scholarly journals Supernova Remnant Shocks in an Inhomogeneous Interstellar Medium

1988 ◽  
Vol 101 ◽  
pp. 205-222 ◽  
Author(s):  
Christopher F. McKee
Keyword(s):  
Interstellar Medium ◽  
Supernova Remnant ◽  
Circumstellar Matter ◽  
Infrared Emission ◽  
Circumstellar Material ◽  
Hot Gas ◽  
Wide Range ◽  
Low Mass ◽  
Late Stages ◽  
Intercloud Medium

AbstractThe inhomogeneity of the interstellar medium (ISM) has a profound effect on the propagation of the interstellar shock generated by a supernova and on the appearance of the resulting supernova remnant (SNR). Low mass supernovae produce remnants that interact with the “pristine” ISM, which has density inhomogeneities (clouds) on a wide range of scales. The shock compresses and accelerates the clouds it encounters; inside the blast wave, the clouds are hydrodynamically unstable, and mass is injected from the clouds into the intercloud medium. Embedded clouds interact thermally with the shock also, adding mass to the hot intercloud medium via thermal evaporation or subtracting it via condensation and thermal instability. Mass injection into the hot intercloud medium, whether dynamical or thermal, leads to infrared emission as dust mixes with the hot gas and is thermally sputtered. The remnants of massive supernovae interact primarily with circumstellar matter and with interstellar material which has been processed by the ionizing radiation and wind of the progenitor star. After passing through any circumstellar material which may be present, the shock encounters a cavity which tends to “muffle” the SNR. The remnants of massive supernovae therefore tell us more about the late stages of the evolution of massive stars than about the ISM.

scholarly journals Pulsar-Driven Jets in Supernovae, Gamma-Ray Bursts, and the Universe

2012 ◽  
Vol 2012 ◽  
pp. 1-26
Author(s):  
John Middleditch
Keyword(s):  
Near Infrared ◽  
Gamma Ray ◽  
Infrared Emission ◽  
Gamma Ray Bursts ◽  
First Stars ◽  
Ss 433 ◽  
Circumstellar Material ◽  
Distant Galaxies ◽  
Low Mass ◽  
X Ray Binaries

The bipolarity of Supernova 1987A can be understood through its very early light curve from the CTIO 0.4 m telescope and IUE FES and following speckle observations of the “Mystery Spot”. These indicate a beam/jet of light/particles, with initial collimation factors >104and velocities >0.95 c, involving up to 10−5 M⊙interacting with circumstellar material. These can be produced by a model of pulsar emission from polarization currents induced/(modulated faster than c) beyond the pulsar light cylinder by the periodic electromagnetic field (supraluminally induced polarization currents (SLIP)). SLIP accounts for the disruption of supernova progenitors and their anomalous dimming at cosmological distances, jets from Sco X-1 and SS 433, the lack/presence of pulsations from the high-/low-luminosity low-mass X-ray binaries, and long/short gamma-ray bursts, and it predicts that their afterglows are thepulsedoptical-/near-infrared emission associated with these pulsars. SLIP may also account for the TeV e+/e−results from PAMELA and ATIC, the WMAP “Haze”/Fermi “Bubbles,” and ther-process. SLIP jets from SNe of the first stars may allow galaxies to form without dark matter and explain the peculiar nongravitational motions between pairs of distant galaxies observed by GALEX.

scholarly journals Future Studies of the Local Interstellar Medium With Space Telescope and Columbus

1984 ◽  
Vol 81 ◽  
pp. 331-343 ◽  
Author(s):  
Blair D. Savage
Keyword(s):  
Interstellar Medium ◽  
Wavelength Region ◽  
High Sensitivity ◽  
Short Wavelength Region ◽  
Space Telescope ◽  
Hot Gas ◽  
New Information ◽  
Wide Range ◽  
Multicomponent Nature ◽  
Thermal Line

