evolutionary population synthesis models divakara mayya inaoeydm advanced lectures on galaxies (2008...
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Evolutionary Population Evolutionary Population Synthesis modelsSynthesis models
Divakara MayyaDivakara Mayya
INAOEINAOE
http://www.inaoep.mx/~ydmhttp://www.inaoep.mx/~ydm
Advanced Lectures on Galaxies (2008 INAOE): Chapter 4
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What do we try to synthesize?What do we try to synthesize?
Mayya
Observed quantities (spectrum, colors, Luminosity etc.) from a region of a galaxy which consists of
Stars: emit lightDust : absorb and re-radiateGas : ionize and re-radiate
In general the three componentsare mixed even for parsec size regions such as the Super Star Cluster R136.
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What do we try to synthesize?What do we try to synthesize?
Mayya
The aim is to obtain the ages and masses of all important stellar groups the in a given region, by comparing the observedquantities with the theoretically computed quantities.
The region in study may be as simple as an old globular cluster (GC) or as complex as a starburstin an interacting galaxy such as the Antennae.
GCs are relatively simple --- all the stars are of the same age, hardly any gas and dust
Starburst systems are complex --- - Age spread - Metallicity spread - In-homogenous dust distribution - Underlying background
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The Simplest modelThe Simplest modelSimple Stellar Populations (SSP)Simple Stellar Populations (SSP)
or or Instantaneous Bursts (IB)Instantaneous Bursts (IB)
Stars:Stars:Total Stellar Flux = Number of living stars * Flux of each starTotal Stellar Flux = Number of living stars * Flux of each star - all the living stars have the same age and metallicity- all the living stars have the same age and metallicity - mass distribution is power-law (Salpeter IMF)- mass distribution is power-law (Salpeter IMF)
Dust: Correct the observed fluxes using a derived extinction assuming Dust: Correct the observed fluxes using a derived extinction assuming foreground dust model and an extinction curve (Cardelli et al. 1989)foreground dust model and an extinction curve (Cardelli et al. 1989)
Gas: Add the fluxes calculated from photo-ionization modelsGas: Add the fluxes calculated from photo-ionization models for an HII region to the synthesized stellar fluxes (Osterbrock’s text)for an HII region to the synthesized stellar fluxes (Osterbrock’s text)
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SSP: SSP: Basic equations and IngredientsBasic equations and Ingredients
Mayya
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SSP: SSP: Basic equations and IngredientsBasic equations and Ingredients
Mayya
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SSP: SSP: Basic equations and IngredientsBasic equations and Ingredients
Mayya
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SSP: SSP: Basic equations and IngredientsBasic equations and Ingredients
Mayya
Stellar Evolutionary tracks (Isochrones) - Geneva - Padova
Uncertainties:-Mass-loss rates?-Rotation?
Stellar Atmospheric models - Kurucz (LTE) models - Observed stellar spectra
Uncertainties:-non-LTE effects?-Hot star models
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SSP: SSP: The methodThe method
MayyaIsochrone Interpolation schemes
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SSP: SSP: The methodThe method
Mayya
Effect of rotation: rotating (_____) non-rotating (---)
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SSP: SSP: The outputThe output
Mayya
1. Nebular Lines
2. Continuum band luminosity
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SSP: SSP: The outputThe output
Mayya
3. Colors and equivalent widths - U-B, B-V, V-K etc. - EW(Ha), EW(Hb) etc.
4. Selected spectral features - CaT from RSGs - Broad 4686 from Wolf-Rayet
5. Radio continuum - Thermal flux from HII region - Non-thermal flux from SNRs
6. Far-infrared continuum in dusty galaxies - Bolometric luminosity
7. Mechanical energy - Power from stellar winds and SN explosions
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(Class II) SSP: Results(Class II) SSP: Results
Mayya
Discussion of the paper Sec. 3: Dependence of SSP evolution with input parameter, comparison with observations etc.
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(Class III) SSP: observable phases(Class III) SSP: observable phases
Mayya
1. Nebular ( < 6 Myr) : Emission lines2. Wolf-Rayet (3-5 Myr) : HeII 4686 broad spectral feature3. Red Supergiant (7-20 Myr): Calcium Triplet in absorption4. A-star (50-500 Myr) : Balmer lines in absorption5. Intermediate (0.5-2 Gyr) : Balmer and CaII H and K line ratios6. Old population (>2 Gyr): 4000 Ang break and other Lick indices
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SSP: spectral evolutionSSP: spectral evolution
Mayya
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Continuous Star formation (CSF) vs IB:Continuous Star formation (CSF) vs IB:Ionizing photonsIonizing photons
Mayya
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CSF vs IB: MagnitudeCSF vs IB: Magnitude
Mayya
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CSF vs IB: colorsCSF vs IB: colors
Mayya
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CSF vs IB: SEDCSF vs IB: SED
Mayya
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Deriving Age and Mass: diagnostic diagramsDeriving Age and Mass: diagnostic diagrams
Mayya
1. Color vs Color : age/extinction2. Magnitude vs Color: age/extinction and mass3. EW(Ha) vs Color : age and extinction4. Spectral fitting : age and extinction5. Lick Indices : age/metallicity
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CSF vs IB: RSG featuresCSF vs IB: RSG features
Mayya
Mayya 1997
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The real case:The real case:star formation history of star formation history of starburst nucleistarburst nuclei
Mayya
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The real case:The real case: star formation history of star formation history of starburst nucleistarburst nuclei
Mayya
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Star formation history of M82 diskStar formation history of M82 disk
Mayya
Mayya et al. (2006)
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Other applications: SFROther applications: SFR
Mayya
Kennicutt 1998
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Other applications: Other applications: Galaxy formation and evolution
Mayya
1. Fossil analysis (MOPED)2. Integrated approach (GRASIL)