Modelling the Local Interstellar Medium As A Supernova Remnant In A Multiphase Gas

Trying to understand the local interstellar gas in detail may be a hopeless task for a theorist. In the interstellar medium as a whole, we can at least address global properties and perhaps come to some reasonable “time averaged” conclusions such as those of Cox and his collaborators (e.g. Cox and Smith 1974, Cox 1979) or McKee and Ostriker (1977). Even this is quite uncertain of course, both because the ISM gas has structure on scales from at least 1 Pc (and probably much smaller) all the way up to the size of the galaxy, and because none of us are quite sure which physical processes (such as thermal evaporation or heating of cooler gas by magnetohydrodynamic processes) are really important. However, in the local ISM things are significantly worse in that we no longer have even the ergodic hypothesis available to us – rather we have to try and deal with individual events and structures. On the other hand, we do have more detailed observations and hence a laboratory to try to decide on the importance of the various physical processes.

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Abundances in the Gaseous Galactic Halo

Highlights of Astronomy ◽

10.1017/s1539299600020049 ◽

1998 ◽

Vol 11 (1) ◽

pp. 86-89

Author(s):

Ulysses J. Sofia

Keyword(s):

Interstellar Medium ◽

Gas Phase ◽

High Velocity ◽

Galactic Halo ◽

Solar Neighborhood ◽

Local Interstellar Medium ◽

The Galaxy ◽

Metal Abundances ◽

High Velocity Clouds

Abstract The well measured gas-phase abundances in the low halo suggest that this region of the Galaxy has total (gas plus dust) metal abundances which are close to those in the solar neighborhood. The gas-phase abundances in the halo are generally higher than those seen in the disk, however, this affect is likely due to the destruction of dust in the halo clouds. Observations of high velocity clouds (HVCs) in the halo suggest that these clouds have metal abundances which are substantially lower than those measured for the local interstellar medium. These determinations, however, are often of lower quality than those for the low halo because of uncertainties in the hydrogen abundances along the sightlines, in the incorporation of elements into dust, and in the partial ionization of the clouds.

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Atomic and Ionized Microstructures in the Diffuse Interstellar Medium

Annual Review of Astronomy and Astrophysics ◽

10.1146/annurev-astro-081817-051810 ◽

2018 ◽

Vol 56 (1) ◽

pp. 489-540 ◽

Cited By ~ 10

Author(s):

Snežana Stanimirović ◽

Ellen G. Zweibel

Keyword(s):

Interstellar Medium ◽

Supernova Remnants ◽

Spatial Scales ◽

Physical Processes ◽

Interstellar Gas ◽

Local Bubble ◽

Turbulent Dissipation ◽

Atomic Structures ◽

Discrete Structures ◽

Turbulent Cascade

It has been known for half a century that the interstellar medium (ISM) of our Galaxy is structured on scales as small as a few hundred kilometers, more than 10 orders of magnitude smaller than typical ISM structures and energy input scales. In this review we focus on neutral and ionized structures on spatial scales of a few to ∼104AU, which appear to be highly overpressured, as these have the most important role in the dynamics and energy balance of interstellar gas: the tiny scale atomic structures (TSASs) and extreme scattering events (ESEs) as the most overpressured example of the tiny scale ionized structures (TSISs). We review observational results and highlight key physical processes at AU scales. We present evidence for and against microstructures as part of a universal turbulent cascade and as discrete structures, and we review their association with supernova remnants, the Local Bubble, and bright stars. We suggest a number of observational and theoretical programs that could clarify the nature of AU structures. TSAS and TSIS probe spatial scales in the range of what is expected for turbulent dissipation scales and are therefore of key importance for constraining exotic and not-well-understood physical processes that have implications for many areas of astrophysics. The emerging picture is one in which a magnetized, turbulent cascade, driven hard by a local energy source and acting jointly with phenomena such as thermal instability, is the source of these microstructures.

