SPHEREx is a recently selected NASA Medium Explorer mission — the first all-sky spectral survey — designed to 1) set constraints on the physics of the very early Universe, in particular by looking for signals of non-Gaussianity in primordial density fluctuations traced via measurements of galaxy positions and redshifts, 2) study the origin and evolution of galaxies via measurements of the extragalactic background light, and 3) determine the origin of water and other biogenic molecules in planetary systems. SPHEREx will be equipped with a near-infrared spectrograph (0.75-5.0 um, implemented using linear variable filters with resolving power varying from R=40-130). SPHEREx has a very robust and simple design driven by maximization of spectral throughput and efficiency; once the sun shield and aperture cover are deployed, it has no moving parts. SPHEREx has an overlapping scan strategy and will observe the sky multiple times during the planned two-year mission (one all-sky survey every six months, two deep surveys at the North and South ecliptic poles).
Argonne CPAC group members contribute to the activities of the SPHEREx science team. This work includes the development of cosmological simulations for SPHEREx galaxies, the identification of SPHEREx sources and the computation of their redshifts, the determination of the effect of different types of non-Gaussianity on the large-scale structure of the Universe, the detection of cluster of galaxies and the determination of their properties, and the estimation of the abundance of high redshift quasars. The spectral information provided by SPHEREx will be a very useful complement to the photometric datasets obtained by LSST, another area of great interest to our group.

In this movie, we fly through the distribution of galaxies that future mission SPHEREx will observe. As the movie advances, we get farther and farther away from Earth, observing galaxies that populated the distant universe; indeed, the inset shows the path of the observer through the lightcone. Galaxies are biased tracers of the underlying distribution of dark matter, which is indicated using blue colors. The visualization is based on the trillion-particle Outer Rim simulation carried out with HACC.