spin alignment of stars in old open clusters...oct 17, 2017 · • angular momentum from the cloud...

Spin alignment of starsin old open clusters

Y U E H - N I N G L E E , R A FA E L A . G A R C Í A , PAT R I C K H E N N E B E L L E , S AV I TA M AT H U R , PA U L G . B E C K , S T E P H A N E M AT H I S , D E N N I S S T E L L O & J E R O M E B O U V I E R

E N R I C O C O R S A R O

OCA Seminar 17 October 2017

Marie Sklodowska-Curie Fellow AstroFIt2INAF - Osservatorio Astrofisico di Catania

O U T L I N E

• Star and Stellar Cluster formation

• Stellar oscillations

• Observations, analysis & new results

PA R T I

PA R T I I

PA R T I I I

S TA R A N D S T E L L A R C L U S T E R F O R M AT I O N

PA R T I

Very difficult to access:

• SFR are dense and obscured by dust (only IR and Radio)

• MC change density by 10 orders - Hierarchical step approaches required

S TA R F O R M AT I O N

E N R I C O C O R S A R O - 1 7 O C T O B E R 2 0 1 7 - O C A S E M I N A R

S H U E T A L . 1 9 8 7 ; M C K E E & O S T R I K E R 2 0 0 7

B A R N A R D 6 8 D A R K C L O U D . © E S O

I N T R O D U C T I O N

• Fundamental problem in Astrophysics

• Gravitational collapse of turbulent molecular clouds (MC)

• Physical and chemical properties and dynamics of star forming regions (SFR)

• Origin of stellar mass distribution (IMF)

• Star and planet formation rates

• Link to stellar evolution and planet formation

• Formation, structure, and evolution of galaxies

• Half star formation in Milky Way occurring in 24 giant MC (up to 107 MSun each)

M A S S I V E S F R

• Star formation very diffused in Galaxy

• ~1300 massive SFR identified with IR, sub-mm, radio surveys across inner Galaxy

L E E E T A L . 2 0 1 2 ; L O N G M O R E E T A L . 2 0 1 4

AT L A S G A L © U R Q U H A R T E T A L . 2 0 1 4


U R Q U H A R T E T A L . 2 0 1 4


• Giant MC can form hundreds of proto-clusters each with up to 105 MSun (many Jeans masses!)

• Stellar clusters are common and likely to form (high mass clumps)

• Understand clusterformation is critical to understand star formation

• Sun and Solar System likely originated from a cluster

P R O T O - C L U S T E R S

I M M E R A L . 2 0 1 2 ; L O N G M O R E E T A L . 2 0 1 2

AT L A S G A L © U R Q U H A R T E T A L . 2 0 1 4


A D A M S 2 0 1 0


O P E N C L U S T E R S

• Open clusters (OC) important:

• Can be observed in multi bands because no or little ISM (not embedded)Not possible in SFR because covered by dust

• Stars are sparse (~1 MSun pc-3) —> precise follow-up studies possible Not possible in e.g. Globular Clusters, too dense!

• Stars in cluster can preserve imprint of initial cdts of progenitor MC Not possible with field stars because from dissolved small stellar systems

L A D A & L A D A 2 0 0 3 ; L O N G M O R E E T A L . 2 0 1 4

O P E N C L U S T E R N G C 2 6 5 © N A S A / E S A

B E N C H M A R K S O F S TA R F O R M A T I O N


• 3D numerical simulations of MC collapse and cluster formation to study morphology and dynamics

• Stars can form either isolated, in filaments or in clusters (more common)

I M P R I N T O F I N I T I A L C O N D I T I O N S ?S T E L L A R C L U S T E R S A N D 3 D S I M U L A T I O N S

C L O U D C O L L A P S E © B AT E E T A L . 2 0 0 9

• Kinematic signatures of MC might not live long enough to be observed

B AT E E T A L . 2 0 0 9 ; K U Z N E T S O VA E T A L . 2 0 1 5


• From 3D MHD simulations of proto-cluster formation

• Angular momentum from the cloud is not efficiently passed to stars

• Less general cloud’s rotation at scales of forming stars (several AU)

C L O U D ’ S A N G U L A R M O M E N T U M

P R O T O - C L U S T E R F O R M AT I O N © L E E & H E N N E B E L L E 2 0 1 6

Ekin

= Etur

+ Erot

S T E L L A R C L U S T E R S A N D 3 D S I M U L A T I O N S

L E E & H E N N E B E L L E 2 0 1 6

Erot

<1

2E

tur


Turbulence fields counteract cloud’s globalrotation in producing spin alignment

O B S E R VAT I O N A L R E S U LT S

• Evolution of cloud’s AM not well understood

• Stellar-spin axis randomly distributed in nearby OC Pleiades and Alpha Persei (d ~ 150 pc, Age~80 Myr)

• Clouds’ average AM scrambled by turbulence at different scales

• Imprint of cloud’s global rotation lost during star formation

J A C K S O N & J E F F R I E S 2 0 1 0

P L E I A D E S W I T H D S S © N A S A / E S A


E . G . S H U , A D A M S & L I Z A N O 1 9 8 7 ; D O N G L A I 2 0 1 4


O B S E R VAT I O N A L L I M I TAT I O N S

• Observational technique requires combination of several observations:

• Prot from light curve spot modulation (active stars!)