AbstractThe spectrographs aboard Space Telescope and Columbus will provide important new information about the interstellar medium in the immediate vicinity of the sun. The Space Telescope high resolution spectrograph (HRS) will produce resolutions, λ/Δλ, of about 18,000 and 70,000 with high sensitivity between 1200 and 3200 A and greatly reduced sensitivity between 1060 and 1200 A. The highest resolution is adequate to define the multicomponent nature of interstellar absorption lines and to measure thermal line widths exceeding 3 km s-1 . The Columbus mission is in the planning stages. However, it is likely that the spacecraft will contain spectrographs capable of resolutions of 3 x 104 between 912 and 1200 A and 500 between 100 and 900 A. In the longer wavelength region, the very important lines of 0 VI, S VI, H2, H I , and D I are available for study. In the short wavelength region, lines of He I and II, are observable. If the 3x104 resolution spectrograph can provide extended wavelength coverage to 770 A, lines of Ne VIII which are expected from 8x105 K gas are accessible. Astronomers using the ST HRS and Columbus spectrographs will be able to study a wide range of problems relating to cold, warm, and hot gas in the local ISM. Some of the most important observing projects are described.

GG Tau: the Ringworld Revisited

2001 ◽  
Vol 200 ◽  
pp. 229-233 ◽  
Author(s):  
Stéphane Guilloteau ◽  
Anne Dutrey
Keyword(s):  
Circumstellar Disks ◽  
Gas Content ◽  
Unstable Region ◽  
Circumstellar Material ◽  
Hot Gas ◽  
Near Ir ◽  
Inner Radius ◽  
Low Mass ◽  
Fourth Component ◽  
Ir Light

GG Tau is a textbook example of a binary system. The circumstellar material around GG Tau is divided in several distinct regions: 1) small, low mass, circumstellar disks, detected in the near-IR and mm domain, 2) a well defined ring, of inner radius 180 AU, detected in the mm domain and in scattered near-IR light, 3) a more extended, colder disk detected in the 13CO(2–1) and 13CO(1–0) lines. Recent observations of the 12CO(2–1) clearly show this extended disk, but also reveal a fourth component of the circumstellar material: (relatively) diffuse and hot gas in the tidally unstable region. Estimate of the gas content suggest this material may be feeding the inner disks at about 10−6 M⊙/yr.

scholarly journals 2D Chemodynamical Simulations of Low-Mass Galaxies

1998 ◽  
Vol 11 (1) ◽  
pp. 139-140
Author(s):  
G. Hensler ◽  
A. Rieschick
Keyword(s):  
Interstellar Medium ◽  
Dynamical Behaviour ◽  
Gravitational Energy ◽  
Disk Galaxies ◽  
Gas Phases ◽  
Supernova Explosions ◽  
Low Mass ◽  
Gas Interactions ◽  
Multi Phase ◽  
Intercloud Medium

Because of their low gravitational energy, low-mass galaxies are seriously affected by energetical processes in their interstellar medium, such as supernova explosions, or by gravitational perturbations, e.g., by neighbouring galaxies. This can reasonably explain their variety of morphological types. If the evolutionary timescales of galaxies are predominantly determined by internal processes, the multi-phase character as well as star-gas interactions and phase transitions have to be taken into account. For this purpose we have developed a numerical treatment of the dynamical behaviour of gas and stars, which also accounts for the metal dependence of some processes and which can trace the chemical evolution for different elements. This so-called chemodynamical treatment is described in detail in Theis et al. (1992) and Samland et al. (1997). It considers three stellar components and devides the gas into clouds (CM, with a mass spectrum) and a hot intercloud medium (ICM). Since the element enhancement of the interstellar medium is produced by different processes with different lifetimes of their progenitors, O, Fe, and N are used as tracer elements to represent supernovae type II (SNell), type la (SNela), and planetary nebulae (PNe) contributions. While supernovae form the ICM, PNe only attribute to the CM so that only mixing effects of both gas phases can alter abundance ratios. Due to limited computer capacities the first chemodynamical simulations of dwarf galaxies could be performed only one-dimensionally so far (see e.g., Hensler et al. 1993, 1998). The recently developed two-dimensional chemodynamical code CoDEx (Samland 1994) was first applied to massive disk galaxies and produced models of which a particular one could represent various chemical and structural observations of the Milky Way with striking agreement (Samland et al. 1997).

