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 AstrophysicsAcademia 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

Shaping must occur either at the end of AGB phase or during the short transition stage (proto-planetary nebula PPN).

Morphology of envelope

AGB phase: spherically symmetric

PN phase: wide variety of shapes

PPN phase: Bipolar more common

Program to study the structure of envelopes

with the Sub-millimeter Array

IRC+10216CIT 6R Scl

V HyaPi Gru

IRC+10420VY CMa

IRAS 07134+1005NGC 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

V - band

Groenewegen et al. (1997)

Maurron & Huggins (1999)

VLA data of HC5N J=98 at 23 GHz.

Synthesized beam ~ 4 arcsec.

Lucas & Guelin (1999)

IRC+10216

SMA CO J=21 emission from R Scl Detached shell !

Detached shell: Vexp ~ 15 km/s

Present day wind: Vexp ~ 10 km/s

Dynamical age ~ 1700 yr

Helium flash ?

CO J=21

Gru CO J=2-1 emission

Poster by Chiu et al. 2005

Disk & high velocity outflow are present in envelope of a normal AGB star.

Molecular emission from V Hya

Poster by Hirano et al. 2005

Disk & collimated high velocity outflow are present

Mid-IR image (Kwok et al. 2002) BIMA CO J=10 image

21 m Proto-Planetary nebula IRAS 07134+105

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.

AGB wind

Torus Torus

To observer

NorthSchematic view of IRAS 07134+1005

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

• 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

NGC 7027

HST optical images in H, OIII & NII.

HST near IR images

@230 GHzBeam : 2.65’’ x 1.52’’ (77°)Total flux : ~ 3.6 Jy

JCMT : 3.8 0.2 Jy(Knapp et al. 1993)

@ 345 GHzBeam : 1.71’’ x 0.85’’ (73°)Total flux : ~ 1.45 Jy

CONTINUUM

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.

Scattered light polarization

CO J=21

R Scl

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