Globular clusters role in formation of the halo

Globular clusters Globular clusters role in formation of role in formation of

the halothe halo

Raffaele GrattonRaffaele Gratton

INAF – Osservatorio INAF – Osservatorio Astronomico di PadovaAstronomico di Padova

Chemical evolution in the Universe

CollaboratorsCollaborators

Angela BragagliaAngela Bragaglia Eugenio CarrettaEugenio Carretta Sara LucatelloSara Lucatello Valentina D’OraziValentina D’Orazi Yazan MomanyYazan Momany Chris SnedenChris Sneden

Franca D’AntonaFranca D’Antona Paolo VenturaPaolo Ventura Santi CassisiSanti Cassisi Giampaolo PiottoGiampaolo Piotto Anna Fabiola MarinoAnna Fabiola Marino Antonino MiloneAntonino Milone Alessandro VillanovaAlessandro Villanova


GCs and Open ClustersGCs and Open ClustersGCs are more massive and GCs are more massive and older than OCsolder than OCs

GCs host multiple stellar GCs host multiple stellar populations; OC do notpopulations; OC do not

GC formation scenario GC formation scenario (Carretta et al. 2010)(Carretta et al. 2010)

Interaction between a still gaseous proto-dSph and Interaction between a still gaseous proto-dSph and the MW (or between proto-dSph’s) (Bekki)the MW (or between proto-dSph’s) (Bekki)

Formation of a precursor population, with a raise in Formation of a precursor population, with a raise in [Fe/H], sometimes fast[Fe/H], sometimes fast

Triggering formation of a large primordial Triggering formation of a large primordial population (first generation)population (first generation)

Winds from massive stars and core collapse SNe Winds from massive stars and core collapse SNe stop further star formation and clean the region stop further star formation and clean the region from primordial ISMfrom primordial ISM

Low velocity wind from massive AGB stars Low velocity wind from massive AGB stars generates a cooling flow (Ventura et al., D’Ercole et generates a cooling flow (Ventura et al., D’Ercole et al.)al.)

Second generation stars form in this cooling flowSecond generation stars form in this cooling flow Core collapse SNe for this second generation stops Core collapse SNe for this second generation stops

further star formationfurther star formation In the meantime, decoupling between DM and gasIn the meantime, decoupling between DM and gas


Possible variationsPossible variations

Other polluters have been proposed:Other polluters have been proposed: Fast Rotating Massive Stars (Decressin et al.)Fast Rotating Massive Stars (Decressin et al.) Novae (Smith & Kraft; Maccarone et al.)Novae (Smith & Kraft; Maccarone et al.) Massive interacting binaries (De Mink et al.)Massive interacting binaries (De Mink et al.) Super Massive Stars (Denissenkov & Hartwick)Super Massive Stars (Denissenkov & Hartwick)

However, most features of the scenario However, most features of the scenario remain validremain valid Globular clusters should have been much more Globular clusters should have been much more

massive at their origin than now (from a few to massive at their origin than now (from a few to ~15)~15)


GC and dSph luminosity GC and dSph luminosity functions overlapfunctions overlap

We constructed a We constructed a luminosity function for luminosity function for GCs (Harris catalogue) GCs (Harris catalogue) and DSph (likely and DSph (likely incomplete at faint incomplete at faint end)end)

Total integrated Mv for Total integrated Mv for MW:MW: GCs: -13.3 (initially: GCs: -13.3 (initially:

from -15 up to -16)from -15 up to -16) dSph: -14.4dSph: -14.4


Globular clusters and Globular clusters and dwarf galaxies: mass-to-dwarf galaxies: mass-to-

light ratiolight ratio

From Dabringhausen et al. 2008 MNRAS 386 864

There is scarce evidence of dark matter in both GCs and UCD galaxies, in agreement with expectations for small dark matter halo.

GCs have lower mass-to-light ratio likely because of dynamical evolution (since they are relaxed objects)


The luminosity-metallicity The luminosity-metallicity relationrelation

Kirby et al. 2008, arXiv:0807.1925


The luminosity-metallicity The luminosity-metallicity relationrelation

• dSph (mean) metallicity depends on luminosity (present baryonic mass?). This agrees with the concept that dSph make their own metals

• GCs metallicity is fairly independent of luminosity (mass?). This agrees with the concept that they inherited the metallicity of the medium where they formed

• GCs have a bimodal metallicity distribution (Disk/Halo) with a minimum at [Fe/H]~-0.9

• At a given metallicity, the dSph luminosity is a lower envelope of GCs metallicities Halo GCs formed in objects that were more massive than they currently are!

