Splinter Meeting CosmicRays
Impact of Cosmic Rays on the Physics and Chemistry of Dense Molecular Gas
Time: Monday September 13, 09:00-13:00
Room: virtual Cosmic
Convenor(s): Brandt Gaches , Thomas Bisbas , Alexei Ivlev , Andrew Strong 
 Uni Köln,  MPE
Cosmic rays (CRs) are energetic charged particles that are accelerated in extreme environments. In dense molecular gas that is shielded from external UV radiation, the ionization of atoms and molecules by CRs plays a crucial role in driving chemical and physical processes
as well as in affecting the emission of ionic, atomic and molecular lines. At high column densities, CRs ionize H2 initiating a diverse chemistry through fast ion-neutral reactions. The
interaction of CRs with the dense gas induces UV photons via H2 electronic excitation. These influence the chemistry in icy grain mantles, as does the deposition of energy by direct CR
bombardment. In chemical models, the above processes are controlled by the so-called “cosmic-ray ionization rate”, ζ, making it one of the most important parameters for the underlying
physics and chemistry of dense gas. In molecular clouds, ζ is most sensitive to the flux of low-energy CRs (1–100 MeV). However, the transport of low-energy CRs through dense gas is poorly constrained, and estimates of ζ in such regions are highly uncertain. Furthermore, recent
observations in dense cores suggest a conflict with current cosmic-ray transport models.
Therefore, understanding both the transport of CRs and the chemistry they drive is vital. During this splinter session, we will bring together researchers across a range of communities, including astrochemists and cosmic-ray transport modellers. These communities do not often meet together, despite how intertwined the research can be. We will focus on talks by junior
researchers and develop an interdisciplinary session. We anticipate a fruitful discussion which will help the astrochemical, star formation and high-energy astrophysics communities.
Important questions that will be discussed during this session will be:
What is the impact of cosmic-rays on gas- and ice-phase chemistry, particularly in regions with high cosmic-ray ionization rates?
What are the best observations and calibrations to constrain the cosmic-ray ionization rate?
How do low-energy cosmic rays transport through dense molecular gas? What observations need to be done to constrain this?
Is there an observable correlation between the star-formation rate and the cosmic-ray ionization rate?
Looking forward: what kinds of observational facilities and instruments and theoretical models are needed to constrain the transport of low-energy cosmic rays and the cosmic-ray ionization rate in dense gas?
Monday September 13, 09:00-13:00
Impact of Cosmic Rays on the Physics and Chemistry of Dense Molecular Gas (virtual Cosmic)