Radial variations in the stellar initial mass function of early-type galaxies

Abstract

The hypothesis of a universal initial mass function (IMF) -- motivated by observations in nearby stellar systems -- has been recently challenged by the discovery of a systematic variation of the IMF with the central velocity dispersion, σ, of early-type galaxies (ETGs), towards an excess of low-mass stars in high-σ galaxies. This trend has been derived so far from integrated spectra, and remains unexplained at present. To test whether such trend depends on the local properties within a galaxy, we have obtained new, extremely deep, spectroscopic data, for three nearby ETGs, two galaxies with high σ (~300 km/s), and one lower mass system, with σ ~ 100 km/s. From the analysis of IMF-sensitive spectral features, we find that the IMF depends significantly on galactocentric distance in the massive ETGs, with the enhanced fraction of low-mass stars f mostly confined to their central regions. In contrast, the low-σ galaxy does not show any significant radial gradient in the IMF, well described by a shallower distribution, relative to the innermost regions of massive galaxies, at all radii. Such a result indicates that the IMF should be regarded as a local (rather than global) property, and suggests a significant difference between the formation process of the core and the outer regions of massive ETGs.

17 pages, 13 figures. Accepted for publication in MNRAS

References in corpus (4)

• Evolutionary Stellar Population Synthesis with MILES. Part I: The Base Models and a New Line Index System
• A systematic variation of the stellar initial mass function in early-type galaxies
• Gravitational fragmentation and the formation of brown dwarfs in stellar clusters
• Variations in the initial mass function in early-type galaxies: A critical comparison between dynamical and spectroscopic results

Cited by in corpus (61)

