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Observations of Circumstellar Disks around YSOs

Observations of Circumstellar Disks around YSOs. Nagayoshi Ohashi, ASIAA. Kyoto Univ. 09 .11.2009. Outline of Talk. Brief introduction of the SMA Project Star formation and disk formation/evolution Overview Disks around PMSs; HD 142527 Disks around protostars; B335. SMA Project.

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Observations of Circumstellar Disks around YSOs

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  1. Observations of Circumstellar Disks around YSOs Nagayoshi Ohashi, ASIAA Kyoto Univ. 09.11.2009

  2. Outline of Talk • Brief introduction of the SMA Project • Star formation and disk formation/evolution • Overview • Disks around PMSs; HD 142527 • Disks around protostars; B335 LAB, France 07.01.2009

  3. SMA Project • Joint project of the SAO and ASIAA. • ASIAA joined the project in 1996. • SMA consists of eight 6-m telescopes operating at submm wavelengths (1mm to 350 mm) at the top of Mauna Kea. • ASIAA has delivered two telescopes with receiver systems. • Currently 230, 345, and 690 GHz bands are under regular operation. • The SMA was dedicated in November 2003. • The SMA is the fore-runner to ALMA. Kyoto Univ. 09.11.2009

  4. Science using SMA Syfert/AGN Outflow • Star formation • Jet/outflow • Circumstellar disks • Magnetic field • Extragalactic • Nearby galaxies/AGN • High-z galaxies • Evolved stars • Astrochemistry • Solar system Solar system Magnetic field LAB, France 07.01.2009

  5. Optically invisible! Girart et al. 2006 Takakuwa et al. 2003 Lada et al. 2003, Alves et al. 2001 Star and Planet Formation: Overview • A low-mass star (protostar) is formed in a dense molecular cloud core through its gravitational collapse. • The dense cloud becomes flatted (along the associated magnetic field). The associated magnetic field is also dragged inward. • A circumstellar disk is also formed around a YSO. • A molecular outflow takes place at some point. • Infall is terminated and a dense core is dispersed. The central star becomes optically visible (T Tauri star). • Planets are formed in the circumstellar disk? Dense molecular cloud LAB, France 07.01.2009

  6. Research on Protostellar Disks and Protoplanetary Disks • Formation of protostellar/protoplanetary disks; early phase (class 0 or even younger protostars) • Evolution of PSD/PPD; intermediate phase (class I and II) • Dissipation of PPD/Planet formation; late phase (class II and III) • Disks around massive stars and brown dwarfs. LAB, France 07.01.2009

  7. HH211 SiO 8–7 at 0.2” (60 AU) resolution Lee et al. ApJ in press A possible velocity gradient across the innermost pair of knots ~0.5 km /s at ~10 AU LAB, France 07.01.2009

  8. Dust Polarization & Magnetic Field NGC1333/IRAS4A 345 GHz Total Intensity and Linear Polarization (B field) Crutcher (2006), Science, 313, 771 LAB, France 07.01.2009 Girart et al. 2006

  9. Protoplanetary Disk:the site of planet formation • Protoplanetary disks (PPDs) are most probable sites for planet formation. • Important to understand their physical conditions. • Common characteristics or more variety? • More than 150 extra-solar planets have been discovered. • More systems with hot Jupiters and high eccentricity. • How were these extra-solar planets formed? LAB, France 07.01.2009

  10. 1.3 mm cont 0.6” x 0.7” (~80 AU x 100 AU) MM High Resolution Images of PPDs GM Aur (Dutrey et al. 1998) • Geometry: compact, disklike structures • Kinematics: Kepler motions LAB, France 07.01.2009

  11. Protoplanetary disks with spiral arms AB Aur @ 1.6 micron HD 142527 @ 1.6 micron Fukagawa et al. 2004 Fukagawa et al. 2006 LAB, France 07.01.2009

  12. HD 142527 • Herbig Ae star (F6 IIIe; M* ~ 2Mo) • Subaru observations revealed that the disk has a spiral arm (Fukagawa et al. 2006) • Subaru observations at MIR revealed a hole in the disk (Fujiwara et al. 2006). • ASTE observations suggested existence of a gas disk. • There was no mm interferometric observations due to its low declination. LAB, France 07.01.2009

  13. HD142527: Subaru Infrared Images 24.5 mm COMICS image (Fujiwara et al. ‘06) 1.6 mm CIAO image (Fukagawa et al. ‘06) LAB, France 07.01.2009

  14. SMA Observations of HD142527 • 12CO 3-2 and 340 GHz continuum simultaneous observations • One track with the compact configuration • One track with the extended configuration • 1.2” x 0.6” for dust continuum • 2.1” x 1.1” for 12CO 3-2 • Ohashi & Momose (‘09, submitted) SMA is a joint project between the SAO and the ASIAA. LAB, France 07.01.2009

  15. SMA Results: 340 GHz Continuum HD 142527 • 340 GHz continuum distribution resembles to the 1.6 m scattered emission. • An arc-like structure enclosing the central star • two peaks; one at the NE and the other at the NW. • Peak positions are shifted to the N as compared to those seen at 1.6 m. • No clear emission on the southern side. • Total flux density ~1.2 Jy LAB, France 07.01.2009

  16. SMA Result：12CO 3-2 • 12CO also shows a central hole, with peak emissions coincident with the infrared features. LAB, France 07.01.2009

  17. SMA Results: Spiral arms in gas? LAB, France 07.01.2009

  18. 12CO 3-2 Mean Velocity • Clear velocity gradient from NW to SE, which is probably due to rotation. • Roughly consistent with Kepler rotation around a 2Mo star. • Disk axis is from NE to SW? • Additional velocity gradient suggestive of non-circular motion. • Any relationship with gas possibly associated with the spiral arm? LAB, France 07.01.2009

