Euclid preparation LXXIV. Euclidised observations of Hubble Frontier Fields and CLASH galaxy clusters

Abstract

<p>We present HST2EUCLID, a novel Python code to generate <em>Euclid</em> realistic mock images in the <em>H</em>_E, <em>J</em>_E, <em>Y</em>_E, and <em>I</em>_E photometric bands based on panchromatic <em>Hubble</em> Space Telescope observations. The software was used to create a simulated database of <em>Euclid</em> images for the 27 galaxy clusters observed during the Cluster Lensing And Supernova survey with <em>Hubble</em> (CLASH) and the Hubble Frontier Fields (HFF) program. Since the mock images were generated from real observations, they incorporate, by construction, all the complexity of the observed galaxy clusters. The simulated <em>Euclid</em> data of the galaxy cluster MACS J0416.1−2403 were then used to explore the possibility of developing strong lensing models based on the <em>Euclid</em> data. In this context, complementary photometric or spectroscopic follow-up campaigns are required to measure the redshifts of multiple images and cluster member galaxies. By Euclidising six parallel blank fields obtained during the HFF program, we provide an estimate of the number of galaxies detectable in <em>Euclid</em> images per deg² per magnitude bin (number counts) and the distribution of the galaxy sizes. Finally, we present a preview of the <em>Chandra</em> Deep Field South that will be observed during the Euclid Deep Survey and two examples of galaxy-scale strong lensing systems residing in regions of the sky covered by the Euclid Wide Survey. The methodology developed in this work lends itself to several additional applications, as simulated <em>Euclid</em> fields based on HST (or JWST) imaging with extensive spectroscopic information can be used to validate the feasibility of legacy science cases or to train deep learning techniques in advance, thus preparing for a timely exploitation of the Euclid Survey data.<br></p>