IMF at the lower and upper mass end.

IMF studies of ETGs in the local universe infers/has-shown a high abundance of low mass stars [@vanDokkum2010; @Ferreras2013; @LaBarbera2013] with strong evidence for IMF variations as a function of galaxy velocity dispersion [@Cappellari2012; @vanDokkum2012; @Cappellari2013; @Conroy2013b], metallicity [@Navarro2015c] and radial distance within a galaxy [@Navarro2015a]. These results suggest that the IMF of ETGs are most likely to depend on the physical conditions of the galaxy when it formed bulk of its stars. Local star-forming galaxies show evidence for IMF variation as a function of galaxy luminosity [@Schombert1990; @Lee2004; @Hoversten2008; @Meurer2009; @Meurer2011], metallicity [@Rigby2004], and SFR [@Gunawardhana2011]. Comparisons between HI selected low and high surface brightness galaxies have shown the need for a systematic variation of the upper mass cutoff and/or the slope of the IMF to model the far-ultraviolet (far-UV) and [H$\alpha$]{} luminosities [@Meurer2009; @Meurer2011]. [H$\alpha$]{} EW and optical colour analysis of the SDSS [@York2000] data showed that low-luminous galaxies may be deficient in high mass stars [@Hoversten2008], while a similar analysis on the GAMA survey [@Driver2009] showed an excess of high mass stars in high star-forming galaxies [@Gunawardhana2011], both compared to expectations from a Salpeter IMF.

In spite of IMF being 