Smecker-Hane TIARA tabel

8/13/2019 Smecker-Hane TIARA tabel

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The Physics GoverningThe Physics Governing

Stars & Stellar EvolutionStars & Stellar Evolution

4.4. PressurePressure

Ideal Gas Law: P =Ideal Gas Law: P = kTkT//

5.5. Hydrostatic EquilibriumHydrostatic Equilibrium

At every radius in the star, the force exerted byAt every radius in the star, the force exerted bythe outward gas pressure must balance thethe outward gas pressure must balance theweight of the material on topweight of the material on top

Theoretical Stellar Evolutionary ModelsTheoretical Stellar Evolutionary Models

successfully predict the properties of thesuccessfully predict the properties of theSun and other stars from these basic inputs!Sun and other stars from these basic inputs!

The Interior of a StarThe Interior of a Star


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The Interior of a StarThe Interior of a Star

TheThe HertzsprungHertzsprung--Russell Diagram (HRD)Russell Diagram (HRD)

The MainThe Main

Stages ofStages of

StellarStellar

EvolutionEvolution

Note: By convention, theNote: By convention, the TTeffeff axis in an HRD is reversed. Hotter,axis in an HRD is reversed. Hotter,

bluer stars are to the left and cooler, redder stars are to thebluer stars are to the left and cooler, redder stars are to the right.right.


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TheThe HertzsprungHertzsprung--Russell Diagram (HRD)Russell Diagram (HRD)

Massive StarsMassive Stars

changechange TTeffeff at fixedat fixed

L when they evolveL when they evolve

and becomeand become

SupergiantSupergiant starsstars

Low Mass StarsLow Mass Stars

change in bothchange in both TTeffeffand L when theyand L when they

evolve andevolve andbecomebecome Red GiantRed Giant

starsstars

Star ClustersStar Clusters

As the cluster ages, stars evolve off the main-sequence,

go through their various evolutionary stages, then they

die and disappear from the HR Diagram


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Quiz on Cluster AgesQuiz on Cluster Ages

Here is a table of the temperatures of stars at theHere is a table of the temperatures of stars at the

main sequence turnoff in four clusters. Whichmain sequence turnoff in four clusters. Which

cluster is the oldest?cluster is the oldest?

7,0007,000M 67M 67DD

5,0005,0004747 TucTucCC

9,0009,000NGC 188NGC 188BB

22,00022,000OrionOrionAA

TTeffeff ((K)K)NameNameClusterCluster

The Sun is a very

typical star.

Most of the stars are

seen places where

they spend the

longest time.

Stellar Lifetimes:

90% on MS, ~5% on

RGB, ~5% HB

HipparcosHipparcos Catalog: Stars Nearest the SunCatalog: Stars Nearest the Sun


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Main Sequence LifetimeMain Sequence Lifetime

Lifetime = Energy Available / Rate UsedLifetime = Energy Available / Rate Used

ttMSMS M / LM / L

The mass M dictates the L of a star. In fact,The mass M dictates the L of a star. In fact,LL MM3.53.5 for most main sequence stars.for most main sequence stars.

Therefore,Therefore,

ttMSMS

M / LM / L

M / MM / M3.53.5

MM--2.52.5

ttMSMS = 10= 101010 yrs x (M/Myrs x (M/M))

--2.52.5

Main Sequence LifetimeMain Sequence Lifetime

Stars have masses from 0.08 MStars have masses from 0.08 M < M < 130 M< M < 130 M What is the main sequence lifetimes of aWhat is the main sequence lifetimes of a

10 M10 M star?star?ttMSMS = 32 million yr= 32 million yr

What is the lifetime of a 0.5 MWhat is the lifetime of a 0.5 M star?star?ttMSMS = 56 Gyr, which is > the age of the Universe, 13.7 Gyr!= 56 Gyr, which is > the age of the Universe, 13.7 Gyr!

