The forbidden line of S II lambda 6716 in the galactic emission-line background

Reynolds, R. J.

doi:10.1086/163294

Cited by 144 publications

(104 citation statements)

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“…Line widths of Hα and the relatively narrow [S ii] line allow us to constrain the temperature of the ionized gas, assuming the ionized hydrogen and sulfur are fully mixed (Reynolds 1985): (2) where W H and W S are the full widths at half maximum of the Hα and [S ii] lines. This solution requires a distribution of nonthermal velocities with the most probable value…”

Section: Temperaturementioning

confidence: 99%

Ionized Gas in the Smith Cloud

Hill

Haffner

Reynolds

2009

ApJ

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We present Wisconsin Hα Mapper observations of ionized gas in the Smith Cloud, a high-velocity cloud which Lockman et al. have recently suggested is interacting with the Galactic disk. Our Hα map shows the brightest Hα emission, 0.43 ± 0.04 R, coincident with the brightest H i, while slightly fainter Hα emission (0.25 ± 0.02 R) is observed in a region with H i intensities < 0.1 times as bright as the brightest H i. We derive an ionized mass of 3 × 10 6 M , comparable to the H i mass, with the H + mass spread over a considerably larger area than that of H i. An estimated Galactic extinction correction could adjust these values upward by 40%. Hα and [S ii] line widths toward the region of brightest emission constrain the electron temperature of the gas to be between 8000 K and 23,000 K. A detection of [N ii] λ6583 in the same direction with a line ratio [N ii]/Hα = 0.32 ± 0.05 constrains the metallicity of the cloud: for typical photoionization temperatures of 8000-12,000 K, the nitrogen abundance is 0.15-0.44 times solar. These results lend further support to the claim that the Smith Cloud is new material accreting onto the Galaxy.

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Section: Temperaturementioning

confidence: 99%

Ionized Gas in the Smith Cloud

Hill

Haffner

Reynolds

2009

ApJ

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“…Brinks & Bajaja 1986) argues for a much lower volume filling factor of the hot phase there. Since at the same time the extended H (Lockman 1984) and H (Reynolds 1985) layers of the Milky Way were discovered, it seemed plausible that break-out of supernova remnants (SNRs) was inhibited (unless they occurred at a significant height above the disk) and only the most energetic superbubbles (SBs) with at least 800 SNe in concert (see Koo & McKee 1992) would achieve blow-out of the disk. Things might even become worse, once a disk parallel magnetic field is considered, which according to observations should have a regular component of the order of 3 µG or even higher (s. Beck 2004).…”

Section: Introductionmentioning

confidence: 99%

Global dynamical evolution of the ISM in star forming galaxies

Avillez¹,

Breitschwerdt²

2005

A&A

321

266

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Abstract. In star forming disk galaxies, matter circulation between stars and the interstellar gas, and, in particular the energy input by random and clustered supernova explosions, determine the dynamical and chemical evolution of the ISM, and hence of the galaxy as a whole. Using a 3D MHD code with adaptive mesh refinement developed for this purpose, we have investigated the rôle of magnetized matter circulation between the gaseous disk and the surrounding galactic halo. Special emphasis has been put on the effect of the magnetic field with respect to the volume and mass fractions of the different ISM "phases", the relative importance of ram, thermal and magnetic pressures, and whether the field can prevent matter transport from the disk into the halo. The simulations were performed on a grid with an area of 1 kpc 2 , centered on the solar circle, extending ±10 kpc perpendicular to the galactic disk with a resolution as high as 1.25 pc. The simulations were run for a time scale of 400 Myr, sufficiently long to avoid memory effects of the initial setup, and to allow for a global dynamical equilibrium to be reached in case of a constant energy input rate. The main results of our simulations are: (i) The T ≤ 10 3 K gas is mainly concentrated in shock compressed layers, exhibiting the presence of high density clouds with sizes of a few parsecs and T ≤ 200 K. These structures are formed in regions where several large scale streams of convergent flow (driven by SNe) occur. They have lifetimes of a few free-fall times, are filamentary in structure, tend to be aligned with the local field and are associated with the highest field strengths; (ii) the magnetic field has a high variability and it is largely uncorrelated with the density, suggesting that it is driven by superalfvenic inertial motions; (iii) ram pressure controls the flow for 200 < T ≤ 10 5.5 K. For T ≤ 200 K magnetic pressure dominates, while the hot gas (T > 10 5.5 K) in contrast is controlled by the thermal pressure, since magnetic field lines are swept towards the dense compressed walls; (iv) up to 49% of the mass in the disk is concentrated in the classical thermally unstable regime 200 < T ≤ 10 3.9 K with ∼65% of the warm neutral medium (WNM) mass enclosed in the 500 ≤ T ≤ 5000 K gas, consistent with recent observations; (v) the volume filling factors of the different temperature regimes depend sensitively on the existence of the duty cycle between the disk and halo, acting as a pressure release mechanism for the hot phase in the disk. We find that in general gas transport into the halo in 3D is not prevented by an initial disk parallel magnetic field, but only delayed initially, for as long as it is needed to punch holes into the thick magnetized gas disk. The mean volume filling factor of the hot phase in the disk is similar in HD and MHD (the latter with a total field strength of 4.4 µG) runs, amounting to ∼17−21% for the Galactic supernova rate.

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“…Although warm ionized hydrogen is a significant component of the interstellar medium (e.g., Reynolds 1993;Kulkarni & Heiles 1987), the nature of this gas and the source of its ionization are not yet clear. It has been proposed, for example, that the diffuse H is the fully ionized portion of a pervasive ϩ warm intercloud medium (e.g., Miller & Cox 1993), that the H is confined to H ii-H i interfaces on the surfaces of clouds ϩ (McKee & Ostriker 1977), and that much of the H is mixed ϩ with the neutral hydrogen, forming partially ionized, primarily neutral regions (Spitzer & Fitzpatrick 1993;Sciama 1990).…”

Section: Introductionmentioning

confidence: 99%

Detection of [O [CSC]i[/CSC]] λ6300 Emission from the Diffuse Interstellar Medium

Reynolds

Hausen

Tufte

et al. 1998

The Astrophysical Journal

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The Wisconsin Ha Mapper facility was used to obtain spectra of [O i] l6300 in three directions that sample the warm ionized component of the interstellar medium at the Galactic midplane and at pc. Weak z Ӎ Ϫ300 interstellar [O i] emission was clearly detected toward all three directions, with [O i] l6300/Ha intensity ratios for individual radial velocity components that range from less than 0.01 to approximately 0.04. According to photoionization models of the warm ionized medium, these [O i]/Ha ratios suggest that most of the Ha originates from density-bounded, nearly fully ionized regions along the lines of sight rather than from partially ionized H i clouds or layers of H ii on the surfaces of H i clouds.

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The forbidden line of S II lambda 6716 in the galactic emission-line background

Cited by 144 publications

References 0 publications

Ionized Gas in the Smith Cloud

Ionized Gas in the Smith Cloud

Global dynamical evolution of the ISM in star forming galaxies

Detection of [O [CSC]i[/CSC]] λ6300 Emission from the Diffuse Interstellar Medium

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