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Using deep HST/ACS observations, we demonstrate that the sub-solar stellar initial mass function (IMF) of 6 ultra-faint dwarf Milky Way Satellites (UFDs) is more bottom light than the IMF of the Milky Way disk. Our data have a lower mass…

The stellar initial mass functions (IMFs) for the Galactic bulge, the Milky Way, other galaxies, clusters of galaxies, and the integrated stars in the Universe are composites from countless individual IMFs in star clusters and associations…

Astrophysics · Physics 2008-11-26 Bruce G. Elmegreen

We describe the use of our chemical evolution model to reproduce the abundance patterns observed in a catalog of elliptical galaxies from the SDSS DR4. The model assumes ellipticals form by fast gas accretion, and suffer a strong burst of…

Astrophysics of Galaxies · Physics 2018-01-10 Carlo Maria De Masi , Francesca Matteucci , Fiorenzo Vincenzo

The stellar initial mass function (IMF) in star clusters is reviewed. Uncertainties in the observations are emphasized. We suggest there is a distinct possibility that cluster IMFs vary systematically with density or pressure. Dense…

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

Recent results form the James Webb Space Telescope (JWST) report space densities for bright and massive galaxies at z>7 that far exceed expectations of theoretical models of galaxy formation, prompting a revision of our understanding of the…

Recent observations and theories have presented a strong challenge to the universality of the stellar initial mass function (IMF) in extreme environments. A notable example has been found for starburst conditions, where evidence favours a…

Astrophysics of Galaxies · Physics 2024-05-10 Ziyi Guo , Zhi-Yu Zhang , Zhiqiang Yan , Eda Gjergo , Allison Man , R. J. Ivison , Xiaoting Fu , Yong Shi

The initial mass function (IMF) is one of the most important functions in astrophysics because it is key to reconstructing the cosmological matter cycle, understanding the formation of super-massive black holes, and deciphering the light…

Astrophysics of Galaxies · Physics 2024-12-30 Pavel Kroupa , Eda Gjergo , Tereza Jerabkova , Zhiqiang Yan

The stellar initial-mass function (IMF) represents a fundamental quantity in astrophysics and cosmology, describing the mass distribution of stars from low to very-high masses. It is intimately linked to a wide variety of topics, including…

High Energy Astrophysical Phenomena · Physics 2024-09-17 Francesco Gabrielli , Lumen Boco , Giancarlo Ghirlanda , Om Sharan Salafia , Ruben Salvaterra , Mario Spera , Andrea Lapi

Observations of both galaxies in the distant Universe and local starbursts are showing increasing evidence for very hard ionizing spectra that stellar population synthesis models struggle to reproduce. Here we explore the effects of the…

Astrophysics of Galaxies · Physics 2019-01-23 E. R. Stanway , J. J. Eldridge

The stellar initial mass function (IMF) is a fundamental property of star formation, offering key insight into the physics driving the process as well as informing our understanding of stellar populations, their by-products, and their…

Astrophysics of Galaxies · Physics 2019-03-14 M. W. Hosek , J. R. Lu , M. Andersen , T. Do , D. Kim , N. Z. Rui , P. Boyle , B. F. Williams , S. Chakrabarti , R. L. Beaton

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…

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

We examine the cosmic evolution of a stellar initial mass function (IMF) in galaxies that varies with the Jeans mass in the interstellar medium, paying particular attention to the K-band stellar mass to light ratio (M/L_K) of present-epoch…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-11 Desika Narayanan , Romeel Davé

The stellar initial mass function (IMF), which is often assumed to be universal across unresolved stellar populations, has recently been suggested to be "bottom-heavy" for massive ellipticals. In these galaxies, the prevalence of…

We use stellar dynamics, strong lensing, stellar population synthesis models, and weak lensing shear measurements to constrain the dark matter (DM) profile and stellar mass in a sample of 53 massive early-type galaxies. We explore three DM…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-19 M. W. Auger , T. Treu , R. Gavazzi , A. S. Bolton , L. V. E. Koopmans , P. J. Marshall

This paper aims at understanding if the normalization of the stellar initial mass function (IMF) of massive early-type galaxies (ETGs) varies with cosmic time and/or with mean stellar mass density Sigma (M*/2\pi Re^2). For this purpose we…

Astrophysics of Galaxies · Physics 2015-01-14 A. Gargiulo , P. Saracco , M. Longhetti , S. Tamburri , I. Lonoce , F. Ciocca

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…

Much of our understanding of modern astrophysics rest on the notion that the Initial Mass Function (IMF) is universal. Our observations of a sample of HI-selected galaxies in the light of H-alpha and the far-ultraviolet (FUV) challenge this…

Cosmology and Nongalactic Astrophysics · Physics 2010-08-25 G. R. Meurer

Does the IMF vary? Is it significantly different in metal-rich environments than in metal-poor ones? Theoretical work predicts this to be the case. But in order to provide robust empirical evidence for this, the researcher must understand…

Astrophysics · Physics 2007-05-23 Pavel Kroupa

We measure the high-mass stellar initial mass function (IMF) from resolved stars in M33 young stellar clusters. Leveraging \textit{Hubble Space Telescope's} high resolving power, we fully model the IMF probabilistically. We first model the…