• v sini measurement from spectroscopic observations

• stellar radius R from cluster distance + angular diameter

• cluster distance from parallax (Hipparcos)

• angular diameter from magnitude (de-reddened) + color index relation recalibrated with interferometry on MS and SG stars

J A C K S O N & J E F F R I E S 2 0 1 0


sin i =v sin iP

rot

2⇡R

K E R V E L L A E T A L . 2 0 0 4

Only young active stars possible Strong sensitivity to cluster distance

Prone to large systematics


S T E L L A R O S C I L L AT I O N SPA R T I I

A S T E R O S E I S M O L O G Y• Most stars with M ~ 1-3 MSun

oscillate like the Sun (helioseismology)

• ~ 100 K known today

• Space missions MOST, CoRoT, NASA’s Kepler & K2

• More to follow: NASA TESS, ESA PLATO space missions

P R O B I N G T H E I N T E R I O R O F S TA R S

© E S O

C H R I S T E N S E N - D A L S G A A R D 1 9 8 7


S O L A R - L I K E O S C I L L AT I O N S

Acoustic waves (p modes) propagate in outer CZ


© C R E D I T: G A B R I E L P E R E Z D I A Z , I A C ( M U LT I M E D I A S E R V I C E )


S O L A R - L I K E O S C I L L AT I O N S

• Produce tiny brightness variations (from few ppm to ppt) in light curve

• Fourier analysis (Power Spectrum) reveals Gaussian envelope of oscillations


© V I R G O / S P M O N B O A R D S O H O

⌫max

/ g/p

Te↵


O S C I L L AT I O N M O D E S

• Oscillation mode identified by 3 quantum numbers (n, ℓ, m, for spherical harmonic)

• Surface distribution depends on oscillation mode


ℓ = 3, m = 1 ℓ = 3, m = 2 n ~ 10-20

© B E C K & K A L L I N G E R , 2 0 1 3 S & W


A S Y M P T O T I C PAT T E R N

• When radial order n >> 1, regime becomes asymptotic

• Modes with same angular degree ℓ are equally spaced in frequency

• Large frequency separation Δν probes mean stellar density


2�= 2 2

0

� = 0 0

33� = 3

1

1 �=1

© B E D D I N G , K J E L D S E N E T A L . 2 0 0 3

�⌫ / ⇢

M,R

⌫max

/ g/p

Te↵


n ~ 10-20

D E TA I L E D M O D E P R O P E R T I E S

• Each oscillation mode is characterized by 3 parameters

• An individual PS can require hundreds of free parameters to be modeled


Damped oscillation

Lorentzian profile

⌫0

�

H

Tobs

� ⌧� / ⌧�1 ⌫0,�, H


R E D G I A N T S

© T H O M A S K A L L I N G E R

Main Sequence Red Giant Branch

E V O LV E D S O L A R - T Y P E S TA R S

Red Clump


R G O S C I L L AT I O N S

• Giants are very luminous: can be observed more far away than MS (dwarfs)

• Useful for Galactic Archeology: map Galaxy structure and evolution, Globular Clusters

• Solar-like oscillations in outer CZ

• Couple with gravity waves from RZ

• Dipole (ℓ=1) mixed modes observable, with both g- and p- character

E V O LV E D S O L A R - T Y P E S TA R S

p modes

g modes

© C H R I S T E N S E N - D A L S G A A R D

M I G L I O E T A L . 2 0 1 3 , 2 0 1 6


M I X E D M O D E S PAT T E R NE V O LV E D S O L A R - T Y P E S TA R S

• Mixed dipole modes have regular separation in period

�⇧1

ℓ = 1 Mixed Modes forest

ℓ = 0

ℓ = 0

ℓ = 2

ℓ = 2

g-dominated g-dominated

p-dominated

He-core burningH-shell burning

B E D D I N G E T A L . 2 0 1 1 N AT U R E ; M O S S E R E T A L . 2 0 1 2


I N T E R N A L R O TAT I O N

B E C K E T A L . 2 0 1 2 N AT U R E

M E A S U R I N G S T E L L A R A M

B E C K E T A L . 2 0 1 1 S C I E N C E ; M O S S E R E T A L . 2 0 1 2


S P I N I N C L I N AT I O N A N G L E• Stellar oscillations accurately probe rotation rate and spin axis

inclination

• Rotational degeneracy of ℓ=1 (dipolar) modes gives (2ℓ + 1) m-components


G I Z O N & S O L A N K I 2 0 0 3 ; B A L L O T E T A L . 2 0 0 6 ; B E C K E T A L . 2 0 1 2 N AT U R E ; D E H E U V E L S E T A L . 2 0 1 2 ; H U B E R E T A L . 2 0 1 3 S C I E N C E

