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ASTR 1040 ASTR 1040 AccelAccel AstroAstro:: Stars & GalaxiesStars & Galaxies

Prof. Prof. JuriJuri ToomreToomre TA: Kyle TA: Kyle AugustsonAugustsonLecture 23 Tues 8 Apr 08Lecture 23 Tues 8 Apr 08zeus.colorado.edu/astr1040zeus.colorado.edu/astr1040--toomretoomre

Tour of GalaxiesTour of Galaxies•• Briefly revisit Briefly revisit Monster in the Milky Way Monster in the Milky Way

((supermassivesupermassive black hole at the center)black hole at the center)•• Hubble using Hubble using CepheidsCepheids showed showed AndromedaAndromeda is a is a

distinct distinct ““island universeisland universe”” –– another Galaxy !another Galaxy !•• Today turn toToday turn to Galaxies (Chap 20) Galaxies (Chap 20) starting with starting with

HubbleHubble’’s scheme to classify spiral galaxies, s scheme to classify spiral galaxies, ellipticalsellipticals, and irregulars , and irregulars

•• Look at our Look at our local group of galaxieslocal group of galaxies (Milky Way, (Milky Way, Andromeda, Andromeda, TriangulumTriangulum, LMC, SMC + dwarfs), LMC, SMC + dwarfs)

•• ReRe--readread 20.120.1 Galaxy Types,Galaxy Types, and for Thurs lectureand for Thurs lecture20.220.2 Measuring Cosmic Distances Measuring Cosmic Distances and and 20.3 20.3 HubbleHubble’’s Laws Law

•• NewNew Homework Set 10Homework Set 10 passed outpassed out•• PlanetariumPlanetarium listed for 10 Apr replaced by lecturelisted for 10 Apr replaced by lecture

RadioRadiomappingmappingof galacticof galacticcentercenter

REVISITREVISITBlack HoleBlack Holeat MW centerat MW center

240 240 lyly

SgrSgr A*A*

VLTVLTIR+AOIR+AO

VLT in IR + adaptive opticsVLT in IR + adaptive opticsSgrSgr A* A* orbits orbits

Star motionStar motionaround around black hole black hole at galacticat galacticcentercenter

VLT: IR+AOVLT: IR+AO

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SgrSgr A*A*orbitsorbits

Rotation velocity at galaxy centerRotation velocity at galaxy center

Black holeBlack hole still less than 1/1000 of MW massstill less than 1/1000 of MW mass

Some of central mass Some of central mass is stars, joined by is stars, joined by 3.7 +/3.7 +/-- 0.2 million 0.2 million solar masssolar massBLACK HOLEBLACK HOLE

But further 20%But further 20%uncertainty fromuncertainty fromdistance determinationdistance determination

QuestionQuestion:: Why no powerful jet and accretion Why no powerful jet and accretion disk near disk near MWMW’’ss supermassivesupermassive black hole?black hole?

•• Why not much Why not much emission in emission in XX--rays ? rays ? …….though .though other signs of other signs of activityactivity

•• AnswerAnswer: : maybe it hasmaybe it haseaten all it caneaten all it can–– at least for at least for now ?now ?

LargeLarge--scale structure in Milky Wayscale structure in Milky Way

•• We can observe the atomic hydrogen in We can observe the atomic hydrogen in interstellar gas in Milky Way with _______.interstellar gas in Milky Way with _______.

•• A.A. spacespace--based ultraviolet telescopesbased ultraviolet telescopes

•• B.B. xx--ray telescopesray telescopes

•• C.C. groundground--based visible light telescopes based visible light telescopes

•• D.D. 21 cm observations by radio telescopes21 cm observations by radio telescopes

D.D.

