The initial mass function of stars and the star-formation rates of galaxies

Abstract

The measured star-formation rates (SFRs) of galaxies comprise an important constraint on galaxy evolution and also on their cosmological boundary conditions. Any available tracer of the SFR depends on the shape of the mass-distribution of formed stars, i.e. on the stellar initial mass function (IMF). The luminous massive stars dominate the observed photon flux while the dim low-mass stars dominate the mass in the freshly formed population. Errors in the number ratio of the massive to low-mass stars lead to errors in SFR measurements and thus to errors concerning the gas-accretion-rates and the gas-consumption time-scales of galaxies. The stellar IMF has traditionally been interpreted to be a scale-invariant probability density distribution function (PDF), but it may instead be an optimal distribution function. In the PDF interpretation, the stellar IMF observed on the stales of individual star clusters is equal to the galaxy-wide IMF (gwIMF) which, by implication, would be invariant. In this Chapter we discuss the fundamental properties of the IMF and of the gwIMF, the nature of both and their systematic variability as indicated by measurements and theoretical expectations, and we discuss the implications for the SFRs of galaxies and their main sequence. The importance of the putative most-massive-star-mass vs stellar-mass-of-the-hosting-embedded-cluster (mmax-Mecl) relation and its possible establishment during the proto-stellar formation phase, is emphasised.

arXiv commentLaTex, 62 pages, 8 figures. This is Chapter 2 in the book "Star-formation Rates of Galaxies", edited by Veronique Buat and Andreas Zezas, published in April 2021 by Cambridge University Press [ISBN: 9781107184169]. This arXiv version contains additional material in Sec. 1.1.1, 1.1.2, 1.2, 1.3 and 1.7.1

References in corpus (131)

