SPACE: the spectroscopic all-sky cosmic explorer

Abstract

We describe the scientific motivations, the mission concept and the instrumentation of SPACE, a class-M mission proposed for concept study at the first call of the ESA Cosmic-Vision 2015-2025 planning cycle. SPACE aims to produce the largest three-dimensional evolutionary map of the Universe over the past 10 billion years by taking near-IR spectra and measuring redshifts for more than half a billion galaxies at 0 < z < 2 down to AB ∼ 23 over 3π sr of the sky. In addition, SPACE will also target a smaller sky field, performing a deep spectroscopic survey of millions of galaxies to AB ∼ 26 and at 2 < z < 10+. These goals are unreachable with ground-based observations due to the ≈500 times higher sky background (see e.g. Aldering, LBNL report number LBNL-51157, 2001). To achieve the main science objectives, SPACE will use a 1.5 m diameter RitcheyChretien telescope equipped with a set of arrays of Digital Micro-mirror Devices covering a total field of view of 0.4 deg 2 , and will perform large-multiplexing multi-object spectroscopy (e.g. ≈6000 targets per pointing) at a spectral resolution of R∼400 as well as diffraction-limited imaging with continuous coverage from Owing to the depth, redshift range, volume coverage and quality of its spectra, SPACE will reveal with unique sensitivity most of the fundamental cosmological signatures, including the power spectrum of density fluctuations and its turnover. SPACE will also place high accuracy constraints on the dark energy equation of state parameter and its evolution by measuring the baryonic acoustic oscillations imprinted when matter and radiation decoupled, the distanceluminosity relation of cosmological supernovae, the evolution of the cosmic expansion rate, the growth rate of cosmic large-scale structure, and high-z galaxy clusters. The datasets from the SPACE mission will represent a long lasting legacy for the whole astronomical community whose data will be mined for many years to come. Keywords

Anisotropy in the Matter Distribution Beyond the Baryonic Acoustic Oscillation Scale

“…The next generation of large galaxy surveys, like the Panoramic Survey Telescope & Rapid Response System (Pan-STARRS, Kaiser et al 2002), the Dark Energy Survey (DES, The Dark Energy Survey Collaboration 2005), the Baryonic Oscillation Spectroscopic Survey (BOSS, Schlegel et al 2009), BigBOSS (Schlegel et al 2011), the Hobby Eberly Telescope Dark Energy Experiment (HETDEX, Hill et al 2004) and the space based Euclid mission (Cimatti et al 2009), will cover volumes much larger than current datasets, allowing for much more accurate determinations of the BAO.…”

Simulations of Dark Energy Cosmologies

“…Using a density-velocity relation, we provide a cosmology independent formula for generating the velocity power spectrum from the non-linear matter power spectrum. These results are timely and will be relevant for future galaxy redshift surveys such as Euclid and BigBOSS (Cimatti et al, 2009;Schlegel et al, 2007). Current galaxy redshift surveys can provide only very weak constraints on P δ θ and P θ θ (Tegmark et al, 2002) but both BigBOSS and Euclid plan to map the galaxy distribution at higher redshifts and to a greater precision than previously possible.…”

“…For example, ESA's Euclid mission (Cimatti et al, 2009) which plans to survey 20,000 deg 2 with ∆z = 0.1, corresponding to a volume of ∼ 1Gpc 3 at z = 0.1, will be able to constrain the linear growth rate to < 2% and the dark energy equation of state parameters w 0 and w a to 2% and 10% respectively. Our results indicate that using a correct model for the power spectrum in redshift space, a constraint on the linear growth rate of better than 2% for several redshift bins from z = 0 to z = 2, together with an accurate measurement of the expansion history to < 4% would identify variations in Newton's gravitational constant, providing a strong signal that modified gravity describes our Universe.…”

“…eROSITA (extended ROentgen Survey with an Imaging Telescope Array) is a German-French collaboration which aims to detect 50-100 thousand clusters of galaxies at z ∼ 1.3 (Predehl et al, 2006) . The second misson, Euclid (Cimatti et al, 2009), has emerged from combining the Dark Universe Explorer (DUNE) and the SPACE concepts which aim to measure weak lensing and baryonic acoustic oscillations at redshifts 0.5 < z < 2. In Chapter 5…”

Durham optical design of EUCLID, the merged SPACE/DUNE ESA Dark Energy Mission

“…This remains true for the design of the EUCLID spectrograph channel but many of the characteristics are different. A complete description of the SPACE proposal, especially the science drivers, can be found in [4]. Other designs than the Durham design has also been studied; they can be found in [5].…”