Astrochemical MHD simulations and synthetic observations

A short overview

Stars form in molecular clouds (MCs). However, it is to date still a highly debated question how fast MCs evolve and how fast they form stars. Similar, it is of great interest how much stars they form, in which regions and under which physical and chemical conditions. In C6 we aim to assess the accuracy of observational methods used to answer these questions by direct comparison of (synthetic) obser- vations and simulations. The project is therefore based on three “pillars of experience”: (i) magneto- hydrodynamical (MHD) simulations (ii) astrochemistry (iii) and synthetic observations. We combine these aspects in two work projects which will focus on the early evolution of molecular clouds.

In the first project we will investigate which molecular tracers are suitable to determine the mix of different thermal and chemical phases in MCs via observations. We will study both the effect of different environ- mental conditions and observing conditions. For this purpose, we will produce synthetic observations from 3D-MHD simulations of MC formation performed in project C5 including a chemical network suit- able for the ISM. We will investigate the origin of the [C I] and [C II] emission lines in MCs and simulate the emission of OH, ArH+, HF, and HCl. Based on the outcomes we plan to write an observing proposal for OH in collaboration with observational (A) projects to test the results obtained in this work.

In the second projects we aim to understand whether deuterated molecules can serve as chemical clocks, not only in dense cores but also in the less dense MC itself. We will study in detail the time evolution of the H2 ortho-para-ratio – a crucial parameter for age determination, which is not accessible via direct observations – in dense cores and how accurate age estimates based on this ratio are. For this purpose, we plan to implement a network for deuteration in FLASH and apply it in 3D-MHD simulations of MC formation. The results of this work can thus be used to guide future observations in their search for deuterated molecules.

The project will serve as a pathfinder, which allows us to tighten the connection between theory and observations – within the CRC 956 and beyond. Beside the collaboration with C5, we plan to compare our synthetic observations to actual observations from A3, A4, and A5 and collaborate with B2 on the implementation of the deuteration network.

Selected Publications

• 2022

• Kim, W.-J. and 13 colleagues (including S. Walch) 2022. "HyGAL: Characterizing the Galactic ISM with observations of hydrides and other small molecules II. The absorption line survey with the IRAM 30 m telescope." arXiv e-prints 2212.09334.
• Panessa M., Seifried D., Walch S., Gaches B., Barnes A. T., Bigiel F., Neumann L. 2022. "The evolution of HCO+ in molecular clouds using a novel chemical post-processing algorithm." arXiv e-prints 2210.06251.
• Ebagezio, S., Seifried, D., Walch, S., Nürnberger, P. C., Rathjen, T. E., Naab, T. 2022. "CO and [CII] line emission of molecular clouds – the impact of stellar feedback and non-equilibrium chemistry." arXiv e-prints 2206.06393.
• Seifried D., Beuther H., Walch S., Syed J., Soler J. D., Girichidis P., Wünsch R. 2022. "On the accuracy of H I observations in molecular clouds - More cold H I than thought?." Monthly Notices of the Royal Astronomical Society 512, 4765–4784. doi:10.1093/mnras/stac607
• Jacob, A. M. and 25 colleagues 2022. "HyGAL: Characterizing the Galactic Interstellar Medium with Observations of Hydrides and Other Small Molecules. I. Survey Description and a First Look Toward W3(OH), W3 IRS5, and NGC 7538 IRS1." The Astrophysical Journal 930. doi:10.3847/1538-4357/ac540

• 2021

• Reissl, S., Stutz, A. M., Klessen, R. S., Seifried, D., Walch, S. 2021. "Magnetic fields in star-forming systems - II: Examining dust polarization, the Zeeman effect, and the Faraday rotation measure as magnetic field tracers." Monthly Notices of the Royal Astronomical Society 500, 153–176. doi:10.1093/mnras/staa3148

• 2020

• Seifried, D., Walch, S., Weis, M., Reissl, S., Soler, J. D., Klessen, R. S., Joshi, P.R. 2020. "From parallel to perpendicular - On the orientation of magnetic fields in molecular clouds." Monthly Notices of the Royal Astronomical Society 497, 4196–4212. doi:10.1093/mnras/staa2231
• Seifried, D., Haid, S., Walch, S., Borchert, E. M. A., Bisbas, T. G. 2020. "SILCC-Zoom: H2 and CO-dark gas in molecular clouds - the impact of feedback and magnetic fields." Monthly Notices of the Royal Astronomical Society 492, 1465–1483. doi:10.1093/mnras/stz3563

• 2019

• Seifried, D., Walch, S., Reissl, S., Ibáñez-Mejía, J. C. 2019. "SILCC-Zoom: Polarization and depolarization in molecular clouds." Monthly Notices of the Royal Astronomical Society 482, 2697–2716. doi:10.1093/mnras/sty2831