Barbara Ercolano

Massive-Star Supernovae as Major Dust Factories

We present late-time optical and mid-infrared observations of the Type II supernova 2003gd in the galaxy NGC 628. Mid-infrared excesses consistent with cooling dust in the ejecta are observed 499 to 678 days after outburst and are accompanied by increasing optical extinction and growing asymmetries in the emission-line profiles. Radiative-transfer models show that up to 0.02 solar masses of dust has formed within the ejecta, beginning as early as 250 days after outburst. These observations show that dust formation in supernova ejecta can be efficient and that massive-star supernovae could have been major dust producers throughout the history of the universe.

mocassin: a fully three-dimensional Monte Carlo photoionization code

The study of photoionized environments is fundamental to many astrophysical problems. Up to the present most photoionization codes have numerically solved the equations of radiative transfer by making the extreme simplifying assumption of spherical symmetry. Unfortunately very few real astronomical nebulae satisfy this requirement. To remedy these shortcomings, a self-consistent, three-dimensional radiative transfer code has been developed using Monte Carlo techniques. The code, MOCASSIN, is designed to build realistic models of photoionized nebulae having arbitrary geometry and density distributions, with both the stellar and diffuse radiation fields treated self-consistently. In addition, the code is capable of treating one or more exciting stars located at non-central locations. The gaseous region is approximated by a cuboidal Cartesian grid composed of numerous cells. The physical conditions within each grid cell are determined by solving the thermal equilibrium and ionization balance equations. This requires a knowledge of the local primary and secondary radiation fields, which are calculated self-consistently by locally simulating the individual processes of ionization and recombination. The structure and the computational methods used in the MOCASSIN code are described in this paper. MOCASSIN has been benchmarked against established one-dimensional spherically symmetric codes for a number of standard cases, as defined by the Lexington/Meudon photoionization workshops: at Meudon in 1985 and at Lexington in 1995 and 2000. The results obtained for the benchmark cases are satisfactory and are presented in this paper. A performance analysis has also been carried out and is discussed here.

The dusty mocassin: fully self-consistent 3D photoionization and dust radiative transfer models

We present the first 3D Monte Carlo (MC) photoionization code to include a fully self-consistent treatment of dust radiative transfer (RT) within a photoionized region. This is the latest development (version 2.0) of the gas-only photoionization code MOCASSIN and employs a stochastic approach to the transport of radiation, allowing both the primary and secondary components of the radiation field to be treated self-consistently, whilst accounting for the scattering of radiation by dust grains mixed with the gas, as well as the absorption and emission of radiation by both the gas and the dust components. An escape probability method is implemented for the transfer of resonance lines that may be absorbed by the grains, thus contributing to their energy balance. The energetics of the co-existing dust and gas components must also take into account the effects of dust‐gas collisions and photoelectric emission from the dust grains, which are dependent on the grain charge. These are included in our code using the average grain potential approximation scheme. A set of rigorous benchmark tests have been carried out for dust-only spherically symmetric geometries and 2D disc configurations. The results of MOCASSIN are found to be in agreement with those obtained by well-established dust-only RT codes that employ various approaches to the solution of the RT problem. A model of the dust and of the photoionized gas components of the planetary nebula NGC 3918 is also presented as a means of testing the correct functioning of the RT procedures in a case where both gas and dust opacities are present. The two components are coupled via the heating of dust grains by the absorption of both UV continuum photons and resonance line photons emitted by the gas. The MOCASSIN results show agreement with those of a 1D dust and gas model of this nebula published previously, showing the reliability of the new code, which can be applied to a variety of astrophysical environments. Ke yw ords: radiative transfer ‐ dust, extinction ‐ H II regions ‐ planetary nebulae: general.

Ionizing feedback from massive stars in massive clusters – II. Disruption of bound clusters by photoionization

We present an SPH parameter study of the dynamical effect of photoionization from O--type stars on star--forming clouds of a range of masses and sizes during the time window before supernovae explode. Our model clouds all have the same degree of turbulent support initially, the ratio of turbulent kinetic energy to gravitational potential energy being set to

X-Ray-Irradiated Protoplanetary Disk Atmospheres. I. Predicted Emission-Line Spectrum and Photoevaporation

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Ionizing feedback from massive stars in massive clusters – III. Disruption of partially unbound clouds

=0.7. We allow the clouds to form stars and study the dynamical effects of the ionizing radiation from the massive stars or clusters born within them. We find that dense filamentary structures and accretion flows limit the quantities of gas that can be ionized, particularly in the higher density clusters. More importantly, the higher escape velocities in our more massive (10

Hierarchical star formation in M33: fundamental properties of the star-forming regions

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Theoretical spectra of photoevaporating protoplanetary discs: an atlas of atomic and low-ionization emission lines

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X-Ray Enabled MOCASSIN: A Three-dimensional Code for Photoionized Media

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SN 2007od: A TYPE IIP SUPERNOVA WITH CIRCUMSTELLAR INTERACTION

) clouds prevent the HII regions from sweeping up and expelling significant quantities of gas, so that the most massive clouds are largely dynamically unaffected by ionizing feedback. However, feedback has a profound effect on the lower--density 10