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The stellar initial mass function (IMF) is a key parameter to study galaxy evolution. Here we measure the IMF mass normalization for a sample of 68 field galaxies in the redshift range 0.7 to 0.9 within the Extended Groth Strip. To do this…

Astrophysics of Galaxies · Physics 2014-06-19 Shravan Shetty , Michele Cappellari

We present new evidence for a variable stellar initial mass function (IMF) in massive early-type galaxies, using high-resolution, near-infrared spectroscopy from the Folded-port InfraRed Echellette spectrograph (FIRE) on the Magellan Baade…

We estimate the fraction of mass that is composed of compact objects in gravitational lens galaxies. This study is based on microlensing measurements (obtained from the literature) of a sample of 29 quasar image pairs seen through 20 lens…

Cosmology and Nongalactic Astrophysics · Physics 2014-11-20 E. Mediavilla , J. A. Munoz , E. Falco , V. Motta , E. Guerras , H. Canovas , C. Jean , A. Oscoz , A. M. Mosquera

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

It is now well-established that the stellar initial mass function (IMF) can be determined from the absorption line spectra of old stellar systems, and this has been used to measure the IMF and its variation across the early-type galaxy…

Astrophysics of Galaxies · Physics 2017-03-22 Charlie Conroy , Pieter van Dokkum , Alexa Villaume

Most structural and evolutionary properties of galaxies strongly rely on the stellar initial mass function (IMF), namely the distribution of the stellar mass formed in each episode of star formation. As the IMF shapes the stellar population…

Astrophysics of Galaxies · Physics 2023-01-31 Jiadong Li , Chao Liu , Zhi-Yu Zhang , Hao Tian , Xiaoting Fu , Jiao Li , Zhi-Qiang Yan

We present new observations of the three nearest early-type galaxy (ETG) strong lenses discovered in the SINFONI Nearby Elliptical Lens Locator Survey (SNELLS). Based on their lensing masses, these ETGs were inferred to have a stellar…

Astrophysics of Galaxies · Physics 2017-08-30 Andrew B. Newman , Russell J. Smith , Charlie Conroy , Alexa Villaume , Pieter van Dokkum

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

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

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

Systematic variations of the IMF in early-type galaxies, and their connection with possible drivers such as velocity dispersion or metallicity, have been much debated in recent years. Strong lensing over galaxy scales combined with…

Astrophysics of Galaxies · Physics 2016-04-27 Dominik Leier , Ignacio Ferreras , Prasenjit Saha , Stéphane Charlot , Gustavo Bruzual , Francesco La Barbera

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

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

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 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…

Low-redshift strong-lensing galaxies can provide robust measurements of the stellar mass-to-light ratios in early-type galaxies (ETG), and hence constrain variations in the stellar initial mass function (IMF). At present, only a few such…

Astrophysics of Galaxies · Physics 2020-03-11 William P. Collier , Russell J. Smith , John R. Lucey

This paper revisits the classical Kennicutt method for inferring the stellar initial mass function (IMF) from the integrated light properties of galaxies. The large size, uniform high quality data set from the Sloan Digital Sky Survey DR4…

Astrophysics · Physics 2011-04-20 Erik A. Hoversten , Karl Glazebrook

We use a large sample of galaxies from the Two Micron All Sky Survey (2MASS) and the Sloan Digital Sky Survey (SDSS) to calculate galaxy luminosity and stellar mass functions in the local Universe. We estimate k-corrections, evolution…

Astrophysics · Physics 2011-05-05 Eric F. Bell , Daniel H. McIntosh , Neal Katz , Martin D. Weinberg

The stellar initial mass function (IMF) describes the mass distribution of stars at the time of their formation and is of fundamental importance for many areas of astrophysics. The IMF is reasonably well constrained in the disk of the Milky…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-20 Pieter van Dokkum , Charlie Conroy

The strength of gravity-sensitive absorption lines in the integrated light of old stellar populations is one of the few direct probes of the stellar initial mass function (IMF) outside of the Milky Way. Owing to the advent of fully depleted…

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