Periodic Reporting for period 2 - Chemtrip (The chemical trail in protostars: From the deeply embedded phase to the planet forming disk)
Berichtszeitraum: 2023-03-01 bis 2024-08-31
Solar-type stars form in clouds of gas and dust in the universe. Observations show that Class 0 protostars, which represent the earliest stage of the star formation process, harbour a rich chemistry in their warm inner regions. How the chemistry evolves between this stage and the time when planet, comet and asteroid form is unknown. Do the molecules detected in the young protostars survive, or are they destroyed and reformed at a later stage before being transferred into planets, comets, and asteroids? The objectives of this EU-funded Chemtrip project are to characterize the chemical composition of protostars at different evolutionary stages with high-angular resolution observations and determine the origin(s) of the observed chemical differences with chemical models. The results obtained in this project should provide clues to the formation of our solar system, and consequently lead to a better understanding of our origins.
In the first half of the project, we developed tools that are needed to reach the objectives. These tools help us search for data of interest in the archive of the ALMA observatory, analyze such observations and also produce synthetic observations of protostellar objects. These tools are released publicly, as they present an interest for other researchers in astrochemistry. We also submitted several proposals to obtain observing time with various telescopes and we were very successful. For example, 125 hours were scheduled to observe 11 solar-type protostars at different evolutionary stages and arising from different environments with ALMA. These observations will allow us to answer the questions raised by this project. So far half of the data have been observed and reduced, and their analysis has just started. Other observations were analyzed and published in this project.
Among the main results achieved so far, we detected a molecule called 3-hydroxypropenal (or malonaldehyde, HOCHCHCHO) for the first time in the interstellar medium. It was detected in the warm inner regions of the protostar IRAS 16293-2422. The presence of this molecule was not predicted by astrochemical models. In collaboration with an expert in chemistry, we were able to constrain its formation pathways in star-forming regions.
We also analyzed thoroughly the chemical content of a Class I protostar called L1551 IRS5. This source has probably experienced a luminosity outburst, which would explain its rich organic chemistry. We search for other complex organic molecules in similar sources and detected them for the first time in 3 other protostars of that type. These objects are consequently ideal targets to characterize the chemistry at relatively evolved stages of the star formation process.
The deuterium fractionation of molecules, i.e. the abundance ratio between their deuterated form and their non-deuterated form, provides a wonderful tool to reconstruct the history of star-forming regions. Determining the deuterium fractionation of water in a Class I protostar is challenging since most of these sources are too cold to harbor significant gas phase abundances of water. By focusing on an object that probably experienced a luminosity outburst (L1551 IRS5), we succeeded in determining the HDO/H2O ratio in a Class I protostar. It is similar to the values found for Class 0 protostars, which suggests little variation for water between the Class 0 and Class I stages.
Among the main results achieved so far, we detected a molecule called 3-hydroxypropenal (or malonaldehyde, HOCHCHCHO) for the first time in the interstellar medium. It was detected in the warm inner regions of the protostar IRAS 16293-2422. The presence of this molecule was not predicted by astrochemical models. In collaboration with an expert in chemistry, we were able to constrain its formation pathways in star-forming regions.
We also analyzed thoroughly the chemical content of a Class I protostar called L1551 IRS5. This source has probably experienced a luminosity outburst, which would explain its rich organic chemistry. We search for other complex organic molecules in similar sources and detected them for the first time in 3 other protostars of that type. These objects are consequently ideal targets to characterize the chemistry at relatively evolved stages of the star formation process.
The deuterium fractionation of molecules, i.e. the abundance ratio between their deuterated form and their non-deuterated form, provides a wonderful tool to reconstruct the history of star-forming regions. Determining the deuterium fractionation of water in a Class I protostar is challenging since most of these sources are too cold to harbor significant gas phase abundances of water. By focusing on an object that probably experienced a luminosity outburst (L1551 IRS5), we succeeded in determining the HDO/H2O ratio in a Class I protostar. It is similar to the values found for Class 0 protostars, which suggests little variation for water between the Class 0 and Class I stages.
With all the observations obtained during the first phase of the project, we can now characterize in an unbiased way the chemical content of a significant number of protostars at different evolutionary stages and from various environments. By comparing the chemical abundances of complex organic molecules as well as deuterium fractionation ratios of various molecules in these protostars, we will determine which species show significant differences and which ones have very similar abundances in all sources. With state-of-the-art physicochemical models, we will constrain the possible origins of the differentiations (environment, evolution, ...) and better understand the conditions required for the presence of species with a prebiotic interest in other nascent stellar systems.