Extreme nitrogen enhancement relative to oxygen, recently found in very high-redshift galaxies, has been seen in local star-forming galaxies displaying high log (N/O) values (\!-1. 1) at relatively low O abundances, 12+log (O/H) 8. Understanding the physical origins of these extreme N-emitters at low redshifts enables us to better constrain chemical enrichment mechanisms that drove such high log (N/O) values in the early Universe. With direct N and O abundances derived for 944 SFGs with spectroscopic observational data from the Dark Energy Spectroscopic Instrument Data Release 1 (DESI DR1), we report the discovery of 19 extreme N-emitters at low-z (z<0. 5). Our sample of N-emitters represents a five-fold increase in their known number at low-z with 12+log (O/H) 8, and statistically, 2. 210. 91\% of DESI DR1 SFGs with reliable O and N abundances obtained directly, are extreme N-emitters. The sample spans a mass range of 10⁷ - 10^10~M_ with 12+log (O/H) range of 7. 1 - 8. 2, and the N-emitter fraction is found to increase with increasing stellar mass and decreasing metallicity. The most extreme N-emitter in our sample has log (N/O) =-0. 530. 13, while also having the lowest 12+log (O/H) =7. 080. 09 and the highest stellar mass, log (M*/M_) =9. 950. 13 among our sample. With galactic chemical evolution models, we show that sustained N-enhancement by asymptotic giant branch stars, in conjunction with presence of outflows, can well explain the high log (N/O) of low-z extreme N-emitters. While single starbursts with outflow are sufficient to explain lower-mass N-emitters, more massive ones require a dual starburst scenario where a secondary starburst is triggered by inflow of gas.
Bhattacharya et al. (Sat,) studied this question.