Tuesday

There is currently a hot debate on the ever-green question of the universality of the stellar initial mass function (IMF) in galaxies. The IMF is a crucial player in galaxy evolution: it strongly influences feedback and the chemical enrichment in galaxies.The determination of the IMF from integrated galaxy spectra exploits a few spectral absorption in the near-IR (NaI, CaT, FeH), which are sensitive to the ratio of dwarf to giant stars. A striking recent result finds that the most massive galaxies seem to host a bottom-heavy IMF, with a large fraction of low-mass stars (below 0.5 Msol). This result, if confirmed, has the potential to modify our view of galaxy formation and evolution on cosmological timescales.

Here we present results on the radial variation of the IMF in galaxies of various masses, using data from the IFU survey SDSS-IV/MaNGA. Trends with galaxy radius and mass were compared to stellar population models for a range of absorption features in order to separate out degeneracies due to changes in stellar population parameters, such as age and metallicity, with potential changes in the IMF. In particular, we also consider the effect of specific elements, e.g. Sodium, Calcium and Iron, on the aforementioned lines. I will present our results for 600 galaxies and discuss the implications for galaxy formation.