Galactic-Field Initial Mass Functions of Massive Stars

By Pavel Kroupa, C. Weidner. 2003

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Over the past years observations of young and populous star clusters have shown that the stellar initial mass function (IMF) appears to be an invariant featureless Salpeter power law with an exponent α = 2.35 for stars more massive than a few M☉. A consensus has also emerged that most, if not all, stars form in stellar groups and star clusters and that the mass function of young star clusters in the solar neighborhood and in interacting galaxies can be described, over the mass range of a few 10 to 107 M☉, as a power law with an exponent β ≈ 2. These two results imply that galactic-field IMFs for early-type stars cannot, under any circumstances, be a Salpeter power law, but that they must have a steeper exponent, αfield ≳ 2.8. This has important consequences for the distribution of stellar remnants and for the chemodynamical and photometric evolution of galaxies.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/a7d12a93877c380b11f7cd1db2fcbcaa947da601

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Citations in the corpus

The ATLAS3D project – XX. Mass–size and mass–σ distributions of early-type galaxies: bulge fraction drives kinematics, mass-to-light ratio, molecular gas fraction and stellar initial mass function (2012, background): “As pointed out by Kroupa & Weidner (2003), even if the IMF was universal in every cluster in a galaxy, the integrated galactic IMF would be different from the universal one, due to the non-uniform mass distribution of star clusters (see Kroupa et al. 2013 for an in-depth discussion).”
A HIGHLY CONSISTENT FRAMEWORK FOR THE EVOLUTION OF THE STAR-FORMING “MAIN SEQUENCE” FROM z ∼ 0–6 (2014, background): “…,ΩΛ) = (0.7, 0.3, 0.7) Wilkinson Microwave Anisotropy Probe (WMAP) concordance cosmology (Spergel et al. 2003), AB magnitudes (Oke & Gunn 1983), a Kroupa (Kroupa 2001; Kroupa & Weidner 2003) IMF (integrated from 0.1 – 100M⊙), KE12 L –ψ relations7, and Bruzual & Charlot (2003) (BC03) SPS models.”
DOUBLE COMPACT OBJECTS. II. COSMOLOGICAL MERGER RATES (2013, methodology): “The mass of the primary component is randomly chosen from the initial mass function adopted from Kroupa et al. (1993) and Kroupa & Weidner (2003): Ψ(M1) ∝ ⎧⎨ ⎩ M−1.31 0.08 M M1 < 0.5 M M−2.21 0.5 M M1 < 1.0 M M−α1 1.0 M M1 < 150 M , (8) where α = 2.7 is our standard choice for field populations.”
A Universal Stellar Initial Mass Function? A critical look at variations in extreme environments (2010, background): “This rather small difference in β has a significant effect on whether or not the IMF and IGIMF are the same (Kroupa & Weidner 2003; Elmegreen 2006).”
Gravitational waves from scattering of stellar-mass black holes in galactic nuclei (2008, methodology): “Paumard et al. (2006) found that the stars in an apparent disc around Sgr A* are best fit with a flattened IMF ∝ m−βimf with β imf ≈ 0.85–1.35 and a depletion of low-mass stars.”
Merging binary black holes formed through chemically homogeneous evolution in short-period stellar binaries (2015, background): “• fmass When drawing from the Kroupa initial mass function (IMF), ∼ 0.03% of primary stars have a mass above 60M , where a significant window exists for chemically homogeneous evolution in binaries (see Figure 2).”
(Star)bursts of FIRE: observational signatures of bursty star formation in galaxies (2015, background): “In our simulations, these effects are caused mostly by bursty star formation without accounting for IMF variations (as done in Kroupa & Weidner 2003; Weidner & Kroupa 2005) or stochastic IMF sampling.”
