in the $z\sim4-5$ galaxies but the origin couldn’t be distinguished between a shallow high-mass IMF scenario or a metallicity dependent ionizing spectrum. Using broad-band imaging and SED fitting techniques to infer [H$\alpha$]{} flux has underlying uncertainties from the contamination of other emission lines that fall within the same observed filter (eg., [\[\]]{}, [\[\]]{}) and assumptions of IMF, SFH, metallicity, and dust law of the SED templates.

In this paper we use the MOSFIRE NIR spectra of galaxies obtained as a part of the ZFIRE survey [@Nanayakkara2016] along with multi-band photometric data from the ZFOURGE survey [@Straatman2016] to study the high-mass IMF of a mass complete sample of star-forming galaxies at $z\sim2$. MOSFIRE spectra has higher resolution and is able to probe into redder wavelengths (up to K band) compared to *Hubble Space Telescope (HST)* grism spectra [eg., @Zeimann2014], thus allows us to detect clear [H$\alpha$]{} nebular emissions up to $z\sim2.7$. Galaxies follow nearly the same locus in [H$\alpha$]{} EW, optical colour as long as their SFHs are smoothly increasing or decreasing [@Kennicutt1983] and we show this in later figures. The change in galaxy evolutionary tracks due to IMF is largely orthogonal to the changes in tracks due to effects of 