fundamental to galaxy evolution, our understanding of it at higher redshifts ($z\gtrsim2$) is extremely limited. IMF studies of strong gravitational lenses at $z>1$ have shown no deviation from Salpeter IMF [@Pettini2000; @Steidel2004; @Quider2009], but quiescent galaxies at $z<1.5$ have shown systematic trends for the IMF with stellar mass [@Navarro2015b]. Using local analogues to $z\sim2$ galaxies, @Navarro2015d finds evidence for an abundance of low mass stars in the early universe.

Understanding the *relic* IMF at high redshift requires populations of quiescent galaxies which are relatively rare at high redshift, extremely long integration times to obtain absorption line/kinematic features, and complicated modelling of stellar absorption line features. Since IMF defines the mass distribution of formed stars at a given time, in the context of understanding the role of IMF in galaxy evolution, it should be investigated *in situ* at an era when most galaxies are in their star forming phase and evolving rapidly to produce large elliptical galaxies found locally. Furthermore, high mass stars are absent in ETGs and therefore star-forming galaxies are imperative to study the high mass end of the IMF. Simulations have shown that $z\sim2$ universe is ideal for such studies [@Hopkins2006]. rest frame optical spectra of high redshift 