Bologna, January 29, 2008

ASTRO – ARCHEOLOGY

TRACERSTRACERS of the structure & history of the structure & history of the Galaxyof the Galaxy

ASTRO – ARCHEOLOGY

TRACERSTRACERS of the structure & history of the structure & history of the Galaxyof the Galaxy

ASTRO – TIMING

LABORATORYLABORATORYfor theoretical modelsfor theoretical models of stellar evolutionof stellar evolution

ASTRO – TIMING

LABORATORYLABORATORYfor theoretical modelsfor theoretical models of stellar evolutionof stellar evolution

GALACTIC GALACTIC GLOBULARCGLOBULARCLUSTERSLUSTERS

ASTRO – DYNAMICS

LABORATORYLABORATORY environment environment SE SE

ASTRO – DYNAMICS

LABORATORYLABORATORY environment environment SE SE

EXOTIC OBJECTS:

• better understanding of the relaxation and the core collapse process and the role of the binary systems in the dynamical evolution of the parent cluster

• the photometric properties, the incidence and the spatial distribution of collisionally induced stellar populations show signatures of the clusterdynamical evolution

probing the cluster dynamics

UVE UVE

by-products ofby-products ofbinary systemsbinary systems

“ “perturbing” perturbing” effects oneffects on “canonical” “canonical”evolutionary sequencesevolutionary sequences

studying studying ANOMALOUSANOMALOUS sequences as sequences as Blue Stragglers StarsBlue Stragglers Stars and exotic objectsand exotic objects

UV sensitivityUV sensitivity , , high resolutionhigh resolution

systematic studies of hot SPs in the core of high density GGCs

HST

IBs: IBs: Mass transfer binaries in whichMass transfer binaries in which

a WD is accreting material from a a WD is accreting material from a Companion through a UV emitting Companion through a UV emitting

accretion disk accretion disk

MSP companions:MSP companions:He-WD = remnant ofHe-WD = remnant of

the recycling process the recycling process

BSS: BSS: stars more massive than the stars more massive than the

““normal” cluster starsnormal” cluster starsOriginated by “coaelescence” of twoOriginated by “coaelescence” of two

low mass stars low mass stars (binaries+collisions) (binaries+collisions)

Blue Hook HB stars: Blue Hook HB stars: Hot Helium flashers ?Hot Helium flashers ?

(stars ignite He after heavy (stars ignite He after heavy mass-loss)mass-loss)

Normal Helium-rich HB stars?Normal Helium-rich HB stars? Binaries by-product?Binaries by-product?

??

according to their position in the CMD, according to their position in the CMD, BSSBSS should be should be more massivemore massive than than

normal normal starsstars(see also Shara et al 1997)(see also Shara et al 1997)

BSS have been detected for the first time BSS have been detected for the first time by Sandage (1953)by Sandage (1953)

merger of 2 low-mass starsmerger of 2 low-mass stars unevolved, massive starunevolved, massive star

primordialprimordialBinariesBinaries

……evolving in isolationevolving in isolationIn low density GCsIn low density GCs

directdirectCollisionsCollisions

..in the central region of..in the central region ofhigh density GCshigh density GCs

BSS BSS crucial link between crucial link betweenstellar evolution & stellar dynamicsstellar evolution & stellar dynamics

PB-BSSPB-BSS COL-BSSCOL-BSS

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are needed to see this picture.

<1990<1990

loose GGCs natural habitat low c, low for BSS

>1990>1990

high resolution studies high resolution studies BSSBSS also in the inner regionalso in the inner region

of high density GGCsof high density GGCs

• NGC6397 NGC6397 Auriere et al. 1990 Auriere et al. 1990 • 47 Tuc 47 Tuc Paresce et al. 1991 Paresce et al. 1991 • M15 M15 Ferraro & Paresce 1993 Ferraro & Paresce 1993

Catalogs:Catalogs: Fusi Pecci et al. 1992Fusi Pecci et al. 1992Sarajedini et al. 1992Sarajedini et al. 1992

Ferraro, Fusi Pecci, Bellazzini 1995Ferraro, Fusi Pecci, Bellazzini 1995Guhathakurta et al. 1994, 1998 Guhathakurta et al. 1994, 1998

Piotto et al 2004Piotto et al 2004

BSS BSS are a common population of GGCs, are a common population of GGCs, found in each cluster properly observed found in each cluster properly observed

Paresce et al (1991,Nature,352,297) Paresce et al (1991,Nature,352,297)

UV-planeUV-plane ideal to study ideal to study the photometric propertiesthe photometric properties of theof the BSSBSS population population::

- the distribution is almost vertical- the distribution is almost vertical- span more than 3 magnitudes- span more than 3 magnitudes

Ferraro et al (1997,A&A,324,915)Ferraro et al (1997,A&A,324,915)

Ferraro et al (2001,ApJ,561,337)Ferraro et al (2001,ApJ,561,337)

305 305 BSSBSS !! !! The largest population The largest population ever observed in aever observed in a GGCGGC

The most concentrated The most concentrated

BSSBSS population population ever found in a GGCever found in a GGC

M80 is the densest, not-M80 is the densest, not-PCCPCC cluster of the Galaxycluster of the Galaxy

Log = 5.8 Ms/pc3

Could the dynamical evolution Could the dynamical evolution of the cluster play a role in the of the cluster play a role in the formation of formation of BSSBSS??

