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(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

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 study the recent star formation histories (SFHs) of 575 intermediate-mass galaxies (IMGs, $10^{9} \leq M/M_{\odot} \leq 10^{10}$) in COSMOS at $0.3<z<0.4$ by comparing their H$\alpha$ and UV luminosities. These two measurements trace…

Astrophysics of Galaxies · Physics 2023-03-15 Shannon G. Patel , Daniel D. Kelson , Louis E. Abramson , Zahra Sattari , Brian Lorenz

The stellar initial mass function (IMF) is among the most fundamental distributions in astrophysics, defined as the mass spectrum of stars produced in a single star-formation event. Even in the solar neighbourhood, where measurements can be…

Astrophysics of Galaxies · Physics 2026-04-15 Yu-Ting Wang , Chao Liu , Jiadong Li

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

(Abridged) Accurate luminosity functions (LF) for a dozen globular clusters have now been measured at or just beyond their half-light radius using HST. They span almost the entire cluster main sequence below ~ 0.75 Msolar. All these…

Astrophysics · Physics 2016-01-27 Francesco Paresce , Guido De Marchi

The hypothesis of a universal initial mass function (IMF) -- motivated by observations in nearby stellar systems -- has been recently challenged by the discovery of a systematic variation of the IMF with the central velocity dispersion,…

It has been shown recently that the dynamical V-band mass-to-light ratios of compact stellar systems with masses from 10^6 to 10^8 Solar masses are not consistent with the predictions from simple stellar population (SSP) models. Top-heavy…

Astrophysics of Galaxies · Physics 2010-02-25 J. Dabringhausen , P. Kroupa , H. Baumgardt

It is frequently debated in literature whether a "standard" Initial Mass Function (IMF) - meaning an IMF of the kind usually adopted to explain the chemical evolution in the local Solar Neighbourhood - can account for the observed metal…

Astrophysics · Physics 2009-11-10 L. Portinari , A. Moretti , C. Chiosi , J. Sommer-Larsen

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

We make use of a semi-analytical model of galaxy formation to investigate the origin of the observed correlation between [a/Fe] abundance ratios and stellar mass in elliptical galaxies. We implement a new galaxy-wide stellar initial mass…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-18 I. D. Gargiulo , S. A. Cora , N. D. Padilla , A. M. Muñoz Arancibia , A. N. Ruiz , A. A. Orsi , T. E. Tecce , C. Weidner , G. Bruzual

We report deep Subaru Halpha observations of the XUV disk of M83. These new observations enable the first complete census of very young stellar clusters over the entire XUV disk. Combining Subaru and GALEX data with a stellar population…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-04 Jin Koda , Masafumi Yagi , Samuel Boissier , Armando Gil de Paz , Masatoshi Imanishi , Jennifer Donovan Meyer , Barry F. Madore , David A. Thilker

The stellar masses, mean ages, metallicities, and star formation histories of galaxies are now commonly estimated via stellar population synthesis (SPS) techniques. SPS relies on stellar evolution calculations from the main sequence to…

Astrophysics · Physics 2009-08-18 Charlie Conroy , James E. Gunn , Martin White

Recent observational evidence for initial mass function (IMF) variations in massive quiescent galaxies at $z = 0$ challenges the long-established paradigm of a universal IMF. While a few theoretical models relate the IMF to birth cloud…

Astrophysics of Galaxies · Physics 2017-08-30 Kirsten Blancato , Shy Genel , Greg Bryan

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…

In our previous work, we derive the CR-IGIMF: a new scenario for a variable stellar initial mass function (IMF), which combines numerical results on the role played by cosmic rays in setting the thermal state of star forming gas, with the…

Some ultra-compact dwarf galaxies have large dynamical mass to light (M/L) ratios and also appear to contain an overabundance of LMXB sources, and some Milky Way globular clusters have a low concentration and appear to have a deficit of…

Astrophysics of Galaxies · Physics 2020-03-18 Pavel Kroupa

Observations of mergers of multi-compact object systems offer insights to the formation processes of massive stars in globular clusters. Simulations of stellar clusters, may be used to understand and interpret observations. Simulations…

Astrophysics of Galaxies · Physics 2018-12-27 Indulekha Kavila , Megha Viswambharan

One of the key observations regarding the stellar initial mass function (IMF) is its near-universality in the Milky Way (MW), which provides a powerful way to constrain different star formation models that predict the IMF. However, those…

Astrophysics of Galaxies · Physics 2018-04-25 David Guszejnov , Philip F. Hopkins , Xiangcheng Ma

Recent results indicate the stellar initial mass function is not a strong function of star-forming environment or ``initial conditions'' (e.g. Meyer et al. 2000). Some studies suggest that a universal IMF may extend to sub-stellar masses…

Astrophysics · Physics 2015-11-11 M. R. Meyer , J. Greissl , M. Kenworthy , D. McCarthy