Sterrenstelsels en Kosmologie Docent: Huub Röttgering, kamer 465, email: [email protected] College assistent: Chael Kruip, kamer 401, email: [email protected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ijfer 1. Mondeling tentamen 2. Opgaven moeten worden ingeleverd bij het volgende college. Antwoorden tellen mee voor 30 % voor tentamen cijfer, indien tentamen wordt afgelegd voor 1 augustus 2010 Brief content of the course 1) Introduction What is a galaxy ? What is an active galaxy? Classifications, multiwavelength observations, luminosity functions 2) Keeping a galaxy together: Gravity, Potentials 3) Galactic Dynamics Equilibrium, Collisions, Virial Theorem 4) Galactic Dynamics continued Timescales, Orbits 5) Collisionless Boltzmann Equation equilibrium, phase mixing derivation of distribution function 6) Velocity Moments Jeans equations comparison to observations 7) Mass distribution and dark matter Evidence for dark matter from rotation curves Solar neighbourhood, Oort limit Elliptical galaxies and hot gas Candidate dark matter particles 8) Galaxy formation Universe expansion Cosmic microwave background Growth of galaxies by gravity Galaxy scaling relations 9) Galaxy formation - forming the stars Gas cooling and star formation formation of disks dynamical friction and mergers tidal tails in mergers 10) Clusters and Large scale structure 11) Active Galaxies Classification Building blocks Feedback mechanisms Overview • Our galaxy (PS 1.1 - 1.2.3) • History of early galaxy studies (PS. p. 87) • Optical classification and galaxy profiles (PS. 3.1.1, 3.2.1,3.2.2,3.3.2) • Multi-wavelength view • Luminosity functions (PS 3.7 intro, 3.7.1) • Active galactic nuclei (a bit of 5.1.1-3, 5.2) • Main questions Our galaxy (PS 1.1 - 1.2.3) • A panorama of the Milky Way, as seen from Death Valley, 2005. • see: http://en.wikipedia.org/wiki/Milky_Way ZF8%Y>[> YY ZF8%Y>[> • =QD%*6/0",%@K]%.%@K]%/$'6*)9%@?%N;'%/#%[?%O;' • IJ%#(*4%U/4%5:$%0/1/.7,% – 5:$%4:)%/#%]K?%N;'9% – 5$L*2)0%/#%V>>?%N6T49% – #/N*)0%>[?%6*11*5)%7"/$4 • L$*0(#%L1:"%N)5#4,%75:)0%4#/$4 • $"+%015U,%51+%4#/$49%6/*)17%*)%#("%L:10" • 0/1/.7%#5%#("%1"^,%+*4#5$#"+%'56;/)*5)%0/1/.7 Y> NGC 4013 Y[ ZF8%_?Y[ • 5L4"$R"+%"+0"<5)%L7%`:LL1" • +*4N%5L4':$"+%L7%+:4# • '")#$/1%L:10" Y_ a:$%0/1/.7 Y\ D("%F/1/.7 • #(*)%+*4N%5J%75:)0%4#/$4%/)+%0/4%U*#(%/%$/+*:4% 5J%>?%N;'%/)+%/%4'/1"%("*0(#%5J%[??%;'K% • V%Y%N;'%#(*'N%+*4N%U(*'(%'5)#/*)4%/)%51+"$% 4#"11/$%;5;:1/25)%'56;/$"+%#5%#("%#(*)%+*4N • /%'")#$/1%L:10"%5J%51+%4#/$4% • 4;("$*'/1%(/15%'5)#/*)*)0%654#%5J%#("%015L:1/$% '1:4#"$4%/)+%456"%5J%#("%51+"4#%4#/$4% Y@ b5#/25)%/)+%+/$N%6/S"$ Yc • b5#/25)%R"15'*#7, GM(r0) V0 = R0 • R*4*L1"%6/S"$%0*R"4%J5$%#("%4:)%/#%b5%d%]%N;'% Y@?%N6T4% • e"%6"/4:$"%>>?%N6T4%+:"%#5%E+/$N%6/S"$H • Z/#:$"%5J%6/S"$%:)N)5U)K – U"/N17%*)#"$/'2)0%;/$2'1"4f – J$""%g5/2)0%$5'N4f Y] History of early galaxy studies (PS. p. 87) Messier (1730-1817) compiled his ”Catalogue des Nébuleuses et des John Dreyerʼs AY]\><Yh>@B% Amas d’Étoiles” (“Catalogue of Nebulae contribution was the monumental and Star Clusters”) New General Catalogue of Nebulae and Clusters of Stars >? 1920: Great debate on the nature of galaxies between Slipher and in Curtis. Vesto Melvin Slipher Are the nebulae in or (1875 - 1969) outside our galaxy? demonstrated that galaxies rotate >Y %%%%%()*&+,-.//'$ Yh>\,% !"$*5+%1:6*)54*#7%$"1/25)% J5$%8";("*+4%*)%/)+$56"+/, O[Y%/#%/%+*4#/)'"%5J%>]\% N;'%AJ/'#5$%[%#55%46/11B >> `*4#5$7 • O"44*"$%AYc[?<Y]YcB%1*4#4%Y?[%+*i:4"%5Lj"'#4 – O[Y,%3)+$56"+/%)"L:1/ • X5()%G$"*"$%AY]\><Yh>@B,%Z"U%F")"$/1%'/#/150:" – ]???%5Lj"'#4 • YhY>,%="4#5%&1*;("$%6"/4:$"+%#(/#%4;*$/1%)"L:1/"%/$"% $5#/2)0 • Yh>?,%F$"/#%+"L/#"%L"#U"")%&(/;1"7%/)+%8:$24 – /$"%)"L:1/"%*)4*+"%5$%5:#4*+"%#("%0/1/.7f% • Yh>\,%!"