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Trends along the Hubble Sequence☛ Metallicity: Zaritzky et al. 1994trend of HII region metallicities among spiral typesradial gradients in HII abundances across disks➜ compare metallicities at 1 R eSd/IrrSaTrends along the Hubble Sequence☛ Morphology : Bulge/disk light ratio☛ Colours☛ Spectra☛ SFR 0☛ Luminosities☛ Composition: stars, gas, dust☛ Metallicities: : chemical compositionAll trends can be explained by differences in theStar Formation Histories (= SFHs)Ψ(t)|E ~e~e -t/1GyrΨ(t)|Sp ~ a Sp G(t)a Sa > a Sb > a Sc > a SdΨ(t)|Sd ~ constU. Fritze, HD Grad. Days 2008SFR = Star Formation Rate; SFH = SFR(t)U. Fritze, HD Grad. Days 2008Trends along the Hubble Sequence☛ Morphology : Bulge/disk light ratio☛ Colours☛ Spectra☛ SFR 0☛ Luminosities☛ Composition: stars, gas, dust☛ Metallicities: : chemical compositionAll trends can be explained by differences in theStar Formation Histories (= SFHs)The Star Formation History of the Milky WaySbc galaxyRocha-PintoPinto+2000, , Rocha-Pinto & Maciel 1997, 1998from individual star age and metallicity determinationsΨ(t)|E ~e~e -t/1GyrΨ(t)|Sp ~ a Sp G(t)a Sa > a Sb > a Sc > a SdΨ(t)|Sd ~ constSFR = Star Formation Rate; SFH = SFR(t)U. Fritze, HD Grad. Days 2008Decrease by factor ~4 since the beginning +short-term (10(8 yr) fluctuations by factor < 2 around simplemodel SFHBroad (>factor 10) stellar metallicity distribution〈[Fe/H]〉 < 0 subsolar U. Fritze, HD Grad. Days 200816