Mv of the GC progenitorsMv of the GC progenitorsUsing the mass-metallicity relation for DSph we may assign an Mv to the progenitor of each GCFor the halo the median ratio progenitor/GCs is 27 (depends on the exact form of the relation)

Equal Mv

See also Leaman et al. 2013, arXiv1309.0822

Median progenitor Mv~-

11.5

GCs are tidally limited, GCs are tidally limited, dSph’s are notdSph’s are not

According to this scenario, GCs and dSph’s originated from similar systems but:

GCs progenitors interacted with the MW while still mainly gaseous

dSph’s evolved in isolation ( luminosity-metallicity relation)

NFW halo

Green: dSph’sRed: Bulge/thick disk GCsBlue: Inner Halo GCsBlack: Outer Halo GCs


Tidally limited region

Evolved in isolation

GC and dwarf galaxies as GC and dwarf galaxies as survivors (tidal tails)survivors (tidal tails)

Odenkirchen et al. 2001, ApJ 548, L165GC: Pal 5dSph: Sagittarius

Belokurov et al. 2006, ApJ 642, L137


Halo and GCsHalo and GCs Current cosmological models (White & Rees Current cosmological models (White & Rees

1978; Moore et al. 1999): the Milky Way’s stellar 1978; Moore et al. 1999): the Milky Way’s stellar halo was assembled from many smaller systemshalo was assembled from many smaller systems

The metal-poor ([Fe/H]<-2) part of the halo may The metal-poor ([Fe/H]<-2) part of the halo may be made of objects like the smallest DSph’sbe made of objects like the smallest DSph’s

The bulk of the halo The bulk of the halo (-2<[Fe/H]<-1) is clearly (-2<[Fe/H]<-1) is clearly different from DSph’s stars of similar metallicity different from DSph’s stars of similar metallicity (largest DSPh’s) (e.g. the run of [(largest DSPh’s) (e.g. the run of [αα/Fe] is /Fe] is different)different)

The primordial (FG) population of GCs is a The primordial (FG) population of GCs is a plausible candidate (see also Vesperini et plausible candidate (see also Vesperini et al., Martell & Grebel, Conroy)al., Martell & Grebel, Conroy)


Stars lost from the GCsStars lost from the GCs Violent relaxationViolent relaxation following gas expulsion and following gas expulsion and

mass loss from the most massive stars (see e.g. mass loss from the most massive stars (see e.g. Baumgardt, Kroupa & Parmentier 2008)Baumgardt, Kroupa & Parmentier 2008)

On a longer timescale: On a longer timescale: evaporationevaporation due to two- due to two-body encounters and other mechanims (e.g. disk body encounters and other mechanims (e.g. disk shocking: see e.g. Aguilar, Hut & Ostriker 1988) shocking: see e.g. Aguilar, Hut & Ostriker 1988)

Due to this second effect, some per cent of the Due to this second effect, some per cent of the stars should be removed within a relaxation time stars should be removed within a relaxation time (~10(~1088-10-1099 yr at half mass, longer for more yr at half mass, longer for more massive GCs, with a median value of about 5x10massive GCs, with a median value of about 5x1088 yr: Harris 1996)yr: Harris 1996)

A substantial fraction of the original GC A substantial fraction of the original GC mass should have been lost, this loss being mass should have been lost, this loss being more efficient among smaller GCsmore efficient among smaller GCs


EvidencesEvidences Tidal tails around some GCsTidal tails around some GCs (see e.g. (see e.g.

Odenkirchen et al. 2003)Odenkirchen et al. 2003)

Deficiency of small mass stars Deficiency of small mass stars preferentially lost if energy preferentially lost if energy equipartition holdsequipartition holds (Henon 1969; (Henon 1969; Richer et al. 1991; De Marchi et al. 2007; Richer et al. 1991; De Marchi et al. 2007; De Marchi & Pulone 2007)De Marchi & Pulone 2007)

Current GCs are the survivors of a Current GCs are the survivors of a potentially larger initial populationpotentially larger initial population


A major issue is whether a part A major issue is whether a part (even large) of the Galactic field (even large) of the Galactic field stars were formed in GCs and later stars were formed in GCs and later ended up as a main component of ended up as a main component of the halothe halo

