The optimally-sampled galaxy-wide stellar initial mass function - Observational tests and the publicly available GalIMF code

Abstract

Here we present a full description of the integrated galaxy-wide initial mass function (IGIMF) theory in terms of the optimal sampling and compare it with available observations. Optimal sampling is the method we use to discretize the IMF into stellar masses deterministically. Evidence has been indicating that nature may be closer to deterministic sampling as observations suggest a smaller scatter of various relevant observables than random sampling would give, which may result from a high level of self-regulation during the star formation process. The variation of the IGIMFs under various assumptions are documented. The results of the IGIMF theory are consistent with the empirical relation between the total mass of a star cluster and the mass of its most massive star, and the empirical relation between a galaxy's star formation rate (SFR) and the mass of its most massive cluster. Particularly, we note a natural agreement with the empirical relation between the IMF's power-law index and a galaxy's SFR. The IGIMF also results in a relation between the galaxy's SFR and the mass of its most massive star such that, if there were no binaries, galaxies with SFR $<10^{-4}$ M${}_{\odot }$/yr should host no Type II supernova events. In addition, a specific list of initial stellar masses can be useful in numerical simulations of stellar systems. For the first time, we show optimally-sampled galaxy-wide IMFs (OSGIMF) which mimics the IGIMF with an additional serrated feature. Finally, A Python module, GalIMF, is provided allowing the calculation of the IGIMF and OSGIMF in dependence on the galaxy-wide SFR and metallicity.

15 pages, 15 figures, A&A, in press; paper remains unchanged (version1 equals version2); the GalIMF module is downloadable at github

References in corpus (17)

• The present-day star formation rate of the Milky-Way determined from Spitzer detected young stellar objects
• Galaxies as simple dynamical systems: observational data disfavor dark matter and stochastic star formation
• From star clusters to dwarf galaxies: The properties of dynamically hot stellar systems
• Converting H$\alpha$ Luminosities into Star Formation Rates
• Diverging UV and Halpha fluxes of star forming galaxies predicted by the IGIMF theory
• Short GMC lifetimes: an observational estimate with the PdBI Arcsecond Whirlpool Survey (PAWS)
• APOGEE Chemical Abundances of the Sagittarius Dwarf Galaxy
• The Origin of the Arches Stellar Cluster Mass Function
• Pismis 24-1: The Stellar Upper Mass Limit Preserved
• Characterizing the Brown Dwarf Formation Channels from the Initial Mass Function and Binary-star Dynamics
• Star formation triggered by galaxy interactions in modified gravity
• Stellar clusterings around "Isolated" Massive YSOs in the LMC
• The chemical evolution of galaxies with a variable IGIMF
• Towards a fully consistent Milky Way disc model - III. Constraining the initial mass function
• Sampling methods for stellar masses and the mmax-Mecl relation in the starburst dwarf galaxy NGC 4214
• The initial mass function and star formation law in the outer disc of NGC 2915
• On the origin of the Schechter-like mass function of young star clusters in disk galaxies

Cited by in corpus (2)

• The Star Forming Main Sequence of Dwarf Low Surface Brightness Galaxies
• The formation of UCDs and massive GCs: Quasar-like objects for testing for a variable stellar initial mass function (IMF)