The publication is the result of five years of work, which includes theoretical development, observation proposals and collection of vital data for the result obtained, which corroborates previous theories on the propagation of cosmic rays in the interstellar medium.
Communications UdeC.- Through an article in The Astrophysical Journal Letters on April 10, 2023, Dr. Stefano Bovino, an academic from the UdeC Department of Astronomy and CATA researcher, shared the results of a frontier study on ionization rates in star-forming zones. .
“First ALMA Maps of Cosmic-Ray Ionization Rate in High-mass Star-forming Regions” is the title of the scientific publication, which also features the work of astronomers Giovanni Sabatini and Elena Redaelli, from the Istituto Nazionale di Astrofisica in Italy and the Max Planck Institute for Extraterrestrial Physics in Germany, respectively.
This study, which is based on data obtained from ALMA observations in 2021, would validate previous theories on the propagation of cosmic rays in star-forming zones.
Furthermore, the results suggest that the ionization rates in these zones depend on global factors in the environment where the nuclei are formed, and not local ones.
“Cosmic rays are high-energy particles. When light enters molecular clouds, they encounter “walls” of dust that block the light, so these Ionization processes do not exist because photons cannot pass through, but cosmic rays do, colliding with the gas and ionizing molecules and atoms in dense clouds where stars form, starting a chain of fundamental chemical reactions in astrochemistry”, explained the astronomer.
The importance of this process resides in the fact that all the chemistry of these regions occurs thanks to the action of cosmic rays and molecules and atoms, forming over time the essential components for life.
For example, cosmic rays are essential for the fractionation process that leads to D/H enrichment in water, important for understanding the origin of the oceans on Earth.
“That is the motivation for the study, because they are fundamental aspects to understand the chemistry of star-forming regions, which in turn is connected to the formation of prebiotic molecules and also to planetary formation.”
The role of ALMA and the mathematical bases of Dr. Stefano
The Atacama Large Millimeter/submillimeter Array (ALMA), an observatory on the Chajnantor plain, in northern Chile, was essential to achieve the results presented in the ApJ Letters paper, since with the data obtained the group of researchers was able to estimate accurately the variation of the ionization rate (how many ionizations of hydrogen molecules performed per second) of cosmic rays in two regions of interest: AG351 and AG354.
In addition, a vital point of the study is found in the methodology, which is based on an analytical formula proposed by the UdeC astronomer in 2020.
“This is based on some works that are 20 or 30 years old. And although the new formula was never used, it is a modification of something pre-existing to apply it in different conditions”, explained Stefano.
Since 2018 the group has been working on this project, first with an observation proposal for ALMA, in which they sought to obtain data on H2D+ (the first deuterated form of the H3+ ion and a fundamental molecule for this study), to complement the studies in 2021 with observations of CO, HCO+ and DCO+. “The mixture of these molecules has allowed us to estimate the rate of ionization” added the astronomer.
“In recent months we have prepared the document for ApJ Letters with the results that are super interesting because they are in line with theoretical forecasts. There is a theoretical model of cosmic ray propagation in the interstellar medium and our data lie on the same curves. This would come to give validity to the theory”.
In the future, they hope to have a broader range of observations, which would allow for better statistical analysis, which could give more validity to the previous theorizing.