Infant cluster mortality might be the Infant cluster mortality might be the major source of halo stars (see e.g. major source of halo stars (see e.g. Baumgardt et al. 2008)Baumgardt et al. 2008)


The SG population is typical of GCs The SG population is typical of GCs (Gratton et al. 2001)(Gratton et al. 2001)

The fraction (~2.5%) of Na-rich The fraction (~2.5%) of Na-rich and/or CN-rich stars in the field halo and/or CN-rich stars in the field halo (Carretta et al. 2010a; Martell & (Carretta et al. 2010a; Martell & Grebel 2010) Grebel 2010) stars evaporated from GCsstars evaporated from GCs

Multiple stellar Multiple stellar generationsgenerations


GC stellar populationsGC stellar populations FG with the typical composition of the ejecta of FG with the typical composition of the ejecta of

core-collapse SNe (e.g. Truran & Arnett 1971) core-collapse SNe (e.g. Truran & Arnett 1971) are only 1/3 of the current total populationare only 1/3 of the current total population

To reproduce n(FG)/n(SG), a large fraction of To reproduce n(FG)/n(SG), a large fraction of

stars of the FG must have been lost from GCsstars of the FG must have been lost from GCs

The same from theoretical studies and The same from theoretical studies and numerical simulations of dynamical evolution numerical simulations of dynamical evolution (Decressin et al. 2008, D’Ercole et al. 2008 and (Decressin et al. 2008, D’Ercole et al. 2008 and references in Carretta et al. 2010a)references in Carretta et al. 2010a)


The present mass of the GCs The present mass of the GCs compared to the mass of the halocompared to the mass of the halo

Mass of the inner halo GCs vs field population Mass of the inner halo GCs vs field population from in situ star counts (Juric et al. 2008)from in situ star counts (Juric et al. 2008)

To avoid contamination by the galactic thick disk, To avoid contamination by the galactic thick disk, polar caps defined (polar caps defined (ZZ>5 kpc, and r>5 kpc, and rgalactocentricgalactocentric<18 kpc).<18 kpc).

We summed up the luminosity of all GCs in the We summed up the luminosity of all GCs in the Harris (1996) catalogue that are within this volume Harris (1996) catalogue that are within this volume + + M/LM/LVV = 2 (Mandushev et al. 1991; Pryor & Meylan = 2 (Mandushev et al. 1991; Pryor & Meylan 1993)1993)

mass(GCs)=4.1x10mass(GCs)=4.1x1066 MMoo


Mass of the haloMass of the halo Mass of halo stars: Mass of halo stars:

Density law for the halo by Juric et al. (2008)Density law for the halo by Juric et al. (2008) Their normalisation of halo/thin disk density in the Their normalisation of halo/thin disk density in the

solar neighbourhoodsolar neighbourhood Local stellar density of 0.038 Local stellar density of 0.038 MMoo//pcpc33 (Jahreiss & Wielen (Jahreiss & Wielen

1997)1997)

mass(Halo)=3.3x10mass(Halo)=3.3x1088 MMoo mass(GCs)~1.2% of mass(Halo)mass(GCs)~1.2% of mass(Halo)

Similar value for the whole halo outside 4 kpcSimilar value for the whole halo outside 4 kpc Total stellar mass within halo GCs ~1.4x10Total stellar mass within halo GCs ~1.4x1077 MMoo, in the field ~1.2x10, in the field ~1.2x1099 MMoo


The original GC massThe original GC mass

Carretta et al. (2009): SG=2/3 of GC starsCarretta et al. (2009): SG=2/3 of GC stars

Carretta et al. (2010) and Martell and Grebel Carretta et al. (2010) and Martell and Grebel (2010): (2010): stars with a composition similar to SG in GCs (i.e. Na-rich stars with a composition similar to SG in GCs (i.e. Na-rich

and/or CN-rich): ~2.5% of current halo starsand/or CN-rich): ~2.5% of current halo stars

If: If: They are SG stars lost by GC They are SG stars lost by GC SG stars are lost after GC formation at the same rate as SG stars are lost after GC formation at the same rate as

FG onesFG ones

stars lost by GCs after the formation of SG stars stars lost by GCs after the formation of SG stars ~3.7% of the current halo stars~3.7% of the current halo stars


The original GC massThe original GC mass Currently 1.2% of the halo mass is Currently 1.2% of the halo mass is

still in GCs still in GCs they should have lost they should have lost some 75% of their original masssome 75% of their original mass

