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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

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…

This paper shows how a self-consistent dynamical model can be obtained by fitting the gravitational potential of the Milky Way to the stellar kinematics and densities from Gaia data. Using the Besancon Galaxy Model we derive a potential and…

We present a simple method for fitting parametrized mass models of the Milky Way to observational constraints. We take a Bayesian approach which allows us to take into account input from photometric and kinematic data, and expectations from…

Astrophysics of Galaxies · Physics 2015-05-27 Paul J. McMillan

We determine the initial mass function (IMF) of the ``thin disk'' by means of a direct comparison between synthetic stellar samples (for different matching choices of IMF, star formation rate SFR and depletion) and a complete…

Astrophysics · Physics 2009-11-07 K. -P. Schröder , B. Pagel

There is good evidence that the centers of massive early-type galaxies have a bottom-heavy stellar initial mass function (IMF) compared to the IMF of the Milky Way. Here we study the radial variation of the IMF within such galaxies, using a…

Astrophysics of Galaxies · Physics 2017-05-31 Pieter van Dokkum , Charlie Conroy , Alexa Villaume , Jean Brodie , Aaron Romanowsky

Statistical sampling from the stellar initial mass function (IMF) for all star-forming regions in the Galaxy would lead to the prediction of ~1000 Msun stars unless there is a rapid turn-down in the IMF beyond several hundred solar masses.…

Astrophysics · Physics 2009-10-31 Bruce G. Elmegreen

The local stellar mass density is observed to be significantly lower than the value obtained from integrating the cosmic star formation history (SFH), assuming that all the stars formed with a Salpeter initial mass function (IMF). Even…

Astrophysics · Physics 2009-11-13 Stephen M. Wilkins , Andrew M. Hopkins , Neil Trentham , Rita Tojeiro

Despite the fundamental importance of the Milky Way's star formation history (SFH) and initial mass function (IMF), their consistent derivation remains elusive. We aim to simultaneously infer the IMF and the SFH of the Galactic disc…

Astrophysics of Galaxies · Physics 2025-05-21 Marc del Alcázar-Julià , Francesca Figueras , Annie C. Robin , Olivier Bienaymé , Friedrich Anders

Strong gravitational lensing can provide accurate measurements of the stellar mass-to-light ratio $\Upsilon$ in low-redshift ($z$ $\lesssim$ 0.05) early-type galaxies, and hence probe for possible variations in the stellar initial mass…

Astrophysics of Galaxies · Physics 2018-09-05 Russell J. Smith , John R. Lucey , William P. Collier

Context. Thanks to recent large scale surveys in the near infrared such as 2MASS, the galactic plane that most suffers from extinction is revealed and its overall structure can be studied. Aims. This work aims at constraining the structure…

Astrophysics · Physics 2009-12-08 C. Reyle , D. J. Marshall , A. C. Robin , M. Schultheis

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

The stellar initial mass function (IMF) is thought to be bottom-heavy in the cores of the most massive galaxies, with an excess of low mass stars compared to the Milky Way. However, studies of the kinematics of quiescent galaxies at 2<z<5…

Astrophysics of Galaxies · Physics 2024-09-10 Pieter van Dokkum , Charlie Conroy

Given a flurry of recent claims for systematic variations in the stellar initial mass function (IMF), we carry out the first inventory of the observational evidence using different approaches. This includes literature results, as well as…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-05 Crescenzo Tortora , Aaron J. Romanowsky , Nicola R. Napolitano

Several independent lines of evidence suggest that the stellar initial mass function (IMF) in early-type galaxies becomes increasingly `bottom-heavy' with increasing galaxy mass and/or velocity dispersion, sigma. Here we consider evidence…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-16 Charlie Conroy , Aaron A. Dutton , Genevieve J. Graves , J. Trevor Mendel , Pieter G. van Dokkum

We model vertical breathing mode perturbations in the Milky Way's stellar disc and study their effects on estimates of the local dark matter density, surface density, and vertical force. Evidence for these perturbations, which involve…

Astrophysics of Galaxies · Physics 2016-11-22 Nilanjan Banik , Lawrence M. Widrow , Scott Dodelson

The stellar initial mass function (IMF) is a fundamental property in the measurement of stellar masses and galaxy star formation histories. In this work we focus on the most massive galaxies in the nearby universe…

Astrophysics of Galaxies · Physics 2022-06-29 Meng Gu , Jenny Greene , Andrew B. Newman , Christina Kreisch , Matthew Quenneville , Chung-Pei Ma , John P. Blakeslee

We use recent microlensing observations toward the central bulge of the Galaxy to probe the overall stellar plus brown dwarf initial mass function (IMF) in these regions well within the brown dwarf domain. We find that the IMF is consistent…

Astrophysics of Galaxies · Physics 2023-02-22 Gilles Chabrier , Romain Lenoble

We present constraints on the stellar initial mass function (IMF) in two ultra-faint dwarf (UFD) galaxies, Hercules and Leo IV, based on deep HST/ACS imaging. The Hercules and Leo IV galaxies are extremely low luminosity (M_V = -6.2, -5.5),…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-15 M. Geha , T. M. Brown , J. Tumlinson , J. Kalirai , J. D. Simon , E. Kirby , D. VandenBerg , R. M. Munoz , R. Avila , P. Guhathakurta , H. Ferguson

We use Gaia DR2 to measure the initial mass function (IMF) of stars within 250 pc and masses in the range 0.2 < m/Msun < 1.0, separated according to kinematics and metallicity, as determined from Gaia transverse velocity, v_T, and location…

Astrophysics of Galaxies · Physics 2021-08-11 Na'ama Hallakoun , Dan Maoz