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Photoionization models frequently assume constant temperature or density within HII regions. We investigate this assumption by measuring the detailed temperature and density structures of four HII regions in the Large Magellanic Cloud and…

Astrophysics of Galaxies · Physics 2023-10-04 Yifei Jin , Ralph Sutherland , Lisa Kewley , David Nicholls

After briefly reviewing the impact of various parameters on photoionization models, we illustrate the importance of the nebular geometry by two examples: we first compare the results from models with thin shell and full shell geometry, and…

Astrophysics · Physics 2007-05-23 G. Stasinska

Spatially resolved studies of star forming regions show that the assumption of spherical geometry is not realistic in most cases, with a major complication posed by the gas being ionised by multiple non-centrally located stars or star…

Astrophysics · Physics 2009-06-23 B. Ercolano , N. Bastian , G. Stasinska

A present prevailing open problem planetary nebulae research, and photoionized gaseous nebulae research at large, is the systematic discrepancies in ionic abundances derived from recombination and collisionally excited lines in many H II…

Solar and Stellar Astrophysics · Physics 2017-09-26 Manuel A. Bautista , Ehab E. Ahmed

The Messenger Interface Monte-Carlo Mappings V (M^3) is a photoionization code adopting the fully self-consistent Monte-Carlo radiative transfer technique, which presents a major advance over previous photoionization models with simple…

Astrophysics of Galaxies · Physics 2022-04-04 Yifei Jin , Lisa Kewley , Ralph Sutherland

The three-dimensional Monte Carlo photoionization code Mocassin has been applied to construct a realistic model of the planetary nebula NGC 3918. Three different geometric models were tried. The effects of the interaction of the diffuse…

Astrophysics · Physics 2009-11-07 B. Ercolano , C. Morisset , M. J. Barlow , P. J. Storey , X. -W. Liu

We study the structural evolution of turbulent molecular clouds under the influence of ionizing radiation emitted from a nearby massive star by performing a high resolution parameter study with the iVINE code. The temperature is taken to be…

Solar and Stellar Astrophysics · Physics 2015-05-19 Matthias Gritschneder , Andreas Burkert , Thorsten Naab , Stefanie Walch

A prevailing open problem in planetary nebulae research, and photoionized gaseous nebulae research at large, is the systematic discrepancies in electron temperatures and ionic abundances as derived from recombination and collisionally…

Solar and Stellar Astrophysics · Physics 2018-10-17 Manuel A. Bautista , Ehab E. Ahmed

Extensive photoionization model grids for single star HII regions using a variety of recent state-of-the-art stellar atmosphere models have been computed with the main aim of constraining/testing their predicted ionizing spectra against…

Astrophysics · Physics 2009-11-10 C. Morisset , D. Schaerer , J. -C. Bouret , F. Martins

Radiative turbulent mixing layers should be ubiquitous in multi-phase gas with shear flow. They are a potentially attractive explanation for the high ions such as OVI seen in high velocity clouds and the circumgalactic medium (CGM) of…

Astrophysics of Galaxies · Physics 2019-05-17 Suoqing Ji , S. Peng Oh , Phillip Masterson

We present high resolution simulations on the impact of ionizing radiation of massive O-stars on the surrounding turbulent interstellar medium (ISM). The simulations are performed with the newly developed software iVINE which combines…

Solar and Stellar Astrophysics · Physics 2009-11-13 Matthias Gritschneder , Thorsten Naab , Stefanie Walch , Andreas Burkert , Fabian Heitsch

I review recent results derived from numerical simulations of the turbulent interstellar medium (ISM), in particular concerning the nature and formation of turbulent clouds, methods for comparing the structure in simulations and…

Astrophysics · Physics 2018-03-28 Enrique Vázquez-Semadeni

We investigate the interplay between the ionization radiation from massive stars and the turbulence inside the surrounding molecular gas thanks to 3D numerical simulations. We used the 3D hydrodynamical code HERACLES to model an initial…

Solar and Stellar Astrophysics · Physics 2015-06-05 P. Tremblin , E. Audit , V. Minier , W. Schmidt , N. Schneider

Observations of infrared fine-structure lines provide direct information on the metallicity and ionization structure of HII regions and indirectly on the hardness of the radiation field ionizing these nebulae. We have analyzed a sample of…

We compare emission line intensities from photoionization models of smooth and fractal shell geometries for low density H II regions, with particular focus on the low-ionization diagnostic diagram [N II]/H-alpha vs H-alpha. Building on…

Astrophysics of Galaxies · Physics 2015-06-15 Kenneth Wood , J. E. Barnes , Barbara Ercolano , L. M. Haffner , R. J. Reynolds , J. Dale

Reliable nebular emission line diagnostics are essential for accurately inferring the physical properties (e.g. electron temperature, density, pressure, and metallicity) of H II regions from spectra. When interpreting spectra, it is typical…

Astrophysics of Galaxies · Physics 2026-02-06 Larrance Xing , Nicholas Choustikov , Harley Katz , Alex J. Cameron

We present a grid of photoionization models for the emission from photoevaporative interfaces between the ionized gas and molecular cloud in blister HII regions. For the density profiles of the emitting gas in the models, we use a general…

Astrophysics · Physics 2009-10-31 Ravi Sankrit , J. Jeff Hester

We present a new set of analytic models for the expansion of HII regions powered by UV photoionisation from massive stars and compare them to a new suite of radiative magnetohydrodynamic simulations of turbulent, self-gravitating molecular…

Astrophysics of Galaxies · Physics 2016-06-08 Sam Geen , Patrick Hennebelle , Pascal Tremblin , Joakim Rosdahl

Aims. The main objective of this article is to provide a simple physical framework with permits a quantitative comparison of measurements of the temperature fluctuations in the ionized interstellar medium with possible mechanisms which can…

Astrophysics · Physics 2007-05-23 C. Giammanco , J. E. Beckman

Pulsars moving through ISM produce bow shocks detected in hydrogen H$\alpha$ line emission. The morphology of the bow shock nebulae allows one to probe the properties of ISM on scales $\sim 0.01$ pc and smaller. We performed 2D RMHD…

High Energy Astrophysical Phenomena · Physics 2020-06-17 Maxim Barkov , Maxim Lyutikov , Dmitry Khangulyan
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