Abstract
We present a machine learning framework to simulate realistic galaxies for theEuclidSurvey, producing more complex and realistic galaxies than the analytical simulations currently used inEuclid. The proposed method combines a control on galaxy shape parameters offered by analytic models with realistic surface brightness distributions learned from realHubbleSpace Telescope observations by deep generative models. We simulate a galaxy field of 0.4 deg2as it will be seen by theEuclidvisible imager VIS, and we show that galaxy structural parameters are recovered to an accuracy similar to that for pure analytic Sérsic profiles. Based on these simulations, we estimate that theEuclidWide Survey (EWS) will be able to resolve the internal morphological structure of galaxies down to a surface brightness of 22.5 mag arcsec−2, and theEuclidDeep Survey (EDS) down to 24.9 mag arcsec−2. This corresponds to approximately 250 million galaxies at the end of the mission and a 50% complete sample for stellar masses above 1010.6 M⊙(resp. 109.6 M⊙) at a redshiftz ∼ 0.5 for the EWS (resp. EDS). The approach presented in this work can contribute to improving the preparation of future high-precision cosmological imaging surveys by allowing simulations to incorporate more realistic galaxies.
Highlights
The Euclid Survey (Laureijs et al 2011) will observe 15 000 deg2 (35% of the visible sky) over six years, both in the near-infrared and in the optical at a spatial resolution approaching that of the Hubble Space Telescope (HST)
We have presented a data-driven method for simulating deconvolved and noise-free galaxies with morphologies more realistic and complex than pure analytic Sérsic profiles
The proposed approach is based on a combination of deep generative neural networks trained on observations, which allows one to generate realistic galaxies while preserving a control of the global shape of the surface brightness profiles
Summary
The Euclid Survey (Laureijs et al 2011) will observe 15 000 deg (35% of the visible sky) over six years, both in the near-infrared and in the optical at a spatial resolution approaching that of the Hubble Space Telescope (HST). With a field of view of 0.53 deg, compared to that of the HST (0.003 deg2), it will probe the sky at a rate around 175 times faster. It will only take around five hours to observe an area equivalent to the COSMOS field (Scoville et al 2007), which is still the largest contiguous area. In addition to the EWS at an expected nominal depth of 24.5 mag at 10σ for extended sources in the visible (Cropper et al 2016), Euclid will observe 40 deg about two magnitudes deeper (EDS). We refer the reader to Scaramella et al (in prep.) for precise information about the Euclid surveys and their depths
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