Molecular fractionation in star forming regions
ABSTRACT: Fractionation is the substitution of an atom in a molecular compound with one of its isotopes, creating a so-called isotopologue. In the last decades, these processes have raised great interest because they are considered an important diagnostic tool to follow the different phases of star formation, from its early stages up to the planetary disk formation and evolution. In my work, I focus on the fractionation of two among the most abundant elements in the Universe, hydrogen and nitrogen.
Concerning nitrogen fractionation, I will show results regarding the abundant molecular ion diazenylium (N2H+) towards both pre-stellar and proto-stellar low-mass cores. I will show how the 14N/15N isotopic ratio is significantly higher in pre-stellar sources if compared to proto-stellar ones, and I will discuss these findings in the context of the most recent chemical models.
The fractionation of hydrogen is also know as deuteration. I will show our recent, high-sensitivity maps of the rotational transitions of N2H+ and HCO+, obtained using the IRAM 30m telescope. From these data, I have derived reliable values of the molecular column density of each species. I then infer the searched isotopic ratio dividing the rare isotolopogue column density by that of the corresponding main species. The D/H ratios found in N2H+ and HCO+ are 26% and 3.5% respectively at the core centre, and they can be explained by the different chemistry that these two ions exhibit. Finally, I will also discuss the recent observations of the deuterated molecule H2D+ obtained with ALMA towards two high-mass clumps. These data show how deuterated molecules can be an important probe of the early stages of star forming regions.
You can find more information about program, speakers and detailed connection info here:
https://laurabassiseries.inaf.it/
The colloquium will be held online
Daniela Bettoni
