Martin Kuemmel

  • works in the area of sky surveys since ~20 years;
  • extensive experience working with HST data;
  • works for the cataloging module of the Euclid Science Ground System;

Affiliation – LMU Faculty of Physics

Talks

Tiling the Euclid Sky

The Euclid satellite is an ESA mission scheduled for launch in 2022. It will observe an area of 15,000 deg^2 with two instruments, the Visible Imaging Channel (VIS) and the Near IR Spectrometer and imaging Photometer (NISP). Ground based imaging data in griz from surveys such as the Dark Energy Survey and LSST complement the Euclid data to enable photo-z determination. The mission investigates the distance-redshift relationship and the evolution of cosmic structures by measuring shapes and redshifts of galaxies and clusters of galaxies out to redshifts ~2.

Data processing is done in chunks that cover a specific area on the sky which are called tiles. When dividing a survey sky into tiles certain requirements need to be fulfilled: * the tiling needs to cover the entire survey area; * the tile size needs to be manageable by the infrastructure (data bases, storage and computing facilities) and should not create bottlenecks; * the tiling needs to partition the resulting object catalogs such that each object uniquely exists in only one catalog;

We present the tiling that was developed to cover the Euclid Surveys. Each tile consists of an extended area to compute the object properties and a core area to uniquely associate each object to one tile. The core area is defined in healpix indices and stored as Multi-Order Coverage (MOC) maps. Special tiling is applied for the Euclid Deep Surveys, to have data transfer and computing time within reasonable limit. We also create larger tiles around bright, large galaxies to allow also measuring their properties. We discuss the Euclid tiling in the context of the processing that had been applied in other surveys such as SDSS and 2MASS, among others.