bimodal regime in young massive clusters leading to ... · introduction motivation: cooling winds...

Bimodal regime in young massive clusters leadingto formation of subsequent stellar generations

Richard WünschJ. Palouš, G. Tenorio-Tagle, C. Muñoz-Tuñón, S. Ehlerová

Astronomical institute, Czech Academy of Sciences

14th August 2015

Wünsch (AsU CAS) 2G with bimodal regime 14.8.2015 1 / 1

Introduction

Motivation: Cooling winds→ multiple populations

young massive clusters have windsstellar winds, SNe→ collisions→ hot shocked wind→ outflow

the wind may become thermally unstable inside the clusterif the cluster is massive and compact enough

dense warm/cold clumps are formeddepends whether they can self-shield against ionising stellar radiation

new stars form either in-situ or after clumps sink into the centre2nd generation (2G) stars enriched by products of massive stars chemical evolution

similarities with FRMS scenario (desressin+07)

- even fast winds can be captured

predicts formation of 2G stars in the centre (may help with mass budget problem)

Wünsch (AsU CAS) 2G with bimodal regime 14.8.2015 2 / 1

Introduction

Motivation: Cooling winds→ multiple populations

young massive clusters have windsstellar winds, SNe→ collisions→ hot shocked wind→ outflow

the wind may become thermally unstable inside the clusterif the cluster is massive and compact enough

dense warm/cold clumps are formeddepends whether they can self-shield against ionising stellar radiation

new stars form either in-situ or after clumps sink into the centre2nd generation (2G) stars enriched by products of massive stars chemical evolution

similarities with FRMS scenario (desressin+07)

- even fast winds can be captured

predicts formation of 2G stars in the centre (may help with mass budget problem)

Wünsch (AsU CAS) 2G with bimodal regime 14.8.2015 2 / 1

Introduction

Motivation: Cooling winds→ multiple populations

young massive clusters have windsstellar winds, SNe→ collisions→ hot shocked wind→ outflow

the wind may become thermally unstable inside the clusterif the cluster is massive and compact enough

dense warm/cold clumps are formeddepends whether they can self-shield against ionising stellar radiation

new stars form either in-situ or after clumps sink into the centre2nd generation (2G) stars enriched by products of massive stars chemical evolution

similarities with FRMS scenario (desressin+07)

- even fast winds can be captured

predicts formation of 2G stars in the centre (may help with mass budget problem)

Wünsch (AsU CAS) 2G with bimodal regime 14.8.2015 2 / 1

Introduction

Motivation: Cooling winds→ multiple populations

young massive clusters have windsstellar winds, SNe→ collisions→ hot shocked wind→ outflow

the wind may become thermally unstable inside the clusterif the cluster is massive and compact enough

dense warm/cold clumps are formeddepends whether they can self-shield against ionising stellar radiation

new stars form either in-situ or after clumps sink into the centre2nd generation (2G) stars enriched by products of massive stars chemical evolution

similarities with FRMS scenario (desressin+07)

- even fast winds can be captured

predicts formation of 2G stars in the centre (may help with mass budget problem)

Wünsch (AsU CAS) 2G with bimodal regime 14.8.2015 2 / 1

The cluster wind

Star cluster wind: semi-analytical model

by Chevalier & Clegg (1985, Nat., 317, 44)Ekin of stellar winds and SN ejectathermalized, hot gas fills the clustersources (stars) distributed according totop-hat profilesolution of 1D spherically sym. HDequations, cooling neglectedsonic point at the cluster bordertested by Cantó+00, Raga+01 and othersfor stellar windsinteraction of the wind with the parentalcloud not covered here(harper-clark&murray09, krause+12,14, rogers&pittard13,

rosen+14, herrera+, . . . )

Wünsch (AsU CAS) 2G with bimodal regime 14.8.2015 3 / 1

The cluster wind

Star cluster wind: semi-analytical model

by Chevalier & Clegg (1985, Nat., 317, 44)Ekin of stellar winds and SN ejectathermalized, hot gas fills the clustersources (stars) distributed according totop-hat profilesolution of 1D spherically sym. HDequations, cooling neglectedsonic point at the cluster bordertested by Cantó+00, Raga+01 and othersfor stellar windsinteraction of the wind with the parentalcloud not covered here(harper-clark&murray09, krause+12,14, rogers&pittard13,

rosen+14, herrera+, . . . )

Wünsch (AsU CAS) 2G with bimodal regime 14.8.2015 3 / 1

The cluster wind

Star cluster wind: semi-analytical model

by Chevalier & Clegg (1985, Nat., 317, 44)Ekin of stellar winds and SN ejectathermalized, hot gas fills the clustersources (stars) distributed according totop-hat profilesolution of 1D spherically sym. HDequations, cooling neglectedsonic point at the cluster bordertested by Cantó+00, Raga+01 and othersfor stellar windsinteraction of the wind with the parentalcloud not covered here(harper-clark&murray09, krause+12,14, rogers&pittard13,

rosen+14, herrera+, . . . )

