Chemistry in regions of star formation (Objectives)
The process of star formation begins with the slow diffusion
of the neutrals with respect to the ions under the influence
of self gravity, which will lead to a gradual loss of the
supporting magnetic field and brings dark cloud cores to the
brink of collapse. The degree of ionization is controlled
by large molecules, which provide efficient neutralization
channels. During the subsequent collapse phase,
cooling by molecular species - specifically HO - is of
key importance in regulating the energy balance of the
surrounding gas and hence the thermal support. In turn, the
newly formed star directly influences the chemical
composition of its environment.
In the dark cloud core, ion-molecule chemistry dominates the
formation of molecules and hence the chemical composition is
directly linked to the degree of ionization. After the star
formation process has commenced, in the warm gas, directly
surrounding the protostar, neutral-neutral reactions convert
simple molecules (such as alcohols) into more complex ones
(such as ethers and esters). The protostar also drives
strong shock waves into its surrounding which affects the
composition of its environment. Observationally, SO, SO
and SiO are known to be indicators of shock activity.
At the same time, far-ultraviolet photons (
the newly formed star break down small molecules into
radicals and ions. At the same time, neutral-neutral
reactions drive the chemistry towards complexity in the
circumstellar disk surrounding the protostar. All of these
processes will influence the chemical reservoir available to
the planets that may form in this environment.
The network will explore all aspects of chemistry in star
forming regions starting from dark cloud cores, through
their slow ambipolar contraction phase, their gravitational
collapse phase, the formation and evolution of a
circumstellar planetary disk, to the eventual disruption of
the cloud by the newly formed star. The network will employ
experimental studies on relevant reactions and their
products, quantum chemical studies, supported by laboratory
studies, on the excitation characteristics of the species
formed this way, and astronomical models including detailed
radiative transfer in these molecular lines.
We anticipate a major breakthrough for the following
- What are the important reactions that affect
the chemical evolution of matter in regions of star
- What is the role of large molecules in the ionization
balance of molecular clouds and how does this influence the
star formation process as well as the chemical composition
of the cloud ?
- What is the role of molecular coolants in the energy
balance of star forming regions and how does that influence
the process of star formation ?
- How do heating by the protostar, strong shocks driven
by protostellar outflows and energetic UV photons from the
newly formed star affect the chemistry of the prenatal
- What are the important spectroscopic chemical
signatures of the different stages of star formation (dark
cloud cores, disks, hot cores, infalling envelopes) ?