Letters of Intent received in 2016

LoI 2018-1924
Complex Organic Molecules (COMs) in the Universe: Current Understanding and Prospectives

Topics

- COM chemical surveys and new detections.
- COM inventory and spatial distribution in low-mass and high-mass star-forming regions.
- COMs in protoplanetary disks.
- COMs in Solar-system bodies and links to previous phases of star and planet formation.
- Delivery of COMs in (exo)planets and (exo)moons.
- COMs in the near Universe and beyond.
- State-of-the-art chemical codes of COMs: Limitations and improvements.
- COM formation on grain surfaces: Monte Carlo vs Quantum Mechanical calculations.
- COM formation in the gas phase: Kinetic calculations of rate coefficients.
- Laboratory experiments of COM formation: Limitations and improvements.
- Spectroscopy: the bottleneck to understanding COM chemistry.

Rationale

One of the key questions in modern Astronomy is how life appeared on Earth. It is currently believed that the link between the chemistry observed in the interstellar medium (ISM) and life on Earth is given by Complex Organic Molecules (COMs), carbon-based molecular species with more than 6 atoms in their molecular structure. Most of the detections of COMs in the ISM have been reported toward either the central region of our Galaxy, the Galactic Center, or toward hot molecular cores and hot corinos, representative of the early stages of high-mass and low-mass star formation. As a consequence, it has been traditionally assumed that COMs form on the surface of dust grains via hydrogenation and radical-radical reactions in hot environments, as COM formation is favoured by the heating from the central protostar.

In the past decade, new instrumentation has allowed studies of COMs at much higher sensitivity and spectral resolution, and toward a variety of astronomical objects. The results from these studies have shown that COMs are not exclusive of hot sources such as massive hot cores and hot corinos. COMs are indeed detected in meteorites and comets, like in the recent Rosetta mission, and found in nearby galaxies and even in galaxies at red-shifts as high as ~1. Particularly striking is the detection of these complex organics in harsh environments for COM formation such as photon-dominated regions (PDRs), molecular outflows, protoplanetary disks, cold dark cloud cores and pre-stellar cores. The discovery of COMs in cold sources (with temperatures <10 K) has especially challenged our understanding of COM formation since dust temperatures higher than >30 K are needed for heavy molecular radicals to become mobile on grain surfaces and to react forming COMs.

Triggered by these discoveries, the community has made an extraordinary effort to understand the formation of COMs in unfavourable environments such as protoplanetary disks and cold cores. Firstly, large COM surveys have been, or are currently being, carried out at different facilities such as the IRAM 30m telescope, NOEMA, and ALMA, to furnish a complete inventory of COMs in star-forming regions at different evolutionary stages and under different physical conditions. Secondly, theoretical studies have proposed new mechanisms for COM formation, including gas-phase formation, non-canonical chemical explosions, cosmic-ray induced radical diffusion, impulsive spot heating of grains, or radical-radical recombination after H-atom addition/abstraction reactions on grain surfaces. Some of these mechanisms are controversial and their actual efficiency is, in most cases, unconstrained. Thirdly, experimental measurements are currently being performed in the lab as a result of these theoretical work, to provide constraints on the efficiency of these mechanisms, but general consensus does not exist yet.

This IAU Symposium aims at bringing the community together to identify the key limitations in our understanding of COM chemistry and to discuss ideas to overcome those limitations. With the advent of JWST in October 2018, and with ALMA entering its Full Operations phase, this symposium will help us to gaining a complete and detailed view of our current understanding of COM chemistry, and to design an observing plan to best exploit these facilities.
The symposium will last for 3.5 days during the IAU General Assembly in Vienna and will consist of 1hr-long review talks (no more than two per day) and of 20min-long invited and contributed talks. In the afternoon of the first two days, we will have two poster sessions (1.5h-long) and round tables. The round tables will work as brainstorming sessions where experts on the different fields (theoretical, observational and experimental) will discuss the current limitations in their respective disciplines. The topics that will be covered in the symposium are:
- COM chemical surveys and new detections.
- COM inventory and spatial distribution in low-mass and high-mass star-forming regions.
- COMs in protoplanetary disks.
- COMs in Solar-system bodies and links to previous phases of star and planet formation.
- Delivery of COMs in (exo)planets and (exo)moons.
- COMs in the near Universe and beyond.
- State-of-the-art chemical codes of COMs: Limitations and improvements.
- COM formation on grain surfaces: Monte Carlo vs Quantum Mechanical calculations.
- COM formation in the gas phase: Kinetic calculations of rate coefficients.
- Laboratory experiments of COM formation: grain surface and gas-phase reactions.
- Spectroscopy: the bottleneck to understand COM chemistry.