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The Physics of GalaxiesObservations versus TheoryFrom the Early Universe to the PresentPart 1Prof. Dr. Uta FritzeUniversity of Hertfordshire, UK(Universität Göttingen)Large groundbased & Hubble Space & SatellitesTelescopes Telescopelarge mirrors & fields of viewhigh spatial resolution &γ-ray, X-ray, UV-wavelengths➜ nearby galaxies in enormous detail➜ distant galaxies in large numbers➜ explosion in galaxy researchover the full spectral range γ-rays . . . radioESO - VLT ChileHSTGALEXXX. Heidelberg Physics Graduate DaysSpring 2008U. Fritze, HD Grad. Days 2008U. Fritze, HD Grad. Days 2008M 87HSTNGC 1232 VLTU. Fritze, HD Grad. Days 2008U. Fritze, HD Grad. Days 2008Area 1/100 Full Moon~ 3000 GalaxiesFaintest galaxies :29 mag↳ candle at D moonMulti – band imagingUV – NIRWFPC2 + NICMOS(E. HubbleM 87M 32M 311923ff)LMCNGC 205U. Fritze, HD Grad. Days 2008Cosmic Microwave Background :Universe at z=1000 extremely homogeneous &isotropic? Splendid manifold of local galaxies ?? Relation of distant galaxies to local ones ?Observations = snapshotsEvolution of galaxies ↔ numerical modelsU. Fritze, HD Grad. Days 20081

Program☛ Introduction & basics☛ Local Galaxies : overview☛ Modelling the formation & evolution of galaxies☛ Chemical, spectral & dynamical evolution☛ The Milky Way and the Local Group☛ Resolved stellar populations vs integrated lightGalaxies consist of Stars& eventually of gas (in several coexisting phases)& dustThe sun is “our” star. The Earth is one out of 8 planetsorbiting the sun. Light from the sun travels 8 min. toreach the Earth, 4 h to reach Neptun.☛ Starbursts & interacting galaxies☛ Galaxy transformation in clusters☛ Towards the highest redshifts☛ Galaxy formation scenarios☛ Open question & future perspectivesU. Fritze, HD Grad. Days 2008The nearest star is Proxima Centauri, ~4.2 Lyr away.1 Lyr = c · π · 10 7 km = 300.000 · π · 10 7 km[km/s]] [s/yr[s/yr] = 9 · 10 12 kmU. Fritze, HD Grad. Days 2008The Sun= “our” star, is a gaseous sphere, ~ 4 billion yr old,produces energy by nuclear fusionH + H + H + H -> 4 He + 2e + + 2γ 2 + 2ν2e+ 26.7 MeVhas diameter 1.4 × 10 6 km, mass 1 M ~ 2 × 10 30 kg,mean density 1408 kg/m 3& chemical composition (mass fractions) :H 74%He 24%C, O, Fe, \Ni, Si, , S, Mg, 〉 ~2%Ne, , Ca, Cr /from Fraunhofer’s lines (1814)Astrophysical “semantics” : metals or metallicity Z :=everything heavier than H and He Z ~ 0.02U. Fritze, HD Grad. Days 2008The Sun= “our” star, is a gaseous sphere, ~ 4 billion yr old,produces energy by nuclear fusionH + H + H + H -> 4 He + 2e + + 2γ 2 + 2ν2e+ 26.7 MeVhas diameter 1.4 × 10 6 km, mass 1 M ~ 2 × 10 30 kg,mean density 1408 kg/m 3& chemical composition (mass fractions) :H 74%He 24%C, O, Fe, \Ni, Si, , S, Mg, 〉 ~2%Ne, , Ca, Cr /from Fraunhofer’s lines (1814)Astrophysical “semantics” : metals or metallicity Z :=everything heavier than H and He Z ~ 0.02U. Fritze, HD Grad. Days 2008Galaxies consist of ~ 10 … 1000 billion stars& eventually of gas (in several coexisting phases)& dustStars are born in cooling and collapsing gas/dustclouds, they live & evolve & die.Stars are born with widely different massesbut with a universal mass distribution➔ Stellar Initial Mass Function (Salpeter1955, Kroupa+ + 93, …)lower mass limit : m l ~ 0.04 M hydrogen burning limit,below 0.04 M : Jupiters & brown dwarfsupper mass limit : m u ~ 140 M ? (1 M ~ 2 × 10 30 kg)Stars are social, they are always born in groups orclusters.Log Φ-2.35Most clusters disperse before stars become visibleafter blowing away their natal dust cocoon--> field starsNew stars first appear in the NIR, which can penetratethe dust.U. Fritze, HD Grad. Days 2008Log mNormalisation :∫ mu mlm•Φ(m)dm = 1U. Fritze, HD Grad. Days 20082