Are collisions delaying Are collisions delaying the core collapse and the core collapse and generating COL-generating COL-BSSBSS??

Why M80 has such a large population of BSS ?Why M80 has such a large population of BSS ?M80 is a quite concentrated cluster

(Log = 5.8 Ms/pc3)

BUT other clusters with similar concentration like

47 Tuc (Log = 5.1 Ms/pc3)

NGC2808 (Log = 5.0 Ms/pc3)

NGC6388 (Log = 5.7 Ms/pc3)

have many fewer BSS (NBSS< 100)

M80M80 is not a is not a PCCPCC but it should be !!!! but it should be !!!! its dynamical time scaleits dynamical time scale is much shorter than its age !is much shorter than its age !

This would be theThis would be the

first direct evidencefirst direct evidence !!! !!!

collapsing

NBSS = 129

F = 0.44 – 1.0

PCC?

NBSS = 17

F = 0.16

binaries are preventing binaries are preventing core collapse ?core collapse ?

are binaries destroyedare binaries destroyed during the collapse ?during the collapse ???

M 3Log = 3.5 Ms/pc

3

Log =5.8 Ms

NBSS = 72

F = 0.28

M 13Log = 3.4 Ms/pc

3

Log =5.8 Ms

NBSS = 16

F = 0.07

twin clusters

different primordial different primordial binary population ?binary population ?

clusters in different clusters in different dynamical phases ?dynamical phases ? ??

Sollima et al (2007, MNRAS, 380,781Sollima et al (2007, MNRAS, 380,781))

The Binary fraction in 13 low-density clusters from ACS-HST The Binary fraction in 13 low-density clusters from ACS-HST observationsobservations

12-15% 14-19% 12-15% 14-19% 11-12% 11-12%

10-12% 13-17% 10-12% 13-17% 16-21% 16-21%

12-13% 16-22% 16-21% 12-13% 16-22% 16-21% 28-40%28-40%

33-50% 51-65% 41-51% 33-50% 51-65% 41-51%

M3M3

The BSS radial distributionThe BSS radial distribution is BIMODALis BIMODAL

Radius at which all Radius at which all objects with a massobjects with a masssimilar to BSS have similar to BSS have been sunk into the been sunk into the core in a time core in a time comparable to the comparable to the cluster agecluster age

Radius of avoidance

Important signaturesImportant signaturesof the dynamical of the dynamical evolution of the parentevolution of the parentcluster is imprinted in thecluster is imprinted in theBSS properties BSS properties

V1 V1 Paresce, De Paresce, De MMarchi & Ferraroarchi & Ferraro

(1992)(1992)

V2 – Dwarf NovaV2 – Dwarf NovaParesce & De Paresce & De MMarchi (1994)archi (1994)

X-ray CHANDRA X-ray CHANDRA catalog by catalog byGrindlay et al Grindlay et al 20012001

IBs : LMXB = accreting NS in binary systems IBs : LMXB = accreting NS in binary systems LLXGC = acceting WD in binary systemsLLXGC = acceting WD in binary systems

These objects are 100 times more abundant in GCs with respectThese objects are 100 times more abundant in GCs with respect to the field !!!! (collisional origin)to the field !!!! (collisional origin)

Dieball et al (2007,ApJ,670,379)Dieball et al (2007,ApJ,670,379)

Knigge et al (2002, ApJ,579,752)Knigge et al (2002, ApJ,579,752)

47 Tuc47 Tuc

M15M15

ONLY the brightest portion of ONLY the brightest portion of the IB region has been explored!!!the IB region has been explored!!!

An extensive search for IBs in GCs An extensive search for IBs in GCs is still lacking:is still lacking:- Which process generate IBs? - Which process generate IBs? COL & PB ?COL & PB ?- Are IBs less abundant in the core - Are IBs less abundant in the core of high density GCs?of high density GCs?- Are collisions destroying or creating- Are collisions destroying or creatingIBs?IBs?

