2400 times larger than this. Even by eye, and with just these three filters, it is possible to separate the redder, more distant galaxies from the pink and blue galaxies at intermediate redshifts and the blue stars in our own galaxy; with all five near-infrared filters (plus complementary optical data from other surveys) we will precisely determine the redshifts (distances) and physical parameters of millions of galaxies, spanning most of the history of the Universe.