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This paper presents improved constraints on the low-mass stellar initial mass function (IMF) of the Bo\"otes I (Boo~I) ultrafaint dwarf galaxy, based on our analysis of recent deep imaging from the Hubble Space Telescope. The identification…

Astrophysics of Galaxies · Physics 2022-11-16 Carrie Filion , Imants Platais , Rosemary F. G. Wyse , Vera Kozhurina-Platais

I review efforts to determine the form and any lower limit to the initial mass function in the Galactic disk, using observations of low-mass stars and brown dwarfs in the field, young clusters and star forming regions. I focus on the…

Solar and Stellar Astrophysics · Physics 2015-06-05 R. D. Jeffries

We present near-infrared $J$, $H$, and $K$ images of four embedded stellar clusters in the Galaxy. We find a significant fraction of pre-main-sequence stars present in at least one of the clusters. For the clusters dominated by…

Astrophysics · Physics 2008-11-26 A. Leistra , A. Cotera , J. Liebert

The stellar initial mass function (IMF) describes how many stars form at which mass. Despite recent observational progress, many fundamental properties of the IMF are still unknown. Specifically the question, whether starbursts are biased…

Astrophysics · Physics 2007-05-23 Frank Eisenhauer

Theoretical and indirect observational evidences suggest that stellar initial mass function (IMF) increases with redshift. On the other hand star formation rates (SFR) may be as high as 100 $M_{\odot}$ yr$^{-1}$ in star burst galaxies.…

Astrophysics of Galaxies · Physics 2015-08-06 Tanuka Chattopadhyay , Tuli De , Bharat Warlu , Asis Kumar Chattopadhyay

The abundance of brown dwarfs (BDs) in young clusters is a diagnostic of star formation theory. Here we revisit the issue of determining the substellar initial mass function (IMF), based on a comparison between NGC1333 and IC348, two…

Solar and Stellar Astrophysics · Physics 2015-06-17 Aleks Scholz , Vincent Geers , Paul Clark , Ray Jayawardhana , Koraljka Muzic

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

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 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…

The initial mass function (IMF) is one of the most important functions in astrophysics because it is key to reconstructing the cosmological matter cycle, understanding the formation of super-massive black holes, and deciphering the light…

Astrophysics of Galaxies · Physics 2024-12-30 Pavel Kroupa , Eda Gjergo , Tereza Jerabkova , Zhiqiang Yan

The stellar initial mas function (IMF) has been described as being invariant, bottom heavy or top-heavy in extremely dense star burst conditions. To provide usable observable diagnostic we calculate redshift dependent spectral energy…

Astrophysics of Galaxies · Physics 2018-01-04 Tereza Jerabkova , Pavel Kroupa , Joerg Dabringhausen , Michael Hilker , Kenji Bekki

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

We investigate the dependence of stellar properties on the mean thermal Jeans mass in molecular clouds. We compare the results from the two largest hydrodynamical simulations of star formation to resolve the fragmentation process down to…

Astrophysics · Physics 2010-04-06 Matthew R. Bate , Ian A. Bonnell

We present a new approach in the study of the Initial Mass function (IMF) in external galaxies based on quasar microlensing observations. We use measurements of quasar microlensing magnifications in 24 lensed quasars to estimate the average…

Astrophysics of Galaxies · Physics 2019-11-05 J. Jiménez-Vicente , E. Mediavilla

I use a sample of more than 120,000 stars in the solar neighbourhood with parallaxes, magnitudes and colours estimated with unprecedented accuracy by the second data release of the Gaia mission to derive the initial mass function of the…

Astrophysics of Galaxies · Physics 2019-09-25 A. Sollima

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

Star formation rates (SFR) larger than 1000 Msun/ yr are observed in extreme star bursts. This leads to the formation of star clusters with masses > 10^6 Msun in which crowding of the pre-stellar cores may lead to a change of the stellar…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-20 Carsten Weidner , Pavel Kroupa , Jan Pflamm-Altenburg

The initial-final mass relation represents a mapping between the mass of a white dwarf remnant and the mass that the hydrogen burning main-sequence star that created it once had. The relation thus far has been constrained using a sample of…

We propose a functional form for the IMF, the L_3 IMF, which is a natural heavy-tailed approximation to the log-normal distribution. It is composed of a low-mass power law and a high mass power-law which are smoothly joined together. Three…

Astrophysics of Galaxies · Physics 2015-06-12 Thomas Maschberger

The statistical parameters of five generalizations of the Lindley distribution, such as the average, variance and moments, are reviewed. A new double truncated Lindley distribution with three parameters is derived. The new distributions are…

Methodology · Statistics 2020-03-31 Lorenzo Zaninetti