Galaxy-wide IMF grids

For a galaxy with metallicity [Fe/H]<0 and SFR>1 M_{sun}_/yr, which is a common condition in the early Universe, we find that the gwIMF is both bottom light (relatively fewer low-mass stars) and top heavy (more massive stars), when compared to the canonical IMF. For a SFR<1M_{sun}/yr the gwIMF becomes top light regardless of the metallicity. For metallicities [Fe/H]>0 the gwIMF can become bottom heavy regardless of the SFR.

The IGIMF models predict that massive elliptical galaxies should have formed with a gwIMF that is top heavy within the first few hundred Myr of the life of the galaxy and that it evolves into a bottom heavy gwIMF in the metal-enriched galactic centre. Using the gwIMF grids, we study the SFR-H{alpha}relation and its dependency on metallicity and the SFR. We also study the correction factors to the Kennicutt SFRK-H{alpha} relation and provide new fitting functions.

Late-type dwarf galaxies show significantly higher SFRs with respect to Kennicutt SFRs, while star-forming massive galaxies have significantly lower SFRs than hitherto thought. This has implications for gas-consumption timescales and for the main sequence of galaxies. We explicitly discuss Leo P and ultra-faint dwarf galaxies.