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One of the most robust observations of the stellar initial mass function (IMF) is its near-universality in the Milky Way and neighboring galaxies. But recent observations of early-type galaxies can be interpreted to imply a bottom-heavy…

Astrophysics of Galaxies · Physics 2019-03-26 David Guszejnov , Philip F. Hopkins , Andrew S. Graus

The stellar initial mass function (IMF) describes the mass distribution of stars at the time of their formation and is of fundamental importance for many areas of astrophysics. The IMF is reasonably well constrained in the disk of the Milky…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-20 Pieter van Dokkum , Charlie Conroy

In this work, we want to find out if the IMF can be determined from colour images, integrated colours, or mass-to-light ratios, especially at high redshift, where galaxies cannot be resolved into individual stars, which would enable us to…

Astrophysics · Physics 2008-11-26 P. Westera , M. Samland , S. J. Kautsch , R. Buser , K. Ammon

The stellar initial mass function (IMF) plays a crucial role in determining the number of surviving stars in galaxies, the chemical composition of the interstellar medium, and the distribution of light in galaxies. A key unsolved question…

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

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

A number of recent studies have proposed that the stellar initial mass function (IMF) of early type galaxies varies systematically as a function of galaxy mass, with higher mass galaxies having bottom heavy IMFs. These bottom heavy IMFs…

We discuss possible sources of biases in the determination of the initial mass function (IMF) introduced by the binning of the data, the uncertainty in the determinations of masses, and the existence of unresolved multiple systems. Those…

Astrophysics · Physics 2007-05-23 J. Maíz Apellániz , L. Úbeda , N. R. Walborn , E. P. Nelan

The characteristic mass M_c and slope Gamma of the IMF are reviewed for clusters, field regions, galaxies, and regions formed during cosmological times. Local star formation has a somewhat uniform M_c and Gamma. Statistical variations in…

Astrophysics · Physics 2008-03-24 Bruce G. Elmegreen

Deviations from a universal, MW-like, Stellar Initial Mass Function (IMF) have been reported for distant galaxies, although the physical reason behind the observed variations is still matter of ongoing debate. In this paper, we present an…

Astrophysics of Galaxies · Physics 2015-06-19 Fabio Fontanot

Many results in modern astrophysics rest on the notion that the Initial Mass Function (IMF) is universal. Our observations of HI selected galaxies in the light of H-alpha and the far-ultraviolet (FUV) challenge this notion. The flux ratio…

The debate about the universality of the stellar initial mass function (IMF) revolves around two competing lines of evidence. While measurements in the Milky Way, an archetypal spiral galaxy, seem to support an invariant IMF, the observed…

The integrated galaxial initial mass function (IGIMF) is the relevant distribution function containing the information on the distribution of stellar remnants, the number of supernovae and the chemical enrichment history of a galaxy. Since…

Astrophysics · Physics 2009-11-10 C. Weidner , P. Kroupa

The stellar initial mass function (IMF) describes the distribution of stellar masses that form in a given star formation event. The long main-sequence lifetimes of low-mass stars mean that the IMF in this regime (below $\sim 1…

The stellar initial mass function (IMF) is commonly assumed to be an invariant probability density distribution function of initial stellar masses being represented by the canonical IMF. As a consequence the galaxy-wide IMF (gwIMF), defined…

Astrophysics of Galaxies · Physics 2018-11-28 T. Jerabkova , A. H. Zonoozi , P. Kroupa , G. Beccari , Z. Yan , A. Vazdekis , Z. -Y. Zhang

The present paper extends our previous theory of the stellar initial mass function (IMF) by including the time-dependence, and by including the impact of magnetic field. The predicted mass spectra are similar to the time independent ones…

Astrophysics of Galaxies · Physics 2015-06-15 Patrick Hennebelle , Gilles Chabrier

The observed stellar initial mass function (IMF) appears to vary, becoming bottom-heavy in the centres of the most massive, metal-rich early-type galaxies. It is still unclear what physical processes might cause this IMF variation. In this…

Astrophysics of Galaxies · Physics 2020-10-07 Timothy A. Davis , Freeke van de Voort

Galaxy formation simulations frequently use Initial Mass Function (IMF) averaged feedback prescriptions, where star particles are assumed to represent single stellar populations that fully sample the IMF. This approximation breaks down at…

Astrophysics of Galaxies · Physics 2021-04-22 Matthew C. Smith

Crucial for star formation is the interplay between gravity and turbulence. The observed cloud virial parameter, $\alpha_{\mathrm{vir}}$, which is the ratio of twice the turbulent kinetic energy to the gravitational energy, is found to vary…

Astrophysics of Galaxies · Physics 2025-01-07 Sajay Sunny Mathew , Christoph Federrath , Amit Seta

(abridged) Here we discuss the question whether the extreme circumstances in the centre of the Milky Way may be the reason for a significant variation of the IMF. By means of stellar evolution models using different codes we show that the…

Astrophysics of Galaxies · Physics 2015-05-14 Ulf Loeckmann , Holger Baumgardt , Pavel Kroupa