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Gravitational microlensing depends primarily on the lens mass and presents a larger occurrence rate in crowded regions, which makes it the best tool to uncover the initial mass function (IMF) of low-mass stars in the Galactic bulge. The…

The Initial-Final Mass-Relation (IFMR) maps the masses of main sequence stars to their white dwarf descendants. The most common approach to measure the IFMR has been to use white dwarfs in clusters. However, it has been shown that wide…

Solar and Stellar Astrophysics · Physics 2023-11-28 Mark A. Hollands , Stuart P. Littlefair , Steven G. Parsons

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

The era of the James Webb Space Telescope ushers stellar population models into uncharted territories, particularly at the high-redshift frontier. In a companion paper, we apply the \texttt{Prospector} Bayesian framework to jointly infer…

Recent results on the non-universality of the Initial Mass Function (IMF) have shown strong evidence of IMF variations with galaxy velocity dispersion, with a corresponding impact on other stellar population parameters, line indices and…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-12 Anna Ferré-Mateu , Alexandre Vazdekis , Ignacio G. de la Rosa

Mass measurements and absorption line studies indicate that the stellar initial mass function (IMF) is bottom-heavy in the central regions of many early-type galaxies, with an excess of low mass stars compared to the IMF of the Milky Way.…

Astrophysics of Galaxies · Physics 2021-12-22 Pieter van Dokkum , Charlie Conroy

(Abridged) The probability of detecting additional companions is essentially unchanged with respect to the single-planet configurations, but after fitting and subtraction of orbits with astrometric signal-to-noise ratio $\alpha/\sigma_d\to…

Astrophysics · Physics 2009-11-07 A. Sozzetti , S. Casertano , R. A. Brown , M. G. Lattanzi

We present a combined analysis of the low-mass Initial Mass Function (IMF) for seven star forming regions. We first demonstrate that the ratios of stars to brown dwarfs are consistent with a single underlying IMF. Assuming the underlying…

Astrophysics · Physics 2009-11-13 M. Andersen , M. R. Meyer , J. Greissl , A. Aversa

The turnover in the stellar initial mass function (IMF) at low mass suggests the presence of two independent mass functions that combine in different ways above and below a characteristic mass given by the thermal Jeans mass in the cloud.…

Astrophysics · Physics 2009-10-31 Bruce Elmegreen

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

We tested the implementation of different IMFs in our model for the chemical evolution of ellipticals, with the aim of reproducing the observed relations of [Fe/H] and [Mg/Fe] abundances with galaxy mass in a sample of early-type galaxies…

Astrophysics of Galaxies · Physics 2018-11-26 C. De Masi , F. Vincenzo , F. Matteucci , G. Rosani , La Barbera , A. Pasquali , E. Spitoni

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…

I discuss two of the possible sources of biases in the determination of the IMF: binning and the existence of unresolved components. The first source is important for clusters with a small number of stars detected in a given mass bin while…

Astrophysics · Physics 2015-05-13 J. Maíz Apellániz

We investigate the cosmic evolution of the internal structure of massive early-type galaxies over half of the age of the Universe. We perform a joint lensing and stellar dynamics analysis of a sample of 81 strong lenses from the SL2S and…

We determine an absolute calibration of stellar mass-to-light ratios for the densest \simeq 3% of early-type galaxies in the local universe (redshift z\simeq 0.08) from SDSS DR7. This sample of \sim 4000 galaxies has, assuming a Chabrier…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-03 Aaron A. Dutton , J. Trevor Mendel , Luc Simard

The stellar initial mass function (IMF) determines the relative number of stars born at a given mass. Despite the tremendous effort to establish a universal IMF, the astronomical literature offers a wealth of diverse evidence for IMF…

Astrophysics · Physics 2007-05-23 Frank Eisenhauer

Several recent observational studies have concluded that the initial mass function (IMF) of stars varies systematically with galaxy properties such as velocity dispersion. In this paper, we investigate the effect of linking the circular…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-18 Sean L. McGee , Ryosuke Goto , Michael L. Balogh

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…

We use the timescale distribution of ~3000 microlensing events measured by the OGLE-III survey, together with accurate new made-to-measure dynamical models of the Galactic bulge/bar region, to measure the IMF in the inner Milky Way. The…

Astrophysics of Galaxies · Physics 2017-07-26 Christopher Wegg , Ortwin Gerhard , Matthieu Portail