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The Molonglo Galactic Plane Survey: MGPS2

Symposium - International Astronomical Union ◽

10.1017/s0074180900169062 ◽

2002 ◽

Vol 199 ◽

pp. 259-261

Author(s):

A. J. Green

Keyword(s):

Interstellar Medium ◽

Supernova Remnant ◽

Galactic Plane ◽

Hii Regions ◽

Radio Galaxies ◽

Radio Continuum ◽

The Galaxy ◽

First Results ◽

Made In

A survey of the southern Galactic Plane is being made in the radio continuum at 843 MHz with the Molonglo Observatory Synthesis Telescope. The area to be covered is 240° ≤ l ≤ 365°, |b| ≤ 10° with a resolution of 43″ × 43″cosec|δ| and a 3σ rms noise of ≤ 5 mJy/beam. This survey (MGPS2) will be used to search for possible new supernova remnant candidates, to image other discrete sources such as HII regions and radio galaxies located behind the Galaxy, and to study the structure of the interstellar medium. Comparison with a first epoch survey (MGPS1) will also be made. Some of the first results from MGPS2 are presented.

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Simulating the interstellar medium and stellar feedback on a moving mesh: implementation and isolated galaxies

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2391 ◽

2019 ◽

Vol 489 (3) ◽

pp. 4233-4260 ◽

Cited By ~ 10

Author(s):

Federico Marinacci ◽

Laura V Sales ◽

Mark Vogelsberger ◽

Paul Torrey ◽

Volker Springel

Keyword(s):

Star Formation ◽

Interstellar Medium ◽

Star Formation History ◽

Moving Mesh ◽

Late Time ◽

Interstellar Gas ◽

Average Mass ◽

Stellar Feedback ◽

The Galaxy ◽

Energy And Momentum

ABSTRACT We introduce the Stars and MUltiphase Gas in GaLaxiEs – SMUGGLE model, an explicit and comprehensive stellar feedback model for the moving-mesh code arepo. This novel sub-resolution model resolves the multiphase gas structure of the interstellar medium and self-consistently generates gaseous outflows. The model implements crucial aspects of stellar feedback including photoionization, radiation pressure, energy, and momentum injection from stellar winds and from supernovae. We explore this model in high-resolution isolated simulations of Milky Way like disc galaxies. Stellar feedback regulates star formation to the observed level and naturally captures the establishment of a Kennicutt–Schmidt relation. This result is achieved independent of the numerical mass and spatial resolution of the simulations. Gaseous outflows are generated with average mass loading factors of the order of unity. Strong outflow activity is correlated with peaks in the star formation history of the galaxy with evidence that most of the ejected gas eventually rains down on to the disc in a galactic fountain flow that sustains late-time star formation. Finally, the interstellar gas in the galaxy shows a distinct multiphase distribution with a coexistence of cold, warm, and hot phases.

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Optical Emission Line Studies and the Warm Ionized Component of the Local Interstellar Medium

International Astronomical Union Colloquium ◽

10.1017/s0252921100098067 ◽

1984 ◽

Vol 81 ◽

pp. 95-108 ◽

Cited By ~ 1

Author(s):

R.J. Reynolds

Keyword(s):