• On the variation of the Initial Mass Function
• The Global Schmidt Law in Star Forming Galaxies
• Star Formation in the Milky Way and Nearby Galaxies
• Binary interaction dominates the evolution of massive stars
• The Initial Mass Function of Stars: Evidence for Uniformity in Variable Systems
• The epochs of early-type galaxy formation as a function of environment
• A Highly Consistent Framework for the Evolution of the Star-Forming "Main Sequence" from z~0-6
• From filamentary clouds to prestellar cores to the stellar IMF: Initial highlights from the Herschel Gould Belt survey
• The Stellar IMF from Turbulent Fragmentation
• Dynamical evolution of star clusters in tidal fields
• The Radial Acceleration Relation in Rotationally Supported Galaxies
• Galactic-Field IMFs of Massive Stars
• A Substantial Population of Low Mass Stars in Luminous Elliptical Galaxies
• Early Star Formation and the Evolution of the Stellar Initial Mass Function in Galaxies
• Cores, filaments, and bundles: hierarchical core formation in the L1495/B213 Taurus region
• The Formation Mechanism of Brown Dwarfs
• Efficiencies of Low-Mass Star and Star Cluster Formation
• Inverse Dynamical Population Synthesis and Star Formation
• Cluster-formation in the Rosette molecular cloud at the junctions of filaments
• An upper limit to the masses of stars
• A Theory of the IMF for Star Formation in Molecular Clouds
• Evidence for top-heavy stellar initial mass functions with increasing density and decreasing metallicity
• The Dynamical Properties of Stellar Systems in the Galactic Disc
• Evidence for a Non-Uniform Initial Mass Function in the Local Universe
• An excess of massive stars in the local 30 Doradus starburst
• Inefficient star formation through turbulence, magnetic fields and feedback
• Evidence for a fundamental stellar upper mass limit from clustered star formation
• Stellar populations dominated by massive stars in dusty starburst galaxies across cosmic time
• The Mass Discrepancy-Acceleration Relation: Disk Mass and the Dark Matter Distribution
• Galaxy And Mass Assembly (GAMA): The star formation rate dependence of the stellar initial mass function
• From Filamentary Networks to Dense Cores in Molecular Clouds: Toward a New Paradigm for Star Formation
• A new chemo-evolutionary population synthesis model for early-type galaxies. II: Observations and Results
• Radial variation of attenuation and star formation in the largest late-type disks observed with GALEX
• The Variation of Integrated Star IMFs among Galaxies
• Implications for the formation of star clusters from extra-galactic star-formation rates
• On the universality of interstellar filaments: theory meets simulations and observations
• A Multi-Wavelength Study of the Young Star Clusters and Interstellar Medium in the Antennae Galaxies (NGC 4038/9)
• A census of dense cores in the Aquila cloud complex: SPIRE/PACS observations from the Herschel Gould Belt survey
• Modeling jet and outflow feedback during star cluster formation
• The impact of the metallicity and star formation rate on the time-dependent galaxy-wide stellar initial mass function
• The ages of young star clusters, massive blue stragglers and the upper mass limit of stars: analysing age dependent stellar mass functions
• The RMS Survey: Galactic distribution of massive star formation
• Evidence for a non-universal stellar initial mass function from the integrated properties of SDSS galaxies
• Thickening of galactic disks through clustered star formation
• Statistical Confirmation of a Stellar Upper Mass Limit
• Collapse of a molecular cloud core to stellar densities: stellar core and outflow formation in radiation magnetohydrodynamics simulations
• The Kinematics of the Scorpius-Centaurus OB Association from Gaia DR1
• Do O-stars form in isolation?
• Leo P: An Unquenched Very Low-Mass Galaxy
• The Dawes Review 8: Measuring the Stellar Initial Mass Function
• Galaxies appear simpler than expected
• The mmax-Mecl relation, the IMF and IGIMF: probabilistically sampled functions?
• The initial stellar mass function from random sampling in hierarchical clouds II: statistical fluctuations and a mass dependence for starbirth positions and times
• SLUG - Stochastically Lighting Up Galaxies. II: Quantifying the Effects of Stochasticity on Star Formation Rate Indicators
• A highly abnormal massive star mass function in the Orion Nebula cluster and the dynamical decay of trapezia systems
• Testing the universality of the star formation efficiency in dense molecular gas
• Gravitational collapse of the OMC-1 region
• Analytical theory for the initial mass function: III time dependence and star formation rate
• The statistical properties of stars and their dependence on metallicity: the effects of opacity
• The Origin and Universality of the Stellar Initial Mass Function
• Dense Stellar Populations: Initial Conditions
• How was the Hubble sequence 6 Gyrs ago?
• The galaxy-wide IMF of dwarf late-type to massive early-type galaxies
• Variations in the initial mass function in early-type galaxies: A critical comparison between dynamical and spectroscopic results
• A giant elliptical galaxy with a lightweight initial mass function
• The (galaxy-wide) IMF in giant elliptical galaxies: From top to bottom
• The Origin of the Arches Stellar Cluster Mass Function
• Variations in the Stellar IMF: from Bottom to Top
• Chemo-Archaeological Downsizing in a Hierarchical Universe: Impact of a Top Heavy IGIMF
• An analytical description of the evolution of binary orbital-parameter distributions in N-body computations of star clusters
• The stellar IMF from Isothermal MHD Turbulence
