IMF and [Na/Fe] abundance ratios from optical and NIR Spectral Features in Early-type Galaxies

Abstract

We present a joint analysis of the four most prominent sodium-sensitive features (NaD, NaI8190, NaI1.14, and NaI2.21), in the optical and Near-Infrared spectral range, of two nearby, massive (sigma~300km/s), early-type galaxies (named XSG1 and XSG2). Our analysis relies on deep VLT/X-Shooter long-slit spectra, along with newly developed stellar population models, allowing for [Na/Fe] variations, up to 1.2dex, over a wide range of age, total metallicity, and IMF slope. The new models show that the response of the Na-dependent spectral indices to [Na/Fe] is stronger when the IMF is bottom heavier. For the first time, we are able to match all four Na features in the central regions of massive early-type galaxies, finding an overabundance of [Na/Fe], in the range 0.5-0.7dex, and a bottom-heavy IMF. Therefore, individual abundance variations cannot be fully responsible for the trends of gravity-sensitive indices, strengthening the case towards a non-universal IMF. Given current limitations of theoretical atmosphere models, our [Na/Fe] estimates should be taken as upper limits. For XSG1, where line strengths are measured out to 0.8Re, the radial trend of [Na/Fe] is similar to [Mg/Fe] and [C/Fe], being constant out to 0.5Re, and decreasing by 0.2-0.3dex at 0.8Re, without any clear correlation with local metallicity. Such a result seems to be in contrast with the predicted increase of Na nucleosynthetic yields from AGB stars and TypeII SNe. For XSG1, the Na-inferred IMF radial profile is consistent, within the errors, with that derived from TiO features and the Wing-Ford band, presented in a recent paper.

arXiv comment22 pages, 8 figure, accepted for publication in MNRAS. The new Na-enhanced models will be available soon at http://miles.iac.es/

References in corpus (82)

