First detection of [N II] 205<i>μ</i>m absorption in interstellar gas

Persson, C. M.; Gérin, M.; Mookerjea, B.; Black, J. H.; Olberg, M.; Goicoechea, J. R.; Hassel, G. E.; Falgarone, É.; Levrier, F.; Menten, K. M.; Pety, J.

doi:10.1051/0004-6361/201423997

Cited by 13 publications

(18 citation statements)

References 42 publications

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“…The electron density of the WIM is quite uncertain, and is often taken to be ∼ 0.01-0.1 cm −3 (e.g. Taylor & Cordes 1993;Goldsmith et al 2015;Persson et al 2014). Heiles et al (1996) found a low volume filling factor and a relatively high n e of 5 cm −3 , using 1.4-GHz radio recombination lines in the Galactic plane.…”

Section: [N Ii] Linesmentioning

confidence: 99%

“…Therefore, the WIM component of them can be easily absorbed against background sources with high brightness temperatures. Using high-spectral-resolution observations from the HIFI instrument onboard Herschel, Persson et al (2014) detected absorption features of the [N II] 205-µm lines toward a few massive Galactic star-forming regions. They found that [N II] emission from ionised gas in the dense and hot H II regions is likely absorbed by widespread low-density and relatively lowtemperature WIM gas in the foreground.…”

Section: Absorptions To the Fine-structure Linesmentioning

confidence: 99%

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Far-infrared Herschel SPIRE spectroscopy of lensed starbursts reveals physical conditions of ionized gas

Zhang

Ivison

George

et al. 2018

Monthly Notices of the Royal Astronomical Society

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The most intensively star-forming galaxies are extremely luminous at far-infrared (FIR) wavelengths, highly obscured at optical and ultraviolet wavelengths, and lie at z ≥ 1-3. We present a programme of Herschel FIR spectroscopic observations with the SPIRE FTS and photometric observations with PACS, both on board Herschel, towards a sample of 45 gravitationally lensed, dusty starbursts across z ∼ 1-3.6. In total, we detected 27 individual lines down to 3-σ, including nine [C II] 158-µm lines with confirmed spectroscopic redshifts, five possible [C II] lines consistent with their far-infrared photometric redshifts, and in some individual sources a few [O III] 88-µm, [O III] 52-µm, [O I] 145-µm, [O I] 63-µm, [N II] 122-µm, and OH 119-µm (in absorption) lines. To derive the typical physical properties of the gas in the sample, we stack all spectra weighted by their intrinsic luminosity and by their 500-µm flux densities, with the spectra scaled to a common redshift. In the stacked spectra, we detect emission lines of [C II] 158-µm, [N II] 122-µm, [O III] 88-µm, [O III] 52-µm, [O I] 63-µm, and the absorption doublet of OH at 119-µm, at high fidelity. We find that the average electron densities traced by the [N II] and [O III] lines are higher than the average values in local star-forming galaxies and ULIRGs, using the same tracers. From the [N II]/[C II] and [O I]/[C II] ratios, we find that the [C II] emission is likely dominated by the photo-dominated regions (PDR), instead of by ionised gas or large-scale shocks.

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Section: [N Ii] Linesmentioning

confidence: 99%

Section: Absorptions To the Fine-structure Linesmentioning

confidence: 99%

Far-infrared Herschel SPIRE spectroscopy of lensed starbursts reveals physical conditions of ionized gas

Zhang

Ivison

George

et al. 2018

Monthly Notices of the Royal Astronomical Society

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“…5.5 below. The fractional contribution of WIM toward W31C is no more than 5%, based on the detection of N II absorption by Persson et al (2014), which leads to N(N + )/N(C + ) = 1/40, i.e., about twenty times lower than the [N]/[C] elemental abundance ratio in the gas.…”

Section: Locally Space-averaged Atomic Molecular and Total Densitiesmentioning

confidence: 99%

Molecular gas in absorption and emission along the line of sight to W31C G10.62-0.38

