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

Reynolds, R. J.; Hausen, N. R.; Tufte, S. L.; Haffner, L. M.

doi:10.1086/311154

Cited by 63 publications

(69 citation statements)

References 19 publications

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“…We use N/H = 9.8 × 10 −5 and S/H = 1.2 × 10 −5 as median values of direct abundances determined from auroral lines detected in five HII regions by Bresolin et al (2005, see their Table 12). We assume that the H and N are 100% and 80% ionized, respectively; in the Milky Way, H + /H > 0.9 for T 4 > 0.8 (Reynolds et al 1998), and N + /N ∼ 0.8 under a range of DIG conditions (Sembach et al 2000). Though N + /N is fairly constant in the DIG, S + /S may vary under these conditions, due to the different second ionization potentials of these species (23.3 eV for S + → S 2+ , 29.6 eV for N + → N 2+ ).…”

Section: Identification Of Dig Emissionmentioning

confidence: 99%

Detection of Extraplanar Diffuse Ionized Gas in M83*

Boettcher

Gallagher

Zweibel

2017

ApJ

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We present the first kinematic study of extraplanar diffuse ionized gas (eDIG) in the nearby, face-on disk galaxy M83 using optical emission-line spectroscopy from the Robert Stobie Spectrograph on the Southern African Large Telescope. We use a Markov Chain Monte Carlo method to decompose the [NII]λλ6548, 6583, Hα, and [SII]λλ6717, 6731 emission lines into HII region and diffuse ionized gas emission. Extraplanar, diffuse gas is distinguished by its emission-line ratios ([NII]λ6583/Hα ∼ > 1.0) and its rotational velocity lag with respect to the disk (∆v = −24 km s −1 in projection). With interesting implications for isotropy, the velocity dispersion of the diffuse gas, σ = 96 km s −1 , is a factor of a few higher in M83 than in the Milky Way and nearby, edge-on disk galaxies. The turbulent pressure gradient is sufficient to support the eDIG layer in dynamical equilibrium at an electron scale height of h z = 1 kpc. However, this dynamical equilibrium model must be finely tuned to reproduce the rotational velocity lag. There is evidence of local bulk flows near star-forming regions in the disk, suggesting that the dynamical state of the gas may be intermediate between a dynamical equilibrium and a galactic fountain flow. As one of the first efforts to study eDIG kinematics in a face-on galaxy, this study demonstrates the feasibility of characterizing the radial distribution, bulk velocities, and vertical velocity dispersions in low-inclination systems.

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Section: Identification Of Dig Emissionmentioning

confidence: 99%

Detection of Extraplanar Diffuse Ionized Gas in M83*

Boettcher

Gallagher

Zweibel

2017

ApJ

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“…[O i] k6300/H , which depends on the neutral fraction of H through a charge exchange reaction, when detected in the halos of edge-on galaxies is generally enhanced relative to the disk (Rand 1998b(Rand , 2000Miller & Veilleux 2003). It is very weak in the Reynolds layer ( Reynolds et al 1998) and has only been detected in one external nonedge-on spiral, M33 ( Voges & Walterbos 2006). He i k5876 is difficult to detect, but He i/H traces the relative ionization fractions of helium and hydrogen and thus is a useful measure of the hardness of the radiation field.…”

Section: Emission Lines From Digmentioning

confidence: 99%

Infrared Spectroscopy of the Diffuse Ionized Halo of NGC 891

Rand

Wood

Benjamin

2008

ApJ

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We present infrared spectroscopy from the Spitzer Space Telescope at one disk position and two positions at a height of 1 kpc from the disk in the edge-on spiral NGC 891, with the primary goal of studying halo ionization. Our main result is that the [Ne iii]/[Ne ii] ratio, which provides a measure of the hardness of the ionizing spectrum free from the major problems plaguing optical line ratios, is enhanced in the extraplanar pointings relative to the disk pointing. Using a 2D Monte Carlo-based photoionization code that accounts for the effects of radiation field hardening, we find that this trend cannot be reproduced by any plausible photoionization model and that a secondary source of ionization must therefore operate in gaseous halos. We also present the first spectroscopic detections of extraplanar PAH features in an external normal galaxy. If they are in an exponential layer, very rough emission scale heights of 330-530 pc are implied for the various features. Extinction may be nonnegligible in the midplane and reduce these scale heights significantly. There is little significant variation in the relative emission from the various features between disk and extraplanar environment. Only the 17.4 m feature is significantly enhanced in the extraplanar gas compared to the other features, possibly indicating a preference for larger PAHs in the halo.

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“…A transfer calibration factor of 0.986 is used to move from H to [O i] 6300 8 (Scherb 1981;Reynolds et al 1998;Morgenthaler et al 2001). For the Hyakutake campaign, H observations were recorded 1996 March 21Y 23.…”

Section: Spectroscopymentioning

confidence: 99%

Large Aperture Oi6300 A Observations of Comet Hyakutake: Implications for the Photochemistry of OH and OiProduction in Comet Hale‐Bopp

Morgenthaler

Harris

Combi

2007

ApJ

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In previous work (Morgenthaler et al. and Glinski et al.), we proposed a revision to the standard OH photochemistry of van Dishoeck & Dalgarno in order to explain the anomalously bright [O i] 6300 8 emission observed by several instruments in comet C/1995 O1 (Hale-Bopp). In order to test the validity of revisions to the OH photochemistry, we present wide-field Fabry-Pérot [O i] 6300 8 observations of comet C/1996 B2 (Hyakutake) and review similar observations recorded for 1P/ Halley and 1989 c1 (Austin). Conventional long-slit spectroscopic observations of several comets in [O i] are also reviewed. The bulk of the evidence suggests that the OH photochemical rates of van Dishoeck & Dalgarno are, on the whole, correct and that the bright [O i] emission observed in Hale-Bopp, particularly at cometocentric distances beyond $3 ; 10 4 km, was unique to that comet, or possibly any comet with such a large production rate.

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

Cited by 63 publications

References 19 publications

Detection of Extraplanar Diffuse Ionized Gas in M83*

Detection of Extraplanar Diffuse Ionized Gas in M83*

Infrared Spectroscopy of the Diffuse Ionized Halo of NGC 891

Large Aperture Oi6300 A Observations of Comet Hyakutake: Implications for the Photochemistry of OH and OiProduction in Comet Hale‐Bopp

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