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* what the hell is [Fe/H] ?Local Galaxies* how to measure stellar abundances/metallicities infrom absorption lines ![Fe/H] : Log stellar metallicity or (luminosityweighted mean) metallicity of a stellarpopulationU. Fritze, HD Grad. Days 2008Gaseous & stellar metallicitiesellipticals/S0s/star clusters:☛ Metallicity: : chemical compositionmetallicity Z := mass fraction of everything > 4 Hesolar (photospheric(photospheric) metallicity Z = 0.02metallicity dominated by O, O …,, C, …,, N, ……, , Fe, …Metallicity of the stellar population : [Fe/H]luminosity-weighted stellar metallicity from stellarabsorption lines in the integrated spectrum[Fe/H] := log (X(Fe/X H) - log (X Fe/X H) X i:= mass fraction of element i[Fe/H] = 0: solar[Fe/H] = -1: 1/10 solar[Fe/H] = -2: 1/100 solar[Fe/H] = +0.4 : 2.5 solarU. Fritze, HD Grad. Days 2008Stellar & GaseousMetallicitiesMetallicity of the Inter Stellar Medium (= ISM): : Zmeasured from HII region emission lines (!),expressed in terms of12 + log (O/H)O/H := N O/N Hnumber(!) densitiesTransformation into [O/H] requires mass number12 + log (O/H) = 8.9 for solar abundance Z 12 + log (C/H) = 8.6 for Z 12 + log (Mg/H) = 7.6 for Z . . . . .12 + log (O/H) = 7.9 for 1/10 Z Solar photospheric abundances→ B. Pagel : Nucleosynthesis & Chem. Evol. . of GalaxiesU. Fritze, HD Grad. Days 2008Local GalaxiesFundamental relations for Ellipticals & dEs :Faber – Jackson relation : central velocity dispersion*(Faber & Jackson 76) increases with luminosity➔ distance / mass determinationU. Fritze, HD Grad. Days 2008Local GalaxiesHow to measure velocity dispersion*E.g. elliptical galaxy : integrated spectrum of all its2 - 2000 billion stars~ 2 - 2000 billion × K-star spectrumK-star spectrum : absorption lines with intrinsic widthElliptical galaxy spectrum : absorption lines arebroadened by stellar velocity dispersion(= random motions of stars)Comparison of galaxy spectrum with star spectrum➜ stellar velocity dispersionU. Fritze, HD Grad. Days 2008Local GalaxiesFundamental relations for Ellipticals & dEs :Faber – Jackson relation : central velocity dispersionincreases with luminosity(Faber & Jackson 76)(Ziegler+05)➔ distance / mass determinationL V ~ σ ε ,σ: : central veloc. disp.M r~ σ 4 / (ρ(r r)➜ M/L increases with Lluminous Es have older stellarpopulations and/ormore Dark Matterε~ ~ 4 for bright galsε~ 3.2 for faint galsε~ ~ 5.4 for cD galsU. Fritze, HD Grad. Days 200812