scholarly journals Simulating the interstellar medium of galaxies with radiative transfer, non-equilibrium thermochemistry, and dust

2020 ◽  
Vol 499 (4) ◽  
pp. 5732-5748 ◽  
Author(s):  
Rahul Kannan ◽  
Federico Marinacci ◽  
Mark Vogelsberger ◽  
Laura V Sales ◽  
Paul Torrey ◽  
...  
Keyword(s):  
Interstellar Medium ◽  
Galaxy Formation ◽  
State Of The Art ◽  
Complex Function ◽  
Ionization State ◽  
Radiation Fields ◽  
Stellar Feedback ◽  
Wide Range ◽  
Dust Distribution ◽  
Non Equilibrium

ABSTRACT We present a novel framework to self-consistently model the effects of radiation fields, dust physics, and molecular chemistry (H2) in the interstellar medium (ISM) of galaxies. The model combines a state-of-the-art radiation hydrodynamics module with a H  and He  non-equilibrium thermochemistry module that accounts for H2 coupled to an empirical dust formation and destruction model, all integrated into the new stellar feedback framework SMUGGLE. We test this model on high-resolution isolated Milky-Way (MW) simulations. We show that the effect of radiation feedback on galactic star formation rates is quite modest in low gas surface density galaxies like the MW. The multiphase structure of the ISM, however, is highly dependent on the strength of the interstellar radiation field. We are also able to predict the distribution of H2, that allow us to match the molecular Kennicutt–Schmidt (KS) relation, without calibrating for it. We show that the dust distribution is a complex function of density, temperature, and ionization state of the gas. Our model is also able to match the observed dust temperature distribution in the ISM. Our state-of-the-art model is well-suited for performing next-generation cosmological galaxy formation simulations, which will be able to predict a wide range of resolved (∼10 pc) properties of galaxies.

scholarly journals Multi-stable composite twisting structure for morphing applications

2012 ◽  
Vol 468 (2141) ◽  
pp. 1230-1251 ◽  
Author(s):  
X. Lachenal ◽  
P. M. Weaver ◽  
S. Daynes
Keyword(s):  
Analytical Model ◽  
Material Properties ◽  
Degrees Of Freedom ◽  
Design Parameters ◽  
Engineering Structures ◽  
The Past ◽  
Wide Range ◽  
Morphing Structure ◽  
Low Mass ◽  
Unstable States

Conventional shape-changing engineering structures use discrete parts articulated around a number of linkages. Each part carries the loads, and the articulations provide the degrees of freedom of the system, leading to heavy and complex mechanisms. Consequently, there has been increased interest in morphing structures over the past decade owing to their potential to combine the conflicting requirements of strength, flexibility and low mass. This article presents a novel type of morphing structure capable of large deformations, simply consisting of two pre-stressed flanges joined to introduce two stable configurations. The bistability is analysed through a simple analytical model, predicting the positions of the stable and unstable states for different design parameters and material properties. Good correlation is found between experimental results, finite-element modelling and predictions from the analytical model for one particular example. A wide range of design parameters and material properties is also analytically investigated, yielding a remarkable structure with zero stiffness along the twisting axis.

Numerical Characterization of Hot Gas Ingestion Through Turbine Rim Seals

2016 ◽  
Author(s):  
Riccardo Da Soghe ◽  
Cosimo Bianchini ◽  
Carl M. Sangan ◽  
James A. Scobie ◽  
Gary D. Lock
Keyword(s):  
Flow Rate ◽  
Numerical Study ◽  
Axial Flow ◽  
Radial Clearance ◽  
Buffering Effect ◽  
Hot Gas ◽  
Numerical Predictions ◽  
Wide Range ◽  
Thermal Buffering

