A tight N/O-potential relation in star-forming galaxies

We report a significantly tighter trend between gaseous N/O and $M_*/R_e$ (a proxy for gravitational potential) than has previously been reported between gaseous metallicity and $M_*/R_e$, for star-forming galaxies in the MaNGA survey. We argue this result to be a consequence of deeper potential wells conferring greater resistance to metal outflows while also being associated with earlier star-formation histories, combined with N/O being comparatively unaffected by metal-poor inflows. The potential-N/O relation thus appears to be both more resistant to short-timescale baryonic processes and also more reflective of a galaxy's chemical evolution state, when compared to previously-considered relations.