scholarly journals 2-D Radiation Transfer Model of Non-Spherically Symmetric Dust Shell in Proto-Planetary Nebulae

2003 ◽  
Vol 209 ◽  
pp. 139-140
Author(s):  
Kate Y. L. Su ◽  
Kevin Volk ◽  
Sun Kwok
Keyword(s):  
Radiation Transfer ◽  
Spectral Energy Distribution ◽  
Planetary Nebulae ◽  
Asymptotic Giant Branch ◽  
Radiative Transfer Model ◽  
Spectral Energy ◽  
Transfer Model ◽  
Agb Stars ◽  
Dust Shell ◽  
Radiation Transfer Model

Resent high-resolution optical imaging has directly revealed reflection nebulosity around proto-planetary nebulae (PPNs), the transition objects between asymptotic giant branch (AGB) stars and planetary nebulae (Sahai et al. 1998, Su et al. 1998, Ueta et al. 2000, Su et al. 2001). The existence of bipolar nebulae observed in the PPN phase suggests the presence of asymmetry in the AGB circumstellar dust shell. In order to model these objects, a self-consistent radiation transfer model is necessary. As a first attempt, we construct an approximate two-dimensional dust radiative transfer model to simultaneously fit the spectral energy distribution (SED) and images of a centrally-heated dust envelope.

scholarly journals Radiative transfer model of the dust structures of CRL 2688

2011 ◽  
Vol 7 (S283) ◽  
pp. 520-521
Author(s):  
Dejan Vinković ◽  
Bruce Balick
Keyword(s):  
Energy Distribution ◽  
Radiation Transfer ◽  
Spectral Energy Distribution ◽  
Polar Axis ◽  
Radiative Transfer Model ◽  
Spectral Energy ◽  
Transfer Model ◽  
Giant Star ◽  
Basic Features ◽  
Radiation Transfer Model

AbstractNew Hubble images of the reflection nebula CRL 2688 from 0.6 to 1.6μm reveal significant variations of color and opacity in the distribution of scattered starlight. We have constructed a detailed radiation-transfer model consisting principally of an optically thick equatorial disk-like structure; bipolar lobes with density enhancements along the polar axis and at the base of lobes; an optically thin extended envelope containing spherical density-enhanced shells to mimic the outer rings of CRL 2688; and a pair of near-stellar caps that collimate and redden the dispersing starlight near its source. Our model nicely reproduces all of the basic features detected in the HST images, including the famous searchlights and arcs, as well as the measured spectral energy distribution (“SED”) of CRL 2688. Assuming a distance of 420 pc we estimate the light originates in a giant star with a temperature T ~ 7000 K and a luminosity L = 5500 ± 1100 L⊙.

scholarly journals Molecular Envelopes of Planetary Nebulae and Proto-Planetary Nebulae

1994 ◽  
Vol 140 ◽  
pp. 152-153
Author(s):  
Sun Kwok
Keyword(s):  
Planetary Nebulae ◽  
Asymptotic Giant Branch ◽  
High Rate ◽  
Radiative Transfer Model ◽  
Spectral Energy ◽  
Transfer Model ◽  
Energy Distributions ◽  
Cool Component ◽  
Dust Envelope ◽  
Peak Energy

As stars evolve up the asymptotic giant branch (AGB), they begin to lose mass at a high rate, and in the process they create extended circumstellar molecular envelopes. Since the transition from AGB to planetary nebula stages is of the order of 1000 yr, the remnant of such molecular envelopes should still be observable in pro to-planetary nebulae (PPN) and planetary nebulae (PN). Recent ground-based survey of cool IRAS sources have discovered ~30 candidates of PPN (Kwok 1992). These sources show the characteristic “double-peak” energy distribution. The cool component is due to the remnant of the AGB dust envelope, and the hot component represents the reddened photosphere. The fact that the two components are clearly separated suggests that the dust envelope is well detached from the photosphere. Radiative transfer model fits to the spectral energy distributions of PPN suggest a typical separation of ~1 arc sec between the dust envelope and the photosphere, and such “hole-in-the-middle” structure can be mapped by millimeter interferometry in CO.

scholarly journals The perturbed sublimation rim of the dust disk around the post-AGB binary IRAS08544-4431

