scholarly journals WARPFIELD-EMP: The self-consistent prediction of emission lines from evolving H ii regions in dense molecular clouds

2020 ◽  
Vol 496 (1) ◽  
pp. 339-363 ◽  
Author(s):  
E W Pellegrini ◽  
D Rahner ◽  
S Reissl ◽  
S C O Glover ◽  
R S Klessen ◽  
...  
Keyword(s):  
Line Emission ◽  
Continuum Emission ◽  
Physical Parameters ◽  
Model Parameters ◽  
Stellar Winds ◽  
H Ii Regions ◽  
Stellar Feedback ◽  
Wide Range ◽  
H Ii Region ◽  
Good Agreement

ABSTRACT We present the warpfield emission predictor, warpfield-emp, which couples the 1D stellar feedback code warpfield with the cloudy H iiregion/PDR code and the polaris radiative transfer code, in order to make detailed predictions for the time-dependent line and continuum emission arising from the H ii region and PDR surrounding an evolving star cluster. warpfield-emp accounts for a wide range of physical processes (photoionization, stellar winds, supernovae, radiation pressure, gravity, thermal conduction, radiative cooling, dust extinction etc.) and yet runs quickly enough to allow us to explore broad ranges of different model parameters. We compare the results of an extensive set of models with SITELLE observations of a large sample of H ii regions in NGC 628 and find very good agreement, particularly for the highest signal-to-noise observations. We show that our approach of modelling individual clouds from first principles (instead of in terms of dimensionless quantities such as the ionization parameter) allows us to avoid long-standing degeneracies in the interpretation of H ii region diagnostics and enables us to relate these diagnostics to important physical parameters such as cloud mass or cluster age. Finally, we explore the implications of our models regarding the reliability of simple metallicity diagnostics, the properties of long-lived embedded clusters, and the role played by winds and supernovae in regulating H ii region and PDR line emission.

Integrated approach to the PDR/H ii complex by the application of carbon radio recombination lines in the millimetre range and fine-structure lines of C ii and O i

2020 ◽  
Vol 492 (1) ◽  
pp. 1049-1060
Author(s):  
S A Siddiqui ◽  
Shafiqullah Khan ◽  
A Qaiyum
Keyword(s):  
Fine Structure ◽  
Theoretical Calculations ◽  
Angular Size ◽  
Line Emission ◽  
Integrated Approach ◽  
Continuum Emission ◽  
Physical Parameters ◽  
H Ii Regions ◽  
Radio Recombination Lines ◽  
Fine Structure Lines

ABSTRACT We have performed self-consistent calculations to estimate the physical parameters of photodissociation regions (PDRs) associated with objects, namely, NGC 2024, Orion A and W3, using far-infrared continuum emission, fine-structure lines of C ii and O i, and radio recombination lines of carbon. Typically, PDRs separate H ii regions from the molecular cloud; therefore, necessary corrections for the contribution to C ii line emission due to the H ii region are made. For that purpose, using observational data, theoretical calculations are performed to obtain the best fit for the said observations. Three parameters, angular size, θ (in arcminutes), far-ultraviolet radiation field G0, and hydrogen density nH (which gives electron density and temperature), are varied, and the sets of parameters (G0 and nH) obtained for the NGC 2024, Orion A and W3 PDRs are (7.6 × 104 and 1.2 × 105 cm−3), (2.8 × 105 and 2.3 × 105 cm−3) and (3.7 × 105 and 1.9 × 105 cm−3), respectively. The relationship between line and continuum emissions from PDRs associated with H ii regions leads us to conclude that exciting stars for the NGC 2024, Orion A and W3 H ii regions are O8–O9V, O6–O7V and O5–O6V, respectively.

scholarly journals Magnetic fields, stellar feedback, and the geometry of H II regions

2008 ◽  
Vol 4 (S259) ◽  
pp. 25-34
Author(s):  
Gary J. Ferland
Keyword(s):  
Magnetic Field ◽  
Magnetic Pressure ◽  
H Ii Regions ◽  
Line Profiles ◽  
Ionized Gas ◽  
Stellar Feedback ◽  
H Ii Region ◽  
Field Lines ◽  
The Magnetic Field ◽  
Simple Picture