All low mass stars with m < 0.85 MAll low mass stars with m < 0.85 M that ever formed in athat ever formed in a

galaxy is still there.galaxy is still there. Measuring the # stars at different parts of the HRMeasuring the # stars at different parts of the HR

Diagram can tell you a galaxys star formation historyDiagram can tell you a galaxys star formation history

Hess DiagramHess Diagram: diagram showing the density of stars in: diagram showing the density of stars inbins of color & magnitude in an HR Diagrambins of color & magnitude in an HR Diagram


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Apply HRD to Star ClustersApply HRD to Star Clusters

Globular Cluster M80Globular Cluster M80 Open Cluster NGC 2420Open Cluster NGC 2420

Star Cluster: a group of stars with different masses that formedat roughly the same time from the same gas cloud. All the stars

have the same chemical composition, age and distance

Milky Way Star ClustersMilky Way Star Clusters

150 Globular Clusters: 12150 Globular Clusters: 12--13 Gyr, metal13 Gyr, metal--poor, stellar halopoor, stellar halo

Thousands of Open Clusters: 0 toThousands of Open Clusters: 0 to ~~10 Gyr old,10 Gyr old, approxiapproxi--

matelymately solarsolar metallicitymetallicity, disk, disk


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MetallicityMetallicity

A stars properties (L, T, R,A stars properties (L, T, R, ttMSMS) also depend on) also depend onthe chemical composition of the star.the chemical composition of the star.

Nomenclature:Nomenclature:

X = the fraction by mass of H = MH/MY = the fraction by mass of He

Z = fraction by mass of metals (>H,He)

[Fe/H] = log [ (XFe/XH) / (XFe/XH)] ~ log (Z/Z)

Sun: Z

= 0.019 (1.9%) and [Fe/H]=0

[Fe/H] = 1 1/10 solar[Fe/H] = 2 1/100 solar

M30M30A MetalA Metal--Poor, GalacticPoor, GalacticGlobular ClusterGlobular Cluster


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Globular Cluster M30Globular Cluster M30

Vandenberg et al.

(2002) stellar

evolutionary model

isochroneisochrone

Comparing theComparing the

observedobserved fiducialfiducial pointspoints

to the theoreticalto the theoretical

isochroneisochrone allows you toallows you to

detereminedeteremine the clustersthe clusters

reddening, distance, &reddening, distance, &

age (chemicalage (chemicalcomposition)composition)

d = 81 pc

Globular ClustersGlobular Clusters

Two different clusters with about the same age, butTwo different clusters with about the same age, but

very different chemical abundances (very different chemical abundances (25)25)

M30: [Fe/H] = 2.1 47Tuc: [Fe/H] = 0.7


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Star Clusters are useful (Star Clusters are useful (although biasedalthough biased))probes of the stellar populations of galaxiesprobes of the stellar populations of galaxies

First an explanation of the classificationFirst an explanation of the classificationscheme for galaxiesscheme for galaxies

Spiral GalaxiesSpiral Galaxies: thin, rotating disk & bulge: thin, rotating disk & bulge

Elliptical GalaxiesElliptical Galaxies: entirely stars, little or no HI: entirely stars, little or no HIgas, shape supported by velocity dispersions ofgas, shape supported by velocity dispersions ofthe starsthe stars

Dwarf GalaxiesDwarf Galaxies: galaxies fainter than M: galaxies fainter than MBB == --16,16,

such as the LMC & SMC or thesuch as the LMC & SMC or the dSphsdSphs Dwarf Irregular (Dwarf Irregular (dIrdIr)): gas rich dwarfs: gas rich dwarfs

DwarfDwarf SpheroidalSpheroidal ((dSphdSph)): all stars, no HI gas: all stars, no HI gas

Four Galaxies are visible hereFour Galaxies are visible here

Gary Stephens

M31, the

Andromeda

Galaxy

M32

NGC 205

Stars inour own

Milky Way


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TheThe FornaxFornax dSphdSph GalaxyGalaxy

