CLEAR: Emission-line Ratios at Cosmic High Noon

We use Hubble Space Telescope WFC3 G102 and G141 grism spectroscopy to measure rest-optical emission-line ratios of 533 galaxies at $z\sim1.5$ in the CANDELS Ly$\alpha$ Emission Reionization (CLEAR) survey. compare $\frac{[OIII]}{H\beta}$ vs. $\frac{[SII]}{(H\alpha +[NII])}$ as an "unVO87" diagram for 461 $\frac{[OIII]}{Hb}$ $\frac{[NeIII]}{[OII]}$ "OHNO" 91 galaxies. The unVO87 does not effectively separate active galactic nuclei (AGN) $[NeV]$ sources from star-forming galaxies, indicating that properties evolve with redshift overlap AGN signatures $z>1$. OHNO separates X-ray $[NeV]$-emitting rest population. find line are significantly anti-correlated stellar mass correlated $\log(L_{H\beta})$, while is $\log(L_{H\beta})$. Comparison MAPPINGS~V photoionization models indicates these trends consistent lower metallicity higher ionization low-mass high-SFR do evidence evolution outside correlations SFR.Our results suggest will be a useful indicator content gas conditions very high-redshift observed by James Webb Telescope.