Liszt

Gérin

2015

A&A

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Context. The sightline to W31C G10.62-0.38 was extensively observed in absorption under the PRISMAS program on Herschel. Aims. We relate absorbing material to the older view of Galactic molecules gained from CO emission. Methods. We used the Arizona Radio Observatory Kitt Peak 12m antenna to observe emission from the J = 1−0 lines of carbon monoxide, HCO + , and HNC, and the J = 2−1 line of CS toward and around the continuum peak used for absorption studies and we compare them with CH, HNC, C + , and other absorption spectra from PRISMAS. We develop a kinematic analysis that allows a continuous description of the spectral properties and relates them to viewing geometry in the Galaxy. Results. As it is for CH, HF, C + , HCO + , and other species observed in absorption, mm-wave emission in CO, HCO + , HNC, and CS is continuous over the full velocity range expected for material between the Sun and W31 4.95 kpc away. CO emission is much stronger than average in the Galactic molecular ring and the mean H 2 density derived from CH, 4 cm −3 < ∼ 2 n(H 2 ) < ∼ 10 cm −3 at 4 < ∼ R < ∼ 6.4 kpc, is similarly elevated. The CO-H 2 conversion factor falls in a narrow range X CO = 1−2 × 10 20 H 2 cm −2 (K − km s −1 ) −1 if the emitting gas is mostly on the near side of the subcentral point, as we suggest. The brightnesses of HCO + , HNC, and CS are comparable (0.83%, 0.51%, and 1.1%, respectively, relative to CO) and have no variation in galactocentric radius with respect to CO. Comparison of the profile-averaged HCO + emission brightness and optical depth implies local densities n(H) ≈ 135 ± 25 cm −3 with most of the excitation of HCO + from electrons. At this level of density, a consistent picture of the H 2 -bearing gas, which also accounts for the CO emission, has a volume filling factor of 3% and a 5 pc clump or cloud size.

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“…However, COBE had a 7 • beam and velocity resolution ∼1000 km s −1 and so could not provide details of the distribution of C + and N + in the Milky Way, locate the emission along the line of sight (LOS), or explore the dynamics of the gas traced by [C ii] and [N ii]. The Heterodyne Instrument in the Far-Infrared (HIFI, de Graauw et al 2010) on the Herschel Space Observatory (Pilbratt et al 2010) provided the first opportunity to obtain a large sample of velocity resolved [C ii] and [N ii] in the Galaxy in emission (Langer et al 2010;Goldsmith et al 2015) and absorption (Persson et al 2014;Gerin et al 2015). The determination of the properties of the ionized gas in emission and absorption probe higher and lower density phases of the ISM, respectively.…”

Section: Introductionmentioning

confidence: 99%

[C II] and [N II] from dense ionized regions in the Galaxy

Langer

Goldsmith

Pineda

2016

A&A

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Context. The interstellar medium (ISM) consists of highly ionized and neutral atomic, as well as molecular, components. Knowledge of their distribution is important for tracing the structure and lifecycle of the ISM. Aims. To determine the properties of the highly ionized gas and neutral weakly ionized gas in the Galaxy traced by the fine-structure can be modeled to determine the true source intensity. In these sources we find that the foreground absorbing gas layer has C + column densities of order 10 18 cm −2 .Conclusions. [C ii] emission arising from strong sources of [N ii] emission is frequently absorbed by low excitation foreground gas complicating the interpretation of the properties of the ionized and neutral gas components that give rise to [C ii] emission.

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

Cited by 13 publications

References 42 publications

Far-infrared Herschel SPIRE spectroscopy of lensed starbursts reveals physical conditions of ionized gas

Far-infrared Herschel SPIRE spectroscopy of lensed starbursts reveals physical conditions of ionized gas

Molecular gas in absorption and emission along the line of sight to W31C G10.62-0.38

[C II] and [N II] from dense ionized regions in the Galaxy

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