dr. alan alves-brito arc super science fellow red giant stars as tracers of the chemical evolution...

Dr. Alan Alves-BritoARC Super Science Fellow

Red giant stars as tracers of the chemical evolution of the

Galactic bulge

Astounding Stories of Super Science - Hobart, April 18-20. 2

Main Collaborators

Dr. Jorge Meléndez (IAG/USP, Brazil)

Prof. Martin Asplund (RSAA, Australia)

Dr. Thomas Bensby (Lund Observatory, Sweden)


Scientific Motivation

age kinematics dynamics chemical enrichment

DIRBE@COBEDwek et al. 1995

OPTICAL IMAGEAxel Mallenhoff 2001


Tracers of the Galactic bulge

K and M giant stars in the field(e.g. Mcwillian & Rich 1994; Fulbright et al. 2006,2007; Zoccali et al. 2006; Lecureur et al. 2007; Zoccali et al. 2008; Meléndez et al. 2008; Ryde et al. 2009; Alves-Brito et al. 2010; Bensby et al. 2010; Alves-Brito et al. 2012b, in preparation)

Giant stars in globular clusters(e.g. Alves-Brito et al. 2006; Barbuy et al. 2006; Barbuy et al. 2009)

Dwarf, sub-giant and giant stars in gravitational microlenses(e.g. Cohen et al. 2008;2009; Bensby et al. 2008;2009; Alves-Brito et al. 2012c, in preparation)


When and how the Galactic bulge was

formed?

Credit: University of Texas, MacDonald Observatory

stellar content

(classical) vs.

morphology(pseudobulg

e)

Kormendy & Kennicutti 2004

see also Elmegreen et al. 2008


Main goal: Galactic genealogy

Big Bang

Fe-peak

Light elements

Neutroncapture

Grevesse & Sauval 1998

Solar Abundance Pattern


Chemical enrichment: [X/Fe] ~ SF

[O/Fe] ---> SNII/SNIa

Tinsley 1979; Chiappini 2004


Bulge (giants) vs. Disks (dwarves)

The bulge chemical enrichment is dominated by SNII (massive stars). It must have formed faster than both the thick and thin disks

Ballero et al. (2007): MDF and [Mg/Fe] imply different IMFs for the bulge and the thick disk.

Lecureur et al. 2007 and previous works

FLAMES:UVES@VLT: R = 20,000 - 40,000[Fe/H] = log(Fe/H)_star - log(Fe/H)_sun


Concerns Giants (bulge) vs. dwarves (disks): Teff

Zero points on stellar parameters

Line list (different lines, atomic data)

Solar abundances

Methods of analysis


High resolution spectra

PHOENIX@GeminiMIKE@MagellanUVES@VLTELODIE@OHP2dcoude@McDonaldHIRES@Keck

R = / ≥ 60,000

[Fe/H] = log(Fe/H)_star - log(Fe/H)_sun-1.5 < [Fe/H] < +0.5


data reduction

heliocentric radial velocity

continuum normalization

EWs, T, logg, vt, [Fe/ H]

atomic data: loggf, damping ctes spectr um synthesis

MARCS and Kurucz models

spectr a @ optical and I R wavelength s

Methods


Alves-Brito, Meléndez, Asplund et al. 2010, A&A, 513, 35Meléndez, Asplund, Alves-Brito et al. 2008 : CNO

Optical data: R = 60,000 : S/N = 200

thick thin

same knee (thick disk)

The bulge and the (local) thick disk are indistinguishable


Bensby, Alves-Brito, Oye et al. 2010, A&A Bensby, Alves-Brito, Oye et al. 2011, ApJ (outer

disk)

Optical data: MIKE@Magellan R = 55,000 : S/N = 100

Inner Disk (44 giants : 3-7 kpc)

inner disk

, local thick and thin disks; * bulge

The metal poor bulge and the (inner) thick disk are indistinguishable


Alves-Brito, Johnson, Bensby et al. 2012, in preparation

The bulge (normal giants and microlensed ones) and the thick disk are indistinguishable


Gonzalez, Rejkuba, Zoccali et al. 2011, A&A; also using Alves-Brito et al. 2010’s data

Different techniques and independent methods ¡confirm our results! The bulge and the thick disk

are indistinguishable

Optical data: FLAMES@VLT R = 30,000 : S/N = 100 474 giants in 4 different fields


Similar chemical evolution: genetic link

Short timescale, similar SFR and IMF

Classical bulge vs. secular/dynamical

Bulge vs. local and inner thick-disk:

Conclusions


What about the heavy elements?

Bulge vs Thin/Thick disk in the Galactic center

The critical -0.3 < [Fe/H] < +0.0 range

Gaia mission (from 2011-2020): ~1 billion of stars to V=20. 3D map of our Galaxy

Australian GMT, HERMES

SIMPLE@E-Extremely Large Telescopes: high R of dwarf stars in the bulge!

More info: bulge vs. inner disks

Age spread, kinematics and chemical abundances can constrain different models of bulge formation

Perspectives


Thank you very much


Bulge MDF


~245,000 starsl,b = 10.25,-20.65

CMD @HST

t = 10Gyr ([Fe/H] = 0) Unevolved MS t = 10Gyr ([Fe/H] =0.5)

t = GC +- 2.5 Gyr (Ortolani et al. 1995; Zoccali et al. 2003)

Sahu et al. 2006


# 19 gigantes do bojo + 49 gigantes de comparação

Meléndez, Asplund, Alves-Brito et al. 2008, A&A : IR: Phoenix@Gemini-S

bulgethick diskthin diskhalo

[O/Fe] vs. [Fe/H]

[(C+N)/Fe] vs. [Fe/H]

[(C+N)/Fe] = cte

[O/Fe] = 0.41 - 0.02*[Fe/H]

[O/Fe] = 0.39 - 0.01*[Fe/H]

[O/Fe] = 0.03 0.09 dexThe bulge and the (local) thick disk are indistinguishable


# 11 giants in the bulge

X Meléndez et al. 2008

Ryde, Gustafson, Edvardson et al. 2009, A&A

IR: CRIRES@VLT : CNO, R = 70,000 : S/N = 40-110

[O/Fe] @ IR : Phoenix and CRIRES results are consistent


Thick disk formationMichelle et al. 2011

Accretion

Heating via a minor merger

Intense SF in a gas turbulent environment

Radial migration


Ages of Disk Stars

Thick disk: ~10 Gyr Thin disk: <8 Gyr

Bensby et al. (2007)


Inner disk stars


Inner disk: Toomre Diagram

Bensby et al. (2010)


Uncertainties

∆T = ±100K : ∆logg = ±0.30 dex : ∆v = ±0.20 Km/s

Fe: 0.03 dex Mg: 0.07 dex

C: 0.11 dex Si: 0.12 dex

N: 0.11 dex Ca: 0.10 dex

O: 0.14 dex Ti: 0.17 dex


Uncertainties

Continuum level Line fitting (?) Damping parameters Stellar atmospheres : 1D models Non-LTE effects

dr. alan alves-brito arc super science fellow red giant stars as tracers of the chemical evolution...

Documents

bulge giants

preparationgiant stars

star logfeh

chemical evolution

galactic bulgek

snii massive stars

thomas bensby lund observatory

magellan uves