2018 ◽  
Vol 616 ◽  
pp. A153 ◽  
Author(s):  
J. Kluska ◽  
M. Hillen ◽  
H. Van Winckel ◽  
R. Manick ◽  
M. Min ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Near Infrared ◽  
Spectral Energy Distribution ◽  
Asymptotic Giant Branch ◽  
Young Stellar Objects ◽  
Radiative Transfer Model ◽  
Spectral Energy ◽  
Transfer Model ◽  
Stellar Objects ◽  
Binary Evolution

Context. Post-asymptotic giant branch (post-AGB) binaries are surrounded by stable dusty and gaseous disks similar to the ones around young stellar objects. Whereas, significant effort has been spent on modeling observations of disks around young stellar objects, the disks around post-AGB binaries have received significantly less attention, even though they pose significant constraints on theories of disk physics and binary evolution. Aims. We want to examine the structure of and phenomena at play in circumbinary disks around post-AGB stars. We continue the analysis of our near-infrared interferometric image of the inner rim of the circumbinary disk around IRAS08544-4431. We want to understand the physics governing this inner disk rim. Methods. We use a radiative transfer model of a dusty disk to reproduce simultaneously the photometry as well as the near-infrared interferometric dataset on IRAS08544-4431. The model assumes hydrostatic equilibrium and takes dust settling self-consistently into account. Results. The best-fit radiative transfer model shows excellent agreement with the spectral energy distribution up to millimeter wavelengths as well as with the PIONIER visibility data. It requires a rounded inner rim structure, starting at a radius of 8.25 au. However, the model does not fully reproduce the detected over-resolved flux nor the azimuthal flux distribution of the inner rim. While the asymmetric inner disk rim structure is likely to be the consequence of disk-binary interactions, the origin of the additional over-resolved flux remains unclear. Conclusions. As in young stellar objects, the disk inner rim of IRAS08544-4431 is ruled by dust sublimation physics. Additional observations are needed to understand the origin of the extended flux and the azimuthal perturbation at the inner rim of the disk.

scholarly journals ISO Observations of AGB Stars in the Small Magellanic Cloud

1999 ◽  
Vol 192 ◽  
pp. 95-99
Author(s):  
J.A.D.L. Blommaert ◽  
M.A.T. Groenewegen ◽  
M. R. Cioni ◽  
H. J. Habing ◽  
J.Th. van Loon ◽  
...  
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Spectral Energy Distribution ◽  
Magellanic Cloud ◽  
Radiative Transfer Model ◽  
Spectral Energy ◽  
Transfer Model ◽  
Agb Stars ◽  
Small Magellanic Cloud

We used ISOCAM and ISOPHOT to observe the spectral energy distribution between 3.6 and 60 μm of AGB stars in the Small Magellanic Cloud detected by IRAS. CAM-CVF spectra are made which enable us to establish the carbon- or oxygen-rich nature of the stars.We are in the process of analysing this data using a radiative transfer model. This will provide us with accurate determinations of luminosity and mass loss rate. Combining the results on the SMC, LMC and Galaxy we hope to address the open question of the metallicity dependencies of the mass loss rate. This in turn is important in the ejection of matter by AGB stars into the interstellar medium.

scholarly journals A radiative transfer model for the spiral galaxy M33★

2020 ◽  
Vol 495 (1) ◽  
pp. 835-863 ◽  
Author(s):  
Jordan J Thirlwall ◽  
Cristina C Popescu ◽  
Richard J Tuffs ◽  
Giovanni Natale ◽  
Mark Norris ◽  
...  
Keyword(s):  
Star Formation ◽  
Radiative Transfer ◽  
Energy Distribution ◽  
Surface Density ◽  
Main Sequence ◽  
Spectral Energy Distribution ◽  
Radiative Transfer Model ◽  
Spectral Energy ◽  
Geometrical Parameters ◽  
Transfer Model

ABSTRACT We present the first radiative transfer (RT) model of a non-edge-on disc galaxy in which the large-scale geometry of stars and dust is self-consistently derived through the fitting of multiwavelength imaging observations from the ultraviolet to the submm. To this end, we used the axisymmetric RT model of Popescu et al. and a new methodology for deriving geometrical parameters, and applied this to decode the spectral energy distribution (SED) of M33. We successfully account for both the spatial and spectral energy distribution, with residuals typically within $7{{\ \rm per\ cent}}$ in the profiles of surface brightness and within $8{{\ \rm per\ cent}}$ in the spatially integrated SED. We predict well the energy balance between absorption and re-emission by dust, with no need to invoke modified grain properties, and we find no submm emission that is in excess of our model predictions. We calculate that $80\pm 8{{\ \rm per\ cent}}$ of the dust heating is powered by the young stellar populations. We identify several morphological components in M33, a nuclear, an inner, a main and an outer disc, showing a monotonic trend in decreasing star formation surface density (ΣSFR) from the nuclear to the outer disc. In relation to surface density of stellar mass, the ΣSFR of these components defines a steeper relation than the ‘main sequence’ of star-forming galaxies, which we call a ‘structurally resolved main sequence’. Either environmental or stellar feedback mechanisms could explain the slope of the newly defined sequence. We find the star formation rate to be ${\rm SFR}=0.28^{+0.02}_{-0.01}{\rm M}_{\odot }{\rm yr}^{-1}$.

