PRISM (Polarized Radiation Imaging and Spectroscopy Mission): An Extended White Paper

TL;DR

PRISM proposes a space-based, all-sky survey of the microwave to far-infrared sky in both intensity and polarization, equipped with a high-resolution polarimetric imager and an absolute spectrometer to deliver precise multi-band maps and the sky’s absolute spectrum. By combining SZ-based cluster surveys, CIB and dusty galaxy science, inflationary B-modes with delensing, CMB spectral distortions, and Galactic ISM polarization, PRISM aims to push cosmology and astrophysics into a regime of percent-level to near-foreground-free constraints across cosmic history. The mission promises a transformative legacy data set, enabling robust dark-energy, gravity, and structure formation tests, while also delivering unprecedented insight into star formation, galaxy evolution, and the Galactic interstellar medium. In addition to its core science, PRISM’s design emphasizes cross-calibration and synergy with contemporaneous facilities (Euclid, SKA, SPICA, LSST, DESI), ensuring broad community impact and maximal scientific return.

Abstract

PRISM (Polarized Radiation Imaging and Spectroscopy Mission) was proposed to ESA in May 2013 as a large-class mission for investigating within the framework of the ESA Cosmic Vision program a set of important scientific questions that require high resolution, high sensitivity, full-sky observations of the sky emission at wavelengths ranging from millimeter-wave to the far-infrared. PRISM's main objective is to explore the distant universe, probing cosmic history from very early times until now as well as the structures, distribution of matter, and velocity flows throughout our Hubble volume. PRISM will survey the full sky in a large number of frequency bands in both intensity and polarization and will measure the absolute spectrum of sky emission more than three orders of magnitude better than COBE FIRAS. The aim of this Extended White Paper is to provide a more detailed overview of the highlights of the new science that will be made possible by PRISM

Figures (24)

• Figure 1: Left panel: Lower mass limits for detection of the labeled SZ effects at signal-to-noise $S/N>5$ as a function of redshift. Right panel: The completeness of the detection for all three effects, as a function of mass. Objects more massive than $4 \times 10^{13}M_\odot$ are detected at more than 5$\sigma$ at all redshifts, a limit extending well down into the relatively unexplored group range (red line). PRISM is able to measure peculiar velocities over most of the cluster range, i.e., for $M>2 \times 10^{14}M_\odot$ (dashed blue line), and relativistic effects, giving access to cluster temperature, for the more massive systems (dot-dashed green line), both out to high redshift. Note that in practice, the detection depth will be lower close to the galactic plane, where a fraction of the clusters will inevitably be missed (although this should be only a very small fraction of the total).
• Figure 2: Simulated PRISM observations in 15 broadband channels from 135 to 1150 GHz. The top left map, at 135 GHz, is dominated by CMB temperature anisotropies, and is observed with 3.8' angular resolution. At 1150 GHz (bottom right), the angular resolution is 27" and the emission is dominated by Galactic dust, nearby galaxies, and CIB emission. The thermal SZ emission is sub-dominant at all frequencies.
• Figure 3: Extraction of thermal SZ emission from a set of simulated PRISM maps. Most of the clusters in the original map are clearly visible after separation of the tSZ component with a straightforward multiscale ILC. Hundreds of SZ clusters are detectable on this very small patch (0.025% of sky).
• Figure 4: Cluster constraints on a four parameter fit with $\Omega_{\rm m}$, $\sigma_8$, and dark energy equation-of-state parameters $w_0$ and $w_1$. Note in the top left panel the tight constraints in the $\Omega_{\rm m}$--$\sigma_8$ plane, marginalized over $w_0$ and $w_1$, and in the bottom right panel the constraints in the $w_0$--$w_1$ plane, marginalized over $\Omega_{\rm m}$ and $\sigma_8$, corresponding to a dark energy FoM of 992.
• Figure 5: SEDs of dusty galaxies (left panel) and of AGNs (right panel) at different redshifts compared with estimated $5\sigma$ detection limits (solid black line) taking into account instrumental and confusion noise summed in quadrature. The instrumental noise refers to the full mission, in 1 arcmin. pixels. The $5\sigma$ detection limits allowing for either component are shown by the dotted and the dashed black lines, showing that PRISM is confusion limited above $\approx 150\,$GHz. We have assumed that component separation techniques, extensively validated both on simulations and on real data, can efficiently remove diffuse emissions such as the CMB (that would otherwise dominate the fluctuation field for $\nu\,\hbox{${<\atop\hbox{$\sim$}}$}\, 220\,$GHz) and Galactic emissions. In the left panel, at $z=0.1$ and 0.5 we have plotted the Arp 220 SED scaled to an IR (8--$1000\,\mu$m) luminosity of $10^{12}\,L_\odot$. At $z\ge 1$ we have used the SED of the $z\approx 2.3$ galaxy SMM J2135-0102 scaled to $L_{\rm IR}=10^{13}\,L_\odot$ for $z=1$ and $z=2$, and to $L_{\rm IR}=3\cdot 10^{13}\,L_\odot$Riechers2013 for $z\ge 3$. In the right panel, the solid colored lines represent SEDs of a type-2 QSO (contribution of the host-galaxy subtracted) with $L_{\rm IR}=10^{13}\,L_\odot$ at several redshifts $\ge 2$, while the dashed colored lines show a schematic representation of the SED of the prototype blazar 3C 273 shifted to redshifts from 1 to 5.