Near-IR bispectrum speckle interferometry, AO imaging polarimetry, and radiative transfer modeling of the proto-planetary nebula Frosty Leonis

High and low-resolution optical and near-IR spectroscopy of the candidate proto-planetary (or very young PN) Vy 2-2 (P-K 45 - 2°1) is reported. This object has associated OH maser emission and an angular diameter of only 0.4 arcsec, found from VLA and optical speckle interferometry. Empirical analysis gives the values Ne ≈3 × 105 cm−3, Te=11000(±1500)K. The electron temperature is quite uncertain because of the high density. Abundances of He, C, N, O, Ne and Ar are reported; the carbon abundance is uncertain as it relies on the C II λ4267Å line, since the object is too highly-reddened (c=1.8 ± 0.2) to be observed with IUE. We find He/H=0.10, O/H=4 × 10−4 and C/O=0.8. The HI Zanstra temperature is 38 000 K (for black-body). The spectrum shows broad stellar lines of He II λ4686, C III λ4647 and N III λ4640; the central star may be of type Of.

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2.5 Dimensional Radiative Transfer Modeling of Proto-Planetary Nebula Dust Shells with 2-DUST

Symposium - International Astronomical Union ◽

10.1017/s0074180900208371 ◽

2003 ◽

Vol 209 ◽

pp. 141-142

Author(s):

Toshiya Ueta ◽

Margaret Meixner

Keyword(s):

Radiative Transfer ◽

Structure Formation ◽

Optical Depth ◽

Inclination Angle ◽

Planetary Nebula ◽

Planetary Nebulae ◽

Asymptotic Giant Branch ◽

Dust Shells ◽

Radiative Transfer Modeling

Our observing campaign of proto-planetary nebula (PPN) dust shells has shown that the structure formation in planetary nebulae (PNs) begins as early as the late asymptotic giant branch (AGB) phase due to intrinsically axisymmetric superwind. We describe our latest numerical efforts with a multi-dimensional dust radiative transfer code, 2-DUST, in order to explain the apparent dichotomy of the PPN morphology at the mid-IR and optical, which originates most likely from the optical depth of the shell combined with the effect of inclination angle.

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High-Resolution Near-Infrared Speckle Interferometry and Radiative Transfer Modeling of the OH/IR Star OH 104.9+2.4

The Power of Optical/IR Interferometry: Recent Scientific Results and 2nd Generation Instrumentation - Eso Astrophysics Symposia ◽

10.1007/978-3-540-74256-2_68 ◽

2007 ◽

pp. 505-506

Author(s):

D. Riechers ◽

T. Driebe ◽

Y. Y. Balega ◽

K.-H. Hofmann ◽

A. B. Men’shchikov ◽

...

Keyword(s):

High Resolution ◽

Radiative Transfer ◽

Near Infrared ◽

Speckle Interferometry ◽

Radiative Transfer Modeling

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Polarized radiative transfer modeling of warped and clumpy dusty tori

Astronomy and Astrophysics ◽

10.1051/0004-6361/201731190 ◽

2017 ◽

Vol 607 ◽

pp. A37 ◽

Cited By ~ 3

Author(s):

F. Marin ◽

M. Schartmann

Keyword(s):

Radiative Transfer ◽

Active Galactic Nuclei ◽

Galactic Nuclei ◽

Complex Model ◽

Polarization Degree ◽

Significant Difference ◽

Model Predictions ◽

Imaging Polarimetry ◽

Radiative Transfer Modeling ◽

Dusty Torus

Context. Active galactic nuclei (AGN) are anisotropic objects surrounded by an optically thick equatorial medium whose true geometry still defies observers. Aims. We aim to explore the optical scattering-induced polarization that emerges from clumpy and warped dusty tori to check whether they can fit the unified model predictions. Methods. We ran polarized radiative transfer simulations in a set of warped and non-warped clumpy tori to explore the differences induced by distorted dust distributions. We then included warped tori in a more complex model representative of an AGN to check, using polarimetry and imaging methods, whether warps can reproduce the expected polarization dichotomy between Seyfert-I and Seyfert-II AGN. Results. The main results from our simulations highlight that isolated warped structures imprint the polarization degree and angle with distinctive signatures at Seyfert-I orientations. Included in an AGN model, the signatures of warps are easily (but not always) washed out by multiple scattering in a clumpy environment. Imaging polarimetry may help to detect warped tori, but we prove that warps can exist in AGN circumnuclear regions without contradicting observations. Conclusions. Two warped tori with a non-significant difference in geometry in terms of photometry or spectroscopy can have entirely different signatures in polarimetry. Testing the geometry of any alternative model to the usual dusty torus using polarized radiative transfer is a necessary approach to verify or reject a hypothesis.

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