Wünsch (AsU CAS) 2G with bimodal regime 14.8.2015 3 / 1

The cluster wind

Star cluster wind: semi-analytical model

by Chevalier & Clegg (1985, Nat., 317, 44)Ekin of stellar winds and SN ejectathermalized, hot gas fills the clustersources (stars) distributed according totop-hat profilesolution of 1D spherically sym. HDequations, cooling neglectedsonic point at the cluster bordertested by Cantó+00, Raga+01 and othersfor stellar windsinteraction of the wind with the parentalcloud not covered here(harper-clark&murray09, krause+12,14, rogers&pittard13,

rosen+14, herrera+, . . . )

Wünsch (AsU CAS) 2G with bimodal regime 14.8.2015 3 / 1

The cluster wind

Catastrophic cooling of the windfor massive clusters, cooling has to betaken into accountradiative solution by silich+03→ T drops at a certain radiuspredicts different observed X-ray flux(silich+04) - good agreement withobserved X-ray fluxes(NGC4303 nuclear SSC; jiménez-bailón+03)

above certain mass limit, no stationary wind solution exists→catastrophic cooling (silich+03):

energy deposition ∝ MSC

cooling ∝ ρ2wind ∝ M2

SC

}⇒ inevitable

tenorio-tagle+05 suggests extreme positive feedback (high SFE)

Wünsch (AsU CAS) 2G with bimodal regime 14.8.2015 4 / 1

The cluster wind

Catastrophic cooling of the windfor massive clusters, cooling has to betaken into accountradiative solution by silich+03→ T drops at a certain radiuspredicts different observed X-ray flux(silich+04) - good agreement withobserved X-ray fluxes(NGC4303 nuclear SSC; jiménez-bailón+03)

above certain mass limit, no stationary wind solution exists→catastrophic cooling (silich+03):

energy deposition ∝ MSC

cooling ∝ ρ2wind ∝ M2

SC

}⇒ inevitable

tenorio-tagle+05 suggests extreme positive feedback (high SFE)

Wünsch (AsU CAS) 2G with bimodal regime 14.8.2015 4 / 1

Bimodal regime

Three wind regimes

quasi-adiabatic regimeidentical with CC85, cooling has no effectmechanical luminosity (cluster mass) substantially below Lcrit

log T

LSC

SCR

critL

rSCR

3 parameters: LSC , MSC︸ ︷︷ ︸given by MSC

, RSC

density

SN s

s

SW

Quasi− v < c

vA,∞ =√

2ηLSC

MSC

thermalization

−adiabatic

sound speed

v > c

temperature

velocity

2

0

8

7

6

5

4

3

1

Wünsch (AsU CAS) 2G with bimodal regime 14.8.2015 5 / 1

Bimodal regime

Three wind regimes

radiative regimemechanical luminosity (cluster mass) slightly below Lcritwind cools down at certain distance out of the cluster

log T

LSC

SCR

critL

rSCR

3 parameters: LSC , MSC︸ ︷︷ ︸given by MSC

, RSC

Radiative density

velocity

temperature

2

0

8

7

6

5

4

3

1

Wünsch (AsU CAS) 2G with bimodal regime 14.8.2015 5 / 1

Bimodal regime

Three wind regimes

bimodal regime (tenorio-tagle+07; wünsch+08), cluster split by Rstouter: wind, stationary solution existsinner: thermal instabilities, mass accumulation - secondary SF

log T

LSC

SCR

critL

rSCR

3 parameters: LSC , MSC︸ ︷︷ ︸given by MSC

, RSC

Bimodalvelocity

temperature

density

Rst

stagnationradius

2

0

8

7

6

5

4

3

1

Wünsch (AsU CAS) 2G with bimodal regime 14.8.2015 5 / 1

Bimodal regime

Heating efficiency and mass loading

hot gas inside cluster seems to be colder than energy / massdeposited by stars→ two new parameters:

ηML: mass loading - additional (pristine) gas added to the hot phaseηHE: heating efficiency - some thermal energy is lost from the hotphase (on the top of standard cooling)

mass loading - evidence for mixing with pristine gas ∼ 1 : 1(e.g. prantzos+07)

obs. evidence for low heating efficiencymissing energy from X-ray luminosities(rosen+14)recombination line profiles of SSCs inAntennae have moderately supersonicwidths (gilbert&graham07)

Wünsch (AsU CAS) 2G with bimodal regime 14.8.2015 6 / 1

Bimodal regime

Heating efficiency and mass loading

hot gas inside cluster seems to be colder than energy / massdeposited by stars→ two new parameters:

