Transcript Slide 1
Structure of circumstellar envelope around AGB and post-AGB stars Dinh-V-Trung Sun Kwok, P.J. Chiu, M.Y. Wang, S. Muller, A. Lo, N. Hirano, M. Mariappan, J. Lim Institute of Astronomy and Astrophysics Academia Sinica Introduction Intermediate mass stars (1 M to 8 M) evolve through Asymptotic Giant Branch (AGB) and eventually become Planetary Nebulae (PN) ● ● Mass loss during the AGB phase: 107 to 104 M/yr Morphology of envelope AGB phase: spherically symmetric PPN phase: Bipolar more common PN phase: wide variety of shapes Shaping must occur either at the end of AGB phase or during the short transition stage (proto-planetary nebula PPN). Program to study the structure of envelopes with the Sub-millimeter Array IRC+10216 CIT 6 R Scl V Hya Pi Gru IRC+10420 VY CMa IRAS 07134+1005 NGC 7027 Envelope around AGB stars is commonly assumed to be spherically symmetric & homogeneous. But in reality the envelope is complicated & interesting ! 1.3 mm dust continuum emission in IRC+10216 Groenewegen et al. (1997) V - band Maurron & Huggins (1999) IRC+10216 Lucas & Guelin (1999) VLA data of HC5N J=98 at 23 GHz. Synthesized beam ~ 4 arcsec. SMA CO J=21 emission from R Scl Detached shell ! CO J=21 Detached shell: Vexp ~ 15 km/s Present day wind: Vexp ~ 10 km/s Helium flash ? Dynamical age ~ 1700 yr Gru CO J=2-1 emission Disk & high velocity outflow are present in envelope of a normal AGB star. Poster by Chiu et al. 2005 Molecular emission from V Hya Disk & collimated high velocity outflow are present Poster by Hirano et al. 2005 21 m Proto-Planetary nebula IRAS 07134+105 Mid-IR image (Kwok et al. 2002) BIMA CO J=10 image Meixner et al. (2004) IRAS 07134+1005 CO J=3-2 ~ 2 arcsec. CO J=3-2 emission superposed on Mid-IR image at 18 m. Schematic view of IRAS 07134+1005 North AGB wind Torus To observer Torus Model parameters for IRAS 07134+1005 ● Expansion velocity of the wind : 10 km/s ● Outer spherical AGB wind with mass loss 2 10-6 M/yr ● Axi-symmetric torus with mass loss ~ 4 10-5 M/yr ● Inner radius of torus ~ 6 1016 cm or 1500 yrs in dynamical age ● Outer radius of torus ~ 9 1016 cm or 2000 yrs in dynamical age ● Envelope is viewed at 45 degrees from below the equator CO J=3-2 observation – channel maps Model channel maps NGC 7027 • Brightest planetary nebula at all wavelengths • Distance ~ 900 pc • Central white dwarf T* ~ 198000 K • Young HII region surrounded by massive molecular envelope. • Rich in molecular lines and carbon chemistry HST optical images in H, OIII & NII. HST near IR images CONTINUUM @ 345 GHz Beam : 1.71’’ x 0.85’’ (73°) Total flux : ~ 1.45 Jy @230 GHz Beam : 2.65’’ x 1.52’’ (77°) Total flux : ~ 3.6 Jy JCMT : 3.8 0.2 Jy (Knapp et al. 1993) 12CO J=2-1 Integrated intensity 12CO(2-1) and 1.3 mm continuum Future work • Combine SMA & single dish (JCMT, CSO, HHT) data recover short spacing flux • Multi-line observations & molecular excitation physical conditions • Effects of high velocity outflow on circumstellar envelope radiation hydrodynamics Better understanding of the physics of circumstellar envelopes. R Scl Scattered light polarization CO J=21 Histogram: CO J=3-2 from HHT 10m telescope Red solid line: CO J=3-2 profile predicted by model CO J=3-2 & continuum