Brief History of Galaxy Research☛ 1923 Edwin Hubble, Mt. Wilson Obs. . :Cepheids in M31 = Andromeda nebula➜ M31 = external galaxyHenrietta Swan Leavitt 1912: period luminosity relationfor Cepheid variables.Cepheid with P=3 d has 800 × luminosity of the sun.Cepheid with P=30 d has 10.000 × luminosity of the sun.Absolute luminosities of Milky WayCepheids from parallaxdistancesM - M = V V -2.5 log L V/LV [mag]L V = 3.8 × 103333 erg/s, M V= 4.83 magMt WilsonBrief History of Galaxy Research☛ 1923 Edwin Hubble, Mt. Wilson Obs. . :Cepheids in M31 = Andromeda nebula➜ M31 = external galaxyHenrietta Swan Leavitt 1912: period luminosity relationfor Cepheid variables.Cepheid with P=3 d has 800 × luminosity of the sun.Cepheid with P=30 d has 10.000 × luminosity of the sun.Absolute luminosities of Milky WayCepheids from parallaxdistancesM - M = V V -2.5 log L V/LV [mag]L V = 3.8 × 103333 erg/s, M V= 4.83 magMt WilsonM V: absolute magnitudem V: apparent magnitudeU. Fritze, HD Grad. Days 2008M V: absolute magnitudem V: apparent magnitudeU. Fritze, HD Grad. Days 2008Brief History of Galaxy Research☛ 1923 - 1925: Hubble sequence of galaxiesBrief History of Galaxy Research☛ 1929 E. Hubble, Mt. Palomar 5m :galaxy redshiftsMt PalomarRecession velocityU. Fritze, HD Grad. Days 2008DistanceU. Fritze, HD Grad. Days 2008Local GalaxiesNormal (= big) galaxies : Hubble sequenceE, S0, Sa, Sb, , Sc, Sd, IrrM 87M 32NGC 205Dwarf galaxies : dE, dSph, dILow surface brightness galaxies : E, disk, dwarfStarburst galaxies, interacting galaxies, radio gals,AGN, ULIRGs, , SCUBA gals, Lyman Break Gals, . . .M 31(E. Hubble 1923ff)LMCU. Fritze, HD Grad. Days 2008Observations at different wavelengths→ complementary informationX-rays : hot gas, binary starsUV : young, hot, high-mass stars→ star formation (=SF)opt. : solar-type, intermed. . massstarsNIR : old, cool, low mass stars→ galaxy massmid- & FIR : dust - therm. . emissionsub-mm : cold, molecular gas→ 1. order reservoir for SFRadio : neutral hydrogen gas→ 2. order reservoir for SF Spiral galaxy M81U. Fritze, HD Grad. Days 20085