  19. 12CO 3-2 Channel Maps LAB, France 07.01.2009

  20. Is 12CO 3-2 emission optically thin? • 12CO shows similar structures to the dust emission. • Low brightness temperature (8.5 K). Chiang & Goldreich ‘97 12CO 3-2 emission may be optically thin. LAB, France 07.01.2009

  21. HD142527: Disk Mass • 345 GHz total flux ~ 1.2 Jy, corresponding to 4.1E-2 Mo • Gas/dust mass ratio 100; Tdust = 50K • 12CO 3-2 integrated flux ~ 15 Jy km/s, corresponding 6.6E-6 Mo. • [H2]/[12CO] = 104; Tex = 50 K • The disk mass derived from 12CO 3-2 is factor of 10000 smaller that that derived from 345 GHz dust. • CO depletion factor ~10000? • H2 dissipation factor ~10000? • Combination of CO depletion and gas dissipation? LAB, France 07.01.2009

  22. Unknown factors to estimate mass • Dust temperature and CO excitation temperature • Even if we assume Td=Tex=100 K, the mass difference is still more than three orders of magnitude. • b-index(mass opacity) • Even if we assume a smaller b-index, the mass derived from dust becomes just a factor of 2 smaller. • CO depletion factor, f(co) • Around TTSs, f(CO) has been estimated to be upto ~200. Since Td would be higher around Herbig Ae stars, f(CO) would be less than 200. Even if we take into account of these unknown factors, it still seems to be difficult to explain the mass difference of 4 orders of magnitude. LAB, France 07.01.2009

  23. Gas dispersal in disk by photoevaporation • Takeuchi et al. (‘05; see also Alexander & Armitage ‘07) studied disk clearing processes. • using a model taking into account combined effects of viscous evolution, photoevaporation, differential radial motion of dust grains and gas. • Around an Herbig Ae/Be star with more ionizing photon, a gas-poor dust ring will be formed in 106 yr. LAB, France 07.01.2009

  24. Takeuchi et al. 2005 • A gap is created at ~17 AU (rg) by photoevapolation • Inside the gap • Both gas and dust accrete onto star due to viscosity. • Outside the gap • Gas is gradually evaporated from the inner edge, and the inner edge gets larger. • Dust accumulates at the inner edge. LAB, France 07.01.2009

  25. Protostellar Disks around Protostars Kyoto Univ 11.09.2009

  26. P-V diagrams C18O (1-0) with NMA (Momose et al. 1998) A2 B2 0.1 Mo A1 B1 Freely infalling and slowly rotating with angular momentum conserved L1551 IRS5: Infalling Envelope Mass ~0.08 M Radius ~ 1200 AU Kyoto Univ 11.09.2009

  27. SMA CS 7-6 Total Intensity NMA C18O 1-0 SMA CS7-6 mean velocity L1551 IRS5: Formation of a protostellar disk Takakauwa, Ohashi + 2003 Kyoto Univ 11.09.2009

  28. Specific Angular Momenta around YSOs Specific angular momentum seems to be constant within a radius of ~6000 AU. Ohashi et al. 1997 + new data (Yen, Takakuwa, Ohashi 2009) Kyoto Univ 11.09.2009

  29. B335 (IRAS 19347+0727) • Class 0 Protostar • Lbol ~ 1.5 Lo, Tdust ~ 30 K • Associated with a well developed outflow (e.g., Hirano et al. ‘88, ‘92) • Infall signatures were observed (Zhou et al. ‘93; Choi et al. ’95; Saito et al. ‘99). Kyoto Univ 11.09.2009

  30. SMA Observations of B335 • 12CO, 13CO, C18O 2-1 and 230 GHz continuum simultaneous observations • One track with the compact configuration • 3.9” x 3.3” for dust continuum • 3.7” x 3.2” for C18O 2-1 • (Yen, Takakuwa, Ohashi ‘09, submitted) SMA is a joint project between the SAO and the ASIAA. LAB, France 07.01.2009

  31. B335: 1.3 mm continuum • Size ~ 740 AU x 350 AU • Mass ~ 0.027 Mo Kyoto Univ 11.09.2009

  32. B335: C18O 2-1 • Size ~ 1500 AU • Partially affected by the outflow. • Mass ~ 5.2 x 10-3 Mo • C18O depletion (fd ~10) Kyoto Univ 11.09.2009

  33. B335: C18O 2-1 kinematics Vinfall ~ 0.31-0.44 km/s @ 370 AU, Mstar ~ 0.02-0.04 Mo, Mass infall rate ~ 4.8-6.9 x 10-6 Mo/yr Kyoto Univ 11.09.2009

  34. B335: C18O 2-1 Kinematics (II) No detectable velocity gradient along the N-S direction; Vrot < 0.04 km/s @ 370 AU Kyoto Univ 11.09.2009

  35. Specific Angular Momentum in B335 • 4.6 x 10-3 km/s pc @ 20000 AU • 5.4 x 10-4 km/s pc @ 1000 AU (Saito et al.’99) • 7 x 10-5 km/s pc @ 370 AU (SMA results) The specific angular momentum is not conserved outside R ~ 370 AU. If the specific angular momentum is conserved within R ~370 AU, Rd ~ 6 AU Kyoto Univ 11.09.2009

  36. With ALMA? • Observations with spatially high dynamic range (10-10000 AU scale) • Kepler disk formation; age estimation based on the disk size? • Observations with high sensitivity and resolution • Pick up the earliest phase of the disk formation. • Signature of the planet formation/disk dissipation. • Observations with a large sample. Kyoto Univ 11.09.2009

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