Nitrogen is thought to have both primary and secondary origins depending on whether the seed carbon and oxygen are produced by the star itself ( primary ) or already present in the interstellar medium ( secondary ) from which star forms .
Damped Ly \alpha ( DLA ) and sub-DLA systems with typical metallicities of -3.0 \lesssim { Z / Z } _ { \odot } \lesssim - 0.5 are excellent tools to study nitrogen production .
We made a search for nitrogen in the European Southern Observatory ( ESO ) Ultraviolet Visual Echelle Spectrograph ( UVES ) advanced data products ( EUADP ) database .
In the EUADP database , we find 10 new measurements and 9 upper limits of nitrogen .
We further compiled DLA/sub-DLA data from the literature with estimates available of nitrogen and \alpha -elements .
This yields a total of 98 systems , i.e .
the largest nitrogen abundance sample investigated so far .
In agreement with previous studies , we indeed find a bimodal [ N/ \alpha ] behaviour : three-quarter systems show a mean value of [ N/ \alpha ] = -0.87 with a scatter of 0.21 dex and one-quarter shows ratios clustered at [ N/ \alpha ] = -1.43 with a lower dispersion of 0.13 dex .
The high [ N/ \alpha ] group is consistent with the blue compact dwarves and dwarf irregular galaxies , suggesting primary nitrogen production .
The low [ N/ \alpha ] group is the lowest ever observed in any astrophysical site and probably provides an evidence of the primary production by fast rotating massive stars in young sites .
Moreover , we find a transition between the two [ N/ \alpha ] groups around [ N/H ] \simeq - 2.5 .
The transition is not abrupt and there are a few systems lying in the transition region .
Additional observations of DLAs/sub-DLAs below [ N/H ] < -2.5 would provide more clues .