No nitrogen fractionation on 600 au scale in the Sun progenitor analogue
  OMC-2 FIR4
  We show the first interferometric maps of the 14N/15N ratio obtained with the
Atacama Large Millimeter Array (ALMA) towards the Solar-like forming
protocluster OMC-2 FIR4. We observed N2H+, 15NNH+, N15NH+ (1-0), and N2D+
(2-1), from which we derive the isotopic ratios 14N/15N and D/H. The target is
one of the closest analogues of the environment in which our Sun may have
formed. The ALMA images, having synthesised beam corresponding to ~600 au, show
that the emission of the less abundant isotopologues is distributed in several
cores of ~10" (i.e. ~0.02~pc or 4000 au) embedded in a more extended N2H+
emission. Overall, our results indicate that: (1) 14N/15N does not change
across the region at core scales, and (2) 14N/15N does not depend on
temperature variations. Our findings also suggest that the 14N/15N variations
found in pristine Solar System objects are likely not inherited from the
protocluster stage, and hence their reason has to be found elsewhere.