scholarly journals Energy Distribution of Planetary Nebulae (UV to Radio)

1993 ◽  
Vol 155 ◽  
pp. 99-108
Author(s):  
C.Y. Zhang
Keyword(s):  
Energy Distribution ◽  
Planetary Nebula ◽  
Spectral Energy Distribution ◽  
Planetary Nebulae ◽  
Central Star ◽  
Spectral Energy ◽  
Significant Progress ◽  
Dust Shell ◽  
The Past ◽  
Entire Wavelength Range

The past decade has seen significant progress in our understanding of spectral energy distribution of planetary nebulae over the entire wavelength range from UV to radio. In this review we show the detailed breakdown of the energy budget for a planetary nebula as a system of the three components, i.e., the central star, the gaseous nebula and the dust shell. This picture of the energy distribution is further discussed in the context of planetary nebula evolution.

scholarly journals Ammonia in circumstellar environment of V Cyg

2020 ◽  
Vol 10 (1) ◽  
pp. 7-11
Author(s):  
B. Etmański ◽  
M. Schmidt ◽  
R. Szczerba
Keyword(s):  
Background Radiation ◽  
Spectral Energy Distribution ◽  
Careful Analysis ◽  
Asymptotic Giant Branch ◽  
Spectral Energy ◽  
Agb Stars ◽  
Circumstellar Envelopes ◽  
Theoretical Predictions ◽  
Red Supergiants ◽  
Molecular Lines

The HIFI instrument on board of the Herschel Space Observatory (HSO) has been very successful in detecting molecular lines from the circumstellar envelopes around evolved stars, like massive red supergiants, Asymptotic Giant Branch (AGB) and post-AGB stars, as well as the planetary nebulae. Among others, ammonia have been found in the circumstellar envelopes of C-rich AGB stars in amounts that significantly exceeded the theoretical predictions for C-rich stars. Few scenarios have been proposed to resolve this problem: formation of ammonia behind the shock front and photochemical processes in the inner part of the envelope partly transparent to UV background radiation due to the clumpy structure of the gas and formation of ammonia on dust grains. Careful analysis of observations may help to put the constraints on one or another mechanism of ammonia formation. Here, we present results of the non-LTE radiative transfer modeling of ammonia transitions including the crucial process of radiative pumping via the v2=1 vibrational band (at ∼10 μm) for V Cyg. Only the ground-based ammonia transition NH3 J = 10-00 at 572.5 GHz has been observed by HIFI. Therefore, to determine the abundance of ammonia we estimate the photodissociation radius of NH3 using chemical model of the envelope consistent with the dust grain properties concluded from the spectral energy distribution.

scholarly journals A multi-scale exploration of a massive young stellar object

2019 ◽  
Vol 625 ◽  
pp. A44 ◽  
Author(s):  
A. J. Frost ◽  
R. D. Oudmaijer ◽  
W. J. de Wit ◽  
S. L. Lumsden
Keyword(s):  
Radiative Transfer ◽  
Spectral Energy Distribution ◽  
Young Stellar Objects ◽  
Radiative Transfer Model ◽  
Spectral Energy ◽  
Absorption Feature ◽  
Transfer Model ◽  
Mass Star ◽  
Low Density ◽  
Circumstellar Environments