TOWARD A UNIFICATION OF STAR FORMATION RATE DETERMINATIONS IN THE MILKY WAY AND OTHER GALAXIES (2011, methodology): “A SN rate of 0.85 events per century is expected for a SFR of 1 M⊙ yr −1, assuming a Kroupa IMF and a SN progenitor mass range of 10–100 M⊙ (calculated using Starburst99 models with the parameters discussed in §2).”
The stellar and sub-stellar IMF of simple and composite populations (2011, methodology): “The semi-analytical calculation of the mmax −Mecl relation by Kroupa & Weidner (2003) and Weidner et al. (2010) is less accurate by not including the correction term mmax.”
Evidence for top-heavy stellar initial mass functions with increasing density and decreasing metallicity (2012, background): “3) has been made use of in Weidner et al. (2011) to include the evidence for a systematically varying IMF into the framework of the theory of the integrated galactic IMF (IGIMF, i.e. the stellar IMF of whole galaxies, Kroupa & Weidner 2003; Weidner & Kroupa 2005).”
MISSING BLACK HOLES UNVEIL THE SUPERNOVA EXPLOSION MECHANISM (2011, background): “As expected, both the rapid and delayed models are dominated by neutron star X-ray binaries (remnants with mass smaller than 2 M⊙), as stars forming these remnants are more abundant than the more massive progenitors of black holes (e.g., Kroupa & Weidner 2003).”
The relation between the most-massive star and its parental star cluster mass (2009, background): “7 The IGIMF concept is discussed in great detail in Kroupa & Weidner (2003) and Weidner & Kroupa (2005) and subsequent papers.”
Radial variations in the stellar initial mass function of early-type galaxies (2014, background): “For a given IMF, the bestfitting parameters are the age and metallicity of the SSP, as well as the polynomial coefficients.”
The RMS survey : Galactic distribution of massive star formation (2013, background): “Furthermore, this suggests that the initial mass function (IMF) is not constant on all scales and supports the cluster-based IMF model (e.g. Kroupa & Weidner 2003).”
A GALEX ULTRAVIOLET IMAGING SURVEY OF GALAXIES IN THE LOCAL VOLUME (2010, background): “Briefly, in the “integrated galactic stellar initial mass function” (IGIMF; Kroupa & Weidner 2003; Weidner & Kroupa 2005, 2006), it is assumed that: (i) all stars form in clusters; (ii) the maximum mass of a star formed in a cluster is a deterministic function of the cluster mass, and this maximum…”
Runaway collisions in young star clusters - II. Numerical results (2005, methodology): “Although this is actually an effective IMF for stars forming the Galactic field, with clusters probably having a Salpeter-like IMF beyond 1M⊙ (Kroupa & Weidner 2003; Weidner & Kroupa 2004), c© 2005 RAS, MNRAS 000, 1–21 we used it in order to investigate the possible effects of a smaller fraction of…”
DUST-CORRECTED STAR FORMATION RATES OF GALAXIES. II. COMBINATIONS OF ULTRAVIOLET AND INFRARED TRACERS (2011, methodology): “The average ratio of the TIR/NUV-corrected NUV luminosity to the Balmer-corrected Hα luminosity is consistent with that expected for a constant star formation history over ≥ 1 Gyr for a Kroupa IMF.”
A z = 0 Multiwavelength Galaxy Synthesis. I. A WISE and GALEX Atlas of Local Galaxies (2019, methodology): “They adopt the stellar initial mass function (IMF) of Kroupa & Weidner (2003) with bounds of 0.1 and 100 M , slope −2.35 between 1 and 100 M , and slope −1.3 between 0.1 and 1 M .”
DOUBLE COMPACT OBJECTS. I. THE SIGNIFICANCE OF THE COMMON ENVELOPE ON MERGER RATES (2012, methodology): “The mass of the primary component is randomly chosen from the initial mass function adopted from Kroupa et al. (1993), and Kroupa & Weidner (2003), Ψ(M1) ∝”
The Baryonic Tully-Fisher Relation of Galaxies with Extended Rotation Curves and the Stellar Mass of Rotating Galaxies (2005, background): “The zero points a of the models are dominated by the choice of IMF, which is fortuitously close (Kroupa & Weidner 2003).”