1 / 18

2013/01/26 ALMA 時代の宇宙の構造形成理論 @ 北海道大学

2013/01/26 ALMA 時代の宇宙の構造形成理論 @ 北海道大学. Disk stability in low- metallicity star formation ~ 低金属量星形成における降着円盤の安定性 ~. K.Tanaka , K.Omukai (Kyoto-U). Primordial stars massive ~ 100Msun zero -metal . ？ ？ ？. Present-day stars low mass ~1Msun dusty (~1wt% ). Low metallicity stars.

saber
Télécharger la présentation

2013/01/26 ALMA 時代の宇宙の構造形成理論 @ 北海道大学

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 2013/01/26 ALMA時代の宇宙の構造形成理論 @北海道大学

  2. Disk stability in low-metallicity star formation ~ 低金属量星形成における降着円盤の安定性 ~ K.Tanaka, K.Omukai (Kyoto-U) Primordial stars massive ~ 100Msun zero-metal. ？ ？ ？ Present-day stars low mass ~1Msun dusty (~1wt%)

  3. Low metallicity stars Low-metal. stars have crucial roles for the evolution of universe!! But we do not understand how they formed… Primordial stars massive high-Mdot zero-metal. Present-day stars low mass low-Mdot solar-metal. ？ What makes difference? → metal/dust cooling must be important.

  4. Free-Fall (compression heating) Importance of dust cooling × Omukai+05etc. metal/dust cooling Zero-metal. low↑ Metallicity high↓ Solar-metal. Dust cooling makes Jeans-mass smaller!

  5. Accretion through disk Most material accretes onto stars through disks. Dose the disks are gravitaitonally stable?

  6. Main accretion phasein low metallicity star formation Since most material accretes onto a star through a disk, the disk property is crucial for newborn stellar mass. We study the disk structure and its stability in low metallicity star formation.

  7. Star formation model We apply simple analytic model. Step.1. We construct Infalling envelope models at various metallicities Step.2. From the envelope models, we evaluate disk structures and its stability.

  8. Infalling envelope structure Accretion rate and disk size depend on infalling envelope One-zone by Omukai05 ・ R&M of envelope, from ρ&T in one-zone model. (Hosokawa&Omukai09b) Acc. rate: Radius:

  9. Pre-stellar core T decreases with metal. ・Mdot (~T3/2) decreases ・Rj increases Core radius We give Ω by hand Ω=0.5xΩKep Abel+02 Hosokawa+11 metal. metal. Acc. rate From core model, we estimate disk size & M. ・ Enclosed mass

  10. Disk structure Standard disk model Local equilibrium : (Heating) = (Cooling) Heating：Viscous heating Cooling：H2line, Gas continuum, Dust collision (Dust emission) Parameters Metallicity：Z=0-Zsun Angular velocity：Ω=0.5xΩKep Viscous parameter：α=1

  11. Disk structure Disk temp. is relatively high. zero-metal. Toomre’s Q value Unstable for Q<1 Kratter+10

  12. Disk structure low-metal. 10-4Zsun solar-metal. zero-metal. T[K] 100Msun 100Msun 1 0.1 0.1 10 100Msun 1 10 100Msun Q 100Msun 1 10 0.1 0.1 100Msun 1 10 R[AU] R[AU] R[AU] Metallicity affects disk structure

  13. Disk stability Low-metal. disk is very unstable!!

  14. Why low-metal. disk is unstable? infalla Disk would be unstable when infall rate exceeds its capacity. accretion Q-value also tells that disk is unstable when Tdisk<Tcore. Dust cooling efficient at disk rather than envelope.

  15. If disk is very unstable… Present-day massive star formation (Peters+10) “Fragmentation-induced starvation” Infalling material divided into multiple stars → Low-metal. stars form as compact clusters (?)

  16. ConclusionSF in various metal. via disk acc. High-Mdot & High-T disk → ~stable Single (or binary) massive star ~ 100Msun mass is limited by photoionization feedback (Hosokawa-san’s talk) In zero-metal. ？ ？ ？ In solar-metal. Low-Mdot & Low-T disk → ~stable Single (or binary) low mass star ~1Msun mass is limited by pre-stellar core mass

  17. ConclusionSF in various metal. via disk acc. High-Mdot & High-T disk → ~stable Single (or binary) massive star ~ 100Msun mass is limited by photoionization feedback (Hosokawa-san’s talk) In zero-metal. In low-metal. 10-5~10-2Zsun High-Mdot & Low-T disk → ~unstable Low-mass stellar cluster by disk fragmentation In solar-metal. Low-Mdot & Low-T disk → ~stable Single (or binary) low mass star ~1Msun mass is limited by pre-stellar core mass

  18. Future work Dynamical evolutions!! Fragmentation, ejection, episodic accretion Radiative hydro. simulation by Dr.Vorobyov (Vienan-U) with our dust/metal cooling (Omukai+05) Vorobyov&Basu10 etc.

More Related