• The chemical composition of the Sun
• Galactic Stellar and Substellar Initial Mass Function
• On the variation of the Initial Mass Function
• Evolutionary tracks and isochrones for low- and intermediate-mass stars: from 0.15 to 7 M_sun, and from Z=0.0004 to 0.03
• Parametric Recovery of Line-of-Sight Velocity Distributions from Absorption-Line Spectra of Galaxies via Penalized Likelihood
• Evolutionary population synthesis: models, analysis of the ingredients and application to high-z galaxies
• MILES: A Medium resolution INT Library of Empirical Spectra
• Evolution of asymptotic giant branch stars II. Optical to far-infrared isochrones with improved TP-AGB models
• A large stellar evolution database for population synthesis studies. I. Scaled solar models and isochrones
• X-shooter, the new wide band intermediate resolution spectrograph at the ESO Very Large Telescope
• The Stellar IMF from Turbulent Fragmentation
• Galactic chemical evolution: Carbon through Zinc
• Stellar population models of Lick indices with variable element abundance ratios
• Evolutionary Stellar Population Synthesis with MILES. Part I: The Base Models and a New Line Index System
• The Two Phases of Galaxy Formation
• 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
• Old Stellar Populations. VI. Absorption-Line Spectra of Galaxy Nuclei and Globular Clusters
• A large stellar evolution database for population synthesis studies. II. Stellar models and isochrones for an alpha-enhanced metal distribution
• An Infrared Spectroscopic Sequence of M, L and T Dwarfs
• A Catalog of Bulge+Disk Decompositions and Updated Photometry for 1.12 Million Galaxies in the Sloan Digital Sky Survey
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• A systematic variation of the stellar initial mass function in early-type galaxies
• The Indo-U.S. Library of Coude Feed Stellar Spectra
• New Grids of ATLAS9 Model Atmospheres
• 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 Lick AGN Monitoring Project: Broad-Line Region Radii and Black Hole Masses from Reverberation Mapping of Hbeta
• A library of high resolution synthetic stellar spectra from 300nm to 1.8 micron with solar and alpha-enhanced composition
• The initial mass function of early-type galaxies
• A new chemo-evolutionary population synthesis model for early-type galaxies. I: Theoretical basis
• Non-LTE calculations for neutral Na in late-type stars using improved atomic data
• Explosive yields of massive stars from Z=0 to Z=Zsun
• Evolutionary stellar population synthesis with MILES - II. Scaled-solar and α-enhanced models
• Empirical calibration of the near-IR Ca II triplet - I. The stellar library and index definition
• MIUSCAT: extended MILES spectral coverage. I. Stellar populations synthesis models
• SPIDER VIII - Constraints on the Stellar Initial Mass Function of Early-type Galaxies from a Variety of Spectral Features
• Yields of AGB and SAGB models with chemistry of low- and high-metallicity Globular Clusters
• Early-Type Galaxy Archeology: Ages, Abundance Ratios, and Effective Temperatures from Full-Spectrum Fitting
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• New ATLAS9 And MARCS Model Atmosphere Grids for the Apache Point Observatory Galactic Evolution Experiment (APOGEE)
• Counting Low-Mass Stars in Integrated Light
• The SEGUE Stellar Parameter Pipeline. III. Comparison with High-Resolution Spectroscopy of SDSS/SEGUE Field Stars
• 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
• Flux-calibrated stellar population models of Lick absorption-line indices with variable element abundance ratios
• Radial variations in the stellar initial mass function of early-type galaxies
• Empirical calibration of the near-IR CaII triplet - IV. The stellar population synthesis models
• 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
• Spectral models for solar-scaled and alpha-enhanced stellar populations
• Near-IR line-strengths in elliptical galaxies: evidence for IMF variations?
• NLTE determination of the sodium abundance in a homogeneous sample of extremely metal-poor stars
• Variations of the stellar initial mass function in the progenitors of massive early-type galaxies and in extreme starburst environments
• Center-to-Limb Variation of Solar 3-D Hydrodynamical Simulations
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• SPIDER VII - Revealing the Stellar Population Content of Massive Early-type Galaxies out to 8Re
• The old and heavy bulge of M31 I. Kinematics and stellar populations
• Radial constraints on the Initial Mass Function from TiO features and Wing-Ford band in Early-type Galaxies
• A giant elliptical galaxy with a lightweight initial mass function
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• An optimized H_βindex for disentangling stellar population ages
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• Galactic Globular Clusters as a test for Very Low-Mass stellar models
• 2DPHOT: A Multi-purpose Environment for the Two-dimensional Analysis of Wide-field Images
• A New Approach to the Study of Stellar Populations in Early-Type Galaxies: K-band Spectral Indices and an Application to the Fornax Cluster
• MILES extended: Stellar population synthesis models from the optical to the infrared
• Stellar population synthesis models between 2.5 and 5 μm based on the empirical IRTF stellar library
• The Detailed Chemical Properties of M31 Star Clusters I. Fe, Alpha and Light Elements
• Further evidence for a time-dependent initial mass function in massive early-type galaxies
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• Fully cosmological virtual massive galaxies at z=0: kinematical, morphological, and stellar population characterisation
• The non-universality of the low-mass end of the IMF is robust against the choice of SSP model
• Individual Alpha Elements, C, N, and Ba in Early Type Galaxies
• On the nature of sodium excess objects. I. Data and observed trends
• The IMF-sensitive 1.14-micron Na I doublet in early-type galaxies
• The Initial Mass Function of Early-type Galaxies: no correlation with [Mg/Fe]
• Non-LTE Model Atmospheres for Late-Type Stars II. Restricted NLTE Calculations for a Solar-Like Atmosphere
• The initial mass functions of M31 and M32 through far red stellar absorption features
• Single stellar populations in the near-infrared II. Synthesis models
• The Panchromatic High-Resolution Spectroscopic Survey of Local Group Star Clusters - I. General Data Reduction Procedures for the VLT/X-shooter UVB and VIS arm

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