AbstractMagnetic pressure has long been known to dominate over gas pressure in atomic and molecular regions of the interstellar medium. Here I review several recent observational studies of the relationships between the H+, H0 and H2 regions in M42 (the Orion complex) and M17. A simple picture results. When stars form they push back surrounding material, mainly through the outward momentum of starlight acting on grains, and field lines are dragged with the gas due to flux freezing. The magnetic field is compressed and the magnetic pressure increases until it is able to resist further expansion and the system comes into approximate magnetostatic equilibrium. Magnetic field lines can be preferentially aligned perpendicular to the long axis of quiescent cloud before stars form. After star formation and pushback occurs ionized gas will be constrained to flow along field lines and escape from the system along directions perpendicular to the long axis. The magnetic field may play other roles in the physics of the H II region and associated PDR. Cosmic rays may be enhanced along with the field and provide additional heating of atomic and molecular material. Wave motions may be associated with the field and contribute a component of turbulence to observed line profiles.

scholarly journals Submillimeter Wave Instrument radiometry of the Jovian icy moons

2020 ◽  
Vol 644 ◽  
pp. A24
Author(s):  
Y. A. Ilyushin ◽  
P. Hartogh
Keyword(s):  
Single Scattering ◽  
Submillimeter Wave ◽  
Skin Depth ◽  
Single Scattering Albedo ◽  
Wave Parameter ◽  
Retrieval Algorithm ◽  
Physical Parameters ◽  
Model Parameters ◽  
Icy Moons ◽  
Wide Range

Context. We address the issue of remote sensing of the surfaces of Galilean icy moons. We investigate the prospects for retrieval of the physical parameters of the surface of the Jovian icy moons from submillimeter wave radiometry data. Aims. We show that the model parameters could not be completely retrieved from the polarized radiometry data, but some of their combinations can be effectively constrained. Methods. The polarized radiative transfer in lossy porous ice was numerically simulated. A Bayesian maximum likelihood retrieval algorithm was developed and tested on the simulated data in a wide range of variation of the model parameters. The uncertainty of the retrievals was evaluated with the Cramer-Rao bounds. We established the combinations of model parameters that can be effectively constrained from the measured data. Results. We reveal that the effective scatterer size can be reliably constrained for a range of values where the scattering asymmetry parameter uniquely depends on the wave parameter, and for relatively high values of the single scattering albedo, for which the scattering in the medium is significant. Similarly, the domains of reliable retrieval of the single scattering albedo and thermal skin depth are established.

scholarly journals The PDR structure and kinematics around the compact H ii regions S235 A and S235 C with [C ii], [13C ii], [O i], and HCO+ line profiles

2020 ◽  
Vol 497 (3) ◽  
pp. 2651-2669
Author(s):  
M S Kirsanova ◽  
V Ossenkopf-Okada ◽  
L D Anderson ◽  
P A Boley ◽  
J H Bieging ◽  
...  
Keyword(s):  
Optical Depth ◽  
Molecular Layer ◽  
Line Emission ◽  
H Ii Regions ◽  
Line Profiles ◽  
Gas Kinematics ◽  
Spherical Models ◽  
Absorbing Material ◽  
H Ii Region ◽  
Integrated Intensities

ABSTRACT The aim of this work is to study structure and gas kinematics in the photodissociation regions (PDRs) around the compact H ii regions S235 A and S235 C. We observe the [C ii], [13C ii], and [O i] line emission, using SOFIA/upGREAT, and complement them by data of HCO+ and CO. We use the [13C ii] line to measure the optical depth of the [C ii] emission, and find that the [C ii] line profiles are influenced by self-absorption, while the [13C ii] line remains unaffected by these effects. Hence, for dense PDRs, [13C ii] emission is a better tracer of gas kinematics. The optical depth of the [C ii] line is up to 10 in S235 A. We find an expanding motion of the [C ii]-emitting layer of the PDRs into the front molecular layer in both regions. Comparison of the gas and dust columns shows that gas components visible neither in the [C ii] nor in low-J CO lines may contribute to the total column across S235 A. We test whether the observed properties of the PDRs match the predictions of spherical models of expanding H ii region + PDR + molecular cloud. Integrated intensities of the [13C ii], [C ii], and [O i] lines are well represented by the model, but the models do not reproduce the double-peaked [C ii] line profiles due to an insufficient column density of C+. The model predicts that the [O i] line could be a more reliable tracer of gas kinematics, but the foreground self-absorbing material does not allow using it in the considered regions.

scholarly journals Initial conditions in the evolution of OB and Wolf-Rayet stars in N 105 of the LMC

