UNIVERSITÄT ZU KÖLN

Oerd Xhemollari

Why Astrochemistry?

Stars are born in vast molecular clouds, where gravity causes dense pockets of gas and dust to collapse. This process, known as star formation, is what shapes the universe as we know it. As these celestial nurseries give birth to new stars, they also serve as unique chemical laboratories, making them a fascinating subject for astrochemistry enthusiasts.

Astrochemistry plays a crucial role in understanding star formation and the evolution of the universe. The chemical composition of molecular clouds directly influences the formation and characteristics of stars and planets. For instance, cosmic rays in star-forming regions can ionize molecular hydrogen, triggering a chain of chemical reactions that produce a variety of complex molecules [1]. These molecules, in turn, affect the cloud's ability to cool and collapse, ultimately impacting the star formation process. Moreover, the study of astrochemistry in star-forming regions provides valuable insights into the origins of the chemical building blocks of life. By examining the molecular inventories of these stellar nurseries, scientists can trace the evolution of chemical complexity from interstellar clouds to planetary systems, potentially shedding light on the conditions that led to life on Earth.

What do we do?

Giant molecular clouds, the birthplaces of massive stars and clusters, contain dense clumps and filamentary structures that serve as crucial nurseries. To understand the channeling of material from parsec scales to individual stars, we aim to characterize key gas properties like density, temperature, and particularly the chemical composition across all scales in molecular clouds.

Here, we present the non-equilibrium abundance of various molecules so far unexplored in 3D Magneto-Hydrodynamic (MHD) simulations. For this, we chemically post-process tracer particles modeled in the SILCC-Zoom simulations [2] with a novel astrochemistry pipeline from Panessa et al. 2023 [3]. These tracer particles have the purpose to trace the conditions around a local area and move with the fluid without interacting with it whatsoever. We use the publicly available, most recent network from the astrochemical database KIDA (with over 8000 reactions and 557 species), in combination with KROME, an astrochemical package that solves the time-dependent evolution (chemical and thermal) of the system.

As preliminary results, we show some of the species that are considered as important when tracing dense gas regions. Our maps (Figure 1) show that N2H+ is quite selective when it comes to highly dense regions, as well as a high abundance of CS very well tracing similar regions. This is exciting since it is also mentioned by recent observations.

Figure 2 displays the number density of N2H+, which in the densest regions appears to be cold.

Thanks to these calculations we can finally look deeper into how long these species last, and therefore understand how long we are able to trace them for in a more realistic manner. Additionally, we can understand how the high density gas is created and is behaving along with the cloud evolution.