Context. The rarity of young massive stars combined with the fact that they are often deeply embedded has limited the understanding of the formation of stars larger than 8 M⊙. Ground based mid-infrared (IR) interferometry is one way of securing the spatial resolution required to probe the circumstellar environments of massive young stellar objects (MYSOs). Given that the spatial-frequency coverage of such observations is often incomplete, direct-imaging can be supplementary to such a dataset. By consolidating these observations with modelling, the features of a massive protostellar environment can be constrained. Aims. This paper aims to detail the physical characteristics of the protostellar environment of the MYSO G305.20+0.21 at three size-scales by fitting one 2.5D radiative transfer model to three different types of observations simultaneously, providing an extensive view of the accreting regions of the MYSO. Methods. Interferometry, imaging and a multi-wavelength spectral energy distribution (SED) are combined to study G305.20+0.21. The high-resolution observations were obtained using the Very Large Telescope’s MIDI and VISIR instruments, producing visibilities in the N-band and near-diffraction-limited imaging in the Q-band respectively. By fitting simulated observables, derived from the radiative transfer model, to our observations the properties of the MYSO are constrained. Results. The VISIR image shows elongation at 100 mas scales and also displays a degree of asymmetry. From the simulated observables derived from the radiative transfer model output we find that a central protostar with a luminosity of ~5 × 104 L⊙ surrounded by a low-density bipolar cavity, a flared 1 M⊙ disk and an envelope is sufficient to fit all three types of observational data for G305.20+0.21. The weak silicate absorption feature within the SED requires low-density envelope cavities to be successfully fit and is an atypical characteristic in comparison to previously studied MYSOs. Conclusions. The fact that the presence of a dusty disk provides the best fit to the MIDI visibilities implies that this MYSO is following a scaled-up version of the low-mass star formation process. The low density, low extinction environment implies the object is a more evolved MYSO and this combined with large inner radius of the disk suggests that it could be an example of a transitional disk around an MYSO.

scholarly journals Constraining the thermally pulsing asymptotic giant branch phase with resolved stellar populations in the Large Magellanic Cloud

2020 ◽  
Vol 498 (3) ◽  
pp. 3283-3301 ◽  
Author(s):  
Giada Pastorelli ◽  
Paola Marigo ◽  
Léo Girardi ◽  
Bernhard Aringer ◽  
Yang Chen ◽  
...  
Keyword(s):  
Mass Loss Rate ◽  
Spectral Energy Distribution ◽  
Stellar Populations ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Asymptotic Giant Branch ◽  
Star Formation History ◽  
Spectral Energy ◽  
Agb Stars ◽  
The Third

ABSTRACT Reliable models of the thermally pulsing asymptotic giant branch (TP-AGB) phase are of critical importance across astrophysics, including our interpretation of the spectral energy distribution of galaxies, cosmic dust production, and enrichment of the interstellar medium. With the aim of improving sets of stellar isochrones that include a detailed description of the TP-AGB phase, we extend our recent calibration of the AGB population in the Small Magellanic Cloud (SMC) to the more metal-rich Large Magellanic Cloud (LMC). We model the LMC stellar populations with the trilegal code, using the spatially resolved star formation history derived from the VISTA survey. We characterize the efficiency of the third dredge-up by matching the star counts and the Ks-band luminosity functions of the AGB stars identified in the LMC. In line with previous findings, we confirm that, compared to the SMC, the third dredge-up in AGB stars of the LMC is somewhat less efficient, as a consequence of the higher metallicity. The predicted range of initial mass of C-rich stars is between Mi ≈ 1.7 and 3 M⊙ at Zi = 0.008. We show how the inclusion of new opacity data in the carbon star spectra will improve the performance of our models. We discuss the predicted lifetimes, integrated luminosities, and mass-loss rate distributions of the calibrated models. The results of our calibration are included in updated stellar isochrones publicly available.

scholarly journals A dust radiative transfer study of the edge-on spiral galaxy NGC 5908

2014 ◽  
Vol 10 (S309) ◽  
pp. 309-309 ◽  
Author(s):  
G. De Geyter ◽  
M. Baes ◽  
P. Camps ◽  
J. Fritz ◽  
S. Viaene
Keyword(s):  
Radiative Transfer ◽  
Spiral Galaxy ◽  
Spectral Energy Distribution ◽  
Radiative Transfer Model ◽  
Spectral Energy ◽  
Transfer Model ◽  
Double Exponential ◽  
Best Fitting ◽  
Dust Distribution ◽  
Transfer Study

AbstractWe present a dust radiative transfer analysis of the edge-on spiral galaxy NGC 5908. In our previous analysis, it was found that the standard assumption of a double-exponential dust distribution resulted in a poor fit. We investigate the possibility of the dust being distributed in one or more rings. The parameters are constrained using FitSKIRT, a code used to automatically determine the best fitting radiative transfer model given a set of observations. We discuss the possible implications of this dust distribution on the predicted spectral energy distribution.

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