WP1: The PAU Survey has been designed to measure accurately the redshift of galaxies using photometric techniques with narrow band filters. Its wide area coverage, the depth reached and the wavelength rage coverage make it a unique survey that can be used to calibrate the intrinsic alignment signal in weak lensing surveys like Euclid. We took observations at the William Herschel Telescope of the Observatorio del Roque de los Muchachos and automatically transfered them to our institutions and archive them. We have developed the algorithms to be able to measure the galaxy fluxes in all the narrow bands observed. We have also implemented the processing into a big data platform hosted at the Port d'Informació Científica (PIC) as the data volume makes it impossible to run in simple machines.
WP2: Photometric redshifts provide an efficient tool to locate galaxies and therefore make them available as tracers of the large-scale structure of the universe. Here, we explored how to best measure galaxy redshifts using the narrow band data collected from PAUCam. With PAUCam, we sample the spectral energy distribution at 40 different wavelengths. Such fine resolution allows us to determine the galaxy redshifts accurately. We have developed template-based photo-z algorithms as well as machine learning techniques. In particular, the inclusion of emission lines in the galaxy spectra improves considerably the performance for emission line galaxies. Our results are consistent with the prediction we obtained in simulations.
WP 3: We measured how galaxies – big clouds of stars - orientate themselves in space. In particular how the 3D shape of a galaxy can be “aligned” (i.e. point towards) big clumps of matter as a result of the effect of gravity. Its really important to measure this effect so we can account for it in the Euclid mission. In the Euclid mission we want to measure the gravitational lensing effect, that changes the observed shapes of galaxies and can be used to determine what the Universe is made of; but without removing the effect of the 3D alignments this measurement would no be possible.
WP 4: During the reporting period the simulation-based tests of the HST Euclidization procedure were expanded, revealing that standard applications for the generation of HST-based Euclid-like weak lensing image simulations can lead to incorrect calibrations of multiplicative shear measurement biases at the few per-cent level. We delivered a refined tile-wise reduction of HST/ACS observations in the CANDELS-Wide fields including complementary PSF models. Revised HST correction software for charge transfer inefficiency has been released at
https://github.com/jkeger/arctic(si apre in una nuova finestra). The routines used to calibrate the model have additionally been released at
https://github.com/jkeger/warm_pixels(si apre in una nuova finestra).
WP 5: The methodology developed and the results of the calibration procedure will be presented in two papers which are in progress at the time of writing. This will represent a fast and efficient way to get rid of the colour gradient bias respecting the requirements set on this kind of bias in the Euclid systematics budget.
WP 6: Synthetic galaxy catalogues play a key role in galaxy surveys. In this project we built a replica of the survey made with PAUCam. We did this by combining a computer model of galaxy formation, with a simulation which models the structure in the dark matter component of the Universe, and its growth over time due to the force of gravity. The output of these simulations is a series of snapshots of the population of model galaxies at fixed times in the history of the universe. We then processed these snapshots with another code to mimic the process of observing the model galaxies with PAUCam.
WP 7: In this WP, we have conducted a survey to obtain the spectroscopic data required for Euclid. As result, we have obtained the redshits for the galaxies included in our programme, improved the coverage of the colour-redshift mapping and simulated the improvement in the bias correction of the tomographic bins.
