Evidence for Two Distinct Stellar Initial Mass Functions : Probing for Clues to the Dichotomy

Abstract

We present new measurements of the velocity dispersions of eleven Local Group globular clusters using spatially integrated spectra, to expand our sample of clusters with precise integrated-light velocity dispersions to 29, over 4 different host galaxies. This sample allows us to further our investigation of the stellar mass function among clusters, with a particular emphasis on a search for the driver of the apparent bimodal nature of the inferred stellar initial mass function. We confirm our previous result that clusters fall into two classes. If, as we argue, this behavior reflects a variation in the stellar initial mass function, the cause of that variation is not clear. The variations do not correlate with formation epoch as quantified by age, metallicity quantified by $[Fe/H]$, host galaxy, or internal structure as quantified by velocity dispersion, physical size, relaxation time, or luminosity. The stellar mass-to-light ratios, ${{\rm Y}}_{\ast }$, of the high and low ${{\rm Y}}_{\ast }$ cluster populations are well-matched to those found in recent studies of early and late type galaxies, respectively.

arXiv commentAccepted for publication in ApJ

References in corpus (27)

• Galactic Stellar and Substellar Initial Mass Function
• On the variation of the Initial Mass Function
• A Universal Stellar Initial Mass Function? A Critical Look at Variations
• Resolved Massive Star Clusters in the Milky Way and its Satellites: Brightness Profiles and a Catalogue of Fundamental Parameters
• A Universal Mass Profile for Dwarf Spheroidal Galaxies?
• A systematic variation of the stellar initial mass function in early-type galaxies
• Are the Magellanic Clouds on their First Passage about the Milky Way?
• A Substantial Population of Low Mass Stars in Luminous Elliptical Galaxies
• The Ages of 55 Globular Clusters as Determined Using an Improved delta V_TO^HB Method Along with Color-Magnitude Diagram Constraints, and Their Implications for Broader Issues
• The ACS Survey of Galactic Globular Clusters. XII. Photometric Binaries along the Main-Sequence
• The Stellar Initial Mass Function in Early-Type Galaxies From Absorption Line Spectroscopy. II. Results
• The initial mass function of early-type galaxies
• The Bifurcated Age-Metallicity Relation of Milky Way Globular Clusters and its Implications For the Accretion History of the Galaxy
• The Stellar Initial Mass Function of Ultra-Faint Dwarf Galaxies: Evidence for IMF Variations with Galactic Environment
• Evidence For A Mild Steepening And Bottom-Heavy IMF In Massive Galaxies From Sodium And Titanium-Oxide Indicators
• The DiskMass Survey. VII. The distribution of luminous and dark matter in spiral galaxies
• Ultra-Deep Hubble Space Telescope Imaging of the Small Magellanic Cloud: The Initial Mass Function of Stars with M <~ 1 Msun
• Toward Equations of Galactic Structure
• High resolution infrared spectra of NGC 6440 and NGC 6441: two massive Bulge Globular Clusters
• Testing Newtonian Gravity with AAOmega: Mass-To-Light Profiles and Metallicity Calibrations From 47 Tuc and M55
• Globular Cluster Abundances from High-Resolution, Integrated-Light Spectroscopy. III. The Large Magellanic Cloud: Fe and Ages
• The photometric evolution of dissolving star clusters: II. Realistic models. Colours and M/L ratios
• Quantifying the Universality of the Stellar Initial Mass Function in Old Star Clusters
• Evidence for Two Distinct Stellar Initial Mass Functions
• Dynamics of the Globular Cluster NGC 362
• Star Clusters, Galaxies, and the Fundamental Manifold
• Evidence for Two Distinct Stellar Initial Mass Functions : Revisiting the Effects of Cluster Dynamical Evolution

Cited by in corpus (21)

• N-body modeling of globular clusters: Masses, mass-to-light ratios and intermediate-mass black holes
• Galactic Dark Matter Halos and Globular Cluster Populations. III: Extension to Extreme Environments
• The Dawes Review 8: Measuring the Stellar Initial Mass Function
• A Dynamical Survey of Stellar-Mass Black Holes in 50 Milky Way Globular Clusters
• Clues to the nature of ultra diffuse galaxies from estimated galaxy velocity dispersions
• Biases in the inferred mass-to-light ratio of globular clusters: no need for variations in the stellar mass function
• Dynamical masses and mass-to-light ratios of resolved massive star clusters -- II. Results for 26 star clusters in the Magellanic Clouds
• Globular Cluster Abundances from High-Resolution, Integrated-Light Spectroscopy. II. Expanding the Metallicity Range for Old Clusters and Updated Analysis Techniques
• The Globular Cluster System of the Coma cD Galaxy NGC 4874 from Hubble Space Telescope ACS and WFC3/IR Imaging
• The Nature of Ultra-diffuse Galaxies in Distant Massive Galaxy Clusters: Abell 370 in the Hubble Frontier Fields
• The emergence of the galactic stellar mass function from a non-universal IMF in clusters
• Implications of a variable IMF for the interpretation of observations of galaxy populations
• MOCCA-SURVEY Database I: Is NGC 6535 a Dark Star Cluster Harboring an IMBH?
• Modelling the Observed Stellar Mass Function and its Radial Variation in Galactic Globular Clusters
• The relation between the mass-to-light ratio and the relaxation state of globular clusters
• Giant disk galaxies : Where environment trumps mass in galaxy evolution
• Dynamical Masses and Mass-to-light Ratios of Resolved Massive Star Clusters. I. NGC 419 and NGC 1846
• Evolution of the Mass and Luminosity Functions of Globular Star Clusters
• The Bottom-Light Present Day Mass Function of the Peculiar Globular Cluster NGC 6535
• A two-phase model of galaxy formation: III. The formation of globular clusters
• When did the initial mass function become bottom-heavy?