Observations at different wavelengths→ complementary informationM31 Caltech – ROSAT – Chandra – GALEX – IRASObservations at different wavelengths→ complementary informationGALEX – SDSS(Gil de Paz+06)UV opt.U. Fritze, HD Grad. Days 2008U. Fritze, HD Grad. Days 2008Observations at different wavelengths➜ complementary informationGALEX M51(Johnson+06)Local GalaxiesNormal (= big) galaxies : Hubble sequenceE, S0, Sa, Sb, , Sc, Sd, Irr(E. Hubble 1923ff)GALEX – optical – SpitzerUV mid-IRFUV : blue 6“ 6 resol.Hα : green degraded to 6“ 624 µm m dust : red 6“ 6 resol.U. Fritze, HD Grad. Days 2008M 87M 32M 31LMCNGC 205Dwarf galaxies : dE, dSph, dILow surface brightness galaxies : E, disk, dwarfStarburst galaxies, interacting galaxies, radio gals,AGN, ULIRGs, , SCUBA gals, Lyman Break Gals, . . .U. Fritze, HD Grad. Days 2008Local GalaxiesNormal (= big) galaxies : EllipticalsM 87Local GalaxiesNormal (= big) galaxies : EllipticalsM 87~ spheroidal e:= 1-b/a, 0 ≤ e ≤ 0.7stellar densities : not measurable➜ surface brightnessde Vaucouleurs r ¼ -surfacebrightness profileR e:= effective radius= half light radiusI e:= intensity within R eU. Fritze, HD Grad. Days 2008disky – boxy Eslow-L – high-Lold, low-mass starsK-star type spectrum, red coloursno HI, no molecular gas, no SFwide range in luminosities : -25 ≤ M B[mag] ≤ -12cD . . . . . . . . . . . dEM - M = V V -2.5 log F V/FV [mag]10 ≤ M/L ≤ 100 (in solar units [M /L ])U. Fritze, HD Grad. Days 20086

Local GalaxiesFerguson+98 : Hα emission from HII regions ( ➜ starformation) beyond the optical radius in spiralsHot gas : HII : emission linestrace physical & chemical conditionsN , T e eabundancesLocal GalaxiesThilker+07,Gil de Paz+05 : Galex UV emission from hotyoung stars beyond the optical radius in spiralsE.g. NGC 4625Galex: : FUV deep B-bandH : Lyman, Balmer, Paschen, ….UV opt.NIRseriesHα, , Hβ, H , Hγ,HH,Hδ,…lines from all elements &ionisation stagesalso forbidden * lines, e.g. [OII]*collisionnally de-excitedF(Hα) [erg/s] ~ SFR [M o /yr] under terrestrial conditions,but not in Hyper-UHV in spaceU. Fritze, HD Grad. Days 2008U. Fritze, HD Grad. Days 2008Observations at different wavelengths→ the GALEX SurpriseGALEX – SDSS (Gil de Paz+06)Observations at different wavelengths→ the GALEX SurpriseGALEX – SDSS (Gil de Paz+06)Some galaxies appear much more extended in the UVthan in the optical, HI, and HαHStar formation extends far beyond the optical disk !(= far beyond where the stars are)➜ inside out formation of disks but :Reservoir ???HII regions ??? (but see Ferguson+04)IMF ??? (cf. Kotulla & Fritze, , in prep.)U. Fritze, HD Grad. Days 2008Some galaxies appear Hα (WIYN) much on top of more GALEX extended UV in the UVthan in the optical, HI, and HαHStar formation extends far beyond the optical disk !(= far beyond where the stars are)➜ inside out formation of disks but :Reservoir ???Arp 78HII regions ??? (but see Ferguson+04)IMF ??? (cf. Kotulla & Fritze, , in prep.)U. Fritze, HD Grad. Days 2008M 32NGC 205Local GalaxiesNormal (= big) galaxies : Spirals Sa, Sb, , Sc, SdM 31differential rotation120 km/s ≤ v rot≤ 240 km/srotational velocity ➔ total(= dynamical) massLocal GalaxiesNormal (= big) galaxies : Spirals Sa, Sb, , Sc, SdM 32NGC 205M 31disks : gradients in- color- extinction- metallicity- stellar agedifficult to disentanglerotation curves ➔ Dark Matter halosU. Fritze, HD Grad. Days 2008U. Fritze, HD Grad. Days 20088

