From space to ground: spectroscopic and weak lensing analysis of galaxy observations and simulations

Abstract

Cosmology and astrophysics have entered an era of increasingly rich data sets, not only from ground- and space-based observations, but also from simulations. This has allowed us to advance in the most compelling science issues to better understand the Universe as a whole, using techniques, such as weak gravitational lensing (WL) and spectroscopic analyses. On the one hand, given their high resolution, Hubble Space Telescope (HST)-observed galaxy images can in principle be used to emulate Euclid observations of sheared galaxy images. In my talk, I describe the testing environment to ‘Euclidize’ emulated HST data and I test shape measurements on this procedure, to quantify the impact of uncertainties for the use of HST images. Finally, I investigate the accuracy of TinyTim PSF models for HST/ACS to correct for the impact of the PSFs on the observed ellipticities. On the other side, we use data from ground-based telescopes to study the nature of the Ultra-Compact Massive Galaxies (UCMGs). I show the results of the spectroscopic analysis of 33 new targets from the Kilo Degree Survey (KiDS), for which I estimate the redshifts and the velocity dispersions. The addition of the newly confirmed objects to our previous sample, allows us to assess the systematics on the system selection, reduce the number density uncertainties, and build the largest sample of confirmed UCMGs.