Multiple populations in GCs · -> If due to helium spread -> ΔY = 0.15 (inconsistent with CMD) Vincent Hénault-Brunet (Surrey) Dynamics of multiple populations in GCs Spatial distribution

Mark GielesOscar Agertz Justin ReadAlice Zocchi

IAU 316: Formation, evolution, and survival of massive star clusters

Multiple populations in GCs:constraints on formation scenariosfrom kinematics & dynamics

Vincent Hénault-Brunet

Vincent Hénault-Brunet (Surrey) Dynamics of multiple populations in GCs

Chemistry

[O/Fe]

[Na/

Fe]

~30% “normal”(primordial)

~70%

(enriched)“anomalous”

(hydro) Dynamics

How to get this pollutingmaterial into a large fraction of GC stars?

- Multiple generations of star formation? e.g. D’Ercole+ 2008

- Accretion onto low-mass PMS stars? Bastian+ 2013

- Something completely different??

ICs long-term dynamical evolution

What is the source of pollution?

low-mass stars

high-mass stars

BHs


GCs are collisional systems

Mixing Mass segregation

timem

ean

radi

us

Aarseth 2012angular momentum

ener

gy

e.g. Hénault-Brunet+ 2015; Vesperini+ 2013 Decressin+ 2008


- mass segregation?

Spatial distribution & kinematics of subpopulations

Nature vs Nurture

- shorter relaxation time- more mixing

- imprints of formation?

- longer relaxation time- less mixing

trl /hv2i3/2

hmi ⇢

M / M0

R h(p

rimor

dial

) / R

h(enr

iche

d)

60% mass lost


Lagr

angi

an ra

dii [

pc]

0.10.20.30.40.50.60.70.80.91.0M(t)/M0

10�2

10�1

100

101

102

r lag

(1,5

,10,

25,5

0,75

,90%

)[n

body

]

MGEN1-nosev

Hénault-Brunet+ 2015Vesperini+ 2013

Spatial and kinematic mixing of subpopulations

M / M0

primordial60%

mass lost

Complete spatial mixing when 60-70% of mass lost due to two-body relaxation

enriched


Hénault-Brunet+ 2015; see also Decressin+ 2008

Spatial and kinematic mixing of subpopulations

Same applies to kinematic differences between populations…

0.10.20.30.40.50.60.70.80.91.0M(t)/M0

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

max

hvfi

[nbo

dy]

MGEN1-nosev

pristine

polluted

all

M / M0

Peak

rota

tion

enrichedprimordial

global

60% mass

lost

Complete spatial mixing when 60-70% of mass lost due to two-body relaxation


Spatial and kinematic mixing of subpopulationsSome memory of ICs should be preserved in outer parts of many GCs

10�1 100 101 102 103

RG [kpc]

102

103

104

105

106

107M

[M�]

evaporation dominated

expansion dominated47 Tuc

NGC 6362

RG [kpc]

M [M

⊙]

see Gieles, Heggie, Zhao 2011data from Harris catalogue


Observations: spatial distribution and kinematics

Enriched population -> more centrally concentrated

e.g. Lardo+ 2011primordial

enriched

Enriched population -> lower velocity dispersion

e.g. Bellazzini+ 2012, Kucinskas+ 2014

enrichedprimordialprimordial enriched

(when kinematic differences are found)



47 Tuc - HST proper motions near R ~2 rh

Richer+ 2013

color group primordialenriched

Enriched stars -> more radially anisotropic velocity distribution

PM d

ispe

rsio

n [m

as/y

r]



NGC 2808 - HST proper motions Bellini+ 2015

Enriched stars -> more radially anisotropic velocity distribution beyond R ~ rh

�ta

n/�

rad�

1

1.5 rh 2 rhrh 1.5 rh 2 rhrh


On the uniqueness of the observed signatures…

Hénault-Brunet+ 2015; see also Mastrobuono-Battisti & Perets 2013

N-body simulations scaled to 47 Tuc

enrichedprimordial enriched

primordial

Disc embedded in spherical cluster Spherical subsystem within spherical cluster


Clues from differential rotation of subpopulations?

10�310�210�1

100101102103104105

n[p

c�3 ]

MGEN1; t=0

pristine

polluted

ACC1; t=0

pristine

polluted

05

1015202530

s z[k

m/s

]

05

1015202530

s x[k

m/s

]

�2.0�1.5�1.0�0.5

0.00.51.0

b

10�1 100 101

r [pc]

0

10

20

30

hvfi

[km

/s]

10�1 100 101

r [pc]

enrichedprimordial

enrichedprimordial

Hénault-Brunet+ 2015

Rota

tion

curv

e

t = 0 t = 0

Formation of 2nd generation-> flattened and rotating enriched pop.

(Bekki 2010, 2011)

Removing >90% of 1st generation removes large fraction of its angular momentum

Enriched stars on preferentially radial orbits -> less rotation

Marginal evidence in clusters fromBellazzini+ 2012


10�310�210�1

100101102103104105

n[p

c�3 ]

MGEN1; t=0

pristine

polluted

ACC1; t=0

pristine

polluted

05

1015202530

s z[k

m/s

]

05

1015202530

s x[k

m/s

]

�2.0�1.5�1.0�0.5

0.00.51.0

b

10�1 100 101

r [pc]

0

10

20

30

hvfi

[km

/s]

10�1 100 101

r [pc]

enrichedprimordial

enrichedprimordial


Rota

tion

curv

e

t = 0 t = 0

0

10

20

30

hv fi[

km/s

]

MGEN1t=0 Myr

pristine

polluted

ACC1t=0 Myr

pristine

polluted

0

10

20

30

hv fi[

km/s

]

MGEN1t=346 Myr

ACC1t=346 Myr

0

10

20

30

hv fi[

km/s

]

MGEN1t=1386 Myr

ACC1t=1386 Myr

10�1 100 101

r [pc]

0

10

20

30

hv fi[

km/s

]

MGEN1t=10745 Myr

10�1 100 101

r [pc]

ACC1t=10745 Myr

enrichedprimordial

t = 0.3 Gyrenrichedprimordial

t = 0.3 Gyr

Clues from differential rotation of subpopulations?Formation of 2nd generation-> flattened and rotating enriched pop.