This paper deals with a numerical study aimed at the characterization of hot gas ingestion through turbine rim seals. The numerical campaign focused on an experimental facility which models ingress through the rim seal into the upstream wheel-space of an axial-turbine stage. Single-clearance arrangements were considered in the form of axial- and radial-seal gap configurations. With the radial-seal clearance configuration, CFD steady-state solutions were able to predict the system sealing effectiveness over a wide range of coolant mass flow rates reasonably well. The greater insight of flow field provided by the computations illustrates the thermal buffering effect when ingress occurs: for a given sealing flow rate, the effectiveness on the rotor was significantly higher than that on the stator due to the axial flow of hot gases from stator to rotor caused by pumping effects. The predicted effectiveness on the rotor was compared with a theoretical model for the thermal buffering effect showing good agreement. When the axial-seal clearance arrangement is considered, the agreement between CFD and experiments worsens; the variation of sealing effectiveness with coolant flow rate calculated by means of the simulations display a distinct kink. It was found that the “kink phenomenon” can be ascribed to an over-estimation of the egress spoiling effects due to turbulence modelling limitations. Despite some weaknesses in the numerical predictions, the paper shows that CFD can be used to characterize the sealing performance of axial- and radial-clearance turbine rim seals.

scholarly journals V392 Orionis: Observations and Evolutionary State of a Low-Mass System

1998 ◽  
Vol 11 (1) ◽  
pp. 371-371
Author(s):  
S. Narusawa ◽  
A. Yamasaki ◽  
Y. Nakamura
Keyword(s):  
Binary Systems ◽  
Main Sequence ◽  
Circumstellar Matter ◽  
Small Mass ◽  
Primary Component ◽  
Close Binary ◽  
Mass System ◽  
Future Evolution ◽  
Short Period ◽  
Low Mass

Although the evolution of binary systems has been qualitatively interpreted with the evolutionary scenario, the quantitative interpretation of any observed system is still unsatisfactory due to the difficulty of the quantitative treatment of mass and angular momentum transfer/loss. To reach a true understanding of the evolution of binary systems, we have to accumulate more observational evidence. So far, we have observed several binaries that are short-period and noncontact, and found the existence of extremely small-mass systems. In the present paper, we study another short-period (P=0.659d), noncontact, eclipsing binary system, V392 Ori. We have made photometric and spectroscopic observations of V392 Ori. The light curves are found to vary, suggesting the existence of circumstellar matter around the system. Combining the photometric and spectroscopic results, we obtain parameters describing the system; we find the mass of the primary component is only 0.6Mʘ- undermassive for its spectral and luminosity class A5V, suggesting that a considerable amount of its original mass has been lost from the system during the course of evolution. The low-mass problem is very important for investigation of the evolution of close binary systems: largemass loss within and/or after the main-sequence will have a significant influence on the future evolution of binary systems.

scholarly journals Resurrecting low-mass axion dark matter via a dynamical QCD scale

2021 ◽  
Vol 2021 (12) ◽  
Author(s):  
Lucien Heurtier ◽  
Fei Huang ◽  
Tim M.P. Tait
Keyword(s):  
Dark Matter ◽  
Standard Model ◽  
Temperature Dependent ◽  
Axion Field ◽  
Wide Range ◽  
The Standard Model ◽  
Low Mass ◽  
Higher Temperature ◽  
Relic Abundance ◽  
Dependent Mass

Abstract In the framework where the strong coupling is dynamical, the QCD sector may confine at a much higher temperature than it would in the Standard Model, and the temperature-dependent mass of the QCD axion evolves in a non-trivial way. We find that, depending on the evolution of ΛQCD, the axion field may undergo multiple distinct phases of damping and oscillation leading generically to a suppression of its relic abundance. Such a suppression could therefore open up a wide range of parameter space, resurrecting in particular axion dark-matter models with a large Peccei-Quinn scale fa ≫ 1012 GeV, i.e., with a lighter mass than the standard QCD axion.

scholarly journals Origin of warm and hot gas emission from low-mass protostars: Herschel-HIFI observations of CO J = 16–15

2017 ◽  
Vol 605 ◽  
pp. A93 ◽  
Author(s):  
L. E. Kristensen ◽  
E. F. van Dishoeck ◽  
J. C. Mottram ◽  
A. Karska ◽  
U. A. Yıldız ◽  
...  
Keyword(s):  
Gas Emission ◽  
Hot Gas ◽  
Low Mass
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