The Initial Mass Function, from Top to Bottom

A RAS Specialist Discussion Meeting organised by *R.J. Smith (Durham); R.L. Davies (Oxford); I. Ferreras (UCL); C. Maraston (Portsmouth); D. Thomas (Portsmouth); *russell.smith@durham.ac.uk The stellar initial mass function (IMF) dictates many properties of galaxies: e.g. mass-to-light ratios, Fundamental Plane evolution, compact binary populations, supernova rates, chemical evolution, contribution of massive stars to re-ionisation, etc. Given the relevance of the IMF to so many aspects of astrophysics, it is essential to establish whether the "standard" Chabrier/Kroupa form, inferred from nearby star-forming regions in the Milky Way, can be safely extrapolated to all types of galaxy, of all masses, and at all redshifts, as is commonly assumed. Recent studies of massive early-type galaxies, and of faint dwarf galaxies, have suggested that the IMF can deviate from the standard form, at least in some extra-galactic environments. These claims have stimulated intense debate over the reality and interpretation of the IMF variations, and over their implications for star formation theories and galaxy evolution models. The ongoing IMF universality debate is inherently "multi-layered", spanning a range of astrophysical disciplines, from parsec-scale theories and models of star-formation through to properties of the galaxy population at large. Accordingly, we aim to bring together researchers studying all aspects of the IMF, including star-forming galaxies (where the high-mass end of the IMF is relevant), and resolved stellar systems in and around the Milky Way, as well as tackling the issue of the low-mass IMF in early-type galaxies. SESSION 1 — Chair: Russell Smith
10:30-10:50 A. Renzini (Padova) "Overview and perspectives"
10:50-11:10 C. Conroy (Harvard) "Low mass IMF and spectral synthesis"
11:10-11:25 C. Maraston (Portsmouth) "Stellar population models and the IMF"
11:25-11:40 A. Vazdekis (IAC) "Stellar population models and the IMF"
11:40-12:00 M. Cappellari (Oxford) "Dynamics, lensing and stellar M/L ratios"
12:00-12:10 S. Vaughan (Oxford) "MUSEings on the IMF and stellar population of NGC 1399"
12:10-12:20 T. Parikh (Portsmouth) "The Spatially Resolved IMF in ~400 Early-Type Galaxies"
12:20-12:30 F. La Barbera (INAF-OAC) "Radial constraints on the stellar IMF of early-type
galaxies from optical and NIR spectral features"
12:30-12:40 Morning wrap-up
SESSION 2 — Chair: Roger Davies
13:40-14:00 M. Bate (Exeter) "Origin and theory of the IMF"
14:00-14:20 F. Schneider (Oxford) "IMF (non-)universality from resolved stellar populations"
14:20-14:40 M. Gunawardhana (Leiden) "high-mass end of the IMF from star-forming galaxies"
14:40-14:50 T. Nanayakkara (Leiden) "JWST and priorities for IMF at cosmic-noon"
14:50-15:00 C. de Masi (Trieste) "The effects of the IMF on the chemical evolution of elliptical
galaxies"
15:00-15:10 J. Lian (Portsmouth) "Variations in IMF? Implications from gas and stellar metallicity
of local star-forming galaxies"
15:10-15:20 C. Barber (Leiden) "Implications of a variable IMF on galaxy properties in the EAGLE
simulations"
15:20-15:30 Afternoon wrap-up https://rasimf2017.wordpress.com