Calibración de trazadores Calibración de trazadores de formación estelar de formación estelar mediante modelos de mediante modelos de

síntesissíntesisHéctor Otí-Floranes, J. M. Mas-Hesse & M. Héctor Otí-Floranes, J. M. Mas-Hesse & M.

CerviñoCerviño

SEA, Santander, 11 de julio de 2008SEA, Santander, 11 de julio de 2008

LAEFF-INTALaboratorio de Astrofísica Espacial y Física

Fundamental

• Regions of intense stellar formationRegions of intense stellar formation• Galaxies Galaxies Starburst galaxies, ULIRGsStarburst galaxies, ULIRGs• Star formation measured byStar formation measured by

– SFR: Star Formation Rate (MSFR: Star Formation Rate (Moo/yr)/yr)– SFS: Star Formation Strength (MSFS: Star Formation Strength (Moo))

• We are interested in the youngest We are interested in the youngest populationpopulation

Massive starsMassive stars• Different SFR tracers:Different SFR tracers:

– UVUV– HH: ionized gas: ionized gas– FIR: heated dustFIR: heated dust– Mechanical energy Mechanical energy X-rays X-rays– [OII][OII]37273727

STARBURSTSSTARBURSTS

GOALS

• Using synthesis models, study the evolution of magnitudes:– FIR– NLyc– UV– Mechanical Energy– Others

• Obtain SFR & SFS calibrations for each of them

• Calibrate the tracers: metallicity, age, etc.

POPULATION SYNTHESIS MODELSPOPULATION SYNTHESIS MODELS

• Initial population with Initial Mass Function:Initial population with Initial Mass Function:IMF(M)IMF(M) M M-2.35-2.35 (M=2-120 M (M=2-120 Moo))

• Evolution of stars:Evolution of stars:– Isochrones: evolution of intrinsic properties (TIsochrones: evolution of intrinsic properties (Teffeff, L, LBOLBOL, etc.), etc.)– Libraries: isochrones data Libraries: isochrones data measurable magnitudes (luminsities, measurable magnitudes (luminsities,

colours, etc.)colours, etc.)• SFR: two types of modelsSFR: two types of models

– EB (extended models, SFR): constant star formationEB (extended models, SFR): constant star formation– IB (instantaneous bursts, SFS): no further formation (usual age 4-6 IB (instantaneous bursts, SFS): no further formation (usual age 4-6

Myr)Myr)• SBS: Star Formation Strenght: initial mass of the burstSBS: Star Formation Strenght: initial mass of the burst

• Unless stated: ZUnless stated: Zoo

• Age < 250 MyrAge < 250 Myr• Models used:Models used:

– CMHK02 (Cerviño, Mas-Hesse & Kunth)CMHK02 (Cerviño, Mas-Hesse & Kunth)– SB99 (Leitherer et al.)SB99 (Leitherer et al.)

IMF CORRECTION• Compare our calibrations with those from:

– Kennicutt (1998)– Salim et al. (2007)

• But they consider M=0.1-100 MMoo (us (us M=2-120 MMoo))

• Two-fold correction:– SFR(0.1-100) = 3.4135 * SFR(2-120)– We include more massive stars. With SB99 calculate

the ratio when steady state is attained (<30 Myr):• L1500/L’1500=1.04

• FIR/FIR’=1.16

• NLyc/N’Lyc=1.16

UV EMISSION 1UV EMISSION 1

•Direct tracer of star formation•But severely affected by extinction•L1500, L2000 and L3500 (U-band)•EB evolution

– steep increase: 0.7 dex in 4-5 Myr– slower raise: 0.3 dex in 250 Myr

•Metallicity: delay in stellar evolution– EB: VERY LOW dependence, <10% Z=0.008

•Good agreement with Kennicutt within 12% after 30 Myr: useful for ages > 20 Myr

•Disagreement with Salim: 30% with respect to Kennicutt– Intrinsic difference between models: 15%– Variety of SFHs of sources of sample: 10%– Z=0.016: 5%

•Z of sample Salim value was expected to be between predictions of models with Z=0.008-0.020

UV EMISSION 2UV EMISSION 2

• Metallicity: delay in stellar evolutionMetallicity: delay in stellar evolution– IB: MEDIUM dependence, 15-25% higher IB: MEDIUM dependence, 15-25% higher

Z=0.008 for LZ=0.008 for L15001500 and L and L20002000

– IB: STRONG dependence, 15-65% for IB: STRONG dependence, 15-65% for LL35003500

FIR EMISSION 1FIR EMISSION 1

• We assume thermal equilibrium of dustWe assume thermal equilibrium of dust

All energy absorbed is reemittedAll energy absorbed is reemitted

• Parameters:Parameters:– Cardelli et al. (1989) extinction law (RCardelli et al. (1989) extinction law (RVV=3.1)=3.1)