$*5+%1:6*)54*#7%$"1/25)%J5$%8";("*+4%*)% /)+$56"+/ – O[Y%/#%/%+*4#/)'"%5J%>]\%N;'%AJ/'#5$%[%#55%46/11B% >[ Optical classification and galaxy profiles (PS. 3.1.1, 3.2.1,3.2.2, 3.3.2) Optical images of galaxies and classification All classification systems are idealisations. Independent of true size of the galaxy ! Classifications problems: Galaxies ‘’look’’ different depending on Depth of image Projection effects Band observed / redshift Often used system: Hubble-Sandage tuning fork diagram >@ M94 - Sa M81 - Sb M101 - Sc M95 - SBa NGC 1300 - SBb NGC 7741 - SBc >] The S0 or lenticular galaxy NGC 3115 QO8%<%I$$%I% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%O]>%<%I$$%II [? Hubble tuning fork diagram Left: ‘early types’, right: `late types’ Elliptical galaxies ellipical isophotes: vary from round to highly elongated En, where n=10[1-(b/a)], with b/a apparent axial radio (note projection effects) Subdivision cD galaxies: central cluster galaxies, M=10^13-10^14 solar mass Giant ellipticals (gE’s) Normal ellipticals -23 < M_B < -15, M=10^8-10^13M Dwarf ellipticals (dE’s), Blue compact dwarf galaxies: bluer than normal, relatively gas-rich Dwarf spheroidals: low luminosity and surface brightness, M=10^7-10^9 M Spirals S: without bar, SB with bar a, ab, b, bc, c, cd, d, from ``early’’ type to ``late’’ type L_bulge/L_tot ~0.3 for a, ~0.13 for b and ~0.05 for c opening angles ~6 deg for a, ~12 deg for b and ~18 deg for c S0 or Lenticular galaxies: ‘ellipticals with signs of disks’’ SB0 or Barred Lenticular galaxies: ‘ellipticals with signs of barred disks’’ Irregulars: Irr I : some regular structure (extension of Sd) Irr II: weak regular structure -11*;2'/1%0/1/.*"4,% L$*0(#)"44%;$5P1" Elliptical galaxies normally follow an r 1/4 law: 1/4 I(R) = Ie exp(!7.67[(R/Re) ! 1]), The constant is chosen so that where Re is the half light radius: half the light is emitted inside Re. Because of uncertainties in the background subtraction, we never know the exact half light radius. The parameter Ie is the surface brightness at R = Re. No galaxy follows the r 1/4 law exactly ! [> C$*0(#)"44%;$5P1"%4;*$/1%0/1/.*"4 In general, the brightness profile of spirals galaxies can be modelled as the sum of (i) an exponential disk for the outer regions I(R) = I0 exp(!R/Rd), where Rd is the disk scale-length. (ii) an r 1/4 law to the bulge Multi-wavelength view: Galaxies emit over the entire electromagnetic spectrum M31 RADIO CONTINUUM EMISSION AT 6 CM 21 CM LINE EMISSION (WSRT) [c Spitzer 24 micron Hot dust Galex UV image Radio cold dust hot dust Optical UV X-ray (center) Galaxies emit in many wavelengths Radio: • Smooth continuum emission following spiral arms: free-free emission due to warm gas • Compact emission regions identified as supernova remnants • Line emission: HI 21 cm, CO, molecular lines from cold gas Infrared: • Continuum emission from dust, heated by young stars in starforming regions Near Infrared: • Red super giants, modest extinction Optical-UV: • Visible stars, dust absorption • Emission lines from hot (10^4 K) gas • Stellar absorption lines •X-Ray: •( Double) stars, neutron stars • Very hot gas Luminosity functions (PS 3.7 intro, 3.7.1) Catalogs of galaxies most catalogs based on optical surveys, e.g.: Revised Shapley-Ames Catalog Sandage and Tammann: Third Reference Catalogue of Bright Galaxies de Vaucouleurs et al Sloan Digital Sky Survey 1 million galaxies + spectra (!) Very important were Palomar Sky Survey Plates, these have been used for systematic surveys UGC: northern galaxies ESO catalog: southern galaxies Selection effects in optical catalogs Consider galaxy with certain luminosity If galaxy too small: misclassified as star if galaxy too big: surface brightness is too low ! > not detected ! Luminosity Function The luminosity function is defined by " dM = number density of galaxies in magnitude range (M,M + dM) ∞ The total density of galaxies is then: ν = Φ(M)dM −∞ Equivalently, "(L)dL is the number density of galaxies in the range (L,L+dL) The distribution of luminosities is well approximated by a Schechter Function #: slope of LF at the faint end, L*: characteristic Luminosity above which the number density drops sharply, "* overall normalization of galaxy density Typical values: where H0 = h 100 km/s The number of galaxies with a luminosity larger than L is given by Total amount of light produced Hence, huge numbers of low luminosity galaxies expected, but finite luminosity. Most of the luminosity comes from galaxies with L=L䌫. A simple approximation is that the universe is filled with L䌫 galaxies with a density "䌫 In practice determining LF is non-trivial: - a large sample of galaxies is needed with well determined absolute luminosities corrected for bandpass, internal absorption and absorption by the Milky Way.