Two Star Clusters in theTwo Star Clusters in the FornaxFornax dSphdSph


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Some very interesting pieces of informationSome very interesting pieces of informationabout galaxy evolution come from studyingabout galaxy evolution come from studyingthe star clusters in galaxiesthe star clusters in galaxies

Nearly all the Milky Way globular clusters haveNearly all the Milky Way globular clusters haveages of 12ages of 12--13 Gyr although they span a13 Gyr although they span arange of chemical abundances. Initially, therange of chemical abundances. Initially, theMilky Way formed very chaoticallyMilky Way formed very chaoticallyglobularsglobulars were probably born out of violentwere probably born out of violentcollisions, similar to the bright, compactcollisions, similar to the bright, compact

clusters we see forming in starclusters we see forming in star--burstburstgalaxies today.galaxies today.


Cosmological simulations of galaxy formation predictCosmological simulations of galaxy formation predictthat large galaxies form first, and small galaxiesthat large galaxies form first, and small galaxiesform later. But what do we see in nearby galaxies?form later. But what do we see in nearby galaxies?

All galaxies have 12All galaxies have 12--13 Gyr old stars! There are no late13 Gyr old stars! There are no lateblooming galaxies in the Local Group (galaxiesblooming galaxies in the Local Group (galaxieswith d < 1with d < 1 MpcMpc), although their star formation), although their star formationhistories are very different.histories are very different.

The Milky Way, LMC,The Milky Way, LMC, FornaxFornax and Sagittariusand Sagittarius dSphsdSphshave globular clusters that are essentiallyhave globular clusters that are essentiallycoco--evaleval, 12, 12--13 Gyr in age.13 Gyr in age.

However the SMC has only 1 globular cluster, and itsHowever the SMC has only 1 globular cluster, and itsage is 2age is 2--3 Gyr younger than in other galaxies.3 Gyr younger than in other galaxies.


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Large and SmallLarge and Small MagellanicMagellanic CloudsClouds

Large and SmallLarge and Small MagellanicMagellanic CloudsClouds

LMC/SMC are interacting withLMC/SMC are interacting with

one another as they orbit theone another as they orbit the

Milky Way; bridge & tidal tailsMilky Way; bridge & tidal tails

HI Maps - neutral hydrogen gas

(M. Putman)

Magellanic

Stream


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The Stellar Populations of the SMCThe Stellar Populations of the SMC

HST survey of star clusters and field stars in theHST survey of star clusters and field stars in theSmallSmall MagellanicMagellanic Cloud done by a largeCloud done by a largecollaboration: Gallagher,collaboration: Gallagher, GrebelGrebel,, NotaNota,, TosiTosi,,SabbiSabbi,, GlattGlatt, etc. including myself, etc. including myself

Goals:Goals: Accurately measure the ages (Accurately measure the ages (0.5 Gyr) and distances0.5 Gyr) and distances

of star clusters in the SMCof star clusters in the SMC

Use the star clusters to trace the evolution of theUse the star clusters to trace the evolution of themetallicitymetallicity over time in this dwarf galaxyover time in this dwarf galaxy

Use the field stars to derive the star formation andUse the field stars to derive the star formation andmetal enrichment historymetal enrichment history

Identify how cluster formation compares to the starIdentify how cluster formation compares to the starformationformation

SMC Globular Cluster NGC 121SMC Globular Cluster NGC 121

Glatt, et al. (2008)

Assumed

[Fe/H]spec= 1.46

Dartmouth

Isochrones

(Dotter et al. 2007)

[/Fe] = +0.2

(m-M)0 = 18.96

d = 61.9 kpc

age = 10.5 0.5 Gyr


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SMC Cluster NGC 121SMC Cluster NGC 121

Glatt, et al. (2008)