Measuring galactic distancesMeasuring galactic distances

Edwin HubbleEdwin Hubble mademadebreakthrough usingbreakthrough usingCepheid variables Cepheid variables to measure distanceto measure distance

Found AndromedaFound Andromedafar outsidefar outside Milky WayMilky Way

Huge step forward inHuge step forward inthinking about universethinking about universe NGC 4414NGC 4414

HOW DID IT ALL BEGIN?HOW DID IT ALL BEGIN?Cepheid variableCepheid variablestarsstars as distanceas distanceindicators:indicators:““standard candlestandard candle””

Vital discovery byVital discovery byHenrietta Leavitt (1912)Henrietta Leavitt (1912)

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Cepheid starsCepheid stars in Hin H--R diagramR diagram•• ““Instability stripInstability strip”” ----

region in Hregion in H--R diagram R diagram with large, bright starswith large, bright stars

•• Outer regions of star are Outer regions of star are unstable and tend to unstable and tend to pulsatepulsate

•• Star expands and Star expands and contractscontracts,, getting brighter getting brighter and fainterand fainter

ReminderReminder(Fig 15.14)(Fig 15.14)

Cepheid variable Cepheid variable starsstars

brighter brighter CepheidsCepheidshave longer periodshave longer periods

Period Period --LuminosityLuminosityrelationrelation

AndromedaAndromeda found to be far found to be far outsideoutside Milky Way Milky Way –– another another ““island universeisland universe”” : galaxy!: galaxy!

•• Edwin Hubble Edwin Hubble in 1924 in 1924 identified identified CepheidsCepheids in in Andromeda (M33) Andromeda (M33) showed they were far showed they were far outside of Milky Way! outside of Milky Way!

•• Now known Now known distancedistance: : 2.3 million 2.3 million lyly

•• His first big discovery His first big discovery (more to come) (more to come) ……

Hubble using new Hubble using new 100100”” Hooker telescopeHooker telescopeat Mt. Wilson (above LA)at Mt. Wilson (above LA)

100100”” Hooker telescope at Mt WilsonHooker telescope at Mt Wilson

Begins new era in 1924 !Begins new era in 1924 !

Andromeda Andromeda –– M31 (M31 (SbSb))

First galaxy shown First galaxy shown by Hubble (1924)by Hubble (1924)to be a distinctto be a distinct““island universeisland universe””

2.5 million 2.5 million lyly away 260,000 away 260,000 lyly in diameterin diameter

NGC205NGC205

M32M32

Andromeda surprises with Spitzer in IRAndromeda surprises with Spitzer in IR

M32M32

NGC205NGC205

3.6 microns (blue), 4.5 (green)3.6 microns (blue), 4.5 (green) 8 microns (red)8 microns (red)

M31M31

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M31: 11,000 image composite with SpitzerM31: 11,000 image composite with Spitzer

1 1 Striking rings of dust and Striking rings of dust and starbirthstarbirth22 Ring splits into two, forming hole on lower rightRing splits into two, forming hole on lower right3 3 Delicate tracings of spiral arms into very centerDelicate tracings of spiral arms into very center

M31: Forensic evidence of galactic collisionM31: Forensic evidence of galactic collision

M32 plunged through disk on polar axis ~210 My ago ??M32 plunged through disk on polar axis ~210 My ago ??

M31: Beautiful neighbor in UV and IRM31: Beautiful neighbor in UV and IR

GALEX:GALEX: FarFar--UV (blue) UV (blue) –– young hot massive stars young hot massive stars NearNear--UV (green) UV (green) –– relatively older starsrelatively older stars

SPITZER:SPITZER: 24 micron IR (red) 24 micron IR (red) –– cool, dusty star formingcool, dusty star forming

HubbleHubble’’ssscheme toscheme tolabel galaxieslabel galaxies

ellipticalsellipticals EE

spirals Sspirals S

barred spirals SBbarred spirals SB

lenticularlenticular

+ some + some ““irregularsirregulars””

““Tuning forkTuning fork”” shown with shown with mugshotsmugshots of galaxiesof galaxies

spiralsspirals--barredbarred

spiralsspirals

ellipticalsellipticals

M101M101

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SpiralsSpirals~80% of galaxies~80% of galaxies•• DisksDisks (with spiral (with spiral

arms) +arms) +•• SpheroidsSpheroids

((bulges+halosbulges+halos))