They were originally ~4 times more They were originally ~4 times more massive than they are nowmassive than they are now

~5% of the halo were in GCs (after ~5% of the halo were in GCs (after the formation of SG stars)the formation of SG stars)


The mass of the FGThe mass of the FG However, mass involved in the However, mass involved in the

process of formation of GCs >> GCs process of formation of GCs >> GCs mass after formation of the SGmass after formation of the SG

Bulk of the SG stars formed from Bulk of the SG stars formed from the ejecta of only a fraction of the the ejecta of only a fraction of the FG starsFG stars


The mass of the FGThe mass of the FG With simple, realistic assumptions on:With simple, realistic assumptions on:

IMFs of FG and SG starsIMFs of FG and SG stars initial-final mass relationinitial-final mass relation on suitable mass ranges for the most favourite on suitable mass ranges for the most favourite

candidate polluters (Carretta et al. 2010) candidate polluters (Carretta et al. 2010)

m(FG)/m(after formation of SG stars) ~5-10m(FG)/m(after formation of SG stars) ~5-10 m(FG) ~25-50% of the halo massm(FG) ~25-50% of the halo mass

Even more if part of the mass lost by the polluters Even more if part of the mass lost by the polluters was not used to form SG starswas not used to form SG stars

The galactic halo might be made The galactic halo might be made of the FG of the FG


TestsTestsMetallicitMetallicity y distributidistributionon

ChemistryChemistry

Density Density DistributiDistributionon

BHB BHB LFsLFs

Filled circles = Filled circles = field stars field stars (Ivezic et al.)(Ivezic et al.)Red solid lines = Red solid lines = generalised generalised histograms for histograms for GCsGCs

Solid line = best Solid line = best fit through datafit through dataDotted line = Dotted line = slope of the slope of the inner halo inner halo density (Juric et density (Juric et al. 2008).al. 2008).

GC (Piotto et al. GC (Piotto et al. 2003) :solid 2003) :solid histogramhistogramField (Brown et Field (Brown et al. 2008: red al. 2008: red dashed line).dashed line).

Black dots = Black dots = field stars (Venn field stars (Venn et al.)et al.)Red solid lines = Red solid lines = range for GCsrange for GCs

(Also binaries: Lucatello et al. 2013, in preparation)Chemical evolution in the Universe

An upper limit from An upper limit from Fornax GCsFornax GCs

We may set an upper limit to the original We may set an upper limit to the original mass of GC by counting stars in GCs and mass of GC by counting stars in GCs and the field in a dSph with a high specific the field in a dSph with a high specific frequency of GCs (Carretta et al. 2010)frequency of GCs (Carretta et al. 2010)

Fornax DSph has 5 GCsFornax DSph has 5 GCs They show a Na-O anticorrelation They show a Na-O anticorrelation

(signature of multiple generations: (signature of multiple generations: Latarte et al. 2006)Latarte et al. 2006)

Our original estimate: an upper limit of Our original estimate: an upper limit of ~15~15


Larsen et al. 2012, A&A, Larsen et al. 2012, A&A, 544, L14544, L14 Cluster [Fe/H]Cluster [Fe/H]

Larsen et al. (2012 A&A, 546, 53)Larsen et al. (2012 A&A, 546, 53) Letarte et al. (2006, A&A, 453, 547)Letarte et al. (2006, A&A, 453, 547) Two sets consistent within 0.1 dexTwo sets consistent within 0.1 dex

Field star [Fe/H]Field star [Fe/H] Battaglia et al. (2006), based on Rutledge et al. Battaglia et al. (2006), based on Rutledge et al.

(1997) calibration of the Ca triplet on the Carretta (1997) calibration of the Ca triplet on the Carretta & Gratton (1997) scale& Gratton (1997) scale

Corrections for distribution within the galaxyCorrections for distribution within the galaxy Conclusion: there are only ~4-5 metal-poor Conclusion: there are only ~4-5 metal-poor

Fornax field stars for every GC starFornax field stars for every GC star


Larsen et al. 2013Larsen et al. 2013



How many GCs should be considered?How many GCs should be considered? F4 is more metal-rich than the four other clustersF4 is more metal-rich than the four other clusters F1 (smaller cluster ) is consistent with pure FG F1 (smaller cluster ) is consistent with pure FG

(D’Antona et al. 2013, MNRAS, 434, 1138)(D’Antona et al. 2013, MNRAS, 434, 1138) Are Fornax GCs identical to those of our galaxy? Are Fornax GCs identical to those of our galaxy?

