Sub-arcsecond far-infrared observatory

1. Sub-arcsecond far-infrared observatory • A science imperative

2. Frank Helmich Principal Investigator for Herschel/HIFI Head of SRON´s Low Energy Astrophysics Division in Groningen, the Netherlands Co-writer of the FIR white paper (2013)

3. An initiative with world-wide support A shortened version of the presentation given by Marc Sauvage at the L2/L3 presentations in Paris • This white paper received support from ~300 scientists, representing 100+ institutes in 20 countries. • A wide geographical diversity (AT, AU, BE, CA, CH, CL, CZ, DE, DK, ES, FR, GB, GR, IE, IT, NL, PT, SE, US, ZA). • A wide range of scientific endeavors (ISM chemistry, dust physics, star formation, galaxy evolution...)

4. The Far-Infrared (FIR) imperative The cosmic background as a function of frequency • About half of all the photons we can collect about any object that existed in the Universe is in the mid to far infrared (25-500µm). • The FIR reveals the cold and dense universe: • Star and planetary system formation, • Galaxy evolution, • The rich interaction between chemistry and physical processes. • The years to come will see continuous progress, but key questions will remain open until a facility such as the one proposed here is available: Evolution of proto-planetary disks and planet formation The intricate co-evolut ion of AGNs and their hosts Star formation at the high-mass end of the mass function These are significant elements of the Cosmic Vision agenda

5. SPICA SPICA will bridge the gap in sensitivity, but its mirror will be the same size as Herschel The sub-arcsecond imperative • The FIR gap: • 1" is a critical scale to build appropriate paradigms for: • planet formation and habitability, • star formation, • galaxy evolution.

6. FIR-specific diagnostics and spectral resolution M82 • The power of FIR astronomy lies in the combination of imaging and spectroscopy: • Medium to high resolution: solid state features (dust grains and ices), bright atomic and molecular cooling lines. • High to very high resolution: molecular features, gas kinematics as a proxy for 3D information. The Galactic Center L1448

7. Evolution of proto-planetary disks and planet formation The intricate co-evolution of AGNs and their hosts Science enabled by a sub-arcsecond FIR observatory Star formation at the high-mass end of the mass function

8. Evolution of proto-planetary disks and planet formation

9. Gas mass in disks, the reservoir for planets • Timescale transition from a gas-rich to a gas-poor disk ~a few 106 years. • This is the timespan for planet formation. • Typical spatial scale ~100 AU. • We need radial mapping of the gas content to build a consistent planet formation scenario (e.g. deficit of massive disks w.r.t. extrasolar gas giants). • How can the gas mass best be traced? • Dust mass (resolved e.g. by ALMA) suffers from large uncertainties due to temperature, emissivity, size distribution, gas-to-dust ratio. • A slew of FIR lines that can faithfully trace the gas mass • Submm CO lines suffer from optical thickness, freeze out, or ambiguity issues. • HD (37, 56, 112 µm), traces H2 accurately (lower abundance but much more emissive). • Order of magnitude level uncertainties on disk density profiles. • Combine with fine structure lines (e.g. [OI]63µm, the brightest line in disks) for a complementary view of the gas mass. Unique to FIR SPICA can detect but not spatially resolve HD emission TW Hydrae

10. Water: a vital question... TW Hydrae • We want to understand the formation of habitable planets: • Identification of "habitable" systems is a fundamental driver for exo-planet research. • Water is key to understand the conditions of their emergence. • Water can only be studied from space: • Vapor lines are in the FIR, more than one is needed to access the associated physics and chemistry. • e.g. Ortho/para ratio measure coupling with dust. • FIR ice features (44, 62 µm) trace the formation scenario for ice in disks (crystaline/amorphous). • unbiased access contrary to MIR features. • Tracing multiple water phases leads to better understanding of mechanisms for its transport/delivery through the disk. 269 µm 538 µm Important water lines fall outside the SPICA range

11. The dust mass and composition in disks Forsterite feature • Observing at the dust thermal peak has a huge impact on the column densities that can be detected (100+ times better than ALMA). • More accurate temperature, thus mass, determination, especially with analysis of solid state features (e.g. Forsterite, 69 µm). • Compare with JWST and ALMA images to provide a comprehensive view of grains of all sizes (understand processing of solids in disk). • Use high angular resolution to identify structures in the dust disks, telltale signs of planets. • Also traces well the evolution of disk beyond the planet formation phase. • Connect the Solar system with its siblings using SPICA's study of the Kuiper and Asteroid belts. Fomalhaut - 7.7pc - 70µm Herschel This mission

12. The intricate co-evolution of AGNs and their hosts

13. Our nearest AGN, the Galactic Center • At 8.5kpc, SgrA* is a unique object to understand active nuclei. • 1" is ~ 0.05pc while central cavity ~1.5pc. • in the GC, star formation and accretion contribute to the power output. • The FIR spectrum is incredibly rich: • CO up to J=30-29 in the circumnuclear disk, to discriminate between heating sources. • Fine structure lines ([OIII], [OI], [CII], [NIII], [NII]) to characterize the ISRF. • Rich variety of key molecular diagnostics (CO, H2O, HCN,...) to trace density, temperature, and cosmic-ray ionization rate. The FIR has all the diagnostics to understand how accretion and star formation contribute to the emitted power, with angular details that will never be accessible on nearby AGNs.