(Bekki 2010, 2011)





10�310�210�1

100101102103104105

n[p

c�3 ]

MGEN1; t=0

pristine

polluted

ACC1; t=0

pristine

polluted

05

1015202530

s z[k

m/s

]

05

1015202530

s x[k

m/s

]

�2.0�1.5�1.0�0.5

0.00.51.0

b

10�1 100 101

r [pc]

0

10

20

30

hvfi

[km

/s]

10�1 100 101

r [pc]

enrichedprimordial

enrichedprimordial


Rota

tion

curv

e

t = 0 t = 0

0

10

20

30

hv fi[

km/s

]

MGEN1t=0 Myr

pristine

polluted

ACC1t=0 Myr

pristine

polluted

0

10

20

30

hv fi[

km/s

]

MGEN1t=346 Myr

ACC1t=346 Myr

0

10

20

30

hv fi[

km/s

]

MGEN1t=1386 Myr

ACC1t=1386 Myr

10�1 100 101

r [pc]

0

10

20

30

hv fi[

km/s

]

MGEN1t=10745 Myr

10�1 100 101

r [pc]

ACC1t=10745 Myr

enrichedprimordial

t = 1 Gyr

enrichedprimordial

t = 1 Gyr


(Bekki 2010, 2011)





10�310�210�1

100101102103104105

n[p

c�3 ]

MGEN1; t=0

pristine

polluted

ACC1; t=0

pristine

polluted

05

1015202530

s z[k

m/s

]

05

1015202530

s x[k

m/s

]

�2.0�1.5�1.0�0.5

0.00.51.0

b

10�1 100 101

r [pc]

0

10

20

30

hvfi

[km

/s]

10�1 100 101

r [pc]

enrichedprimordial

enrichedprimordial


Rota

tion

curv

e

t = 0 t = 0

0

10

20

30

hv fi[

km/s

]

MGEN1t=0 Myr

pristine

polluted

ACC1t=0 Myr

pristine

polluted

0

10

20

30

hv fi[

km/s

]

MGEN1t=346 Myr

ACC1t=346 Myr

0

10

20

30

hv fi[

km/s

]

MGEN1t=1386 Myr

ACC1t=1386 Myr

10�1 100 101

r [pc]

0

10

20

30

hv fi[

km/s

]

MGEN1t=10745 Myr

10�1 100 101

r [pc]

ACC1t=10745 Myr

enrichedprimordial

t = 11 Gyrenrichedprimordial

t = 11 Gyr


(Bekki 2010, 2011)





primord

ial

prim

ordia

l

enric

hed

enric

hed

Spatial distribution of subpopulations: central regions of M15

Larsen+ 2015

Primordial population more centrally concentrated than enriched population!

M15

Mass segregation? -> need Δm ~ 0.25 M⊙ -> If due to helium spread -> ΔY = 0.15 (inconsistent with CMD)


Spatial distribution of subpopulations: central regions of M15

Larsen+ 2015

Nor

mal

ized

sur

face

den

sity

log(R) [pc]


Spatial distribution in central regions: additional considerations

- What about binaries? larger binary fraction for primordial stars (12% vs 1%; D’Orazi+ 2010)

larger core binary fraction?

“global” binary fraction

core binary fraction

Hurley+ 2007 Larsen+ 2015





- Other clusters?

D’Alessandro+ 2011; Iannicola+ 2009NGC 2808: no significant difference in spatial distribution of evolved stars

NGC 2419: giants with blue u-V colors more centrally concentrated

* effect of mass segregation sensitive to cluster concentration

Beccari+ 2013; see also Larsen+ 2015

NGC 2808

surface

brightness

l.o.s.

veloc

ity

dispers

ion


M 15

Multi-mass model using limepy (Gieles & Zocchi 2015)


M 15 NGC 2808


Effect of mass segregation maximal in densest clusters like M15.



M 15 NGC 2808

+ 0.25 M⊙ + 0.25 M⊙

Effect of mass segregation maximal in densest clusters like M15.



- Other clusters?

D’Alessandro+ 2011; Iannicola+ 2009NGC 2808: no significant difference in spatial distribution of evolved stars

NGC 2419: giants with blue u-V colors more centrally concentrated

* effect of mass segregation sensitive to cluster concentration



- Initial conditions matter

Beccari+ 2013; see also Larsen+ 2015

Conclusions


- Spatial/kinematic imprints of the formation of multiple populations can survive to the present day

- All observations consistent with an enriched population forming more centrally concentrated

- Explaining the more centrally concentrated primordial population in the inner regions of M15 in terms of mass segregation remains challenging

- Could binaries play a role??

- None of the observed signatures unique to a given formation scenario. Differential rotation may provide useful constraints.

Documents

Multiple populations in GCs · -> If due to helium spread -> ΔY = 0.15 (inconsistent with CMD) Vincent Hénault-Brunet (Surrey) Dynamics of multiple populations in GCs Spatial distribution