Spirals Sa, Sb, , Sc, Sd:Spiral GalaxiesMasses within 1 R H: 9·1011 . . . 3·10310 10 M Sa Sb Sc SdSFRo(Sa)0.5Z(Sa) > Z(SbSb) > Z(Sc) > Z(SdSd)(B-V)(Sa)> (B-V)(SbSb)> (B-V)(Sc) > (B-V)(SdSd)M/L(Sa) > M/L(SbSb) > M/L(Sc) > M/L(SdSd)~6.2 ~4.4 ~2.6 (Rubin+82)MW : M B= -19.4 mag, M31: M B= -20.5 mag,LMC: M B= -18.1 mag,SMC: M B= -16.6 magU. Fritze, HD Grad. Days 2008Pegasus M 32dSphNGC 205Galaxies beyond the Hubble SequenceM 31LMCDwarf galaxies : dE, dSph, dIM32, NGC 205 - LMC, SMCdE : mini-E 10 7 . . . 10 9 M red, old, metal-poordSph : mini-S0red, ?old?, ?metal-poor?dI : irregular : HI, CO, SFblue, young starslow metallicitydwarf galaxies : by far thedominant population ofgalaxies (by number) --in particular in clustersU. Fritze, HD Grad. Days 2008Galaxies beyond the Hubble SequenceLow surface brightness galaxies : Es, disks, dwarfsparallel sequence to Hubble sequenceLSB Es, dEs : old stellar pops, no gas (diff. to detect)Sagittarius, Canis MajorLSB disks and irregulars : very gas-rich, low SFR,Malin-1young stellar pops, low metallicity? old stellar component ?? formation epoch ?? late formation or slow evolution ?? why ?in isolation or low gal. dens. environm. . !U. Fritze, HD Grad. Days 2008Galaxies beyond the Hubble Malin-1SequenceLow surface brightness galaxies : Es, disks, dwarfsparallel sequence to Hubble sequenceLSB Es, dEs : old stellar pops, no gas (diff. to detect)Sagittarius, Canis MajorLSB disks and irregulars : very gas-rich, low SFR,Malin-1young stellar pops, low metallicity? old stellar component ?? formation epoch ?? late formation or slow evolution ?? why ?in isolation or low gal. dens. environm. . !U. Fritze, HD Grad. Days 2008Galaxies beyond the Hubble SequenceStarbursts, Seyfert galaxies, radio galaxies, quasarsGalaxies beyond the Hubble SequenceStarbursts, Seyfert galaxies, radio galaxies, quasarsStarburst gal. M82SubaruSey NGC 7742SDSS QSO @ z=5.8white/brown: stellar light, red: hot expanding gasRadio gal 3C31 = NGC 383, blue: opt., red: radioU. Fritze, HD Grad. Days 2008Sey NGC 7742SDSS QSO @ z=5.8Radio gal 3C31 = NGC 383, blue: opt., red: radioU. Fritze, HD Grad. Days 20089

Galaxies beyond the Hubble SequenceStarbursts, Seyfert galaxies, radio galaxies, quasarsGalaxies beyond the Hubble SequenceStarbursts, Seyfert galaxies, radio galaxies, quasarsSey NGC 7742Sey NGC 7742U. Fritze, HD Grad. Days 2008Radio gal 3C31 = NGC 383, blue: opt., red: radioU. Fritze, HD Grad. Days 2008Galaxies beyond the Hubble SequenceStarbursts, Seyfert galaxies, radio galaxies, quasarsGalaxies beyond the Hubble SequenceInteracting galaxies,Ultraluminous Infra-Red Galaxies (ULIRGs(ULIRGs)NGC 2207 - IC 2163Arp 220, HST visibleArp 220, Palomar 5mSDSS QSO @ z=5.8Arp 220, ChandraU. Fritze, HD Grad. Days 2008U. Fritze, HD Grad. Days 2008Galaxies beyond the Hubble SequenceInteracting galaxies,Ultraluminous Infra-Red Galaxies (ULIRGs(ULIRGs)Galaxies beyond the Hubble SequenceInteracting galaxies,Ultraluminous Infra-Red Galaxies (ULIRGs(ULIRGs)Arp 220, HST visibleArp 220, Palomar 5mArp 220, HST visibleArp 220, Palomar 5mArp 220, ChandraArp 220, ChandraU. Fritze, HD Grad. Days 2008U. Fritze, HD Grad. Days 200810

