The Goldilocks Molecule: H${}_2$ Emission Lines Can Identify Elusive Dwarf AGN

Abstract

We propose using H${}_2$ emission lines as a novel diagnostic to identify dwarf AGN by running photoionization models incorporating active intermediate-mass black holes and using an observed WISE dwarf AGN as a template. Though many dwarf AGN would be incorrectly classified as star-forming if the H${}_2$~2.12~$\mu$m/Br$\gamma$ ratio is used, ratios between H${}_2$ emission lines can reveal active IMBHs in cases where log $n_{\text{H}}\gtrsim 4.0$. This includes the case where $M_{\text{BH}}=10^3{M}_{\odot }$, even though the optical strong lines and NIR coronal lines would likely go undetected. We conclude that H${}_2$ emission lines show promise in detecting the most elusive IMBHs.

arXiv commentAccepted to RNAAS