⌫0

�

H


P R O J E C T I O N E F F E C T

High angles are easier to observe (projection effect from 3D space)


3 D R A N D O M D I S T R I B U T I O N

No

rmal

ized

Co

unts

0

0,045

0,09

0,135

0,18

Projected spin inclination θ0-10 20-30 40-50 60-70 80-90

θ = 30°θ = 80°

m = +1m = -1

m = 0

© G I Z O N & S O L A N K I 2 0 0 3

© C O R S A R O E T A L . , N AT U R E A S T R O N O M Y, 2 0 1 7

d⌦ = sin(✓)d✓


D E G R E E O F S P I N A L I G N M E N T3 D R A N D O M D I S T R I B U T I O N

No

rmal

ized

Co

unts

0

0,045

0,09

0,135

0,18


↵ =1

3

↵ = 1

3D Random

Perfect alignment

P E R F E C T A L I G N M E N T A L O N G L . O . S .

No

rmal

ized

Co

unts

0

0,25

0,5

0,75

1



↵ =

1

N

NX

i=1

cos

2(✓i)


O B S E R VAT I O N S , A N A LY S I S & N E W R E S U LT S

PA R T I I I

N A S A K E P L E R

© S D S S• Launched 2009 - End nominal mission in 2013

• Mission devoted to exoplanets discovery

• 150,000 stars observed in the Cygnus - Lyra constellations

• Kepler photometric band: 430-890 nm

S PA C E M I S S I O N

© N A S A A M E S R E S E A R C H C E N T E R


O B S E R VAT I O N A L P R O P E R T I E S

• Total mass ~ 5000 MSun

• Distance ~ 4187 pc

• Size ~ 10 pc

© S D S S

© D S S

• Age ~ 8.3 Gyr

• MRG ~ 1.1 MSun

• Class: II3r

• Age ~ 2.4 Gyr

• MRG ~ 1.7 MSun

• Class: I1m

• Total mass ~ 2600 MSun

• Distance ~ 2344 pc

• Size ~ 7 pc

O C F R O M N A S A ’ S KEPLER M I S S I O N

4 Y E A R S P H O T O M E T R Y

P L ATA I S E T A L . 2 0 1 1

K A L I R A I E T A L . 2 0 0 1

B A S U E T A L . 2 0 1 1

B A S U E T A L . 2 0 1 1

M I G L I O E T A L . 2 0 1 2

M I G L I O E T A L . 2 0 1 2

B R O G A A R D E T A L . 2 0 1 2

B R E W E R E T A L . 2 0 1 6

N G C 6 7 9 1

N G C 6 8 1 9


G A L A C T I C P O S I T I O N SO C F R O M N A S A ’ S KEPLER M I S S I O N

N G C 6 7 9 1 N G C 6 8 1 9

Gal. lat. 10.9° Gal. long. 69.95°

h ~ 700 pc

Gal. lat. 8.5° Gal. long. 73.98°

h ~ 300 pc

hthin disk ~ 350 pc


C L U S T E R R E D G I A N T STA R G E T S E L E C T I O N

E V O L U T I O N A R Y S TA G E O F R E D G I A N T S © C O R S A R O E T A L . 2 0 1 2

He-core burningH-shell burning

• 48 cluster red giants with clear evolutionary stage from period spacing of ℓ = 1 mixed modes �⇧1

B E D D I N G E T A L . 2 0 1 1 ; M O S S E R E T A L . 2 0 1 2 C O R S A R O E T A L . 2 0 1 2 ;


B A C K G R O U N D S I G N A L• Bayesian inference code DIAMONDS: public code

https://github.com/EnricoCorsaro/DIAMONDS

• Background signal modeled with granulation and mesogranulation components in 48 cluster red giants

A N A LY S I S O F S T E L L A R O S C I L L A T I O N S

C O R S A R O & D E R I D D E R , 2 0 1 4 , A & A , 5 7 1 , 7 1C O R S A R O , D E R I D D E R , G A R C I A , 2 0 1 5 , A & A , 5 7 9 , 8 3

C O R S A R O E T A L . 2 0 1 7 , I N P R E P.© C O R S A R O & D E R I D D E R , 2 0 1 4


B AY E S I A N P E A K B A G G I N G

• 3900 oscillation modes fitted and identified from 48 red giant stars in NGC 6791 and NGC 6819

• 380 rotationally split ℓ=1 mixed modes used to measure spin-axis inclinations

A N A LY S I S O F S T E L L A R O S C I L L A T I O N S

C O R S A R O E T A L . 2 0 1 6 , I N P R E P.

