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We present a minimum hypothesis model for an IMF that resembles a lognormal distribution at low masses but has a distinct power-law tail. Even if the central limit theorem ensures a lognormal distribution of condensation masses at birth, a…

Astrophysics · Physics 2015-11-11 Shantanu Basu , C. E. Jones

From time to time, and quite more frequently in recent years, claims appear favoring a variable Initial Mass Function (IMF), one way or another, either in time or space. In this chapter we add our two pennies of wisdom, illustrating how the…

Astrophysics of Galaxies · Physics 2020-07-17 Laura Greggio , Alvio Renzini

Observations have not yielded convincing results concerning the form of the stellar initial mass function (IMF) or its variations in space and time, so it is proposed that theoretical models may provide useful guidance. Several classes of…

Astrophysics · Physics 2009-09-25 John Scalo

Recent observations indicate a lower Halpha to FUV ratio in dwarf galaxies than in brighter systems, a trend that could be explained by a truncated and/or steeper IMF in small galaxies. However, at low star formation rates (SFRs), the…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-28 Michele Fumagalli , Robert L. da Silva , Mark R. Krumholz

Classical theories for the stellar initial mass function (IMF) predict a peak mass which scales with the properties of the molecular cloud. In this work, we explore a new theory proposed by Lee & Hennebelle (2018). The idea is that the…

Solar and Stellar Astrophysics · Physics 2020-01-22 Tine Colman , Romain Teyssier

The stellar initial mass function (IMF) is fundamental for many areas of astrophysics, but its origin remains poorly understood. It may be inherited from the core mass function (CMF) or arise as a result of more chaotic, competitive…

Astrophysics of Galaxies · Physics 2021-08-04 Theo J. O'Neill , Giuliana Cosentino , Jonathan C. Tan , Yu Cheng , Mengyao Liu

Stars do not form continuously distributed over star forming galaxies. They form in star clusters of different masses. This nature of clustered star formation is taken into account in the theory of the integrated galactic stellar initial…

Cosmology and Nongalactic Astrophysics · Physics 2014-11-20 Jan Pflamm-Altenburg , Pavel Kroupa

Systematic variations of the IMF in early-type galaxies, and their connection with possible drivers such as velocity dispersion or metallicity, have been much debated in recent years. Strong lensing over galaxy scales combined with…

Astrophysics of Galaxies · Physics 2016-04-27 Dominik Leier , Ignacio Ferreras , Prasenjit Saha , Stéphane Charlot , Gustavo Bruzual , Francesco La Barbera

Power-law (PL) distribution functions (DF) are prevalent in highly diverse systems. The systems range in size from nanometer to mega light years, in complexity from dust grains to living organisms, and characterize the distribution of…

High Energy Astrophysical Phenomena · Physics 2026-04-07 Ari Laor , Igor Gitelman

The stellar initial mass function (IMF) is believed to be non-universal among early-type galaxies (ETGs). Parameterizing the IMF with the so-called IMF mismatch parameter $\alpha_{\rm IMF}$, which is a measure of the stellar mass-to-light…

Astrophysics of Galaxies · Physics 2020-10-14 Carlo Nipoti , Carlo Cannarozzo , Francesco Calura , Alessandro Sonnenfeld , Tommaso Treu

The evolution of the global stellar mass function (MF) of star clusters is studied based on a large set of N-body simulations of clusters with a range of initial masses, initial concentrations, in circular or elliptical orbits in different…

Astrophysics of Galaxies · Physics 2015-06-15 Henny J. G. L. M. Lamers , Holger Baumgardt , Mark Gieles

(abridged) We develop a model which describes the coevolution of the mass function of dense cores and of the IMF in a protocluster clump. In the model, cores injected in the clump evolve under the effect of gas accretion. Accretion onto the…

Astrophysics of Galaxies · Physics 2015-05-14 Sami Dib , Mohsen Shadmehri , Paolo Padoan , G. Maheswar , D. K. Ojha , Fazeleh Khajenabi

The abundance of brown dwarfs (BDs) in young clusters is a diagnostic of star formation theory. Here we revisit the issue of determining the substellar initial mass function (IMF), based on a comparison between NGC1333 and IC348, two…

Solar and Stellar Astrophysics · Physics 2015-06-17 Aleks Scholz , Vincent Geers , Paul Clark , Ray Jayawardhana , Koraljka Muzic

We propose that the stellar initial mass function (IMF) is universal in the sense that its functional form arises as a consequence of the statistics of random supersonic flows. A model is developed for the origin of the stellar IMF, that…

Astrophysics · Physics 2015-06-24 Paolo Padoan , Ake Nordlund , Bernard J. T. Jones

It is frequently debated in literature whether a "standard" Initial Mass Function (IMF) - meaning an IMF of the kind usually adopted to explain the chemical evolution in the local Solar Neighbourhood - can account for the observed metal…

Astrophysics · Physics 2009-11-10 L. Portinari , A. Moretti , C. Chiosi , J. Sommer-Larsen

Globular clusters display an anticorrelation between the fraction of the first generation of stars ($N({\rm G1})/N({\rm tot})$) and the slope of the present-day mass function of the clusters ($\alpha_{pd}$), which is particularly…

Astrophysics of Galaxies · Physics 2023-02-10 Sami Dib , Valery V. Kravtsov , Hosein Haghi , Akram Hasani Zonoozi , José Antonio Belinchón

Recent studies seem to suggest that the stellar initial mass function (IMF) in early-type galaxies might be different from a classical Kroupa or Chabrier IMF, i.e. contain a larger fraction of the total mass in low-mass stars. From a…

Astrophysics of Galaxies · Physics 2016-08-05 Clio Bertelli Motta , Paul C. Clark , Simon C. O. Glover , Ralf S. Klessen , Anna Pasquali

The initial mass function (IMF) for the stars is usually fitted by three straight lines, which means seven parameters. The presence of brown dwarfs (BD) increases to four the straight lines and to nine the parameters. Another common fitting…

Solar and Stellar Astrophysics · Physics 2013-03-25 L. Zaninetti

In a probabilistic framework of the interpretation of the initial mass function (IMF), the IMF cannot be arbitrarily normalized to the total mass, M, or number of stars, N, of the system. Hence, the inference of M and N when partial…

Cosmology and Nongalactic Astrophysics · Physics 2013-07-02 Miguel Cervino , Carlos Romann-Zuniga , Amelia Bayo , Valentina Luridiana , Nestor Sanchez , Enrique Perez

We present optical photometry of Hubble Space Telescope (HST) ACS/WFC data of the resolved stellar populations in the outer disc of the dwarf irregular galaxy DDO 154. The photometry reveals that young main sequence stars are almost absent…

Astrophysics of Galaxies · Physics 2018-05-02 Adam B. Watts , Gerhardt R. Meurer , Claudia D. P. Lagos , Sarah M. Bruzzese , Pavel Kroupa , Tereza Jerabkova