1999 ◽  
Vol 193 ◽  
pp. 470-471
Author(s):  
Patricia Ambrocio-Cruz ◽  
A. Laval ◽  
M. Marcelin ◽  
P. Amram ◽  
F. Comerón
Keyword(s):  
Velocity Field ◽  
Initial Conditions ◽  
Stellar Winds ◽  
H Ii Regions ◽  
Neutral Gas ◽  
Dynamical Simulations ◽  
Large Shell ◽  
H Ii Region ◽  
Size And Morphology ◽  
The Moment

The detailed radial velocity field of the H II region N105, in the LMC, has been obtained for the Hα and [O III] 5007 lines with a spatial sampling of 9″ and a spectral sampling of 16 and 7kms−1. The peculiar velocity field and morphology indicate that N105 contains four bubble shaped nebulae and two bright distinct quasi-spherical H II regions, more or less coeval, embedded inside another large shell nebula. They are essentially formed by the action of stellar winds of a few exciting stars, born deep inside their parental cloud. This result is deduced from the energy input inside the ionized gas by the stellar winds of early type stars and from dynamical simulations combining the effects of stellar winds with those of high density gradients inside the neutral gas. The size and morphology of the H II region are conditioned by the depth inside the natal cloud; the observed dynamical time-scale of the H II region starts at the moment of blow-out of the molecular cloud.

VLE Determination of Carbon Dioxide Loaded Aqueous Alkanolamine Mixtures Using Modified Kent Eisenberg Model

2017 ◽  
Vol 231 (11-12) ◽  
Author(s):  
Humbul Suleman ◽  
Abdulhalim Shah Maulud ◽  
Zakaria Man
Keyword(s):  
Experimental Data ◽  
Carbon Dioxide ◽  
Model Parameters ◽  
Thermodynamic Models ◽  
Carbon Dioxide Absorption ◽  
Proposed Model ◽  
Wide Range ◽  
Experimental Values ◽  
Good Agreement

AbstractA computationally simple thermodynamic framework has been presented to correlate the vapour-liquid equilibria of carbon dioxide absorption in five representative types of alkanolamine mixtures. The proposed model is an extension of modified Kent Eisenberg model for the carbon dioxide loaded aqueous alkanolamine mixtures. The model parameters are regressed on a large experimental data pool of carbon dioxide solubility in aqueous alkanolamine mixtures. The model is applicable to a wide range of temperature (298–393 K), pressure (0.1–6000 kPa) and alkanolamine concentration (0.3–5 M). The correlated results are compared to the experimental values and found to be in good agreement with the average deviations ranging between 6% and 20%. The model results are comparable to other thermodynamic models.

scholarly journals Asteroseismic inference of subgiant evolutionary parameters with deep learning

2020 ◽  
Vol 499 (2) ◽  
pp. 2445-2461
Author(s):  
Marc Hon ◽  
Earl P Bellinger ◽  
Saskia Hekker ◽  
Dennis Stello ◽  
James S Kuszlewicz
Keyword(s):  
Deep Learning ◽  
Diffusion Processes ◽  
Physical Parameters ◽  
Fundamental Parameters ◽  
Fundamental Properties ◽  
Wide Range ◽  
Modelling Techniques ◽  
Subgiant Stars ◽  
Good Agreement

ABSTRACT With the observations of an unprecedented number of oscillating subgiant stars expected from NASA’s TESS mission, the asteroseismic characterization of subgiant stars will be a vital task for stellar population studies and for testing our theories of stellar evolution. To determine the fundamental properties of a large sample of subgiant stars efficiently, we developed a deep learning method that estimates distributions of fundamental parameters like age and mass over a wide range of input physics by learning from a grid of stellar models varied in eight physical parameters. We applied our method to four Kepler subgiant stars and compare our results with previously determined estimates. Our results show good agreement with previous estimates for three of them (KIC 11026764, KIC 10920273, KIC 11395018). With the ability to explore a vast range of stellar parameters, we determine that the remaining star, KIC 10005473, is likely to have an age 1 Gyr younger than its previously determined estimate. Our method also estimates the efficiency of overshooting, undershooting, and microscopic diffusion processes, from which we determined that the parameters governing such processes are generally poorly constrained in subgiant models. We further demonstrate our method’s utility for ensemble asteroseismology by characterizing a sample of 30 Kepler subgiant stars, where we find a majority of our age, mass, and radius estimates agree within uncertainties from more computationally expensive grid-based modelling techniques.

scholarly journals G−0.02−0.07, the compact H ii region complex nearest to the galactic center with ALMA

