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We study degeneracies between parameters in some of the widely used parametrized modified gravity models. We investigate how different observables from a future photometric weak lensing survey such as LSST, correlate the effects of these…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-11 Alireza Hojjati

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…

Recent evidence based independently on spectral line strengths and dynamical modelling point towards a non-universal stellar Initial Mass Function (IMF), probably implying an excess of low-mass stars in elliptical galaxies with a high…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-16 Carsten Weidner , Ignacio Ferreras , Alexandre Vazdekis , Francesco La Barbera

The Stellar Initial Mass Function (IMF) characterizes the mass distribution of newly formed stars in various cosmic environments, serving as a fundamental assumption in astrophysical research. Recent findings challenge the prevalent notion…

Astrophysics of Galaxies · Physics 2024-05-29 Zhiqiang Yan , Jiadong Li , Pavel Kroupa , Tereza Jerabkova , Eda Gjergo , Zhi-Yu Zhang

If the dark matter is unstable, the decay of these particles throughout the universe and in the halo of the Milky Way could contribute significantly to the isotropic gamma-ray background (IGRB) as measured by Fermi. In this article, we…

High Energy Astrophysical Phenomena · Physics 2019-03-20 Carlos Blanco , Dan Hooper

We introduce a new dual power law (DPL) probability distribution function for the mass distribution of stellar and substellar objects at birth, otherwise known as the initial mass function (IMF). The model contains both deterministic and…

Solar and Stellar Astrophysics · Physics 2018-05-23 Karl Heinz Hoffmann , Christopher Essex , Shantanu Basu , Janett Prehl

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 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…

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

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

Recent studies of early-type galaxies have suggested that the initial mass function (IMF) slope is bottom-heavy, i.e. they contain a larger fraction of low-mass stars than the Milky Way. However, measurements of the IMF remain challenging…

Astrophysics of Galaxies · Physics 2020-10-14 A. Feldmeier-Krause , I. Lonoce , W. L. Freedman

We determine an absolute calibration of the initial mass function (IMF) of early-type galaxies, by studying a sample of 56 gravitational lenses identified by the SLACS Survey. Under the assumption of standard Navarro, Frenk & White dark…

Cosmology and Nongalactic Astrophysics · Physics 2014-11-20 T. Treu , M. W. Auger , L. V. E. Koopmans , R. Gavazzi , P. J. Marshall , A. S. Bolton

This contribution describes the difficult task of inferring the IMF from local star-count data, by discussing the mass-luminosity relation, unresolved binary, triple and quadruple systems, abundance and age spreads and Galactic structure,…

Astrophysics · Physics 2007-05-23 Pavel Kroupa

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

Analyses of strong gravitational lenses, galaxy-scale kinematics, and absorption line stellar population synthesis (SPS) have all concluded that the stellar initial mass function (IMF) varies within the massive early-type galaxy (ETG)…

Astrophysics of Galaxies · Physics 2017-11-29 Alexa Villaume , Jean Brodie , Charlie Conroy , Aaron J. Romanowsky , Pieter van Dokkum

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

Low-mass stars (M<0.4Msun) are thought to comprise the bulk of the stellar mass of galaxies but they constitute only of order a percent of the bolometric luminosity of an old stellar population. Directly estimating the number of low-mass…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-30 Charlie Conroy , Pieter van Dokkum

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 recent Cosmic Microwave Background (CMB) measurements indicate that there is power deficiency of the CMB anisotropies at large scales compared with the $\Lambda$CDM model. We have investigated the possibility of explaining such effects…

Astrophysics · Physics 2009-11-13 Rita Sinha , Tarun Souradeep

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