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:
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
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 ?
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
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?
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
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
CO (Bally et al.) 2MASS stars (Carpenter et al.)
850 m dust continuum Northern part of Orion A SCUBA Trapezium
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
Trapezium cluster Proper motions: Van Altena et al. 88 V esc ~ 6 km s -1 2.6 1.8 5 2.5
d253-535 in M43 YSOs with disks and envelopes are common: Facilitate interactions?
M = 20 m = 5 M disk = 1 Close encounters Moeckel & Bally 05
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
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