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In our previous work, we derive the CR-IGIMF: a new scenario for a variable stellar initial mass function (IMF), which combines numerical results on the role played by cosmic rays in setting the thermal state of star forming gas, with the…

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

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

Recent results indicate the stellar initial mass function is not a strong function of star-forming environment or ``initial conditions'' (e.g. Meyer et al. 2000). Some studies suggest that a universal IMF may extend to sub-stellar masses…

Astrophysics · Physics 2015-11-11 M. R. Meyer , J. Greissl , M. Kenworthy , D. McCarthy

We investigate the origin of a bottom-heavy stellar initial mass function (IMF) recently observed in elliptical galaxies by using chemical evolution models with a non-universal IMF. We adopt the Kroupa IMF with the three slopes (alpha_1,…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-17 Kenji Bekki

Metals enhance the cooling efficiency of molecular clouds, promoting fragmentation. Consequently, increasing the metallicity may boost the formation of low-mass stars. Within the integrated galaxy initial mass function (IGIMF) theory, this…

The combination of the high-resolution ALMA, JWST and HST observations provides unprecedented insights into the connection between individual molecular clouds and their internal stellar populations in nearby galaxies. The molecular clouds…

Astrophysics of Galaxies · Physics 2025-07-01 J. W. Zhou , Pavel Kroupa , Sami Dib

The manner in which the stellar initial mass function (IMF) scales with global galaxy properties is under debate. We use two hydrodynamical, cosmological simulations to predict possible trends for two self-consistent variable IMF…

Astrophysics of Galaxies · Physics 2018-10-22 Christopher Barber , Joop Schaye , Robert A. Crain

The stellar initial mass function is of great significance for the study of star formation and galactic structure. Observations indicate that the IMF follows a power-law form. This work derived that when the expected number of stars formed…

Astrophysics of Galaxies · Physics 2025-03-20 Yu-Fu Shen

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…

A universal stellar initial mass function (IMF) should not be expected from theoretical models of star formation, but little conclusive observational evidence for a variable IMF has been uncovered. In this paper, a parameterization of the…

Astrophysics of Galaxies · Physics 2022-06-01 Albert Sneppen , Charles L. Steinhardt , Hagan Hensley , Adam S. Jermyn , Basel Mostafa , John R. Weaver

The presence (and nature) of variations in the stellar initial mass function (IMF) at substantially sub-solar masses and metallicities ($m$$<$0.5M$_{\odot}$, [M/H]$\lesssim$$-$1) remains poorly constrained. Predictions from simulations vary…

Astrophysics of Galaxies · Physics 2026-03-17 Roger E. Cohen , Mario Gennaro , Matteo Correnti , Kristen B. W. McQuinn , Vedant Chandra

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

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…

In the last decade, growing evidence has emerged supporting a non-universal stellar Initial Mass Function (IMF) in massive galaxies, with a larger number of dwarf stars with respect to the Milky-Way (bottom-heavy IMF). However, a consensus…

Observations of normal galactic star-forming regions suggest there is widespread near-uniformity in the initial stellar mass function (IMF) in spite of diverse physical conditions. Fluctuations may come largely from statistical effects and…

Astrophysics · Physics 2007-05-23 B. G. Elmegreen

The stellar initial mass function (IMF) seems to be variable and not universal, as argued in the literature in the last three decades. Several relations among the low-mass end of the IMF slope and other stellar population, photometric or…

Astrophysics of Galaxies · Physics 2021-01-13 C. E. Barbosa , C. Spiniello , M. Arnaboldi , L. Coccato , M. Hilker , T. Richtler

The strength of gravity-sensitive absorption lines in the integrated light of old stellar populations is one of the few direct probes of the stellar initial mass function (IMF) outside of the Milky Way. Owing to the advent of fully depleted…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-05 Pieter van Dokkum , Charlie Conroy

There is substantial evidence that the initial mass function (IMF) may be a function of the local star formation conditions. In particular, the IMF is predicted to flatten with increasing local luminosity density, with the formation of…

Astrophysics · Physics 2009-10-30 Jason A. Taylor

A robust stellar initial mass function (IMF) is crucial in any studies related to star formation. However, the direct measurement of the stellar IMF is confined to the local universe, limited by the resolving power of telescopes. Recently,…

Cosmology and Nongalactic Astrophysics · Physics 2026-02-12 Sung Kei Li