5 isochrones

displayed at 0.5 Gyr

intervals

age = 10.5 0.5 Gyr

SMC Star ClustersSMC Star Clusters

NGC 121 has an age of 10.5 Gyr andNGC 121 has an age of 10.5 Gyr and[Fe/H] =[Fe/H] =1.46 (1.46 (intermediateintermediate metallicitymetallicity))

NGC 121 is theNGC 121 is the onlyonly globular cluster in theglobular cluster in theSMC, and is its oldest star clusterSMC, and is its oldest star cluster

Disruption of Clusters? Total disruption is notDisruption of Clusters? Total disruption is notlikely forlikely for globularsglobulars because of their verybecause of their very

high spatial densityhigh spatial density

So is the SMC a young galaxy? No.So is the SMC a young galaxy? No.


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6 SMC Field Star Areas in Gallagher et al.6 SMC Field Star Areas in Gallagher et al.


Field Stars inField Stars in

6 SMC Locations6 SMC Locations

((SabbiSabbi, et al., et al.

2009)2009)

Z = 0.004

Ages = 50, 100,

& 500 Myr

Z = 0.001

Ages = 3, 5, &

12 Gyr


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Full analysis of theFull analysis of the CMDsCMDs is not complete yet, butis not complete yet, butsimply from comparing thesimply from comparing the CMDsCMDs to isochrones, weto isochrones, wefind thatfind that the SMC does have 10the SMC does have 10--12 Gyr old stars12 Gyr old stars..Just not that many. Thus the SMC had a slow startJust not that many. Thus the SMC had a slow startto its formation which maybe a reason so fewto its formation which maybe a reason so fewglobular clusters formed in it.globular clusters formed in it.

45

50

55

60

65

70

5

10

15

74

73

72

71

70

age [Gyr]

NGC121

Lindsay 1

distances [kpc]

Kron 3

Lindsay 38

NGC152

BS90

NGC416

NGC339

Kron 44

alpha [deg]

Kron 28

NGC411

NGC419

delta[deg]

2

3

4

5

6

7

8

9

10

Mapping the Spatial Distribution of SMC in 3DMapping the Spatial Distribution of SMC in 3D

Using Star ClustersUsing Star Clusters


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AgeAge--MetallicityMetallicity Relationship in SMCRelationship in SMC

0 2 4 6 8 10 12

1.5

1

0.5 Kayser et al. 2008

Da Costa et al. 1998

Parisi et al. 2008

Bica et al. 2008

age [Gyr]

[Fe/H][dex](CG97)

LargeLarge MagellanicMagellanic CloudCloud


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4343

LMC Star Clusters show a largeLMC Star Clusters show a large age gapage gap. Only 1 cluster. Only 1 clusterhas an age of 3has an age of 3 --13 Gyr, e.g.,13 Gyr, e.g., DaDa Costa (2002)Costa (2002)

LMC Star ClustersLMC Star Clusters


SmeckerSmecker--Hane, Cole, GallagherHane, Cole, Gallagher& Stetson (2002) imaged star& Stetson (2002) imaged starfields in the LMC with thefields in the LMC with theWFPC2 on the Hubble SpaceWFPC2 on the Hubble SpaceTelescope (HST)Telescope (HST)

DerivedDerived SFHsSFHs for the Bar andfor the Bar andDisk 1 fields from the # stars asDisk 1 fields from the # stars asa function of magnitude on thea function of magnitude on themainmain--sequencesequence

5% of WFPC2 area shown at5% of WFPC2 area shown atright; mean separation of starsright; mean separation of starswith Vwith V 2525 magmag isis ~~ 6 pix =6 pix =0.60.6