Interstellar Medium ◽

Galactic Disk ◽

Emission Measure ◽

Optical Emission ◽

Ionization Rate ◽

Solar Neighborhood ◽

Dispersion Measure ◽

Local Interstellar Medium ◽

Interstellar Gas ◽

Hα Emission

AbstractObservations of diffuse, galactic Hα, [NII]λ6583, and [SII]λ6716 emission lines provide evidence for a warm (~ 104 K), primarily ionized component of the interstellar medium distributed throughout the galactic disk. This component of the interstellar gas has an electron density ≈ 0.1-0.2 cm-3 and occupies about 10-30% of the interstellar volume. Interstellar Hα emission near the galactic poles, the dispersion measure of a nearby pulsar, and observations of interstellar gas flowing into the solar system indicate that this ionized component is an important constituent of the interstellar medium in the solar neighborhood. The intensity of the Hα background at high galactic latitudes implies that this component is maintained by an average hydrogen ionization rate in the vicinity of the Sun of (2-4) x 106 s-1 per cm2 of galactic disk. The emission measure is 1.3-2.3 cm-6 pc toward the galactic poles. The sources of this ionization have not yet been identified but may include escaping Lyman continuum radiation from planetary nebulae, hot white dwarfs, and early type stars. Investigations of the regions surrounding ζ Oph (09V), the nearest (d ≃ 140 pc) 0 star, and a Vir (Bl IV), one of the nearest (d ≃ 87 pc) early B stars, have revealed areas of enhanced Hα emission extending 6°-12° from each star. However, it appears that these stars do not contribute significantly to the more diffuse ionization within the local interstellar medium.

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Nearby Molecular Hydrogen

International Astronomical Union Colloquium ◽

10.1017/s0252921100098377 ◽

1984 ◽

Vol 81 ◽

pp. 276-279

Author(s):

F. Lebrun

Keyword(s):

Interstellar Medium ◽

Molecular Mass ◽

Molecular Cloud ◽

Molecular Hydrogen ◽

Large Scale ◽

Gamma Ray ◽

The Sun ◽

Local Interstellar Medium ◽

Interstellar Gas ◽

Co Observations

AbstractIf the gas-to-dust ratio is sufficiently uniform throughout the local interstellar medium, galaxy counts may provide a useful probe of the large scale structure of the interstellar gas. This idea substantiated by gamma-ray observations has led to the discovery of nearby molecular cloud complexes. The reddening studies indicate that one of them lies between 80 and 140 pc from the sun. From CO observations, its molecular mass is estimated to be a few 103 M⊙.

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The Second Epoch Molonglo Galactic Plane Survey: Images and Candidate Supernova Remnants

Publications of the Astronomical Society of Australia ◽

10.1017/pasa.2014.37 ◽

2014 ◽

Vol 31 ◽

Cited By ~ 15

Author(s):

A. J. Green ◽

S. N. Reeves ◽

T. Murphy

Keyword(s):

Interstellar Medium ◽

Supernova Remnants ◽

Large Scale ◽

Supernova Remnant ◽

Angular Resolution ◽

Galactic Plane ◽

Postage Stamps ◽

The Galaxy ◽

Complete Survey ◽

Extended Sources

AbstractThe second epoch Molonglo Galactic Plane Survey covers the area 245° ⩽l⩽ 365° and |b| ⩽ 10° at a frequency of 843 MHz and an angular resolution of 45 arcsec × 45 arcsec cosec(δ). The sensitivity varies between 1–2 mJy beam− 1depending on the presence of strong extended sources. This survey is currently the highest resolution and most sensitive large-scale continuum survey of the southern Galactic plane. In this paper, we present the images of the complete survey, including postage stamps of some new supernova remnant (SNR) candidates and a discussion of the highly structured features detected in the interstellar medium. The intersection of these two types of features is discussed in the context of the ‘missing’ SNR population in the Galaxy.

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Interstellar gas in the central region of the Galaxy

Symposium - International Astronomical Union ◽

10.1017/s0074180900101032 ◽

1967 ◽

Vol 31 ◽

pp. 239-251 ◽

Cited By ~ 3

Author(s):

F. J. Kerr

Keyword(s):

Central Region ◽

Galactic Plane ◽

Neutral Hydrogen ◽

Continuum Emission ◽

Galactic Centre ◽

Interstellar Gas ◽

Hydrogen Recombination ◽

The Galaxy ◽

Centre Region ◽

The Relationship

A review is given of information on the galactic-centre region obtained from recent observations of the 21-cm line from neutral hydrogen, the 18-cm group of OH lines, a hydrogen recombination line at 6 cm wavelength, and the continuum emission from ionized hydrogen.Both inward and outward motions are important in this region, in addition to rotation. Several types of observation indicate the presence of material in features inclined to the galactic plane. The relationship between the H and OH concentrations is not yet clear, but a rough picture of the central region can be proposed.

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