• The dynamical evolution of Taurus--Auriga-type aggregates
• The bound fraction of young star clusters
• How can young massive clusters reach their present-day sizes?
• Variability in the stellar initial mass function at low and high mass: 3-component IMF models
• Distribution of Serpens South protostars revealed with ALMA
• Chemodynamical Modelling of the Galactic Bulge and Bar
• The emergence of super-canonical stars in R136-type star-burst clusters
• On the initial binary population for star cluster simulations
• The influence of multiple stars on the high-mass stellar initial mass function and age-dating of young massive star clusters
• An IMF Study of the Dwarf Starburst Galaxy NGC 4214
• Characterizing the Brown Dwarf Formation Channels from the Initial Mass Function and Binary-star Dynamics
• Evidence for feedback and stellar-dynamically regulated bursty star cluster formation: the case of the Orion Nebula Cluster
• Opening the Treasure Chest: A Newborn Star Cluster Emerges from its Dust Pillar in Carina
• Maximum stellar mass versus cluster membership number revisited
• Testing the universality of the IMF with Bayesian statistics: young clusters
• Light breeze in the local Universe
• Two step ejection of massive stars and the issue of their formation in isolation
• Complete ejection of OB stars from very young star clusters and the formation of multiple populations
• Testing the universal stellar IMF on the metallicity distribution in the bulges of the Milky Way and M31
• Further evidence for a time-dependent initial mass function in massive early-type galaxies
• Massive stars reveal variations of the stellar initial mass function in the Milky Way stellar clusters
• Mass distributions of star clusters for different star formation histories in a galaxy cluster environment
• The Effect of Star Formation History on the Inferred Initial Stellar Mass Function
• Stellar clusterings around "Isolated" Massive YSOs in the LMC
• Do all stars in the solar neighbourhood form in clusters? A cautionary note on the use of the distribution of surface densities
• UNIFICATION OF THE NEARBY AND PHOTOMETRIC STELLAR LUMINOSITY FUNCTIONS
• Roll of the Dice: A Stochastically Sampled IMF Alters the Stellar Content of Simulated Dwarf Galaxies
• Do star clusters form in a completely mass-segregated way?
• Why Do Stars Form In Clusters? An Analytic Model for Stellar Correlation Functions
• The chemical evolution of galaxies with a variable IGIMF
• A new method to create initially mass segregated star clusters in virial equilibrium
• Towards a fully consistent Milky Way disc model - III. Constraining the initial mass function
• Star formation in the outskirts of DDO 154: A top-light IMF in a nearly dormant disc
• The JCMT Gould Belt Survey: Dense Core Clusters in Orion A
• On the true shape of the upper end of the stellar initial mass function: The case of R136
• The galactocentric radius dependent upper mass limit of young star clusters: stochastic star formation ruled out
• Gas and stellar spiral arms and their offsets in the grand-design spiral galaxy M51
• Near-infrared adaptive optics imaging of infrared luminous galaxies: the brightest cluster magnitude - star formation rate relation
• Galactic Outflows, Star Formation Histories, and Timescales in Starburst Dwarf Galaxies from STARBIRDS
• Variations in the Mass Functions of Clustered and Isolated Young Stellar Objects
• The IMF as a function of supersonic turbulence
• The Turbulent Interstellar Medium
• Sampling methods for stellar masses and the mmax-Mecl relation in the starburst dwarf galaxy NGC 4214
• The influence of stellar-dynamical ejections and collisions on the relation between the maximum-star and star-cluster-mass
• The Formation and Evolution of Small Star Clusters
• Revisiting the classics: Is [Mg/Fe] a good proxy for galaxy formation time-scales?
• Very massive stars in not so massive clusters
• Possible smoking-gun evidence for initial mass segregation in re-virialized post-gas expulsion globular clusters
• The Star Formation Reference Survey III: A Multi-wavelength View of Star Formation in Nearby Galaxies
• Young massive clusters in the interacting LIRG Arp 299: evidence for the dependence of star cluster formation and evolution on environment
• Does turbulence determine the initial mass function?
• Exploring the IMF of star clusters: a joint SLUG and LEGUS effort
• Ongoing star formation at the outskirts of Sextans A: Spectroscopic detection of early-O type stars
• Kinematic evidence for feedback-driven star formation in NGC 1893
• Was the Milky Way a chain galaxy? Using the IGIMF theory to constrain the thin-disk star formation history and mass
• Dynamical equivalence, the origin of the Galactic field stellar and binary population, and the initial radius--mass relation of embedded clusters
• On the origin of the Schechter-like mass function of young star clusters in disk galaxies
• The initial conditions of star formation: cosmic rays as the fundamental regulators
• The Fundamental Building Blocks of Galaxies
• Star Formation Rate Determinations

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• The effect of the environment-dependent stellar initial mass function on the photometric properties of star-forming galaxies
• Simulations of star forming main sequence galaxies in Milgromian gravity
• A radiation transfer model for the Milky Way. II The global properties and large scale structure
• Decoding NGC 628 with radiative transfer methods
• VALES VIII: Weak ionized gas outflows in star-forming galaxies at $z\sim 0.15$ traced with VLT/MUSE
• Deriving the intrinsic properties of M51 with radiative transfer models