J/A+A/620/A39 Galaxy-wide IMF grids (Jerabkova+, 2018)
Impact of metallicity and star formation rate on the time-dependent
galaxy-wide stellar initial mass function .
Jerabkova T., Zonoozi A.H., Kroupa P., Beccari G., Yan Z., Vazdekis A.,
Zhang Z.-Y.
<Astron. Astrophys. 620, A39 (2018)>
=2018A&A...620A..39J 2018A&A...620A..39J (SIMBAD/NED BibCode)
ADC_Keywords: Models ; Stars, masses ; Abundances, [Fe/H] ; Star Forming Region
Keywords: galaxies: stellar content -
stars: luminosity function, mass function -
galaxies: elliptical and lenticular, cD - galaxies: star formation -
galaxies: dwarfs - stars: formation
Abstract:
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. For a galaxy with metallicity
[Fe/H]<0 and SFR>1 M☉/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_☉/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-Hαrelation 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.
Description:
Theoretical computation of the galaxy-wide initial mass function.
The computations are based on the code published by Yan, Jerabkova and
Kroupa, 2017A&A...607A.126Y 2017A&A...607A.126Y, Cat. J/A+A/607/A126.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
grid.dat 59 90000 IGIMF grid
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See also:
J/A+A/607/A126 : GalIMF version 1.0.0 (Yan+, 2017)
Byte-by-byte Description of file: grid.dat
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Bytes Format Units Label Explanations
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1- 12 F12.5 Msun/yr SFR [0.00001/100000] Value of the SFR for which
the galaxy-wide IMF is computed
14- 15 I2 ---- [Fe/H] [-2/1] Value of metallicity for which the
galaxy-wide IMF is computed
17- 26 F10.5 Msun Mstar [0.08/150] Stellar mass (mass bin)
29- 37 F9.5 Msun-1 IGIMF1 Number of stars in mass bins (dN/dm)
normalized to one solar mass with IGIMF1
40- 48 F9.5 Msun-1 IGIMF2 Number of stars in mass bins (dN/dm)
normalized to one solar mass with IGIMF2
51- 59 F9.5 Msun-1 IGIMF3 Number of stars in mass bins (dN/dm)
normalized to one solar mass with IGIMF3
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Acknowledgements:
Tereza Jerabkova, tjerabko(at)eso.org
(End) Patricia Vannier [CDS] 23-Nov-2018