NLTE modelling of integrated light spectra. Abundances of barium, magnesium, and manganese in a metal-poor globular cluster

Abstract

We study the effects of non-local thermodynamic equilibrium (NLTE) on the abundance analysis of barium, magnesium, and manganese from integrated light spectroscopy, as typically applied to the analysis of extra-galactic star clusters and galaxies. In this paper, our reference object is a synthetic simple stellar population (SSP) representing a mono-metallic alpha-enhanced globular cluster with the metallicity [Fe/H]=-2.0 and the age of 11 Gyr. We used the MULTI2.3 program to compute LTE and NLTE equivalent widths of spectral lines of Mg I, Mn I, and Ba II ions, which are commonly used in abundance analyses of extra-galactic stellar populations. We used ATLAS12 model atmospheres for stellar parameters sampled from a model isochrone to represent individual stars in the model SSP. The NLTE and LTE equivalent widths calculated for the individual stars were combined to calculate the SSP NLTE corrections. We find that the NLTE abundance corrections for the integrated light spectra of the the metal-poor globular cluster are significant in many cases, and often exceed 0.1 dex. In particular, LTE abundances of Mn are consistently under-estimated by 0.3 dex for all optical lines of Mn I studied in this work. On the other hand, Ba II, and Mg I lines show a strong differential effect: the NLTE abundance corrections for the individual stars and integrated light spectra are close to zero for the low-excitation lines, but they amount to -0.15 dex for the strong high-excitation lines. Our results emphasise the need to take NLTE effects into account in the analysis of spectra of individual stars and integrated light spectra of stellar populations.

arXiv comment15 pages, accepted for publication in A&A

References in corpus (77)

