3D and NLTE analysis for large stellar surveys

Karin LindUppsala University, Sweden

Martin Asplund, Paul Barklem, Andrey Belyaev, Maria Bergemann, Remo Collet, Zazralt Magic, Anna Marino, Jorge Meléndez, Yeisson Osorio

Outline- Introduction- 1D LTE/NLTE

- Worst-case scenarios- Recent progress- Calibration techniques- Practical implementation- Applications

- 3D LTE/NLTE- Worst-case scenarios- Observational tests- Mg : 1D/<3D>/LTE/NLTE- Ca : 1D/<3D>/3D/LTE/NLTE - Applications

Motivation

Galactic archaeology by chemical tagging of FGK stars

- Statistics : Soon > 106 stars

- Precision (S/N, wavelength range) : σ[X/H] < 0.1dex, σTeff<150K, σlog(g)<0.3dex

- Accuracy (assumptions: 1D, LTE, atomic data) : σ [X/H]< 0.5 dex, σTeff<400K, σlog(g)< 1 dex

Methods

Model atmosphere Detailed rad. Transfer1D/<3D>/3D LTE 1D/3D LTE/NLTE

R. Collet

NLTE line formation

(1D)

Is it really necessary?

Is it safe?

N-

Worst-case scenario I

NaD lines in metal-poor horisontal branch stars Lind et al. 2011, Marino et al. 2011

B-I

Worst-case scenario II

OI 777nm triplet at very low metallicities

Fabbian et al. 2009

LTE trend

Input data for NLTE analysis

Energy levels + oscillator strengths + photo-ionization cross sectionsRed boxes : have sufficient(?) data

Blue boxes : missing e.g. QM photo-ionisation, but NLTE still attempted

Input data for NLTE analysisBlue boxes : QM hydrogen collisions exist or will exist

Input data for NLTE analysis

Solar neighborhood MDF Halo MDF [X/Fe] vs [Fe/H]

Most important free parameter in NLTEmodelling of Fe is FeI+HI collisional cross-section

Black – LTE Blue – NLTE with no hydrogen collisions

Calibration techniques: ionisation balance

Korn et al. 2003

FeI/FeII ionisation equilibrium calibrated using Hipparcos gravities

S(H)=3

Calibration techniques: excitation balance

Bergemann & Gehren 2008

“Thus, NLTE can solve the discrepancy between the abundances derived from the MnI resonance triplet at 403 nm and excited lines, which is found in analyses of metal-poor subdwarfs and subgiants”

S(H)=0.05

Calibration techniques: CLV

Allende Prieto et al. (2004)Solar centre-to-limb variation of OI lines

Practical implementation I

“Curves-of-growth” from UV-NIR:

3200 FeI lines107 FeII lines

ΔNLTE

Teff=6500Klog(g)=4.0ξ=2km/s

Lind et al. (2012)

Practical implementation IIPre-computed departure coefficients NLTE synthesis

T. Nordlander

FeI NLTE grid

Lind et al. (2012)

Application : metal-poor stars

Ruchti et al. (2012)

LTE NLTE+PHOT

Application : metal-poor stars

LTE NLTE+PHOT

Serenelli et al. (2013)

3D (LTE/NLTE)

Is it really necessary?

Is it safe?

Stagger grid

Magic et al. 2014

Abundance patterns

3D

N-LTE

Keller et al. (2014)

Dashed –200 Msun PISNSolid – 60Msun fallback

Worst-case scenario III

Li isotopic abundances

Asplund et al. 2006Lind et al. 2013

3DN-LTE

Observational tests: the SunPereira et al. 2013

“We confronted the models with observational diagnostics of the [solar] temperature profile: continuum centre-to-limb variations (CLVs), absolute continuum fluxes, and the wings of hydrogen lines. We also tested the 3D models for the intensity distribution of the granulation and spectral line shapes. ”

“We conclude that the 3D hydrodynamical model is superior to any of the tested 1D models.”

Observational tests: low [Fe/H]

Klevas et al. 2013

FeI line assymmetriesin the metal-poor giant HD122563

1.5/3D + NLTE

LiI : Asplund et al. 2003, Sbordone et al. 2010

OI, FeI : Shchukina et al. 2005

OI : Pereira et al. 2010, Prakapavičius et al. 2013

LiI, NaI, CaI : Lind et al. 2013

Ways forward

Model LTE/NLTE Time Performance

1D LTE Seconds

1D NLTE Minutes (seconds using interpolation)

3D LTE Hours

3D NLTE Days The ultimate goal, reference point

<3D> LTE Seconds

<3D> NLTE Minutes (seconds using interpolation)

Mg b in a VMP SG

1D LTE1D NLTE<3D> LTE<3D> NLTE

HD140283

Teff=5780Klog(g)=3.7[Fe/H]=-2.4

“No” free parameters!

Yeisson Osorio

Ca in a VMP dwarf

LTE NLTE1D<3D> 3D

HD19445Teff=6000Klog(g)=4.5[Fe/H]=-2.0

Ca in a VMP dwarf

LTE NLTE1D<3D> 3D

HD19445Teff=6000Klog(g)=4.5[Fe/H]=-2.0

Start ? Goal

Bullets: Optical CaI linesSquares: NIR CaII triplet

Ca in a EMP TO

G64-12Teff=6430Klog(g)=4.0[Fe/H]=-3.0

Start ? Goal

Bullets: Optical CaI linesSquares: NIR CaII triplet

Ca in a EMP TO

Start ? Goal

Bullets: Optical CaI linesSquares: NIR CaII triplet

Ca in a EMP TO

Start ? Goal

Bullets: Optical CaI linesSquares: NIR CaII triplet

Ca in a EMP TO

Start ? Goal

Bullets: Optical CaI linesSquares: NIR CaII triplet

Ca in a EMP TO

Ways forward

Model LTE/NLTE Time Performance

1D LTE Seconds Varied

1D NLTE Minutes (seconds using interpolation)

Improves for ANo change for B

3D LTE Hours May worsen for AImproves for B

3D NLTE Days The ultimate goal, reference point

<3D> LTE Seconds May worsen for AImproves for B

<3D> NLTE Minutes (seconds using interpolation)

Improves for AImproves for B

A : NLTE-sensitive, B : not NLTE-sensitive