Possibly they keep more FG stars…Possibly they keep more FG stars… D’Antona et al. (2013): F2, F3 and F5 contain D’Antona et al. (2013): F2, F3 and F5 contain

substantial fractions of SG stars (0.54 – 0.65)substantial fractions of SG stars (0.54 – 0.65) However, only 2 out of 9 stars observed by Latarte However, only 2 out of 9 stars observed by Latarte

et al. are Na-rich stars et al. are Na-rich stars SG: probability that this SG: probability that this happens by chance is only 2.5% if the fraction of SG happens by chance is only 2.5% if the fraction of SG stars is 0.6stars is 0.6

Are the metallicity scales Are the metallicity scales used for field and GCs used for field and GCs

consistent?consistent? M15:M15:

Latarte et al.: [Fe/H]= -2.40+/-0.03Latarte et al.: [Fe/H]= -2.40+/-0.03 Rutledge et al.: [Fe/H]=-2.02+/-0.04Rutledge et al.: [Fe/H]=-2.02+/-0.04

According to our last scale (According to our last scale (Carretta et Carretta et al. 2009, A&A, 508, 695): [Fe/H]=-2.33+/-al. 2009, A&A, 508, 695): [Fe/H]=-2.33+/-0.02, close to (Latarte et al. 2006)0.02, close to (Latarte et al. 2006)

However, offset of 0.3-0.4 dex However, offset of 0.3-0.4 dex In In Battaglia et al sample, there are ~35 Battaglia et al sample, there are ~35 stars with [Fe/H]<-2 and 47 more with -stars with [Fe/H]<-2 and 47 more with -2<[Fe/H]<-1.72<[Fe/H]<-1.7


A new upper limitA new upper limit The value of 4-5 given by Larsen et al. The value of 4-5 given by Larsen et al.

should be corrected for:should be corrected for: The fraction of SG stars might be lower in The fraction of SG stars might be lower in

Fornax GCs than in typical halo GCs. Let us Fornax GCs than in typical halo GCs. Let us assume ½ rather than 2/3 (~1.3)assume ½ rather than 2/3 (~1.3)

The metallicity scales for GCs and field stars are The metallicity scales for GCs and field stars are inconsistent (~2.3)inconsistent (~2.3)

The product of these factors is ~3The product of these factors is ~3 A ratio of ~15 is consistent with GC A ratio of ~15 is consistent with GC

formation scenario derived from multiple formation scenario derived from multiple populationspopulations


The importance of Larsen et The importance of Larsen et al. paperal. paper

Usually cluster mass Usually cluster mass function assumed to be function assumed to be represented by a Press-represented by a Press-Schechter relationSchechter relation

See e.g. M82 clusters See e.g. M82 clusters from Bastian et al. from Bastian et al. (2013, MNRAS, 419, (2013, MNRAS, 419, 2606) 2606)

Is this appropriate for Is this appropriate for the case of the Fornax the case of the Fornax dSph? dSph? Clear excess Clear excess of massive clusters!of massive clusters!


ConclusionsConclusions GCs are complex objects hosting multiple GCs are complex objects hosting multiple

generation of starsgeneration of stars They are the end result of the evolution of They are the end result of the evolution of

originally much more massive objects, originally much more massive objects, possibly the inner halo counterpart of dSphpossibly the inner halo counterpart of dSph

Currently, ~1.2% of halo stars are in GCs, Currently, ~1.2% of halo stars are in GCs, but likely ~5% of halo stars formed within but likely ~5% of halo stars formed within GCsGCs

Much more might have formed in the Much more might have formed in the episodes that ultimately formed GCsepisodes that ultimately formed GCs


The case of SagittariusThe case of Sagittarius

Mottini & Wallerstein, 2008, AJ 136, 731

Filled circles: Sgr GC’sOpen circles: Sgr field (McWilliam & S,ecker-Hane)Open squares: Sgr field (Sbordone et al.)Filled squares: Fornax GC’s (Letarte et al.)

Heavy s-elementsHeavy s-elements

Mottini & Wallerstein, 2008, AJ 136, 731

Filled circles: Sgr GC’sOpen circles: Sgr field (McWilliam & S,ecker-Hane)Open squares: Sgr field (Sbordone et al.)Filled squares: Fornax GC’s (Letarte et al.)