1.1. High resolution High resolution 2. UV sensitivity 2. UV sensitivity

WFC3/UVISWFC3/UVIS

WFC2WFC2

THE MSP RE-CYCLING SCENARIOTHE MSP RE-CYCLING SCENARIO - MSP are thought to - MSP are thought to form in binary systems containing a NS which is form in binary systems containing a NS which is eventually spun up through mass accretion from an eventually spun up through mass accretion from an evolving companionevolving companion

The result will be a new born MSP + an exhausted The result will be a new born MSP + an exhausted star (which has lost most of its envelope) = the star (which has lost most of its envelope) = the core of a peeled star (He-WD).core of a peeled star (He-WD).

50% of the Galaxy MSP have been found in GGCs50% of the Galaxy MSP have been found in GGCs

Optical identification of MSP companion = optical Optical identification of MSP companion = optical and spectroscopic follow-up.and spectroscopic follow-up. Light curve = orbital inclinationLight curve = orbital inclination+ mass ratio from the velocity curve+ mass ratio from the velocity curve = empirical = empirical estimate of the pulsar mass .. Constraining the estimate of the pulsar mass .. Constraining the state of the degenerate matter in a neutron star state of the degenerate matter in a neutron star

47 TUC47 TUC

Edmonds et al (2001)Edmonds et al (2001)

He WDHe WD

Fully consistent with the Fully consistent with the canonical scenario of the canonical scenario of the MSP recycling processMSP recycling process

MSPMSP J1740-5340 J1740-5340 in in NGC6397NGC6397 shows eclipse of shows eclipse of the radio signal for about 40% of the orbit the radio signal for about 40% of the orbit ((D’Amico et al 2001D’Amico et al 2001) suggesting that the NS is ) suggesting that the NS is orbiting within a large envelope of matter released orbiting within a large envelope of matter released by the companionby the companion

COMJ1740COMJ1740 is is NOTNOT a a WDWD as expected as expected in the framework of the in the framework of the MSPMSP recycling scenariorecycling scenario

Ferraro et alFerraro et al (2001,ApJ,561,L93)(2001,ApJ,561,L93)

Star AStar A is is the the MSPMSP companioncompanion ( ( COMJ1740COMJ1740))

COM J1740COM J1740 isis tidally distorted tidally distorted andand isis loosing mass loosing mass from from

itsits Roche lobe Roche lobe

High-resolution spectroscopic campaign High-resolution spectroscopic campaign with UVES@VLTwith UVES@VLT

Ferraro et alFerraro et al (2002,ApJ, 584,L13) & Sabbi et al (2003, ApJ,589,L41)(2002,ApJ, 584,L13) & Sabbi et al (2003, ApJ,589,L41)

Burderi et al (2002) suggested that the position ofBurderi et al (2002) suggested that the position of COMJ1740 in the CMD is consistent with the COMJ1740 in the CMD is consistent with the evolution of a slighly evolved TO star orbiting the evolution of a slighly evolved TO star orbiting the NS and loosing mass. The evolution would NS and loosing mass. The evolution would generate a He-WDgenerate a He-WD

Mass=0.3 Mo !!!!!Mass=0.3 Mo !!!!!

This bright object is the ideal target for This bright object is the ideal target for Spectroscopic follow-up. Spectroscopic follow-up.

No C in the COM J1740-5340 atmosphere. This would suggests a CN cycle at equilibrium, (when all C has been burned to N), hence it is a deeply peeled star (Ergma & Sarna 2003)

COMJ1740 has the same overall chemical composition

of the SGBs

SGBs

COMJ1740

U in 47 Tuc: U in 47 Tuc: 0.2 Mo He-WD0.2 Mo He-WDEdmonds et al (2001)Edmonds et al (2001)

COMJ1740-5340 in NGC6397:COMJ1740-5340 in NGC6397: 0.3 Mo (pre He-WD)0.3 Mo (pre He-WD)Ferraro et al (2001)Ferraro et al (2001)

W in 47 Tuc: W in 47 Tuc: 0.13 Mo MS0.13 Mo MSEdmonds et al (2002)Edmonds et al (2002)

COMB1620-26 in M4:COMB1620-26 in M4:0.3 Mo He-WD0.3 Mo He-WDSigurdsson et al (2003)Sigurdsson et al (2003)

COMJ1911-5958 in NGC6752:COMJ1911-5958 in NGC6752: 0.2 Mo He-WD0.2 Mo He-WDFerraro et al (2003),Bassa et al (2003)Ferraro et al (2003),Bassa et al (2003)

6 objects in 5 GGCs: 3 are HeWDs + 2 pre HeWD6 objects in 5 GGCs: 3 are HeWDs + 2 pre HeWD

CO-WDCO-WD He-WDHe-WD

COMJ1701-3600B in NGC6266:COMJ1701-3600B in NGC6266: ?? Mo (pre He-WD)?? Mo (pre He-WD)Cocozza et al (2007)Cocozza et al (2007)

