SPICA—A Large Cryogenic Infrared Space Telescope: Unveiling the Obscured Universe

Abstract

Measurements in the infrared wavelength domain allow us to assess directly the physical state and energy balance of cool matter in space, thus enabling the detailed study of the various processes that govern the formation and early evolution of stars and planetary systems in the Milky Way and of galaxies over cosmic time. Previous infrared missions, from IRAS to Herschel, have revealed a great deal about the obscured Universe, but sensitivity has been limited because up to now it has not been possible to fly a telescope that is both large and cold. Such a facility is essential to address key astrophysical questions, especially concerning galaxy evolution and the development of planetary systems.SPICA is a mission concept aimed at taking the next step in mid-and far-infrared observational capability by combining a large and cold telescope with instruments employing state-of-the-art ultrasensitive detectors. The mission concept foresees a 2.5-meter diameter telescope cooled to below 8 K. Rather than using liquid cryogen, a combination of passive cooling and mechanical coolers will be used to cool both the telescope and the instruments. With cooling not dependent on a limited cryogen supply, the mission lifetime can extend significantly beyond the required three years. The combination of low telescope background and instruments with state-of-the-art detectors means that SPICA can provide a huge advance on the capabilities of previous missions.The SPICA instrument complement offers spectral resolving power ranging from R ∼50 through 11000 in the 17-230 µm domain as well as R ∼28.000 spectroscopy between 12 and 18 µm. Additionally SPICA will be capable of efficient 30-37 µm broad band mapping, and small field spectroscopic and polarimetric imaging in the 100-350 µm range. SPICA will enable far infrared spectroscopy with an unprecedented sensitivity of ∼ 5 × 10 −20 W/m 2 (5σ/1hr) -at least two orders of magnitude improvement over what has been attained to date. With this exceptional leap in performance, new domains in infrared astronomy will become accessible, allowing us, for example, to unravel definitively galaxy evolution and metal production over cosmic time, to study dust formation and evolution from very early epochs onwards, and to trace the formation history of planetary systems.

A New Method to Measure Star Formation Rates in Active Galaxies Using Mid-infrared Neon Emission Lines

“…This can enable, for example, studies of circumnuclear star formation out to z ≈ 0.8. On a longer timescale, the superior sensitivity of the Space Infrared Telescope for Cosmology and Astrophysics (SPICA; Swinyard et al 2009;Egami et al 2018;Roelfsema et al 2018;van der Tak et al 2018) promises even greater reach to the early Universe. For instance, the instantaneous wavelength coverage of 34-230 µm by the SPICA Far Infrared Instrument (SAFARI) in principle can detect the rest-frame mid-IR neon lines in the first-generation galaxies and AGNs.…”

Submillimeter and Far-Infrared Polarimetric Observations of Magnetic Fields in Star-Forming Regions

“…These telescopes would be cooled to ≤6 K, and consequently the instrumental loading would be much lower than that of ground-based or stratospheric polarimeters. The design for the SPICA satellite currently includes a sub-mm polarimeter which would operate at 100, 200, and 350 µm (Gaspar Venancio et al, 2017;Roelfsema et al, 2018), while the Concept-2 design for the proposed Origins Space Telescope includes a Far-infrared Polarimeter (FIP), which would operate in both the far-IR and sub-mm (Staguhn et al, 2018). Both satellites would map hundreds of square degrees, with ∼10 ′′ , at 100 and 250 µm, respectively.…”

The dust mass function from z ∼0 to z ∼2.5

“…Without any clear knowledge of such quantity, all the present studies might be underestimating the cosmic dust budget at high redshift, that could be dominated by the faintest galaxies due to their large abundance, as indicated by optical and UV studies (Alavi et al 2016;Parsa et al 2016), and currently missing from the present sample. A significant step forward in this field might come in the future thanks to the SPICA space mission (Roelfsema et al 2018). With an estimated mid-far IR sensitivity more than an order of magnitude better than Spitzer and Herschel (Gruppioni et al 2017), SPICA will allow us a better characterization of the DMF and hopefully a direct measure of its faint-end slope, potentially with a deep impact on studies of the evolution of the dust mass density at z > 1.…”