BinariesBinaries Wide binaries may be destroyed in very dense Wide binaries may be destroyed in very dense

fieldsfields

Within the galactic disk, binaries are more Within the galactic disk, binaries are more common in low density environments (like common in low density environments (like Taurus) rather than in higher density ones Taurus) rather than in higher density ones (like Orion) (Lada & Lada 2003) (like Orion) (Lada & Lada 2003)

The binary frequency and the maximum The binary frequency and the maximum separation may then be used to estimate the separation may then be used to estimate the density of the birth environment (Goodwin, density of the birth environment (Goodwin, 2010)2010)


FieldField

Frequency of spectroscopic binaries with Frequency of spectroscopic binaries with periods less than 6000 days (Carney et al. periods less than 6000 days (Carney et al. 2003):2003):

Field metal poor red giants: 16Field metal poor red giants: 16±±4%4% Field metal-poor dwarfs: 17Field metal-poor dwarfs: 17±±2%2% These values are similar to those obtained These values are similar to those obtained

for population I stars, if we restrict for population I stars, if we restrict ourselves to the same period range, since ourselves to the same period range, since only a third of the binaries in the solar only a third of the binaries in the solar neighbourhood have a period shorter than neighbourhood have a period shorter than 6000 d (Duquennoy and Mayor 1991)6000 d (Duquennoy and Mayor 1991)


Globular ClustersGlobular Clusters Binary fraction in GCs is much lower (Romani & Binary fraction in GCs is much lower (Romani &

Weinberg 1991) Weinberg 1991) From c-m diagrams (Milone et al. 2008): only a From c-m diagrams (Milone et al. 2008): only a

few per cent of stars in GCs are binaries (here, few per cent of stars in GCs are binaries (here, the total fraction of binaries, irrespective of their the total fraction of binaries, irrespective of their periods)periods)

The binary fraction is a strong function of the The binary fraction is a strong function of the cluster mass, from 2% for the most massive GCs, cluster mass, from 2% for the most massive GCs, up to 20% for the less massive onesup to 20% for the less massive ones

The mass weighted average value is at most 1/3 The mass weighted average value is at most 1/3 than for field halo starsthan for field halo stars

Not surprising considering higher density in GCsNot surprising considering higher density in GCs The fraction of wide binaries among halo stars The fraction of wide binaries among halo stars

indicates that they did not originate in GCs which indicates that they did not originate in GCs which subsequently disintegrated (Ryan 1992)subsequently disintegrated (Ryan 1992)


Binaries in FG and SG Binaries in FG and SG starsstars

The incidence of binaries seems to be very The incidence of binaries seems to be very different among FG and SG stars (see different among FG and SG stars (see D’Orazi et al. 2010 and Lucatello et al. D’Orazi et al. 2010 and Lucatello et al. 2010): 2010):

SG: 1%SG: 1% FG: ~15% ~ field metal-poor starsFG: ~15% ~ field metal-poor stars

Consistent with that obtained by Milone et al. Consistent with that obtained by Milone et al. (2008), if:(2008), if:

No long period binaries in GCs (reasonable)No long period binaries in GCs (reasonable) FG made up only 1/3 of the GC population.FG made up only 1/3 of the GC population.


ConsequencesConsequences

The difference between the frequency of binaries in The difference between the frequency of binaries in FG and SG is dramatic:FG and SG is dramatic:

most of the destruction of binaries (or lack of most of the destruction of binaries (or lack of formation) among SG stars occurred before formation) among SG stars occurred before relaxation of the system, because later we do not relaxation of the system, because later we do not expect large differences in the destruction rates expect large differences in the destruction rates between FG and SGbetween FG and SG

only the most compact binaries have a only the most compact binaries have a significant probability to form or survive in the significant probability to form or survive in the very dense regions where SG stars of GC formedvery dense regions where SG stars of GC formed


Chemical Evolution of Dwarf Galaxies and Stellar Clusters - Garching, July 21-25, 2008

GCs vs field: light and GCs vs field: light and --elementselements

GCs vs field: Fe-peak GCs vs field: Fe-peak elementselements

GCs vs field: n-capture GCs vs field: n-capture elementselements

• GCs have a composition similar to that of the galactic halo, save for the O-Na anticorrelation (see last part of the talk)

• The P-population in GCs have a composition virtually identical to that of field stars

Documents

Globular clusters role in formation of the halo