All the MSPs discovered so far inAll the MSPs discovered so far inNGC6266 are in binary systemsNGC6266 are in binary systems

6 MSPs have been discovered in 6 MSPs have been discovered in this cluster by D’Amico et al this cluster by D’Amico et al (2001a,b) and Jacoby et al (2001a,b) and Jacoby et al (2002)(2002)+ 51 X-ray sources (Pooley et al + 51 X-ray sources (Pooley et al 2002) 2002)

Relatively nearbyRelatively nearbycluster (7 Kpc)cluster (7 Kpc)

High reddening GC High reddening GC E(B-V)=0.48 E(B-V)=0.48 ((with some differential with some differential reddeningreddening))

This cluster could be in a dynamical phase This cluster could be in a dynamical phase particularly active in generating COL-particularly active in generating COL-binaries binaries

33 MSPs have been discovered in TERZAN 5 : 33 MSPs have been discovered in TERZAN 5 : this this is the largest population of MSP ever detected in is the largest population of MSP ever detected in a GCa GC

17 MSP are in binary systems: most of them 17 MSP are in binary systems: most of them with a massive (>0.2 Mo) companion with a massive (>0.2 Mo) companion

PC WFPC2PC WFPC2 NICMOSNICMOS

1.1. High resolution High resolution 2. High sensitivity in 2. High sensitivity in

the IR the IR

WFC3/IRWFC3/IR

NICMOS/NIC3NICMOS/NIC3

LOOKING FOR IMBH SIGNATURES in GCsLOOKING FOR IMBH SIGNATURES in GCs

The confirmation of the existence and the frequency ofThe confirmation of the existence and the frequency of IMBH in GCs is one of the most exciting challenge for the IMBH in GCs is one of the most exciting challenge for the new HST eranew HST era

In the litterature there are a few debated examples: M15 (van der Marel et al 2002, In the litterature there are a few debated examples: M15 (van der Marel et al 2002, Baumgardt et al (2003) + G1 in M31 (Gebhardt et al 2002).Baumgardt et al (2003) + G1 in M31 (Gebhardt et al 2002).

A number of potential targets have been suggestedA number of potential targets have been suggestedby Noyola and Gebhardt (2006) on the basis of small by Noyola and Gebhardt (2006) on the basis of small deviation of the surface brightness profile from the deviation of the surface brightness profile from the ““canonical” King Modelcanonical” King Model

IMBHs: which signatures? (Baumgardt et al. 2005;

Miocchi 2007; Heggie et al. 2007; Trenti et al. 2007; Dukier & Bailyn 2003;

Maccarone 2004)

1) intermediate concentration (c=1.8) King profile,

with power-law deviation at the very center:

(r) ~ r -0.2 at r < 0.1 rc

[PCC clusters: c > 2, (r) ~ r -0.8 ]

2) sharp rise in the central velocity dispersion profile (at r < 0.05 rc)

3) presence of few high-velocity (even v ~ 100 km/s) stars

+ possible X-ray and radio emission from accreting gas

SEARCHING FOR IMBH SIGNATURES in GCsSEARCHING FOR IMBH SIGNATURES in GCsBy using a combination of ACS.HR/WFC,WFPC2 and wide field observationsBy using a combination of ACS.HR/WFC,WFPC2 and wide field observationsLanzoni et al (2007, ApJ, 668, L139) has found such a signature in the star Lanzoni et al (2007, ApJ, 668, L139) has found such a signature in the star density profile of NGC6388.density profile of NGC6388.

Attention!!! The critical point here is the accurate determination ofAttention!!! The critical point here is the accurate determination ofthe center of gravity of the cluster: small (0.5 arcsec) errors inthe center of gravity of the cluster: small (0.5 arcsec) errors inthe center determination can clear-out the SB effect the center determination can clear-out the SB effect

c = 1.8 rc = 7.2”

MBH ~ 6 103 Mo

NGC 6388

Determination of the centre

V < 20 (~ 4000 stars)

~2.6” south-east of

the DM93 centre

J2000= 17h 36m 17.23s

J2000= -44o 44’ 7.1”

, ~ 0.2”-0.3”

1.1. ULTRA-ACCURATE SB & SD profiles for the promising ULTRA-ACCURATE SB & SD profiles for the promising clusters clusters High resolution (ACS/HRC) +WFC3/UVISHigh resolution (ACS/HRC) +WFC3/UVIS

2.2. MULTI-EPOCH HR images of the center & Accurate MULTI-EPOCH HR images of the center & Accurate proper motion (a few MAS) measures proper motion (a few MAS) measures to detect High to detect High velocity stars (v>100 Km/s)velocity stars (v>100 Km/s)

1.1. High resolution High resolution 2. Large field of view 2. Large field of view