Structure of Circumstellar Envelopes Around AGB and Post

Structure of circumstellar envelope
around AGB and post-AGB stars
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
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: 107 to 104 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
R Scl
V Hya
Pi Gru
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)
Lucas & Guelin
VLA data of HC5N J=98 at 23 GHz.
Synthesized beam ~ 4 arcsec.
SMA CO J=21 emission from R Scl
Detached shell !
CO J=21
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=10 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
AGB wind
To observer
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
• Rich in molecular lines and carbon chemistry
HST optical images in H, OIII & NII.
HST near IR images
@ 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)
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=21
Histogram: CO J=3-2 from HHT 10m telescope
Red solid line: CO J=3-2 profile predicted by model
CO J=3-2 &
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