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The initial mass function (IMF) is an essential tool with which to study star formation processes. We have initiated the photometric survey of young open clusters in the Galaxy, from which the stellar IMFs are obtained in a homogeneous way.…

Astrophysics of Galaxies · Physics 2015-11-05 Beomdu Lim , Hwankyung Sung , Hyeonoh Hur , Byeong-Gon Park

We explore the assumption, widely used in many astrophysical calculations, that the stellar initial mass function (IMF) is universal across all galaxies. By considering both a canonical Salpeter-like IMF and a non-universal IMF, we are able…

(abridged) The case can be made for a rather universal stellar IMF form that can be approximated by a two-part power-law function in the stellar regime. However, there exists a possible hint for a systematic variation with metallicity. A…

Astrophysics · Physics 2007-05-23 Pavel Kroupa

The universality or non-universality of the initial mass function (IMF) has significant implications for determining star formation rates and star formation histories from photometric properties of stellar populations. We reexamine whether…

Astrophysics of Galaxies · Physics 2024-01-17 R. P. V. Rautio , A. E. Watkins , H. Salo , A. Venhola , J. H. Knapen , S. Comerón

The theory for the formation of the first population of stars (Pop III) predicts an initial mass function (IMF) dominated by high-mass stars, in contrast to the present-day IMF, which tends to yield mostly stars with masses less than 1…

Solar and Stellar Astrophysics · Physics 2016-02-17 Gustavo Dopcke , Simon C. O. Glover , Paul C. Clark , Ralf S. Klessen

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…

Observed variations in the IMF are reviewed with an emphasis on environmental density. The remote field IMF studied in the LMC by several authors is clearly steeper than most cluster IMFs, which have slopes close to the Salpeter value.…

Astrophysics · Physics 2015-11-11 Bruce G. Elmegreen

We have undertaken the largest systematic study of the high-mass stellar initial mass function (IMF) to date using the optical color-magnitude diagrams (CMDs) of 85 resolved, young (4 Myr < t < 25 Myr), intermediate mass star clusters…

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) integrated over an entire galaxy is an integral over all separate star-formation events. Since most stars form in star clusters with different masses the integrated IMF becomes an integral of the…

Astrophysics · Physics 2007-05-23 C. Weidner , P. Kroupa

We derive a semi-empirical galactic initial mass function (IMF) from observational constraints. We assume that the star formation rate in a galaxy can be expressed as the product of the IMF, $\psi (m)$, which is a smooth function of mass…

Astrophysics of Galaxies · Physics 2015-05-20 Antonio Parravano , Christopher F. McKee , David J. Hollenbach

The spectral absorption lines in early-type galaxies contain a wealth of information regarding the detailed abundance pattern, star formation history, and stellar initial mass function (IMF) of the underlying stellar population. Using our…

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

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

Theoretical arguments and indirect observational evidence suggest that the stellar initial mass function (IMF) may evolve with time, such that it is more weighted toward high mass stars at higher redshift. Here we test this idea by…

Astrophysics · Physics 2010-01-07 Pieter van Dokkum

Several observational and theoretical studies suggest that the initial mass function (IMF) slope for massive stars in globular clusters (GCs) depends on the initial cloud density and metallicity, such that the IMF becomes increasingly…

Astrophysics of Galaxies · Physics 2020-12-18 Hosein Haghi , Ghasem Safaei , Akram Hasani Zonoozi , Pavel Kroupa

Accurate specification of a likelihood function is becoming increasingly difficult in many inference problems in astronomy. As sample sizes resulting from astronomical surveys continue to grow, deficiencies in the likelihood function lead…

Instrumentation and Methods for Astrophysics · Physics 2019-04-26 Jessi Cisewski-Kehe , Grant Weller , Chad Schafer

Theoretical and indirect observational evidences suggest that stellar initial mass function (IMF) increases with redshift. On the other hand star formation rates (SFR) may be as high as 100 $M_{\odot}$ yr$^{-1}$ in star burst galaxies.…

Astrophysics of Galaxies · Physics 2015-08-06 Tanuka Chattopadhyay , Tuli De , Bharat Warlu , Asis Kumar Chattopadhyay

We conduct a detailed investigation of the properties of the stellar initial mass function (IMF) in two massive early-type lens galaxies with velocity dispersions of sigma ~245 km/s and sigma ~325 km/s, for which both HST imaging and…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-16 Matteo Barnabè , Chiara Spiniello , Léon V. E. Koopmans , Scott C. Trager , Oliver Czoske , Tommaso Treu

Observations with JWST have revealed an unexpected high abundance of bright z>10 galaxy candidates. We explore whether a stellar initial mass function (IMF) that becomes increasingly top-heavy towards higher redshifts and lower gas-phase…

The stellar initial mass function (IMF) is expressed by $\phi(m) \propto m^{-\alpha}$ with the slope $\alpha$, and known as the poorly-constrained but very important function in studies of star and galaxy formation. There are no sensible…

Astrophysics of Galaxies · Physics 2023-04-13 Shohei Aoyama , Masami Ouchi , Yuichi Harikane