Bibcode
Jeřábková, T.; Hasani Zonoozi, A.; Kroupa, P.; Beccari, G.; Yan, Z.; Vazdekis, A.; Zhang, Z.-Y.
Bibliographical reference
Astronomy and Astrophysics, Volume 620, id.A39, 15 pp.
Advertised on:
11
2018
Journal
Citations
108
Refereed citations
101
Description
The stellar initial mass function (IMF) is commonly assumed to be an
invariant probability density distribution function of initial stellar
masses. These initial stellar masses are generally represented by the
canonical IMF, which is defined as the result of one star formation
event in an embedded cluster. As a consequence, the galaxy-wide IMF
(gwIMF) should also be invariant and of the same form as the canonical
IMF; gwIMF is defined as the sum of the IMFs of all star-forming regions
in which embedded clusters form and spawn the galactic field population
of the galaxy. Recent observational and theoretical results challenge
the hypothesis that the gwIMF is invariant. In order to study the
possible reasons for this variation, it is useful to relate the observed
IMF to the gwIMF. Starting with the IMF determined in resolved star
clusters, we apply the IGIMF-theory to calculate a comprehensive grid of
gwIMF models for metallicities, [Fe/H] ∈ (-3, 1), and galaxy-wide
star formation rates (SFRs), SFR ∈ (10-5,
105) M⊙ yr-1. For a galaxy with
metallicity [Fe/H] < 0 and SFR > 1 M⊙
yr-1, 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 < 1 M⊙ yr-1 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-Hα relation and its dependency on metallicity and the SFR.
We also study the correction factors to the Kennicutt SFRK -
Hα 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.
The IGIMF grid is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr
(ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/620/A39
Related projects
Traces of Galaxy Formation: Stellar populations, Dynamics and Morphology
We are a large, diverse, and very active research group aiming to provide a comprehensive picture for the formation of galaxies in the Universe. Rooted in detailed stellar population analysis, we are constantly exploring and developing new tools and ideas to understand how galaxies came to be what we now observe.
Ignacio
Martín Navarro