1ASTR 1040 ASTR 1040 AccelAccelAstroAstro::Stars & GalaxiesStars & GalaxiesProf. Prof. JuriJuriToomreToomreTA: Nicholas NelsonTA: Nicholas NelsonLecture 25 Tues 12 Apr 2011Lecture 25 Tues 12 Apr 2011zeus.colorado.edu/astr1040zeus.colorado.edu/astr1040--toomretoomreM82 M82 --visiblevisibleTodayToday’’s s ““Ride to the Wild SideRide to the Wild Side””••Today discuss Today discuss making and colliding making and colliding spiral spiral galaxiesgalaxies••Then turn to Then turn to active galaxies active galaxies ––quasars, starburst quasars, starburst galaxies, radio galaxiesgalaxies, radio galaxies••All fromAll fromChap 21: Galaxy Evolution Chap 21: Galaxy Evolution ••Start overview reading Start overview reading Chap 22:Chap 22:Dark Matter, Dark Matter, Dark Energy, Fate of Universe Dark Energy, Fate of Universe ••Third MidThird Mid--Term ExamTerm Examin recitation (Mon April 18). in recitation (Mon April 18). ••Review Set #3Review Set #3passed out, passed out, review sessionreview sessionthis this ThurThur7pm7pm--9pm here by Nick9pm here by Nick••New New Homework Set #11Homework Set #11available, HW #10 dueavailable, HW #10 dueMaking of a Making of a spiral galaxyspiral galaxy••Start with a fairly Start with a fairly uniform cloud of uniform cloud of hydrogenhydrogen••Gravitational collapse Gravitational collapse forms forms protogalacticprotogalacticcloudsclouds••First stars are born in First stars are born in this this spheroid spheroid (such (such stars are billions of stars are billions of years old years old ““fossil fossil recordrecord””))Small variant in spiral making Small variant in spiral making ……••Several Several smaller smaller protogalacticprotogalacticcloudscloudsmay may have merged to have merged to form a single form a single large galaxylarge galaxy••May explain May explain slight variations slight variations in stellar ages in stellar ages in the MWin the MWForming a Forming a disk disk with spiralwith spiral••As more material As more material collapses, collapses, angular angular momentummomentumspins it spins it into a diskinto a disk••Stars now formed Stars now formed in in dense spiral dense spiral armsarms––disk stars disk stars are younger!are younger!Clicker Clicker ––CepheidsCepheidsand distanceand distance••Two Cepheid stars, Fred and Barney, Two Cepheid stars, Fred and Barney, have the have the same apparent brightnesssame apparent brightness. Fred . Fred has a period of 5 days, and Barney of 10 has a period of 5 days, and Barney of 10 days. Which is days. Which is closercloser??••A.A.FredFred••B.B.BarneyBarneyA.A.2Why Why A.A.Fred ?Fred ?••Fred has a Fred has a shorter shorter periodperiodand so must and so must be be less luminousless luminous••Less luminous but Less luminous but the same apparent the same apparent brightness means brightness means that Fred is that Fred is closer closer to usto usPeriodPeriod--Luminosity RelationLuminosity RelationMaking Making ellipticalsellipticals••Higher density: Higher density: much faster star much faster star formationformationuses up uses up all the gas all the gas ••Nothing left to Nothing left to make a diskmake a disk••Now we see Now we see sphere of old starssphere of old starsOr now a Or now a differentdifferentstorystory……..••Spiral galaxy collisionsSpiral galaxy collisionsdestroy disks, destroy disks, leave leave behind behind ellipticalelliptical••Burst of star formation Burst of star formation uses up all the gasuses up all the gas••Leftovers: Leftovers: train wrecktrain wreck••EllipticalsEllipticalsmore more common in dense common in dense galaxy clustersgalaxy clustersNGC 4038/39 AntennaeNGC 4038/39 AntennaeBirth of Birth of galaxiesgalaxiesin clustersin clustersFew galaxiesFew galaxies(none ?)(none ?)BORN aloneBORN aloneCollision ofCollision ofsmall galaxysmall galaxywith big onewith big oneBuilds Builds ““bridgebridge””and and ““counterarmcounterarm””Close passage: M51 + companionClose passage: M51 + companionNGC 5194 + 95NGC 5194 + 953Close passageClose passageof two of two equal massequal massgalaxiesgalaxiesBuilds very longBuilds very long““tailstails””and wispsand wispsTwo galaxies form Two galaxies form ““The AntennaeThe Antennae””Colliding galaxies Colliding galaxies ––““The AntennaeThe Antennae””HST detail: NGC 4038/39HST detail: NGC 4038/39Tidal streams between galaxiesTidal streams between galaxiesHSTHSTInteracting:Interacting:NGC 2207 NGC 2207 + IC 2163+ IC 2163HSTHSTSpitz + HSTSpitz + HSTInteractingInteractingsystemsystemNGC 6745NGC 67454Ring galaxy AM 0644Ring galaxy AM 0644--741741HSTHSTMany Many interacting interacting galaxygalaxysystemssystemsVery distant (Very distant (bigbiglookbacklookbacktimetime))with HSTwith HSTA major puzzle: A major puzzle: ““The MiceThe Mice””NGC 4676NGC 4676““MiceMice””with HST Advanced Camera for Surveyswith HST Advanced Camera for Surveys““MiceMice””in simulation 1in simulation 1Josh BarnesJosh BarnesRotate the Rotate the ““MiceMice””5““MiceMice””in finer simulation 1in finer simulation 1BarnesBarnesLatest simulation 2 of Latest simulation 2 of ““MiceMice””John John DubinskiDubinskiClicker: galaxy collisionsClicker: galaxy collisions••Why are Why are collisions between galaxiescollisions between galaxiesmore more likely than between stars within a galaxy?likely than between stars within a galaxy?••A.A.Galaxies are much larger than starsGalaxies are much larger than stars••B.B.Galaxies travel through space much faster Galaxies travel through space much faster than starsthan stars••C.C.Relative to their sizes, galaxies are closer Relative to their sizes, galaxies are closer together than starstogether than stars••D.D.Galaxies have higher Galaxies have higher redshiftsredshiftsthan starsthan starsC.C.StefanStefan’’s Quintet in HST details Quintet in HST detailIt may happen to us in future!It may happen to us in future!Andromeda (M31) in futureAndromeda (M31) in futureM31 and Milky Way in future collisionM31 and Milky Way in future collisionDubinskiDubinski6Messages from Messages from galaxy interactionsgalaxy interactions1.1.In In dense clustersdense clusters, , galaxy collisionsgalaxy collisions(grazing (grazing or even heador even head--on) must have been on) must have