The 14N/15N isotopic ratio in protoplanetary disks

Isotopic ratios are commonly used to trace the origin of Solar System bodies. This is a fundamental but still highly debated topic. It is still unclear whether most of the organics are inherited from the protosolar nebula or if they are the result of an active chemistry in the protoplanetary disk phase. Disk-averaged 15N enrichments that are similar to comets have been observed in disks. However, spatially resolved observations of N isotopic ratios are needed to elucidate the origin of these 15N enrichments, and ultimately the origins of organics, across the Solar System. I will present ALMA observations of the HCN isotopologues in the V4046 Sgr protoplanetary disk. Assuming a standard isotopic ratio 12C/13C=70, we infer a disk-averaged isotopic ratio of 14N/15N=140 220 at 100 AU. With new higher-angular resolution (0.2'' = 15 au) observations we derive the radial dependence of 14N/15N within the planet and comet forming region. I will discuss how these results compare with observed 14N/15N values in the ISM and in Solar System bodies, and how we can disentangle between the inheritance and disk chemical processing scenarios