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Star formation theories have struggled to reproduce binary brown dwarf population demographics (frequency, separation, mass-ratio). Kernel-phase interferometry is sensitive to companions at separations inaccessible to classical imaging,…

Solar and Stellar Astrophysics · Physics 2023-03-03 Samuel M. Factor , Adam L. Kraus

[abridged] We aim to constrain the stellar initial mass function (IMF) during the epoch of reionization. To this purpose, we build up a semi-empirical model for the reionization history of the Universe, based on various ingredients: the…

Astrophysics of Galaxies · Physics 2024-03-14 A. Lapi , G. Gandolfi , L. Boco , F. Gabrielli , M. Massardi , B. S. Haridasu , C. Baccigalupi , A. Bressan , L. Danese

We present results from the largest numerical simulation of star formation to resolve the fragmentation process down to the opacity limit. The simulation follows the collapse and fragmentation of a large-scale turbulent molecular cloud to…

Astrophysics · Physics 2011-05-05 Matthew R. Bate , Ian A. Bonnell , Volker Bromm

Whether BDs form as stars through gravitational collapse ("star-like") or BDs and some very low-mass stars constitute a separate population which form alongside stars comparable to the population of planets, e.g. through circumstellar disk…

Astrophysics of Galaxies · Physics 2017-09-06 M. Marks , E. L. Martín , V. J. S. Béjar , N. Lodieu , P. Kroupa , M. E. Manjavacas , I. Thies , R. Rebolo López , S. Velasco

Monte Carlo simulations of the field substellar mass function (MF) are presented. Starting from various representations of the MF below 0.1 M$_{\sun}$ and the stellar birth rate, luminosity functions (LFs) and T$_{eff}$ distributions are…

Astrophysics · Physics 2010-01-28 Adam J. Burgasser

The semi-empirical initial-final mass relation (IFMR) connects spectroscopically analyzed white dwarfs in star clusters to the initial masses of the stars that formed them. Most current stellar evolution models, however, predict that stars…

Solar and Stellar Astrophysics · Physics 2019-01-30 Jeffrey D. Cummings , Jason S. Kalirai , Jieun Choi , Cyril Georgy , Pier-Emmanuel Tremblay , Enrico Ramirez-Ruiz

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

The origin of the stellar initial mass function (IMF) is a fundamental issue in the theory of star formation. It is generally fit with a composite power law. Some clues on the progenitors can be found in dense starless cores that have a…

Astrophysics of Galaxies · Physics 2015-09-21 Tingtao Zhou , Chelsea X. Huang , D. N. C. Lin , Matthias Gritschneder , Herbert Lau

Using recently established empirical calibrations for the impact of chromospheric activity on the radii, effective temperatures, and estimated masses of active low-mass stars and brown dwarfs, we reassess the shape of the initial mass…

Solar and Stellar Astrophysics · Physics 2015-06-23 Keivan G. Stassun , Aleks Scholz , Trent Dupuy , Kaitlin Kratter

The stellar initial mass function (IMF) is an underlying distribution function which determines many important observables, from the number of ionizing photons in a population of some age and metallicity, through the creation rate of…

Astrophysics · Physics 2007-05-23 Gerry Gilmore

The current knowledge on the stellar IMF is documented. It appears to become top-heavy when the star-formation rate density surpasses about 0.1Msun/(yr pc^3) on a pc scale and it may become increasingly bottom-heavy with increasing…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-03 Pavel Kroupa , Carsten Weidner , Jan Pflamm-Altenburg , Ingo Thies , Joerg Dabringhausen , Michael Marks , Thomas Maschberger

In this work, we derive the stellar initial mass function (IMF) from the superposition of mass distributions of dense cores, generated through gravoturbulent fragmentation of unstable clumps in molecular clouds (MCs) and growing through…

Solar and Stellar Astrophysics · Physics 2015-05-20 Todor Veltchev , Ralf S. Klessen , Paul C. Clark

We derive and parametrize the Galactic mass function (MF) below 1 $\msol$ characteristic of both single objects and binary systems. We resolve the long standing discrepancy between the MFs derived from the HST and from the nearby luminosity…

Astrophysics · Physics 2011-06-21 Gilles Chabrier

We review five mechanisms for forming brown dwarfs: (i) turbulent fragmentation of molecular clouds, producing very low-mass prestellar cores by shock compression; (ii) collapse and fragmentation of more massive prestellar cores; (iii) disc…

Astrophysics · Physics 2007-05-23 Anthony Whitworth , Matthew R. Bate , Aake Nordlund , Bo Reipurth , Hans Zinnecker

The frequency and properties of multiple star systems offer powerful tests of star formation models. Multiplicity surveys over the past decade have shown that binary properties vary strongly with mass, but the functional forms and the…

Solar and Stellar Astrophysics · Physics 2015-06-05 Adam L. Kraus , Lynne A. Hillenbrand

We review current theories for the origin of the Stellar Initial Mass Function (IMF) with particular focus on the extent to which the IMF can be considered universal across various environments. To place the issue in an observational…

Density probability distribution functions (PDFs) for turbulent self-gravitating clouds should be convolutions of the local log-normal PDF, which depends on the local average density rho-ave and Mach number M, and the probability…

Astrophysics of Galaxies · Physics 2015-05-27 Bruce G. Elmegreen

We calculate the integrated galactic initial stellar mass function (IGIMF) in the presence of IMF variations in clusters. IMF Variations for a population of clusters are taken into account in the form of Gaussian distributions of the IMF…

Astrophysics of Galaxies · Physics 2022-10-19 Sami Dib

In this contributed talk I present recent results on the connection between stellar population properties and the normalisation of the stellar initial mass function (IMF) measured using stellar dynamics, based on a large sample of 260…

Astrophysics of Galaxies · Physics 2015-06-23 Richard M. McDermid

A large fraction of brown dwarfs and low-mass stars may form by gravitational fragmentation of relatively massive (a few 0.1 Msun), extended (a few hundred AU) discs around Sun-like stars. We present an ensemble of radiative hydrodynamic…

Astrophysics of Galaxies · Physics 2015-05-20 Dimitris Stamatellos , Anthony Whitworth
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