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John Bally Center for Astrophysics and Space Astronomy Department of Astrophysical and Planetary Sciences University of Colorado, Boulder Star Formation.

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Presentation on theme: "John Bally Center for Astrophysics and Space Astronomy Department of Astrophysical and Planetary Sciences University of Colorado, Boulder Star Formation."— Presentation transcript:

1 John Bally Center for Astrophysics and Space Astronomy Department of Astrophysical and Planetary Sciences University of Colorado, Boulder Star Formation Star Formation in in Clusters Clusters

2 Outline Outline Most stars form in clusters: - Transient clusters => T, OB associations > 90% of stars:  < few x  cross ~ r /  - Open clusters: few % of stars:  ~ 10 - 10 3 x  cross - Globular clusters: > 10 3 x  cross Dissipation by cores, envelopes, disks: - Collapse, interactions, IMF, mergers (?) Formation of clusters: Feedback from massive stars GMC: V escape Transient? V escape > C II ~ 10 km/s => Open ? V escape >> C II ~ 10 km/s => SSC => Globular ?

3 NGC 1333: 1 Myr, ~ 10 2 YSOs

4 Orion Nebula: 1 Myr, ~ 10 3 YSOs

5 NGC 6603: 4 Myr, ~ 10 4 YSOs

6 30 Dor: 4 Myr, ~ 10 5 YSOs

7 Cluster Formation I Cluster Formation I Turbulent Giant Molecular Clouds: - Dissipation - Shocks => transient clumps - Occasionally, clumps bound by gravity - Graviational collapse:  r ~ 10 7,  ~ 10 21 - Fragmentation => Cluster Star formation: - Competitive accretion: - dM/dt  M, dM/dt high in dense core => Range of masses - Feedback: Outflows, UV, supernovae (SNe) - Interactions: => IMF, binaries, mergers

8 Cluster Formation II Cluster Formation II Interactions: - Facilitated by disks, proto-star envelopes - Capture formed binaries Binary  single star Binary  binary - Stellar mergers (?) => high mass stars, GRBs? Ejection of star(s) : Hardening of surviving binary - High-velocity runaway stars (V > 50 km s -1 ) - Intermediate-velocity runaways (10 stop accretion => final stellar mass - Determined by interactions in N-body system?

9 The Orion/Eridanus Bubble (H  ): d=180 to 500pc; l > 300 pc Orion OB1 Association: ~40 > 8 M stars: ~20 SN in 10 Myr 1a (8 - 12 Myr; d ~ 350 pc)) 1b (3 -6 Myr; d ~ 420 pc) 1c (2 - 6 Myr; d ~ 420 pc) 1d (<2 Myr; d ~ 460 pc) Ori (< 3 Myr) Barnards's Loop Eridanus Loop

10 Orion AE Aur 150 km/s

11 Infrared view of winter sky (10 - 120  m)

12 Orion B Orion A Orion Nebula Orion Molecular Clouds 13 CO 2.6 mm

13

14 20 km/s

15 Orion below the Belt: Horsehead Nebula Orion Nebula NGC 2024 (OB1 d)  Orionis (  c) NGC 1977  Ori NGC1980: Source of  Col + AE Aur ; V ~ 150 km/s runaways, 2.6 Myr ago NGC 1981 Ori OB1c Ori OB1d

16 CO (Bally et al.) 2MASS stars (Carpenter et al.)

17 850  m dust continuum Northern part of Orion A SCUBA Trapezium

18  NKL  Trapezium  OMC1-S (L = 10 5 L o t << 10 5 yr) (L = 10 4 L o, t < 10 5 yr) (L = 10 5 L o t < 10 5 yr ) OMC 1 Outflow   t = 3,000 yr) Orion Nebula

19 Trapezium cluster Proper motions: Van Altena et al. 88 V esc ~ 6 km s -1 2.6 1.8 5 2.5

20 d253-535 in M43 YSOs with disks and envelopes are common: Facilitate interactions?

21 M = 20 m = 5 M disk = 1 Close encounters Moeckel & Bally 05

22 ProgradeRetrograde Moeckel & Bally 05Close encounters

23

24

25 Orion BN/KL H 2 OMC1-S Jets CO HH NICFPS APO 3.5 m First light 21 Nov 04 HH 202 Zapata jet + HH 625 HH 269 HH 530 Schmid-Burgk jet HH 529 HH 203/204 HH 528

26 11.7  m Gemini S TReCS 10 4 AU

27 0.5 – 2.2  m 10 4 AU

28 11.7  m 10 4 AU

29 High-velocity stars: source I, BN (Rodriguez et al. 2005) BN: ~ 30 km s -1 I: ~ 13 km s -1 i ~ 24 o t ~ 500 yrs

30 Arches Cluster Galactic Center Age ~ 2 Myr ~ 50 OB stars 10 3-4 stars (?) 3 X 10 5 stars pc -3 Stolte et al. (2005) ApJ, 628, L113

31 Shallow, broken IMF (Arches) Stolte et al. (2005) Mass segregation Low M cut-off, bias towards massive stars Dynamical evolution? Background  Salpeter = -1.35

32 core annulus Mass segregation in the Arches

33 Massive Stars: HII, SNe & SFE Massive Stars: HII, SNe & SFE Ionization (HII): - Photo-ionization => C s ~ 10 km/s - C s > V escape => Fast blow-out of gas => OB star stops star formation - If SFE < 0.3,  blow-out < t cross => Unbound association - C s Slow removal of gas => Open cluster Supernovae (SN) - M GMC V esc < M eject V eject => SN stops star formation=> Open cluster - M GMC V esc > M eject V eject (supermassive core) => Globular cluster

34 Conclusions Conclusions Most stars form in transient clusters: - Transient T / OB associations Circumstellar gas: - Dissipation - Mass segregation - Capture formed binaries - High-velocity stars - Mergers Impact of Massive Star UV, SN: - V escape Transient association - V escape > C II ~ 10 km/s => Open Cluster - V escape >> C II ~ 10 km/s => SSC => Globular Cluster

35 The End


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