• The MASSIVE Survey - I. A Volume-Limited Integral-Field Spectroscopic Study of the Most Massive Early-Type Galaxies within 108 Mpc
• The SL2S Galaxy-scale Lens Sample. V. Dark Matter Halos and Stellar IMF of Massive Early-type Galaxies out to Redshift 0.8
• Variations in the initial mass function in early-type galaxies: A critical comparison between dynamical and spectroscopic results
• The stellar initial mass function of early type galaxies from low to high stellar velocity dispersion: homogeneous analysis of ATLAS${}^{3D}$ and Sloan Lens ACS galaxies
• Improved Dynamical Constraints on the Mass of the central Black Hole in NGC 404
• IMF shape constraints from stellar populations and dynamics from CALIFA
• Two new confirmed massive relic galaxies: red nuggets in the present-day Universe
• The initial mass function of a massive relic galaxy
• IMF and [Na/Fe] abundance ratios from optical and NIR Spectral Features in Early-type Galaxies
• The Fornax 3D project: a two-dimensional view of the stellar initial mass function in the massive lenticular galaxy FCC 167
• SDSS-IV MaNGA: Radial Gradients in Stellar Population Properties of Early-Type and Late-Type Galaxies
• The SLUGGS Survey: stellar masses and effective radii of early-type galaxies from Spitzer Space Telescope 3.6$\mu$m imaging
• Spatially resolved variations of the IMF mass normalisation in early-type galaxies as probed by molecular gas kinematics
• The signature of primordial black holes in the dark matter halos of galaxies
• The Fornax 3D project: Thick disks in a cluster environment
• Galaxy structure from multiple tracers: III. Radial variations in M87's IMF
• The Initial Mass Function of Early-type Galaxies: no correlation with [Mg/Fe]
• The kinematics of massive quiescent galaxies at $1.4<z<2.1$: dark matter fractions, IMF variation, and the relation to local early-type galaxies
• Radial gradients in initial mass function sensitive absorption features in the Coma brightest cluster galaxies
• A discrete chemo-dynamical model of the giant elliptical galaxy NGC 5846: dark matter fraction, internal rotation and velocity anisotropy out to six effective radii
• The last 6 Gyr of dark matter assembly in massive galaxies from the Kilo Degree Survey
• Gravitational Potential and Surface Density Drive Stellar Populations -- II. Star-Forming Galaxies
• Is it possible to reconcile extragalactic IMF variations with a universal Milky Way IMF?
• The initial mass functions of M31 and M32 through far red stellar absorption features
• Detection of Enhanced Central Mass-to-Light Ratios in Low-Mass Early-Type Galaxies: Evidence for Black Holes?
• Star formation quenching imprinted on the internal structure of naked red nuggets
• What does (not) drive the variation of the low-mass end of the stellar initial mass function of early-type galaxies
• INSPIRE: INvestigating Stellar Population In RElics III. Second data release (DR2): testing the systematics on the stellar velocity dispersion
• HR-pyPopStar: high wavelength-resolution stellar populations evolutionary synthesis model
• Young stellar population gradients in central cluster galaxies from NUV and optical spectroscopy
• The density of dark matter haloes of early-type galaxies in low-density environments
• INSPIRE: INvestigating Stellar Population In RElics IV. The Initial Mass Function slope in relics
• Dynamical masses of brightest cluster galaxies I: stellar velocity anisotropy and mass-to-light ratios
• Stellar dynamics in the strong-lensing central galaxy of Abell 1201: A low stellar mass-to-light ratio, a large central compact mass, and a standard dark matter halo
• Deriving the star formation histories of galaxies from spectra with simulation-based inference
• Merger-driven evolution of the effective stellar initial mass function of massive early-type galaxies
• Nature versus nurture: relic nature and environment of the most massive passive galaxies at $z<0.5$
• The evolution of radial gradients of MaNGA quiescent elliptical galaxies: inside-out quenching or outer mass growth?
• The Stellar Mass Assembly of Low Redshift, Massive, Central Galaxies in SDSS and the TNG300 simulation
• Spatially-resolved stellar populations and kinematics with KCWI: probing the assembly history of the massive early-type galaxy NGC 1407
• The Imprint of Element Abundance Patterns on Quiescent Galaxy SEDs
• Testing the Universality of the Stellar IMF with Chandra and HST
• The differences between mass- and light-derived structural parameters over time for MaNGA Elliptical galaxies
• An assessment of the evidence from ATLAS3D for a variable initial mass function
• The weak dependence of velocity dispersion on disk fractions, mass-to-light ratio and redshift: Implications for galaxy and black hole evolution
• Modeling Nearly Spherical Pure-Bulge Galaxies with a Stellar Mass-to-Light Ratio Gradient under the $\Lambda$CDM and MOND Paradigms: II. The Orbital Anisotropy of Slow Rotators within the Effective Radius
• Unravelling the Origin of the Counter-Rotating Core in IC 1459 with KMOS and MUSE
• Recovery of the low- and high-mass end slopes of the IMF in massive early-type galaxies using detailed elemental abundances
• Simple interpolation functions for the galaxy-wide stellar initial mass function and its effects in early-type galaxies
• Stellar population analysis of MaNGA early-type galaxies: IMF dependence and systematic effects
• Dynamical masses of brightest cluster galaxies II: constraints on the stellar IMF
• The central dark matter fraction of massive early-type galaxies
• A counter-image to the gravitational arc in Abell 1201: Evidence for IMF variations, or a $10^{10}$M${}_{\odot }$ black hole?
• The extended Planetary Nebula Spectrograph (ePN.S) early-type galaxy survey: The specific angular momentum of ETGs
• Initial Mass Function Variation in two Elliptical Galaxies using Near-Infrared Tracers
• Hierarchical Bayesian inference of the Initial Mass Function in Composite Stellar Populations
• Comparing IMF-sensitive indices of intermediate-mass quiescent galaxies in various environments
• Stellar initial mass function variation in massive early-type galaxies: the potential role of the deuterium abundance
• When did the initial mass function become bottom-heavy?
• The Stellar Initial Mass Function and Population Properties of M89 from Optical and NIR Spectroscopy: Addressing Biases in Spectral Index Analysis
• Fornax 3D project: assessing the diversity of IMF and stellar population maps within the Fornax Cluster