+ 30% ionizing photons + 100% Ly+ 30% ionizing photons + 100% Ly– E(B-V): colour excess E(B-V)=0.1-1E(B-V): colour excess E(B-V)=0.1-1

• Similar behaviour to UV radiationSimilar behaviour to UV radiation

Saturation for E(B-V)>0.5 Saturation for E(B-V)>0.5 E(B-V)=1

FIR EMISSION 2FIR EMISSION 2

• Metallicity: delay in stellar evolutionMetallicity: delay in stellar evolution– IB: MEDIUM dependence, 25% higher IB: MEDIUM dependence, 25% higher

Z=0.008Z=0.008– EB: VERY LOW dependence, <11% Z=0.008EB: VERY LOW dependence, <11% Z=0.008

• Kennicutt (1998): lies within 15% after Kennicutt (1998): lies within 15% after 100 Myr100 Myr

Kennicutt only appropiate for long-lived (Kennicutt only appropiate for long-lived (100 Myr) 100 Myr) starburstsstarbursts

IONIZING PHOTONS 1IONIZING PHOTONS 1

•Photons with<912 Å can ionize H atoms

Balmer lines (among others)•Assume a fraction 1-f=0.3 is absorbed

by dust before ionization•Metallicity: delay in stellar evolution

– IB: HIGH dependence, 0.2-0.4 dex higher for Z=0.008

– EB: MEDIUM dependence, 25% higher Z=0.008EB: attains rapidly the steady

state

IONIZING PHOTONS 2IONIZING PHOTONS 2

•Kennicutt value without correction50% higher than models

•After correctionModels & expressions agree

for ages > 8 Myr

When considering 1-f=0.3 in Kennicutt

MECHANICAL ENERGY

• Winds from massive stars and SNe inject mechanical energy into the medium

• LK: energy injected per unit of time• Dominance:

– Early ages: winds– When massive stars comence to die: SNe

• Metallicity:Metallicity:– When ZWhen Z power of winds power of winds , number of WR stars , number of WR stars – IB: HIGH dependence, 60% discrepancies with Z=0.008IB: HIGH dependence, 60% discrepancies with Z=0.008– EB: EXTREMELY LOW dependence in the stationary state EB: EXTREMELY LOW dependence in the stationary state

(>40 Myr) when compared to Z=0.008(>40 Myr) when compared to Z=0.008

EB CALIBRATIONEB CALIBRATION

Magnitude EB (30 Myr) EB (250 Myr)

L1500 3.410-41 2.710-41

L2000 7.110-41 5.110-41

FIR 1.510-44 1.210-44

NLyc 4.110-54 4.110-54

H 3.010-42 3.010-42

LK 1.110-42 9.910-43

Scaled to SFR=1 MMoo/yr

IB CALIBRATIONIB CALIBRATION

Magnitude IB (4 Myr) IB (6 Myr)

L1500 3.310-34 6.910-34

L2000 6.710-34 1.510-33

FIR 1.710-37 3.510-37

NLyc 6.710-47 4.510-46

H 4.910-35 3.310-34

LK 1.110-35 2.010-35

Scaled to SFS=1 MScaled to SFS=1 Moo

CONCLUSIONSCONCLUSIONS• Robust calibrations of SFR and SFS based on Robust calibrations of SFR and SFS based on

several tracers have been obtained using several tracers have been obtained using shynthesis modelsshynthesis models

• Appropriate calibrations should be used depending Appropriate calibrations should be used depending on the burst propertieson the burst properties– Star formation regime: EB or IB Star formation regime: EB or IB VERY IMPORTANTVERY IMPORTANT– Age Age VERY IMPORTANT, especially in IB modelsVERY IMPORTANT, especially in IB models– Metallicity: negligible in EB models for UV and FIRMetallicity: negligible in EB models for UV and FIR– E(B-V), etc.E(B-V), etc.

• Calibrations from literature agree with our models:Calibrations from literature agree with our models:– Kennicutt (1998)Kennicutt (1998)

• UV: good agreement at all ages > 30 MyrUV: good agreement at all ages > 30 Myr• FIR: applies only at ages > 100 MyrFIR: applies only at ages > 100 Myr• NNLycLyc/H/H: after correction for prior dust absorption, at ages > 8 Myr: after correction for prior dust absorption, at ages > 8 Myr

– Salim et al. (2007)Salim et al. (2007)• UV: it underestimates SFRUV: it underestimates SFR