On the temporal evolution of the stellar mass function in Galactic clusters

Abstract

We show that we can obtain a good fit to the present day stellar mass functions (MFs) of a large sample of young and old Galactic clusters in the range 0.1 - 10 Msolar with a tapered power law distribution function with an exponential truncation of the form dN/dm \propto m^alpha [1 - exp-(m/m_c)^beta]. The average value of the power-law index alpha is -2, that of beta is 2.5, whereas the characteristic mass m_c is in the range 0.1 - 0.8 Msolar and does not seem to vary in any systematic way with the present cluster parameters such as metal abundance, total cluster mass or central concentration. However, m_c shows a remarkable correlation with the dynamical age of the cluster, namely m_c/Msolar ~ 0.15 + 0.5 tau_dyn^0.75, where tau_dyn is the dynamical age taken as the ratio of cluster age and dissolution time. The small scatter seen around this correlation is consistent with the uncertainties on the estimated value of tau_dyn. We attribute the observed trend to the onset of mass segregation via two-body relaxation in a tidal environment, causing the preferential loss of low-mass stars from the cluster and hence a drift of the characteristic mass m_c towards higher values. If dynamical evolution is indeed at the origin of the observed trend, it would seem plausible that high-concentration globular clusters, now with median m_c ~ 0.33 Msolar, were born with a stellar MF very similar to that measured today in the youngest Galactic clusters and with a value of m_c ~ 0.15 Msolar. This hypothesis is consistent with the absence of a turn-over in the MF of the Galactic bulge down to the observational limit at ~0.2 Msolar and, if correct, it would carry the implication that the characteristic mass is not set by the thermal Jeans mass of the cloud.

7 pages, 2 figures, accepted for publication in the Astrophysical Journal

References in corpus (16)

• The Stellar Populations of Praesepe and Coma Berenices
• The Stellar Population of the Chamaeleon I Star-Forming Region
• Dynamical mass segregation on a very short timescale
• The fraction of binary systems in the core of thirteen low-density Galactic globular clusters
• Evidence for primordial mass segregation in globular clusters
• Why haven't loose globular clusters collapsed yet?
• Formation & evolution of the Galactic bulge: constraints from stellar abundances
• On the Constancy of the Characteristic Mass of Young Stars
• The Luminosity and Mass Functions of Low-Mass Stars in the Galactic Disk: I. The Calibration Region
• Brown dwarfs and very low mass stars in the Hyades cluster : a dynamically evolved mass function
• Deep ACS Imaging in the Globular Cluster NGC 6397: The Cluster Color Magnitude Diagram and Luminosity Function
• Stars and brown dwarfs in the sigma Orionis cluster: the Mayrit catalogue
• The lower mass function of the young open cluster Blanco 1: from 30 Mjup to 3 Mo
• The Distribution of Stellar Mass in the Pleiades
• Tidal foces as a regulator of star formation in Taurus
• The WFC3 Galactic Bulge Treasury Program: A First Look at Resolved Stellar Population Tools

Cited by in corpus (57)