ηML: mass loading - additional (pristine) gas added to the hot phaseηHE: heating efficiency - some thermal energy is lost from the hotphase (on the top of standard cooling)

mass loading - evidence for mixing with pristine gas ∼ 1 : 1(e.g. prantzos+07)

obs. evidence for low heating efficiencymissing energy from X-ray luminosities(rosen+14)recombination line profiles of SSCs inAntennae have moderately supersonicwidths (gilbert&graham07)

Wünsch (AsU CAS) 2G with bimodal regime 14.8.2015 6 / 1

Bimodal regime

Heating efficiency and mass loading

hot gas inside cluster seems to be colder than energy / massdeposited by stars→ two new parameters:

ηML: mass loading - additional (pristine) gas added to the hot phaseηHE: heating efficiency - some thermal energy is lost from the hotphase (on the top of standard cooling)

mass loading - evidence for mixing with pristine gas ∼ 1 : 1(e.g. prantzos+07)

obs. evidence for low heating efficiencymissing energy from X-ray luminosities(rosen+14)recombination line profiles of SSCs inAntennae have moderately supersonicwidths (gilbert&graham07)

Wünsch (AsU CAS) 2G with bimodal regime 14.8.2015 6 / 1

Bimodal regime

Heating efficiency 2

HII region coinciding with SSCs in M82 are very compact(silich+09)

evidence for high heating efficiency in M82defined globally: ηHE = 30− 100 %, strickland&heckman09)

Wünsch (AsU CAS) 2G with bimodal regime 14.8.2015 7 / 1

Bimodal regime

Heating efficiency 2

HII region coinciding with SSCs in M82 are very compact(silich+09)

evidence for high heating efficiency in M82defined globally: ηHE = 30− 100 %, strickland&heckman09)

Wünsch (AsU CAS) 2G with bimodal regime 14.8.2015 7 / 1

Bimodal regime

Evolution of Massive Compact Clusters (wünsch+11)

evolution of the critical luminosity (Lcrit) for 107 M� cluster withRSC = 3 pcStarburst99 with Geneva evolutionary tracks (HighMass winds)

36

38

40

42

44

0 5 10 15 20 25 30 35 40

log L

SC

, L

crit [e

rg s

-1]

t [Myr]

LSC

Lcrit: ηhe=1, ηml=0

Lcrit: ηhe=0.05, ηml=1

Wünsch (AsU CAS) 2G with bimodal regime 14.8.2015 8 / 1

Bimodal regime

Influence of ionising radiation

Analytical estimate (palouš+14)dense warm gas sinks into centre: stream + centralclumpself-shielding mass of the central clumpmself = NUV,SC

µmHα?

kTionPhot

can streams of falling mass cool before they fall intocentre?tSS = 1

4πq2UV R5

SCR−2st (1 + ηml)

−1M−1SCµmHα

−2∗

(kTPhot

)3.

central clump

stre

am

=

*

SF

ionisedP

*

*

hotP

*

hot

HealPix ray/cone

HealPix ray/cone

target cell

tree node

RHD simulations:radiation treated by TreeRay: tree + reverseray-tracing; wünsch+(in prep.)

Wünsch (AsU CAS) 2G with bimodal regime 14.8.2015 9 / 1

Bimodal regime

Influence of ionising radiation

Analytical estimate (palouš+14)dense warm gas sinks into centre: stream + centralclumpself-shielding mass of the central clumpmself = NUV,SC

µmHα?

kTionPhot

can streams of falling mass cool before they fall intocentre?tSS = 1

4πq2UV R5

SCR−2st (1 + ηml)

−1M−1SCµmHα

−2∗

(kTPhot

)3.

central clump

stre

am

=

*

SF

ionisedP

*

*

hotP

*

hot

HealPix ray/cone

HealPix ray/cone

target cell

tree node

RHD simulations:radiation treated by TreeRay: tree + reverseray-tracing; wünsch+(in prep.)

Wünsch (AsU CAS) 2G with bimodal regime 14.8.2015 9 / 1

Bimodal regime

Influence of ionising radiation

Analytical estimate (palouš+14)dense warm gas sinks into centre: stream + centralclumpself-shielding mass of the central clumpmself = NUV,SC

µmHα?

kTionPhot

can streams of falling mass cool before they fall intocentre?tSS = 1

4πq2UV R5

SCR−2st (1 + ηml)

−1M−1SCµmHα

−2∗

(kTPhot

)3.

central clump

stre

am

=

*

SF

ionisedP

*

*

hotP

*

hot

HealPix ray/cone

HealPix ray/cone

target cell

tree node

RHD simulations:radiation treated by TreeRay: tree + reverseray-tracing; wünsch+(in prep.)

