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Current observational facilities have yet to conclusively detect $10^3 - 10^4M_{\odot}$ intermediate mass black holes (IMBHs) that fill in the evolutionarygap between early universe seed black holes and $z \sim 0$ supermassive blackholes. Dwarf galaxies present an opportunity to reveal active IMBHs amidstpersistent star formation. We introduce photoionization simulations tailored toaddress key physical uncertainties: coincident vs. non-coincident mixing ofIMBH and starlight excitation, open vs. closed surrounding gas cloudgeometries, and different AGN SED shapes. We examine possible AGN emission linediagnostics in the optical and mid-IR, and find that the diagnostics are oftendegenerate with respect to the investigated physical uncertainties. In spite ofthese setbacks, and in contrast to recent work, we are able to show that [OIII]/H$\beta$ typically remains bright for dwarf AGN powered by IMBHs down to$10^3 M_{\odot}$. Dwarf AGN are predicted to have inconsistent star-forming andSeyfert/LINER classifications using the most common optical diagnostics. In themid-IR, [O IV] 25.9$\mu$m and [Ar II] 6.98$\mu$m are less sensitive to physicaluncertainties than are optical diagnostics. Based on these emission lines, weprovide several mid-IR emission line diagnostic diagrams with demarcations forseparating starbursts and AGN with varying levels of activity. The diagrams arevalid over a wide range of ionization parameters and metallicities out to$z\sim0.1$, so will prove useful for future JWST observations of local dwarfAGN in the search for IMBHs. We make our photoionization simulation suitefreely available.

Optical and JWST Mid-IR Emission Line Diagnostics for Simultaneous IMBH and Stellar Excitation in z~0 Dwarf Galaxies