[Fe/H]M 87 NGC 205 M 313 Aspects of Galaxy EvolutionM 32LMCSpectralBruzual '83ffSplendid manifold of local galaxies :? How & when did they form & how did they evolve ?2 approaches :? nature vs. . nurture ?☛ study distant galaxies : identify progenitorshigh redshift☛ study nearby galaxies in detail : traces of their historyastro-archeologyObservations = snapshotsEvolution of galaxies ↔ numerical modelsU. Fritze, HD Grad. Days 2008Tinsley '68ffChemicalObservational relationsDynamicalOriginally modelled one by one independently.Now attempting to couple consistently : GALEV models *S : formation & evolution of stars +/- gas +/- dustC : formation & nucleosynthesis of stars; infall/outflow of gasD : internal & external gravitation, stars + gas + DM* 2003 Hertha-Sponer Research award DPGToomre '72ffU. Fritze, HD Grad. Days 2008Local GalaxiesLocal GalaxiesFundamental relations for Ellipticals & dEs :Fundamental relations for Ellipticals & dEs :Color – magnitude relation : brighter Es are redderColor – magnitude relation : brighter Es are redder(de Vaucouleurs 61, 72, fffff)Luminosity – metallicity relation : brighter Es are moremetal-richFaber – Jackson relation : central velocity dispersionincreases with luminosity➔ distance determinationKormendy's relations :brighter Es have large effective radiibrighter Es have lower (average) surface brightness.Sphs (and GCs) do not follow Kormendy's relations.Fundamental Plane relations : effective radius – surfacebrightness – luminosity – central velocity dispersion➜ M/L increases with L U. Fritze, HD Grad. Days 2008 U. FritzeFritze, HD Grad. Days 2008Local GalaxiesFundamental relations for Ellipticals & dEs :Luminosity – metallicity relation : brighter Es are moremetal-rich*Vader 86,Bica & Alloin 87,Skillman 89U. Fritze, HD Grad. Days 2008Local Galaxies* how to measure stellar abundances/metallicities inellipticals/S0s/star clusters:from absorption lines !The stronger the absorption line of a given atom ormolecule in a stellar spectrum, the more of it must bein the stellar photosphere (c.f. ionization corrections,etc.).In integrated spectra of galaxies it’s s morecomplicated: luminosity weighted mean stellarabundances/metallicities~ 20 Lick indices, measured in extenso in stellarspectra with dependencies on [Fe/H]*, Teff andsurface gravity studied in detail (e.g. Mg2, Mgb, NaD,Fe52, …, TiO, …)U. Fritze, HD Grad. Days 200811

* 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

Local GalaxiesFundamental relations for Ellipticals & dEs :Fundamental Plane relations : effective radius –surface brightness – luminosity – central velocitydispersion3 global parameters enough to describe structure ofnormal ellipticals, , 2-dimensionally correlated: planeL V~ σ eaI ebr e~ σ ecI eda b c dDressler+872.65 -0.65 1.33 -0.83Djorgovski 3.45 -0.86 1.39 -0.90& Davis 87➜ M/L increases with LLocal GalaxiesFundamental relations for Spirals :Luminosity – metallicity relation : for spirals and Irrs:brighter Sps/Irrs have higher ISM metallicitiessimilar to relation for ellipticals (stellar metall.)(Skillman 89)Spirals[Fe/H]Es, dSphsU. Fritze, HD Grad. Days 2008U. Fritze, HD Grad. Days 2008Redshift Evolution of Fundamental PLaneGalaxy mix :Local GalaxiesRedshiftevolutionin the field : normal (=big) galaxies >70% Sps~20% Es

Local GalaxiesLocal luminosity functions for galaxies :field galaxiesbreak-downinto typesfaint end slope α ~ –1.1(N galgal ➙ inf. . for L B ➘)cluster galaxies:steep faint end slopefaint end slope α

Trends along the Hubble Sequence☛ Colours : RC2 (de Vaucouleurs et al. 1977),RC3 (Buta(et al. 1995) . . . . . . . . . . . . . . . . . . . . . . . . .

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