• Only significant peaks considered with peak significance test

• Bayesian model comparison with Bayesian evidence computed with DIAMONDS

© C O R S A R O E T A L . 2 0 1 5

M1

M2

E1/E2 ' 150


B AY E S I A N P E A K B A G G I N GA N A LY S I S O F S T E L L A R O S C I L L A T I O N S

Low spin inclination angle!



O B S E R VAT I O N A L R E S U LT S

• Strong spin alignment in both clusters!

10-7

10-9

M E A S U R I N G S T E L L A R - S P I N I N C L I N A T I O N S

↵ ' 0.75



N - B O D Y I N T E R A C T I O N S ?

• N-body simulations for old open clusters can reproduce observed populations of single and multiple stars

• Individual stars undergo spin down over time: magnetic braking, stellar winds, tidal friction

• Main force influencing spin orientation and orbital configuration is tidal

• But OC stars are sparse (~1 MSun pc-3)

• Tidal forces among stars are negligible already over a few AU (~ 10

-5 pc) and on given timescales

• Spin alignment possible only during cluster formation epoch

O R I G I N O F S P I N A L I G N M E N T

G E L L E R E T A L . 2 0 1 3

M E I B O M E T A L . 2 0 1 1 N AT U R E ; VA N S A D E R S E T A L . 2 0 1 6 N AT U R E

L A D A & L A D A 2 0 0 3 Ftidal / r�3

d✓

dt/

✓R

a

◆6

H U T 1 9 8 1


P R O T O - C L U S T E R F O R M AT I O N

• MC is treated as compressible fluid and evolution resolved with Navier-Stokes equations

• RAMSES: 3D MHD code with adaptive mesh refinement

• Compact (~0.2 pc) and dense (107 H2 cm-3) MC with 103 MSun and isothermal at T = 10 K

• Bonnor-Ebert-like spherical MC with density profile

3 D H Y D R O D Y N A M I C A L S I M U L A T I O N S

L E E & H E N N E B E L L E 2 0 1 6

T E Y S S I E R 2 0 0 2 ; F R O M A N G E T A L . 2 0 0 6

⇢(r) = ⇢0

"1 +

✓r

r0

◆2#�1


P R O T O - C L U S T E R F O R M AT I O N

• Evolution by gravitational collapse + turbulent velocity field (Kolmogrov spectrum) + solid body global rotation

• Sink particles algorithm used to add AM from gas to sink (pre-stellar cores): track evolution of AM at scales of several AU

Ekin

= Etur

+ Erot

Egrav

3D hydrodynamics

3 D H Y D R O D Y N A M I C A L S I M U L A T I O N S


3 D S I M U L AT I O N R E S U LT SP R O T O - C L U S T E R F O R M A T I O N

Erot

/Etur

< 1

Erot

/Etur

' 1

M � 0.7M�

M � 0.7M�

• If cloud rotation absent or low: no spin alignment (random)

• If strong cloud rotation present: significant spin alignment

• Stars with M < 0.7 MSun show no alignment even with strong rotation



S U M M A R Y & C O N C L U S I O N S

Imprint of cloud’s global rotation has survived for more than 8 Gyr!

Detection through asteroseismology

Proto-cluster AM efficiently passed down to individual stars

Proto-cluster has strong rotational energy component

3D hydrodynamics+

Direct observations

Proto-clusterProto-cluster

StarsE

tur

> 2Erot

Erot

& Etur

M � 0.7M�

Strong stellar-spin alignment (~70%) within a stellar cluster

Ekin

= Etur

+ Erot


F U T U R E P R O S P E C T S• Enlarge the sample of open clusters, e.g. M44 and M67 with NASA K2

• Possibly include globular clusters with future space missions NASA TESS and ESA PLATO using asteroseismology

• Compare with astrometric and kinematic observations from ESA Gaia to study global rotation properties in clusters

• Extend study using standard methods from v sini using spectroscopic surveys for accessible open clusters from e.g. APOGEE, Gaia ESO

• Search for prototypes of forming regions in IR with strong rotational components using JWST and ground facilities such as GIARPS@TNG


We can use detailed asteroseismology (coupled with simulations)

to probe the physics of star and stellar cluster formation!

spin alignment of stars in old open clusters...oct 17, 2017 · • angular momentum from the cloud...

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