14. AGNs of the Local Universe • Within the Local Universe we will be able to access most of the AGN components. • Unique tracers to reveal the complex physics at work: • Benefit from high spatial resolution Galactic Center studies. • Molecular lines to probe for outflow motions and measure entrained mass: • Estimate potential impact on the host, in particular with respect to quenching. Mrk 231 CO SLED Dv [km.s-1] We can have a complete mapping of all the physical tracers describing accretion and ejection processes in the AGN

15. Star formation rate Resolve the controversy re. dropping star formation rates at the peak of AGN luminosity 1<z<3 AGN luminosity ~ accretion rate Disentangling the AGN/host co-evolution • z=1-3: period of most vigorous activity. • sub-arcsecond@FIR is vital re. the relative importance of accretion and star formation. • MIR diagnostics are lost to JWST at z≥1, and FIR diagnostics fall in the ALMA bands at z≥3. • Free of the confusion limit, accurate flux measurement can be obtained. • FIR is a more promising domain for the identification of galaxies with AGNs. • Complete census of AGNs, including deeply embedded ones escaping X-ray surveys. • Combine spectroscopic information with angular resolution to confirm object's nature. Build accretion and star formation luminosity functions over the z = 1-3 period.

16. Star formation at the high-mass end

17. ? ? ? ? ? Gravity Turbulence M 16 70μm, 160μm, 250μm DR 21 Structuring and feedback processes • Herschel result: the IMF is in place when high density structure is imprinted in molecular clouds. • Trouble at the high mass end: filaments need to accumulate significant mass beyond linear gravitational instabitility threshold (150 M⊙/pc2). • Massive star-forming regions show clearly how the structure is impacted by feedback. • Progress requires: • Accurate mass tracers, i.e. dust mapped at the peak of thermal emission. • Resolving structures (~0.1pc) in regions forming massive stars (~5kpc away at least). • Capacity to map significant areas. • Spectroscopic signatures to understand the dynamics. ALMA will massive proto-stellar candidates, we explore the origin of scaling laws connecting the local star formation process to the global galactic properties

18. Envelope, broad and narrow outflow, foreground cloud components in IRAS 16272 Highlighting star forming regions with water • Water is one of the most abundant specie in the ISM and acts as a coolant of collapsing interstellar clouds. • The great sensitivity of water abundance to gas temperature (>CO) highlights regions where high-mass star formation occurs. • Need to combine high angular resolution with high spectral resolution to overcome current ambiguities due to the large beams. • H2O abundance surprisingly low in hot cores. • Complementary diagnostics using ortho/para ratio, H2O+ (all FIR) or H218O (ALMA). Water results from a very rich chemical network. Its abundance and properties are powerful probe of the structure and evolutionary stage of massive protostars

19. Mission concepts that will enable this science

20. Three concepts for a FIR observatory

21. Feasibility for an L-Class envelope

22. AGN/host at high-z Gas mass in disks FIRIT High angular resolution Single R~3000 imaging spectrometer local AGNs Dust structures in disks Galactic center SF feedback processes Water in disks Star formation scaling laws Water in star forming regions Higher angular resolution Single R~106 imaging spectrometer lower (<1") angular resolution Mapping telescope ESPRIT TALC The "trade space" Progress to an L-class mission implies investing in trade-off studies between the different concepts The FIR community has identified a series of concepts that can implement significant elements of its science agenda

23. Breaking the arcsecond barrier in the FIR will let us access critical information that isabsolutely vitalto tackle key sectors of the Cosmic Vision program: • Proto-planetary disk evolution, planet formation and the development of habitable conditions on planets. • The complex interplay between a massive black hole and its host, over most of the evolutionary sequence of galaxies. • The mechanisms that trigger and regulate the formation of massive stars, in our Galaxy and beyond. • Significant technological research and developments have already taken place that show that we are in a position to implement a mission that can deliver on these goals in the L2/L3 timeframe after SPICA • I showed the European view. Here in Asia it would be good to discuss with you the Asian point of view(s) and seek the collaboration Conclusions