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LMC BarLMC Disk


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V I

A DifferentialA Differential

Hess DiagramHess Diagram

Black = Larger # stars in

the Bar Field

White = Larger # stars in

the Disk 1 Field

LMC Field StarsLMC Field Stars

Bar: Open Histogram

Disk 1: Hatched Histogram

Bar

Formation



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SFR of the LMC Disk 1 field was nearly constant withSFR of the LMC Disk 1 field was nearly constant withtime, not varying by more than a factor of 2, in thetime, not varying by more than a factor of 2, in the

lastlast ~~ 1 to1 to 14 Gyr14 Gyr

SFH of the LMC Bar field is very different from that ofSFH of the LMC Bar field is very different from that of

the Disk 1 fieldthe Disk 1 field

Initial formation of the barInitial formation of the bar ~~ 4 to 6 Gyr ago, exact4 to 6 Gyr ago, exact

age depends on the assumedage depends on the assumed metallicitymetallicity

SFR in last 1 to 2 Gyr also has been high in BarSFR in last 1 to 2 Gyr also has been high in Bar

We note a distinctWe note a distinct lack of metallack of metal--poor starspoor stars in bothin both

fields,fields, but notbut not a lack of old starsa lack of old stars

Stellar Populations of GalaxiesStellar Populations of Galaxies

Collisions of protoCollisions of proto--galactic fragments early ingalactic fragments early inthe evolution of galaxies are thought causethe evolution of galaxies are thought causedissipation of energy & funneling of gas todissipation of energy & funneling of gas tothe centers, which may create galacticthe centers, which may create galacticbulges (red, old starsbulges (red, old stars))

In addition, early merging of the protoIn addition, early merging of the proto--galacitcgalacitc

fragments and later the continualfragments and later the continualcanniblizatoncanniblizaton of dwarf galaxyof dwarf galaxy satelitessatelites arearethought to make the stellar halos of galaxiesthought to make the stellar halos of galaxiesout of merger debrisout of merger debris


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Hierarchical Formation of GalaxiesHierarchical Formation of Galaxies

CDM NCDM N--bodybodysimulation (darksimulation (dark

matter only)matter only)of the evolution of aof the evolution of a

Milky Way typeMilky Way typegalaxygalaxy

fromfrom

Bullock & JohnstonBullock & Johnston

(2005)(2005)

Stellar Populations of GalaxiesStellar Populations of Galaxies

Questions:Questions:

Do all galaxies have stellarDo all galaxies have stellarhalos?halos?

What about a bulgeWhat about a bulge--lesslessspiral like M33?spiral like M33?

Do the ages andDo the ages and metallicitiesmetallicities of the stars inof the stars inthe halos match the predictions ofthe halos match the predictions ofsophisticated hierarchical galaxysophisticated hierarchical galaxyformation simulations, and can they beformation simulations, and can they betested over a range of galaxytested over a range of galaxyluminosity?luminosity?


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M33 Spectroscopic SurveyM33 Spectroscopic Survey

With MichaelHood, Matt Teig,Annette Ferguson &Mike Irwin, andmyself

Spectra taken w/Keck II 10-mtelescope and theDEep ImagingMulti-Object

Spectrograph(DEIMOS)

The areasstudied indifferentparts of thisproject

DEIMOSspectrscopic

fields arethe long &narrowfields.


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Dispersion = 0.47 /pix, Resolution = 1.8

Exposure time = 3 hrs

Average S/N per pixel = 6 (3.5 to 15)

Average Velocity Error = 9 km/s

Field of View over which slits are placed is16.3 x 5.0

Multiplexing is key to getting to our eventual goal:

observing 400 M33 RGB stars


Initial runs selected stars for spectroscopy basedInitial runs selected stars for spectroscopy basedon Ferguson et al.s photometric survey (Fergusonon Ferguson et al.s photometric survey (Fergusonet al. 2006)et al. 2006)

Judge whether or not M33 or Milky Way stars afterJudge whether or not M33 or Milky Way stars afterthe fact using our DDO51 photometrythe fact using our DDO51 photometry

Kinematic results presented here for 173 starsKinematic results presented here for 173 stars

which are likely M33 members based on DDO51which are likely M33 members based on DDO51photometry and relative densities of stars in thephotometry and relative densities of stars in theHess diagrams of the cleaned MWay and M33Hess diagrams of the cleaned MWay and M33CMDsCMDs


