Galactic fine-structure lines - Morphologies of the warm ionized interstellar medium

Petuchowski, S. J.; Bennett, C. L.

doi:10.1086/172390

Cited by 52 publications

(45 citation statements)

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“…The model intensity ratio of the two fine-structure lines, I(122)/I(205) ≈ 0.6 is somewhat smaller than the global average 1.1 ± 0.1 measured with the FIRAS instrument on the COBE satellite. The ratio is, however, consistent with that expected for diffuse gas since the higher observed ratio was due to higher density ionised gas closely associated with star forming regions excluded from the observations (Petuchowski & Bennett 1993). Models of the WIM or the neutral medium with f e < 0.5 yield optical intensity ratios I(6583)/I(Hα) that are much larger than observed in diffuse emission.…”

Section: Radex Modellingsupporting

confidence: 81%

First detection of [N II] 205μm absorption in interstellar gas

Persson

Gérin

Mookerjea

et al. 2014

A&A

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We present high resolution [N ii] 205 μm ( 3 P 1 − 3 P 0 ) spectra obtained with Herschel-HIFI towards a small sample of far-infrared bright star forming regions in the Galactic plane: W 31C (G10.6−0.4), W 49N (G43.2−0.1), W 51 (G49.5−0.4), and G34.3+0.1. The detection of the 205 μm line in absorption emphasises the importance of a high spectral resolution, and also offers a new tool for investigation of the WIM.

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Section: Radex Modellingsupporting

confidence: 81%

First detection of [N II] 205μm absorption in interstellar gas

Persson

Gérin

Mookerjea

et al. 2014

A&A

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“…Maiolino et al 2005;Iono et al 2006;Maiolino et al 2009;Hailey-Dunsheath et al 2010), is mainly from PDRs rather than Hii regions (e.g., Crawford et al 1985;Stacey et al 1991). Some emission lines arise in both the Hii regions and PDRs (e.g., Petuchowski & Bennett 1993;Heiles 1994;Aannestad & Emery 2003;Abel 2006). The latter class of lines are the most difficult to model, because they have a more complex dependence on the various physical parameters of the clouds, and therefore are not ideal metallicity diagnostics.…”

Section: The Methodsmentioning

confidence: 99%

Metallicity diagnostics with infrared fine-structure lines

Nagao

Maiolino

Marconi

et al. 2011

A&A

109

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Although measuring the gas metallicity in galaxies at various redshifts is crucial to constrain galaxy evolutionary scenarios, only rest-frame optical emission lines have been generally used to measure the metallicity. This has prevented us to accurately measure the metallicity of dust-obscured galaxies, and accordingly to understand the chemical evolution of dusty populations, such as ultraluminous infrared galaxies. Here we propose diagnostics of the gas metallicity based on infrared fine-structure emission lines, which are nearly unaffected by dust extinction even the most obscured systems. Specifically, we focus on fine-structure lines arising mostly from Hii regions, not in photo-dissociation regions, to minimize the dependence and uncertainties of the metallicity diagnostics from various physical parameters. Based on photoionization models, we show that the emission-line flux ratio of ([Oiii] .21 can be used to measure and, therefore, account for the dependences on the gas density and ionization parameter, respectively. We show that these diagnostic fine-structure lines are detectable with Herschel in luminous infrared galaxies out z ∼ 0.4. Metallicity measurements with these fine-structure lines will be feasible at relatively high redshift (z ∼ 1 or more) with SPICA, the future infrared space observatory.

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“…It has been suggested that a significant fraction of the [C ii] emission in the Galaxy observed by COBE emerges from the extended low density warm ionized medium (ELDWIM; Petuchowski & Bennett 1993;Heiles 1994). We estimated the contribution to the observed [C ii] emission from an ionized gas using the Galactic distribution of the electron density used by the NE2001 code (Cordes & Lazio 2002).…”

Section: Ionized Gasmentioning

confidence: 99%

“…Thus, within the a 7 (Petuchowski & Bennett 1993;Heiles 1994). A detailed analysis of the relationship between the Herschel/HIFI [C ii] observations and those from COBE/FIRAS will be presented in a future paper.…”

Section: Ionized Gasmentioning

confidence: 99%

AHerschel[C ii] Galactic plane survey

Pineda

Langer

Velusamy

et al. 2013

A&A

331

497

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Context. The [C ii] 158 μm line is an important tool for understanding the life cycle of interstellar matter. Ionized carbon is present in a variety of phases of the interstellar medium (ISM), including the diffuse ionized medium, warm and cold atomic clouds, clouds in transition from atomic to molecular, and dense and warm photon dominated regions.Aims. Velocity-resolved observations of [C ii] are the most powerful technique available to disentangle the emission produced by these components. These observations can also be used to trace CO-dark H 2 gas and determine the total mass of the ISM.Methods. The Galactic Observations of Terahertz C+ (GOT C+) project surveys the [C ii] 158 μm line over the entire Galactic disk with velocity-resolved observations using the Herschel/HIFI instrument. We present the first longitude-velocity maps of the [C ii] emission for Galactic latitudes b = 0• , ±0.5• , and ±1.0• . We combine these maps with those of H i, 12 CO, and 13 CO to separate the different phases of the ISM and study their properties and distribution in the Galactic plane.Results. [C ii] emission is mostly associated with spiral arms, mainly emerging from Galactocentric distances between 4 and 10 kpc.It traces the envelopes of evolved clouds as well as clouds that are in the transition between atomic and molecular. We estimate that most of the observed [C ii] emission is produced by dense photon dominated regions (∼47%), with smaller contributions from COdark H 2 gas (∼28%), cold atomic gas (∼21%), and ionized gas (∼4%). Atomic gas inside the Solar radius is mostly in the form of cold neutral medium (CNM), while the warm neutral medium gas dominates the outer galaxy. The average fraction of CNM relative to total atomic gas is ∼43%. We find that the warm and diffuse CO-dark H 2 is distributed over a larger range of Galactocentric distances (4−11 kpc) than the cold and dense H 2 gas traced by 12 CO and 13 CO (4−8 kpc). The fraction of CO-dark H 2 to total H 2 increases with Galactocentric distance, ranging from ∼20% at 4 kpc to ∼80% at 10 kpc. On average, CO-dark H 2 accounts for ∼30% of the molecular mass of the Milky Way. When the CO-dark H 2 component is included, the radial distribution of the CO-to-H 2 conversion factor is steeper than that when only molecular gas traced by CO is considered. Most of the observed [C ii] emission emerging from dense photon dominated regions is associated with modest far-ultraviolet fields in the range χ 0 1−30.

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Galactic fine-structure lines - Morphologies of the warm ionized interstellar medium

Cited by 52 publications

References 0 publications

First detection of [N II] 205μm absorption in interstellar gas

First detection of [N II] 205μm absorption in interstellar gas

Metallicity diagnostics with infrared fine-structure lines

AHerschel[C ii] Galactic plane survey

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