• Global Hierarchical Collapse In Molecular Clouds. Towards a Comprehensive Scenario
• The Big Problems in Star Formation: the Star Formation Rate, Stellar Clustering, and the Initial Mass Function
• Stars, Gas, and Dark Matter in the Solar Neighborhood
• The Close Binary Fraction of Solar-type Stars is Strongly Anti-correlated with Metallicity
• The Stellar Initial Mass Function of Ultra-Faint Dwarf Galaxies: Evidence for IMF Variations with Galactic Environment
• On the function describing the stellar initial mass function
• The Dawes Review 8: Measuring the Stellar Initial Mass Function
• Radiation-Hydrodynamic Simulations of the Formation of Orion-Like Star Clusters I. Implications for the Origin of the Initial Mass Function
• A new perspective on globular clusters, their initial mass function, and their contribution to the stellar halo and to cosmic reionisation
• Chemical composition and constraints on mass loss for globular clusters in dwarf galaxies: WLM and IKN
• Star formation in 30 Doradus
• An Analytic Technique for Constraining the Dynamical Origins of Multiple Star Systems Containing Merger Products
• Detailed abundance analysis from integrated high-dispersion spectroscopy: Globular clusters in the Fornax Dwarf Spheroidal
• Variations in the Stellar IMF: from Bottom to Top
• Back to the Future: Estimating Initial Globular Cluster Masses from their Present Day Stellar Mass Functions
• The global mass functions of 35 Galactic globular clusters: I. Observational data and correlations with cluster parameters
• Effects of the environment and feedback physics on the initial mass function of stars in the STARFORGE simulations
• The Initial Mass Function and Disk Frequency of the Rho Ophiuchi Cloud: An Extinction-Limited Sample
• The detection and characterisation of 54 massive companions with the SOPHIE spectrograph -- 7 new brown dwarfs and constraints on the BD desert
• Testing the universality of the IMF with Bayesian statistics: young clusters
• An Initial Mass Function for Individual Stars in Galactic Disks: I. Constraining the Shape of the IMF
• A comparison between the stellar and dynamical masses of six globular clusters
• The very low-mass stellar content of the young supermassive Galactic star cluster Westerlund 1
• The Effect of Orbital Eccentricity on the Dynamical Evolution of Star Clusters
• Metallicity and the Universality of the IMF
• Testing the role of environmental effects on the initial mass function of low-mass stars
• The Panchromatic Hubble Andromeda Treasury IV. A Probabilistic Approach to Inferring the High Mass Stellar Initial Mass Function and Other Power-law Functions
• Looking deep into the Rosette Nebula's heart: the (sub)stellar content of the massive young cluster NGC 2244
• Dissecting the Colour-Magnitude Diagram: A Homogeneous Catalogue of Stellar Populations in Globular Clusters
• Stellar dynamics in gas: The role of gas damping
• The tidal tails of NGC 2298
• Clues to the star formation in NGC 346 across time and space
• Quantifying the Universality of the Stellar Initial Mass Function in Old Star Clusters
• Formation of proto-clusters and star formation within clusters: apparent universality of the initial mass function ?
• Is it possible to reconcile extragalactic IMF variations with a universal Milky Way IMF?
• System IMF of the 25 Ori Group from Planetary-Mass Objects to Intermediate/High-Mass Stars
• The emergence of the galactic stellar mass function from a non-universal IMF in clusters
• Pre-main sequence stars older than 8 Myr in the Eagle Nebula
• The Luminosity Function and stellar Mass to Light ratio of the massive globular cluster NGC2419
• Open clusters and associations in the Gaia era
• Tidal tails of open clusters
• The GALAH survey: Chemical homogeneity of the Orion complex
• The Lifetimes of Star Clusters Born with a Top-heavy IMF
• Characterising brown dwarf companions with IRDIS long-slit spectroscopy: HD 1160 B and HD 19467 B
• Origin of the dense core mass function in contracting filaments
• Measuring the Initial Mass Function of Low Mass Stars and Brown Dwarfs
• Observational constraints on the likelihood of ${}^{26}$Al in planet-forming environments
• The contribution of dissolving star clusters to the population of ultra-faint objects in the outer halo of the Milky Way
• The galaxy-wide stellar initial mass function in the presence of cluster-to-cluster IMF variations
• Light-element abundance variations in globular clusters
• Modifying two-body relaxation in N-body systems by gas accretion
• Stellar collisions in globular clusters: Constraints on the initial mass function of the first generation of stars
• The population of young low-mass stars in Trumpler 14
• The $Hubble$ Missing Globular Cluster Survey. I. Survey overview and the first precise age estimate for ESO452-11 and 2MASS-GC01
• Ultraviolet extinction properties of the 30 Dor Nebula and interpreting observations of starburst clusters
• When did the initial mass function become bottom-heavy?
• Using the Modified Lognormal Power Law Distribution to Model the Mass Function of NGC 1711