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Spectra of the Calcium LinesSpectra of the Calcium Lines

3 Calcium Absorption Lines:3 Calcium Absorption Lines: WavelengthWavelength starstars velocity along the line of sights velocity along the line of sight

DepthDepth abundance of Calcium in the star (Ca/H)abundance of Calcium in the star (Ca/H)

Heliocentric Velocity vs Position AngleHeliocentric Velocity vs Position Angle


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M33 Velocity ResultsM33 Velocity Results

Thin Disk

Intrinsic

= 15 km/s

The Stellar Halo of M33The Stellar Halo of M33

Omitting Rotating Disk

Stars (|v | < 35 km/s),

what is the intrinsic

dispersion in heliocentric

velocity?

N = 34 stars

Simple Calculation: = 170 km/s

RMS implies a Halo

intrinsic = 72 km/s


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M33 Star ClustersM33 Star Clusters

M33 does have a population of star clusters that haveM33 does have a population of star clusters that havemuch higher velocity dispersion than the HI diskmuch higher velocity dispersion than the HI disk

((ChandarChandaret al. 2002)et al. 2002)

Clusters w/Clusters w/

age > 1 Gyrage > 1 Gyr

havehave = 68 km/s= 68 km/s

However only 18However only 18

clusters haveclusters have

kinematics that arekinematics that are

inconsistentinconsistent

with disk rotationwith disk rotation

ConclusionsConclusions

1.1. TheThe HertzsprungHertzsprung--Russell (HR) Diagram is a veryRussell (HR) Diagram is a veryvaluable tool that allows us to measure distances,valuable tool that allows us to measure distances,reddening and ages of star clusters and stellarreddening and ages of star clusters and stellarpopulations of galaxiespopulations of galaxies

2.2. Application to Star Clusters and Field Stars inApplication to Star Clusters and Field Stars inGalaxiesGalaxies Milky Way, LMC,Milky Way, LMC, FornaxFornax dSphdSph and Sagittariusand Sagittarius dSphdSph allall

have globular clusters that are 12have globular clusters that are 12--13 Gyr in age.13 Gyr in age.

SMC has only 1 globular cluster and it is only 10.5SMC has only 1 globular cluster and it is only 10.5 0.50.5Gyr old, however it does have field stars that span theGyr old, however it does have field stars that span the fulllfulllrange in age from 0range in age from 0 12 Gyr.12 Gyr.

The SMC started forming slowing, then after 2The SMC started forming slowing, then after 2--3 Gyr the3 Gyr thestar formation rate increased, and this gasstar formation rate increased, and this gas--rich dwarfrich dwarfgalaxy is still actively forming stars today.galaxy is still actively forming stars today.


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ConclusionsConclusions

2.2. Application to Star Clusters and Field Stars inApplication to Star Clusters and Field Stars inGalaxiesGalaxies

LMC formed stars at nearly a constant rate throughout theLMC formed stars at nearly a constant rate throughout theage of the Universe, probably had a burst about 3age of the Universe, probably had a burst about 3--5 Gyr5 Gyrago when the bar formed.ago when the bar formed.

Galaxies form star clusters at different rates than they formGalaxies form star clusters at different rates than they formfield stars. The formation rate of clusters is not the samefield stars. The formation rate of clusters is not the sameas the star formation rate.as the star formation rate.

Star clusters can be very useful probes of the ageStar clusters can be very useful probes of the age--metallicitymetallicity relationship in a galaxy, overcoming therelationship in a galaxy, overcoming thedegeneraciesdegeneracies in age/in age/metallicitymetallicity inherent in the CMD, butinherent in the CMD, butyou need to study field stars to determine a galaxyyou need to study field stars to determine a galaxys stars starformationformation histioryhistiory..

3.3. More about that in tomorrows lectureMore about that in tomorrows lecture

Thank you for your attention.Thank you for your attention.

Do you have any Questions?Do you have any Questions?

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