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We investigate the time evolution and spatial variation of the stellar initial mass function (IMF) in star-forming disk galaxies by using chemodynamical simulations with an IMF model depending both on local densities and metallicities…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-12 Kenji Bekki , Gerhardt R. Meurer

The study of young stellar populations has revealed that most stars are in binary or higher order multiple systems. In this study the influence on the stellar initial mass function (IMF) of large quantities of unresolved multiple massive…

Astrophysics · Physics 2009-11-13 C. Weidner , P. Kroupa , T. Maschberger

Recent evidence based independently on spectral line strengths and dynamical modelling point towards a non-universal stellar Initial Mass Function (IMF), probably implying an excess of low-mass stars in elliptical galaxies with a high…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-16 Carsten Weidner , Ignacio Ferreras , Alexandre Vazdekis , Francesco La Barbera

We review computational approaches to understanding the origin of the Initial Mass Function (IMF) during the formation of star clusters. We examine the role of turbulence, gravity and accretion, equations of state, and magnetic fields in…

Solar and Stellar Astrophysics · Physics 2015-05-20 Ralph E. Pudritz

The stellar initial mass function (IMF) of early-type galaxies is the combination of the IMF of the stellar population formed in-situ and that of accreted stellar populations. Using as an observable the effective IMF $\alpha_{IMF}$, defined…

Astrophysics of Galaxies · Physics 2017-01-18 Alessandro Sonnenfeld , Carlo Nipoti , Tommaso Treu

(shortened) In this contribution an average or Galactic-field IMF is defined, stressing that there is evidence for a change in the power-law index at only two masses: near 0.5 Msun and 0.08 Msun. Using this supposed universal IMF, the…

Astrophysics · Physics 2011-09-29 Pavel Kroupa

Analyses of strong gravitational lenses, galaxy-scale kinematics, and absorption line stellar population synthesis (SPS) have all concluded that the stellar initial mass function (IMF) varies within the massive early-type galaxy (ETG)…

Astrophysics of Galaxies · Physics 2017-11-29 Alexa Villaume , Jean Brodie , Charlie Conroy , Aaron J. Romanowsky , Pieter van Dokkum

In this review, we examine the successes and weaknesses of modern low-mass star and brown dwarf theory.(1) We first focus on the mechanical (equation of state) and thermal (atmosphere) properties and on the evolution. We then examine the…

Astrophysics · Physics 2016-08-30 G. Chabrier , I. Baraffe , F. Allard , P. H. Hauschildt

In the solar neighborhood, the Initial Mass Function (IMF) follows is canonically described by the Salpeter power-law slope for the high-mass range. The stellar IMF may directly result from a Core Mass Function (CMF) through accretion,…

Astrophysics of Galaxies · Physics 2026-05-06 B. Thomasson , I. Joncour , E. Moraux , F. Motte , T. Yoo , A. Ginsburg

It is now well-established that the stellar initial mass function (IMF) can be determined from the absorption line spectra of old stellar systems, and this has been used to measure the IMF and its variation across the early-type galaxy…

Astrophysics of Galaxies · Physics 2017-03-22 Charlie Conroy , Pieter van Dokkum , Alexa Villaume

We investigated a volume-limited sample of LAMOST main-sequence stars with masses from 0.25 to 1 $M_{\odot}$ and distances of 150-350 pc to explore how the stellar initial mass function (IMF) varies with metallicity. We corrected the…

Solar and Stellar Astrophysics · Physics 2025-11-07 Dan Qiu , Chao Liu , Jennifer A. Johnson , Jiadong Li , Bo Zhang

It has been shown recently that the dynamical V-band mass-to-light ratios of compact stellar systems with masses from 10^6 to 10^8 Solar masses are not consistent with the predictions from simple stellar population (SSP) models. Top-heavy…

Astrophysics of Galaxies · Physics 2010-02-25 J. Dabringhausen , P. Kroupa , H. Baumgardt

Several independent lines of evidence suggest that the stellar initial mass function (IMF) in early-type galaxies becomes increasingly `bottom-heavy' with increasing galaxy mass and/or velocity dispersion, sigma. Here we consider evidence…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-16 Charlie Conroy , Aaron A. Dutton , Genevieve J. Graves , J. Trevor Mendel , Pieter G. van Dokkum

Three component models of the IMF are made to consider possible origins for the observed relative variations in the numbers of brown dwarfs, solar-to-intermediate mass stars, and high mass stars. Three distinct physical processes are noted.…

Astrophysics · Physics 2009-11-10 Bruce G. Elmegreen

The stellar initial mass function (IMF) is a fundamental astrophysical quantity that impacts a wide range of astrophysical problems from heavy element distribution to galactic evolution to planetary system formation. However, the origin and…

Solar and Stellar Astrophysics · Physics 2017-01-11 S. S. R. Offner

The birth of stars and the formation of galaxies are cornerstones of modern astrophysics. While much is known about how galaxies globally and their stars individually form and evolve, one fundamental property that affects both remains…

Astrophysics of Galaxies · Physics 2019-02-20 A. M. Hopkins

This contribution describes the difficult task of inferring the IMF from local star-count data, by discussing the mass-luminosity relation, unresolved binary, triple and quadruple systems, abundance and age spreads and Galactic structure,…

Astrophysics · Physics 2007-05-23 Pavel Kroupa

We present observational evidence of the correlation between the high-mass slope of the stellar initial mass function (IMF) in young star clusters and their stellar surface density, $\sigma_{*}$. When the high-mass end of the IMF is…

Astrophysics of Galaxies · Physics 2023-11-03 Sami Dib

Peaks and lulls in the star formation rate (SFR) over the history of the Galaxy produce plateaux and declines in the present day mass function (PDMF) where the main-sequence lifetime overlaps the age and duration of the SFR variation. These…

Astrophysics · Physics 2009-11-13 Bruce G. Elmegreen , John Scalo

Observed variations in the slope of the initial stellar mass function are shown to be consistent with a model in which the protostellar gas is randomly sampled from hierarchical clouds at a rate proportional to the square root of the local…

Astrophysics · Physics 2009-10-31 B. G. Elmegreen