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John Bally

Delve into the intricate process of star formation within clusters, exploring transient, open, and globular formations. Learn about feedback mechanisms from massive stars, interactions shaping the Initial Mass Function, and the implications of high-velocity stars and stellar mergers. Gain insights into the significance of massive star UV radiation and supernova events in cluster evolution. Discover the diverse formation mechanisms, such as competitive accretion and gravitational collapse, driving the birth of stars within turbulent Giant Molecular Clouds.

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John Bally

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

  2. Outline • Most stars form in clusters: • - Transient clusters => T, OB associations • > 90% of stars:t < few x tcross ~ r / s • - Open clusters: • few % of stars:t ~ 10 - 103 x tcross • - Globular clusters: • <<1% of stars: t >> 103 x tcross • Dissipation by cores, envelopes, disks: • - Collapse, interactions, IMF, mergers (?) • Formation of clusters: Feedback from massive stars • GMC: Vescape < CII ~ 10 km/s => Transient? • Vescape > CII ~ 10 km/s => Open ? • Vescape >> CII ~ 10 km/s => SSC => Globular ?

  3. NGC 1333: 1 Myr, ~ 102 YSOs

  4. Orion Nebula: 1 Myr, ~ 103 YSOs

  5. NGC 6603: 4 Myr, ~ 104 YSOs

  6. 30 Dor: 4 Myr, ~ 105 YSOs

  7. Cluster Formation I • Turbulent Giant Molecular Clouds: • - Dissipation • - Shocks => transient clumps • - Occasionally, clumps bound by gravity • - Graviational collapse: Dr ~ 107, Dr ~ 1021 • - Fragmentation => Cluster • Star formation: • - Competitive accretion: • - dM/dt a M, dM/dt high in dense core • => Range of masses • - Feedback: Outflows, UV, supernovae (SNe) • - Interactions: => IMF, binaries, mergers

  8. 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 <V < 50 km s-1) • - Field multiple star distribution? • Mass-segregation • Initial Mass Function • - Ejection => stop accretion => final stellar mass • - Determined by interactions in N-body system?

  9. The Orion/Eridanus Bubble (Ha): d=180 to 500pc; l > 300 pc Orion OB1 Association: ~40 > 8 M stars: ~20 SN in 10 Myr l Ori (< 3 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) Eridanus Loop Barnards's Loop

  10. AE Aur 150 km/s Orion

  11. Infrared view of winter sky (10 - 120 mm)

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

  13. 20 km/s

  14. NGC 2024 (OB1 d) Horsehead Nebula s Orionis (OB 1 c) NGC 1981 NGC 1977 Orion Nebula i Ori NGC1980: Source ofm Col + AE Aur ; V ~ 150 km/s runaways, 2.6 Myr ago Orion below the Belt: Ori OB1c Ori OB1d

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

  16. Northern part of Orion A 850 mm dust continuum SCUBA Trapezium

  17. OMC 1 Outflow (H2 t = 3,000 yr) Orion Nebula BNKL Trapezium (L = 105 Lo t << 105 yr) (L = 105 Lo t < 105 yr) OMC1-S (L = 104 Lo , t < 105 yr)

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

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

  20. M = 20 m = 5 Mdisk= 1 Close encounters Moeckel & Bally 05

  21. Retrograde Prograde Close encounters Moeckel & Bally 05

  22. Orion BN/KL H2 OMC1-S Jets CO HH NICFPS APO 3.5 m First light 21 Nov 04 HH 202 Zapata jet + HH 625 HH 529 HH 269 HH 530 Schmid-Burgk jet HH 203/204 HH 528

  23. 104 AU 11.7 mm Gemini S TReCS

  24. 104 AU 0.5 – 2.2 mm

  25. 104 AU 11.7 mm

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

  27. Arches Cluster • Galactic Center • Age ~ 2 Myr • ~ 50 OB stars • 103-4 stars (?) • 3 X 105 stars pc-3 • Stolte et al. (2005) • ApJ, 628, L113

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

  29. Mass segregation in the Arches core annulus

  30. Massive Stars: HII, SNe & SFE • Ionization (HII): • - Photo-ionization => Cs ~ 10 km/s • - Cs > Vescape => Fast blow-out of gas • =>OB star stops star formation • - If SFE < 0.3, tblow-out < tcross • => Unbound association • - Cs < Vescape => Slow removal of gas • => Open cluster • Supernovae (SN) • - MGMC Vesc < Meject Veject • => SN stops star formation=> Open cluster • - MGMC Vesc > Meject Veject (supermassive core) • =>Globular cluster

  31. 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: • - Vescape < CII ~ 10 km/s => Transient association • - Vescape > CII ~ 10 km/s => Open Cluster • - Vescape >> CII ~ 10 km/s => SSC => Globular Cluster

  32. The End

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