• The chemical composition of the Sun
• The epochs of early-type galaxy formation as a function of environment
• Na-O Anticorrelation and HB. VII. The chemical composition of first and second-generation stars in 15 globular clusters from GIRAFFE spectra
• Stellar Chemical Signatures And Hierarchical Galaxy Formation
• Line formation in solar granulation: IV. [O I], OI and OH lines and the photospheric O abundance
• De Re Metallica: The cosmic chemical evolution of galaxies
• Multiple Stellar Populations in Globular Clusters
• Na-O Anticorrelation and HB. VIII. Proton-capture elements and metallicities in 17 globular clusters from UVES spectra
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. I. Overview of the Project and Detection of Multiple Stellar Populations
• A new chemo-evolutionary population synthesis model for early-type galaxies. I: Theoretical basis
• The formation and assembly history of the Milky Way revealed by its globular cluster population
• NLTE line formation of Fe for late-type stars. I. Standard stars with 1D and <3D> model atmospheres
• Multi-Element Abundance Measurements from Medium-Resolution Spectra. III. Metallicity Distributions of Milky Way Dwarf Satellite Galaxies
• Departures from LTE for neutral Li in late-type stars
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. V. Constraints on Formation Scenarios
• The ACS Survey of Galactic Globular Clusters. II. Stellar Evolution Tracks, Isochrones, Luminosity Functions, and Synthetic Horizontal-Branch Models
• The Metallicity of Galaxy Disks: Infall versus Outflow
• NLTE abundances of Mn in a sample of metal-poor stars
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. XVI. The helium abundance of multiple populations
• Non-LTE line formation of Fe in late-type stars - III. 3D non-LTE analysis of metal-poor stars
• Chromium: NLTE abundances in metal-poor stars and nucleosynthesis in the Galaxy
• Chemical abundances of the Milky Way thick disk and stellar halo II.: sodium, iron-peak and neutron-capture elements
• Metal-rich, Metal-poor: Updated Stellar Population Models for Old Stellar Systems
• A Possible Origin of the Mass-Metallicity Relation of Galaxies
• Chemo-spectrophotometric evolution of spiral galaxies: III. Abundance and colour gradients in discs
• NLTE analysis of Co I/Co II lines in spectra of cool stars with new laboratory hyperfine splitting constants
• Non-LTE aluminium abundances in late-type stars
• Chemical Cartography with APOGEE: Multi-element abundance ratios
• Ionization balance of Ti in the photospheres of the Sun and four late-type stars
• Chemical abundances in LMC stellar populations. II. The bar sample
• Non-LTE Line-Formation and Abundances of Sulfur and Zinc in F, G, and K Stars
• Non-LTE oxygen line formation in 3D hydrodynamic model stellar atmospheres
• Red Supergiant Stars as Cosmic Abundance Probes: II. NLTE Effects in J-band Silicon Lines
• The solar photospheric nitrogen abundance. Analysis of atomic transitions with 3D and 1D model atmospheres
• Kinetic equilibrium of iron in the atmospheres of cool stars III. The ionization equilibrium of selected reference stars
• Non-local thermodynamic equilibrium stellar spectroscopy with 1D and <3D> models - I. Methods and application to magnesium abundances in standard stars
• Mg line formation in late-type stellar atmospheres: I. The model atom
• NLTE analysis of Sr lines in spectra of late-type stars with new R-matrix atomic data
• Multi-level 3D non-LTE computations of lithium lines in the metal-poor halo stars HD140283 and HD84937
• Accounting for Stochastic Fluctuations when Analysing Integrated Light of Star Clusters. I: First Systematics
• Chemical composition and constraints on mass loss for globular clusters in dwarf galaxies: WLM and IKN
• Evolution of Cluster Red-Sequence Galaxies from redshift 0.8 to 0.4: ages, metallicities and morphologies
• Globular Cluster Abundances from High-Resolution Integrated Light Spectra, I: 47 Tuc
• Detailed abundance analysis from integrated high-dispersion spectroscopy: Globular clusters in the Fornax Dwarf Spheroidal
• M31 Globular Cluster Abundances from High-Resolution, Integrated-Light Spectroscopy
• Non-LTE line formation of Fe in late-type stars IV: Modelling of the solar centre-to-limb variation in 3D
• Effective temperature determinations of late-type stars based on 3D non-LTE Balmer line formation
• Grid of theoretical NLTE equivalent widths of four Ba II lines and barium abundance in cool stars
• The extreme chemistry of multiple stellar populations in the metal-poor globular cluster NGC 4833
• Manganese Abundances in Cluster and Field Stars
• NLTE model calculations for the solar atmosphere with an iterative treatment of opacity distribution functions
• Unveiling systematic biases in 1D LTE excitation-ionisation balance of Fe for FGK stars. A novel approach to determination of stellar parameters
• Red Supergiant Stars as Cosmic Abundance Probes: NLTE Effects in J-band Iron and Titanium Lines
• Red Supergiant Stars as Cosmic Abundance Probes. III. NLTE effects in J-band Magnesium lines
• The mass-metallicity relations for gas and stars in star-forming galaxies: strong outflow vs variable IMF
• Mg line formation in late-type stellar atmospheres: II. Calculations in a grid of 1D models
• Globular Cluster Abundances from High-Resolution, Integrated-Light Spectroscopy. IV. The Large Magellanic Cloud: $\alpha$, Fe-peak, Light, and Heavy Elements
• A NLTE line blanketed model of a solar type star
• The Detailed Chemical Properties of M31 Star Clusters I. Fe, Alpha and Light Elements
• NLTE Strontium and Barium in metal poor red giant stars
• A grid of NLTE corrections for magnesium and calcium in late-type giant and supergiant stars: application to Gaia
• Influence of inelastic collisions with hydrogen atoms on the non-LTE modelling of Ca I and Ca II lines in late-type stars
• The non-LTE line formation of neutral carbon in late-type stars
• Photometry and spectroscopy of multiple populations along the AGB of NGC2808 and NGC6121 (M4)
• NLTE line formation for Mg\ione\ and Mg\ii\ in atmospheres of B-A-F-G-K stars
• The Populations of Carina. II. Chemical Enrichment
• Integrated Light Chemical Tagging Analyses of Seven M31 Outer Halo Globular Clusters from the Pan-Andromeda Archaeological Survey
• Spectrum Syntheses of High Resolution Integrated Light Spectra of Galactic Globular Clusters
• MASSCLEANcolors - Mass Dependent Integrated Colors for Stellar Clusters Derived from 30 Million Monte Carlo Simulations -
• Detailed abundance analysis of globular clusters in the Local Group: NGC 147, NGC 6822, and Messier 33
• Formation of MnI lines in the solar atmosphere
• Non-LTE analysis of neutral copper in the late-type metal-poor stars
• Detailed abundances from integrated-light spectroscopy: Milky Way globular clusters
• Copper abundance from Cu I and Cu II lines in metal-poor star spectra: NLTE vs LTE
• The Gaia-ESO Survey: Detailed Abundances in the Metal-poor Globular Cluster NGC 4372
• NLTE 1.5D Modeling of Red Giant Stars
• NLTE Stellar Population Synthesis of Globular Clusters using Synthetic Integrated Light Spectra I: Constructing the IL Spectra

Cited by in corpus (12)

• APOGEE Data and Spectral Analysis from SDSS Data Release 16: Seven Years of Observations Including First Results from APOGEE-South
• Observational constraints on the origin of the elements II. 3D non-LTE formation of Ba ii lines in the solar atmosphere
• The Gaia-ESO survey: 3D NLTE abundances in the open cluster NGC 2420 suggest atomic diffusion and turbulent mixing at the origin of chemical abundance variations
• Observational constraints on the origin of the elements. III. Evidence for the dominant role of sub-Chandrasekhar SN Ia in the chemical evolution of Mn and Fe in the Galaxy
• Phosphorus-rich stars with unusual abundances are challenging theoretical predictions
• The chemical composition of globular clusters in the Local Group
• Evidence for sub-Chandrasekhar Type Ia supernovae from the last major merger
• An extremely metal-deficient globular cluster in the Andromeda Galaxy
• The Stars in M15 Were Born with the r-process
• Validating Stellar Abundance Measurements from Multi-Resolution Spectroscopy
• Chemical abundances of Young Massive Clusters in NGC 1313
• Full abundance study of two newly discovered barium giants