2019 ◽  
Vol 71 (6) ◽  
Author(s):  
Masato Tsuboi ◽  
Yoshimi Kitamura ◽  
Kenta Uehara ◽  
Atsushi Miyazaki ◽  
Ryosuke Miyawaki ◽  
...  
Keyword(s):  
Shock Wave ◽  
Galactic Center ◽  
Emission Lines ◽  
Continuum Emission ◽  
Molecular Gas ◽  
H Ii Regions ◽  
Recombination Line ◽  
The Galaxy ◽  
H Ii Region ◽  
Absorption Features

Abstract We have observed the compact H ii region complex nearest to the dynamical center of the Galaxy, G−0.02−0.07, using ALMA in the H42α recombination line, CS J = 2–1, H13CO+J = 1–0, and SiO v = 0, J = 2–1 emission lines, and the 86 GHz continuum emission. The H ii regions HII-A to HII-C in the cluster are clearly resolved into a shell-like feature with a bright half and a dark half in the recombination line and continuum emission. The analysis of the absorption features in the molecular emission lines show that H ii-A, B, and C are located on the near side of the “Galactic center 50 km s−1 molecular cloud” (50MC), but HII-D is located on the far side of it. The electron temperatures and densities ranges are Te = 5150–5920 K and ne = 950–2340 cm−3, respectively. The electron temperatures in the bright half are slightly lower than those in the dark half, while the electron densities in the bright half are slightly higher than those in the dark half. The H ii regions are embedded in the ambient molecular gas. There are some molecular gas components compressed by a C-type shock wave around the H ii regions. From the line width of the H42α recombination line, the expansion velocities of HII-A, HII-B, HII-C, and HII-D are estimated to be Vexp = 16.7, 11.6, 11.1, and 12.1 km s−1, respectively. The expansion timescales of HII-A, HII-B, HII-C, and HII-D are estimated to be tage ≃ 1.4 × 104, 1.7 × 104, 2.0 × 104, and 0.7 × 104 yr, respectively. The spectral types of the central stars from HII-A to HII-D are estimated to be O8V, O9.5V, O9V, and B0V, respectively. These derived spectral types are roughly consistent with the previous radio estimation. The positional relation among the H ii regions, the SiO molecule enhancement area, and Class-I maser spots suggest that a shock wave caused by a cloud–cloud collision propagated along the line from HII-C to HII-A in the 50MC. The shock wave would have triggered the massive star formation.

scholarly journals The case for thermalization as a contributor to the [C ii] deficit

2021 ◽  
Vol 503 (1) ◽  
pp. 911-919
Author(s):  
Jessica Sutter ◽  
Daniel A Dale ◽  
Karin Sandstrom ◽  
J D T Smith ◽  
Alberto Bolatto ◽  
...  
Keyword(s):  
Far Infrared ◽  
Infrared Emission ◽  
Continuum Emission ◽  
H Ii Regions ◽  
Observable Universe ◽  
Star Forming ◽  
Star Forming Regions ◽  
Wide Range ◽  
Nearby Galaxies ◽  
Selection Of

ABSTRACT The [C ii] deficit, which describes the observed decrease in the ratio of [C ii] 158 μm emission to continuum infrared emission in galaxies with high star formation surface densities, places a significant challenge to the interpretation of [C ii] detections from across the observable universe. In an attempt to further decode the cause of the [C ii] deficit, the [C ii] and dust continuum emission from 18 Local Volume galaxies has been split based on conditions within the interstellar medium where it originated. This is completed using the Key Insights in Nearby Galaxies: a Far-Infrared Survey with Herschel (KINGFISH) and Beyond the Peak (BtP) surveys and the wide-range of wavelength information, from UV to far-infrared emission lines, available for a selection of star-forming regions within these samples. By comparing these subdivided [C ii] emissions to isolated infrared emission and other properties, we find that the thermalization (collisional de-excitation) of the [C ii] line in H ii regions plays a significant role in the deficit observed in our sample.

scholarly journals The Quasar Continuum

2009 ◽  
Vol 5 (S267) ◽  
pp. 55-64
Author(s):  
Martin Elvis
Keyword(s):  
Continuum Emission ◽  
Spectral Energy ◽  
Scaling Relations ◽  
Physical Parameters ◽  
Spectral Energy Distributions ◽  
Energy Distributions ◽  
X Ray ◽  
Wide Range

AbstractThe powerful compact continuum emission from quasars is understood only in outline. New surveys allow investigation of the quasar continuum over a wide range of parameters (z, L, L/LEdd) and wavelengths (radio to X-ray). I review the spectral energy distributions of quasars and how new scaling relations with physical parameters promise to take us to a deeper understanding of the quasar continuum.

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