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We present the results of a narrow-band near-infrared imaging survey forMolecular Hydrogen emission-line Objects (MHOs) toward 26 regions containinghigh-mass protostellar candidates and massive molecular outflows. We havedetected a total of 236 MHOs, 156 of which are new detections, in 22 out of the26 regions. We use H$_2$ 2.12-$\mu$m/H$_2$ 2.25-$\mu$m flux ratios, togetherwith morphology, to separate the signatures of fluorescence associated withphoto-dissociation regions (PDRs) from shocks associated with outflows in orderto identify the MHOs. PDRs have typical low flux ratios of ~ 1.5 - 3, while thevast majority of MHOs display flux ratios typical of C-type shocks (~ 6-20). Afew MHOs exhibit flux ratios consistent with expected values for J-type shocks(~ 3-4), but these are located in regions that may be contaminated withfluorescent emission. Some previously reported MHOs have low flux ratios, andare likely parts of PDRs rather than shocks indicative of outflows. We identifya total of 36 outflows across the 22 target regions where MHOs were detected.In over half these regions, MHO arrangements and fluorescent structures tracefeatures present in CO outflow maps, suggesting the CO emission traces acombination of dynamical effects, which may include gas entrained in expandingPDRs as well as bipolar outflows. Where possible, we link MHO complexes todistinct outflows and identify candidate driving sources.

MHOs toward HMOs: A Search for Molecular Hydrogen emission-line Objects toward High-Mass Outflows