NGC 4414NGC 4414

M100M100centercenter

Barred spiralBarred spiralgalaxiesgalaxies

•• Spiral arms emergeSpiral arms emergefrom from central barcentral bar

NGC 1300NGC 1300

NGC 1365NGC 1365

HST: Center of barred spiral NGC 1365HST: Center of barred spiral NGC 1365

IR viewIR view

LenticularsLenticulars(lens(lens--shaped)shaped)

•• Disks, but less gas Disks, but less gas and star formationand star formation

•• Note lack of dust & Note lack of dust & pink nebulaepink nebulae

EllipticalsEllipticals~15% of galaxies~15% of galaxies•• Round or slightly Round or slightly

flattenedflattened

•• Very littleVery little cold gas, cold gas, dust, or young starsdust, or young stars

•• Reddish color = old Reddish color = old stars (red giants, red stars (red giants, red main sequence)main sequence)

Dwarf Dwarf ellipticalsellipticals•• Most common type of Most common type of

galaxy?galaxy?•• Only know nearby Only know nearby

ones (since faint !)ones (since faint !)

NGC 205 NGC 205 2MASS2MASS

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IrregularsIrregulars•• Galaxies in Galaxies in

transformation?transformation?Often LOTS of Often LOTS of star birth star birth

M82M82

NGC 674NGC 674

•• SpiralsSpirals –– mostly mostly in groups (3in groups (3--10 10 galaxies)galaxies)

Where do spirals and Where do spirals and ellipticalsellipticals live?live?

HST: HST: HicksonHickson CG 87CG 87

•• EllipticalsEllipticals --most often in most often in dense clusters dense clusters of galaxiesof galaxies(involve 100(involve 100’’s s to 1000to 1000’’s)s)

HST: HST: AbellAbell 16891689

The Big PictureThe Big Picture:: Universe is Universe is filledfilled with with network of galaxies in groups and clustersnetwork of galaxies in groups and clusters

~100 billion galaxies!~100 billion galaxies!

Pattern of galaxiesPattern of galaxies (3 million+),15(3 million+),15oo portion of skyportion of sky

Brighter =Brighter =more galaxiesmore galaxies

Clicker Clicker –– reading aheadreading ahead

•• What are the What are the MagellanicMagellanic CloudsClouds??

•• A.A. Two nebulae in disk of Milky Way visible Two nebulae in disk of Milky Way visible only in southern hemisphereonly in southern hemisphere

•• B.B. Clouds of dust and gas in many places Clouds of dust and gas in many places throughout the Milky Way galaxythroughout the Milky Way galaxy

•• C.C. Two small galaxies that orbit Milky WayTwo small galaxies that orbit Milky Way•• D.D. StarStar--forming clouds in constellation Orionforming clouds in constellation Orion

C.C.

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Our Our ““local grouplocal group””of galaxiesof galaxies

3 spirals:3 spirals:Andromeda (M31)Andromeda (M31)Milky WayMilky WayTriangulumTriangulum (M33)(M33)2 irregulars:2 irregulars:LMCLMCSMCSMC16+ dwarfs16+ dwarfs

Biggest is Biggest is AndromedaAndromeda ((SbSb -- M31)M31)•• Andromeda is Andromeda is

~3 million light years ~3 million light years away (or ~30 MW away (or ~30 MW diameters), has ~1.5 diameters), has ~1.5 mass of MW mass of MW

•• We see her as We see her as ““sheshe’”’”was 3 million years was 3 million years ago, not as she is ago, not as she is today! today! –– this is this is lookbacklookback timetime

•• Oops! she may crash Oops! she may crash into MW in about 2 into MW in about 2 billion yearsbillion years

TriangulumTriangulum(M33)(M33)

•• 1/5 mass of MW, 1/5 mass of MW, spiral classified as spiral classified as ScSc

•• Several bright (pink) Several bright (pink) star forming regionsstar forming regions

Large & Small Large & Small MagellanicMagellanic CloudsClouds

LMCLMC

SMCSMC

LMC has 30 LMC has 30 DoradusDoradus, home , home

of SN 1987Aof SN 1987A

SN 1987a SN 1987a –– before and afterbefore and after