Wünsch (AsU CAS) 2G with bimodal regime 14.8.2015 9 / 1

Bimodal regime Simulations

RHD simulation

AMR code Flash

1283 grid

M&E src: Schusterdistribution

optically thincooling:raymond+76

fixed stellar gravity

self-gravity: treecode (wünsch+15)

heating by ionisingradiation: TreeRay

Wünsch (AsU CAS) 2G with bimodal regime 14.8.2015 10 / 1

Bimodal regime Simulations

Evolution of accumulated mass

2

2.5

3

3.5

4

4.5

5

5.5

6

0 0.5 1 1.5 2 2.5 3 3.5 4 2

2.5

3

3.5

4

4.5

5

5.5

6

log m

ass [M

Sun]

time [Myr]

Msc = 107 MSun, β = 1.5, Rh = 2.38 pc, ηHE = 0.05, ηML = 1.0

firstsupernova

total mass insertedsinks+gas

sinksgas

windcal

Wünsch (AsU CAS) 2G with bimodal regime 14.8.2015 11 / 1

Bimodal regime Simulations

Evolution of accumulated mass

2

2.5

3

3.5

4

4.5

5

5.5

6

0 0.5 1 1.5 2 2.5 3 3.5 4 2

2.5

3

3.5

4

4.5

5

5.5

6

log m

ass [M

Sun]

time [Myr]

Msc = 107 MSun, β = 1.5, Rh = 2.38 pc, ηHE = 0.05, ηML = 1.0

firstsupernova

total mass insertedsinks+gas

sinksgas

windcal

Mass budget at 3.5 Myr:1G stellar mass: 107 M�inserted by winds: 4× 105 M�mass loaded: 4× 105 M�2G stellar mass: 7× 105 M�→ very compact, in the centre→ should stay in the cluster during1G tidal removal (khalaj&baumgardt15)

remains in dense phase: 14000 M�→ rapidly removed by SNe

Wünsch (AsU CAS) 2G with bimodal regime 14.8.2015 11 / 1

Bimodal regime Simulations

Parameter space study

0

1

2

3

4

5

0.001 0.01 0.1 1

ηm

l

ηhe

log

accu

mu

late

d m

ass [

MS

un]

4

4.5

5

5.5

6

6.5

bimodal butno self-shielding

not bimodal

extended 2G

co

mp

act

2G

Wünsch (AsU CAS) 2G with bimodal regime 14.8.2015 12 / 1

Summary & conclusions

Summary

wind cooling leading to bimodal regime is inevitable for high andcompact enough clusterdense gas formed by thermal instability stays in the cluster andself-shields against ionising radiation→ secondary SFheating efficiency⇒ compact/extended 2G

low heating efficiency→ SF in the central clump: 2G concentratedin the cluster centre;high heating efficiency→ SF in streams: 2G dispersed throughoutthe cluster

much more difficult to capture SN ejecta; rapidly removeremaining accumulated gas

Wünsch (AsU CAS) 2G with bimodal regime 14.8.2015 13 / 1

Summary & conclusions

Summary

wind cooling leading to bimodal regime is inevitable for high andcompact enough clusterdense gas formed by thermal instability stays in the cluster andself-shields against ionising radiation→ secondary SFheating efficiency⇒ compact/extended 2G

low heating efficiency→ SF in the central clump: 2G concentratedin the cluster centre;high heating efficiency→ SF in streams: 2G dispersed throughoutthe cluster

much more difficult to capture SN ejecta; rapidly removeremaining accumulated gas

Wünsch (AsU CAS) 2G with bimodal regime 14.8.2015 13 / 1

Summary & conclusions

Summary

wind cooling leading to bimodal regime is inevitable for high andcompact enough clusterdense gas formed by thermal instability stays in the cluster andself-shields against ionising radiation→ secondary SFheating efficiency⇒ compact/extended 2G

low heating efficiency→ SF in the central clump: 2G concentratedin the cluster centre;high heating efficiency→ SF in streams: 2G dispersed throughoutthe cluster

much more difficult to capture SN ejecta; rapidly removeremaining accumulated gas

Wünsch (AsU CAS) 2G with bimodal regime 14.8.2015 13 / 1

Summary & conclusions

Summary

wind cooling leading to bimodal regime is inevitable for high andcompact enough clusterdense gas formed by thermal instability stays in the cluster andself-shields against ionising radiation→ secondary SFheating efficiency⇒ compact/extended 2G

low heating efficiency→ SF in the central clump: 2G concentratedin the cluster centre;high heating efficiency→ SF in streams: 2G dispersed throughoutthe cluster

much more difficult to capture SN ejecta; rapidly removeremaining accumulated gas

Wünsch (AsU CAS) 2G with bimodal regime 14.8.2015 13 / 1

Summary & conclusions

Thank you!

Wünsch (AsU CAS) 2G with bimodal regime 14.8.2015 14 / 1