Laura Colzi, que actualmente trabaja en el grupo de Medio Interestelar y Circunestelar del CAB, ha ganado el premio a la mejor tesis doctoral de 2020 en la categoría científica de la Universidad de Florencia con la tesis titulada: “Isotopic fractionation study towards massive star-forming regions across the Galaxy”

Resumen de la tesis:

This Ph.D. thesis studies the chemical journey across our Galaxy, the Milky Way, of the carbon and nitrogen isotopes present in the gas and dust between stars, i.e., in the interstellar medium. An isotope is an atom of the same chemical element but with a different number of neutrons. In nature, the stable isotopes of carbon and nitrogen are ¹²C and ¹⁴N, the most abundant ones, and ¹³C and ¹⁵N, which have an extra neutron.  These elements can be created during the lifetime of stars, as well as during their death, after which they return to the interstellar medium and become part of the dense molecular clouds in which new stars and planets will form.

In this thesis work, the ¹²C/¹³C and ¹⁴N/¹⁵N abundance ratios have been studied towards massive molecular clouds, which are thought to be similar to the environment in which our Sun formed. In particular, by analysing observations obtained with powerful radio telescopes, such as IRAM 30m in the Sierra Nevada in Spain, the most important differences in the production of ¹⁴N and ¹⁵N during the life and formation of stars have been studied. Among the main results, a positive trend of the ¹⁴N/¹⁵N ratio with the Galactocentric distance has been found, and can be explained by an important production of ¹⁵N during the so-called novae explosions. The latter are the process in which low-mass stars belonging to a binary system, together with a red giant, die.

In addition, this thesis has provided important new input on the understanding of local chemical processes, i.e., towards individual molecular clouds, that favour the production of molecules with different isotopes in star-forming regions (e.g., N₂H⁺ e ¹⁵NNH⁺, H¹⁵NC e HN¹³C). Finally, the observations have been compared with astrochemical theoretical models, developed by Dr. Laura Colzi, which led to the understanding of the results obtained by introducing new chemical processes, such as chemical reactions that form and destroy these types of molecules.

Part of the thesis work has been published in peer-reviewed scientific journal such as Astronomy & Astrophysics and Monthly Notices of the Royal Astronomical Society.