Further constraints on variations in the IMF from LMXB populations

Abstract

We present constraints on variations in the initial mass function (IMF) of nine local early-type galaxies based on their low mass X-ray binary (LMXB) populations. Comprised of accreting black holes and neutron stars, these LMXBs can be used to constrain the important high mass end of the IMF. We consider the LMXB populations beyond the cores of the galaxies ($>0.2R_e$; covering $75-90\%$ of their stellar light) and find no evidence for systematic variations of the IMF with velocity dispersion ($\sigma$). We reject IMFs which become increasingly bottom heavy with $\sigma$, up to steep power-laws (exponent, $\alpha >2.8$) in massive galaxies ($\sigma >300$km/s), for galactocentric radii $>1/4R_e$. Previously proposed IMFs that become increasingly bottom heavy with $\sigma$ are consistent with these data if only the number of low mass stars $(<0.5M_{\odot }$) varies. We note that our results are consistent with some recent work which proposes that extreme IMFs are only present in the central regions of these galaxies. We also consider IMFs that become increasingly top-heavy with $\sigma$, resulting in significantly more LMXBs. Such a model is consistent with these observations, but additional data are required to significantly distinguish between this and an invariant IMF. For six of these galaxies, we directly compare with published IMF mismatch parameters from the Atlas3D survey, ${\alpha }_{dyn}$. We find good agreement with the LMXB population if galaxies with higher ${\alpha }_{dyn}$ have more top-heavy IMFs -- although we caution that our sample is quite small. Future LMXB observations can provide further insights into the origin of ${\alpha }_{dyn}$ variations.

arXiv comment13 pages, 7 figures, accepted for publication in ApJ

References in corpus (59)

• Galactic Stellar and Substellar Initial Mass Function
• On the variation of the Initial Mass Function
• Evolutionary population synthesis: models, analysis of the ingredients and application to high-z galaxies
• The propagation of uncertainties in stellar population synthesis modeling I: The relevance of uncertain aspects of stellar evolution and the IMF to the derived physical properties of galaxies
• The SBF Survey of Galaxy Distances. IV. SBF Magnitudes, Colors, and Distances
• The propagation of uncertainties in stellar population synthesis modeling III: model calibration, comparison, and evaluation
• The Atlas3D project -- I. A volume-limited sample of 260 nearby early-type galaxies: science goals and selection criteria
• A Universal Stellar Initial Mass Function? A Critical Look at Variations
• The Atlas3D project - XX. Mass-size and mass-sigma distributions of early-type galaxies: bulge fraction drives kinematics, mass-to-light ratio, molecular gas fraction and stellar initial mass function
• A systematic variation of the stellar initial mass function in early-type galaxies
• The ACS Fornax Cluster Survey. V. Measurement and Recalibration of Surface Brightness Fluctuations and a Precise Value of the Fornax--Virgo Relative Distance
• A Substantial Population of Low Mass Stars in Luminous Elliptical Galaxies
• The Stellar Initial Mass Function in Early-Type Galaxies From Absorption Line Spectroscopy. II. Results
• The Atlas3D Project - XXX. Star formation histories and stellar population scaling relations of early-type galaxies
• The initial mass function of early-type galaxies
• A new chemo-evolutionary population synthesis model for early-type galaxies. I: Theoretical basis
• The galaxy stellar mass-star formation rate relation: Evidence for an evolving stellar initial mass function?
• The ACS Virgo Cluster Survey. VII. Resolving the Connection Between Globular Clusters and Ultra-Compact Dwarf Galaxies
• SPIDER VIII - Constraints on the Stellar Initial Mass Function of Early-type Galaxies from a Variety of Spectral Features
• Measuring Distances and Probing the Unresolved Stellar Populations of Galaxies Using Infrared Surface Brightness Fluctuations
• Unification of the Fundamental Plane and Super-Massive Black Holes Masses
• Dark Matter Contraction and the Stellar Content of Massive Early-type Galaxies: Disfavoring "Light" Initial Mass Functions
• Systematic variation of the stellar Initial Mass Function with velocity dispersion in early-type galaxies
• A new chemo-evolutionary population synthesis model for early-type galaxies. II: Observations and Results
• The Stellar Initial Mass Function of Ultra-Faint Dwarf Galaxies: Evidence for IMF Variations with Galactic Environment
• Radial variations in the stellar initial mass function of early-type galaxies
• Evidence For A Mild Steepening And Bottom-Heavy IMF In Massive Galaxies From Sodium And Titanium-Oxide Indicators
• The stellar IMF determined in early-type galaxies from a non-degenerate set of optical line indices
• Near-IR line-strengths in elliptical galaxies: evidence for IMF variations?
• The Nature of UCDs: Internal Dynamics from an Expanded Sample and Homogeneous Database
• Dynamical models of NGC 3115
• The orbital structure and potential of NGC 1399
• Dissecting the Red Sequence - III. Mass-to-Light Variations in 3D Fundamental Plane Space
• The galaxy-wide IMF of dwarf late-type to massive early-type galaxies
• A Synthesis of Data from Fundamental Plane and Surface Brightness Fluctuation Surveys
• Confirmation of Enhanced Dwarf-sensitive Absorption Features in the Spectra of Massive Elliptical Galaxies: Further Evidence for a Non-universal Initial Mass Function
• A giant elliptical galaxy with a lightweight initial mass function
• The (galaxy-wide) IMF in giant elliptical galaxies: From top to bottom
• The puzzlingly small CaII triplet absorption in elliptical galaxies
• IMF and [Na/Fe] abundance ratios from optical and NIR Spectral Features in Early-type Galaxies
• Dependence of the LMXB population on stellar age
• An extreme IMF as an explanation for high M/L ratios in UCDs? The CO index as a tracer of bottom heavy IMFs
• Evidence for a non-universal stellar initial mass function in low-redshift high-density early-type galaxies
• Comparing GC and Field LMXBs in Elliptical Galaxies with deep Chandra and Hubble data
• The stellar initial mass function in red-sequence galaxies: 1-micron spectroscopy of Coma Cluster galaxies with Subaru/FMOS
• X-ray Properties of Young Early Type Galaxies: I. X-ray Luminosity Function of LMXBs
• Orbit-Based Dynamical Models of the Sombrero Galaxy (NGC 4594)
• On the Effects of Bursts of Massive Star Formation During the Evolution of Elliptical Galaxies
• Connection between dynamically derived IMF normalisation and stellar population parameters
• Radial Trends in IMF-Sensitive Absorption Features in Two Early-Type Galaxies: Evidence for Abundance-Driven Gradients
• The non-universality of the low-mass end of the IMF is robust against the choice of SSP model
• The IMF-sensitive 1.14-micron Na I doublet in early-type galaxies
• The X-ray Luminosity Functions of Field Low Mass X-ray Binaries in Early-Type Galaxies: Evidence for a Stellar Age Dependence
• The Initial Mass Function of Early-type Galaxies: no correlation with [Mg/Fe]
• Evidence for a constant IMF in early-type galaxies based on their X-ray binary populations
• The X-ray luminosity function of low mass X-ray binaries in early-type galaxies, their metal-rich, and metal-poor globular clusters
• Testing the Universality of the Stellar IMF with Chandra and HST
• Destruction of wide binary stars in low mass elliptical galaxies: implications for initial mass function estimates
• Deep Chandra observations of NGC~7457, the X-ray point source populations of a low mass early-type galaxy

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