Origin of diffuse C II 158 micron and Si II 35 micron emission in the Carina nebula

Mizutani, Manabu; Onaka, Takashi; Shibai, Hiroshi

doi:10.1051/0004-6361:20041063

Cited by 30 publications

(28 citation statements)

References 81 publications

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“…We have emphasized that the chemistry of our dust models is consistent with observed abundances in the CNO-processed nebula, supported by analysis of 12 CO and 13 CO lines that indicates a subsolar abundance ratio of CO/H 2 and an enhancement of 13 C. Some caution is needed about the isotopic abundance ratio, however, since chemical fractionation of carbon driven by the reaction 13 C + + CO  12 C + + 13 CO + 34.8 K can occur in dense photodissociation regions (PDRs; Langer et al 1984;Gerin et al 1998; (Mizutani et al 2004) formed at the interface between the HII region and molecular cloud mapped out in CO (Brooks et al 1998;Zhang et al 2001; see also Cox 1995;Smith et al 2000;Brooks et al 2003, for reviews of the large-scale structure of the Carina cloud). Our PACS spectroscopy shows significant emission in the vicinity of the Homunculus, the strongest being in the direct sightline.…”

Section: The Carbon Isotope Ratio and The Question Of C + In The Homusupporting

confidence: 76%

η Carinae's Dusty Homunculus Nebula from Near-infrared to Submillimeter Wavelengths: Mass, Composition, and Evidence for Fading Opacity

Morris

Gull

Hillier

et al. 2017

ApJ

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Infrared observations of the dusty, massive Homunculus Nebula around the luminous blue variable η Carinae are crucial to characterize the mass-loss history and help constrain the mechanisms leading to the great eruption. We present the 2.4-670 μm spectral energy distribution, constructed from legacy Infrared Space Observatory observations and new spectroscopy obtained with the Herschel Space Observatory. Using radiative transfer modeling, we find that the two best-fit dust models yield compositions that are consistent with CNO-processed material, with iron, pyroxene and other metal-rich silicates, corundum, and magnesium-iron sulfide in common. Spherical corundum grains are supported by the good match to a narrow 20.2 μm feature. Our preferred model contains nitrides AlN and Si 3 N 4 in low abundances. Dust masses range from 0.25 to 0.44tot in both cases, due to an expected high Fe gas-to-dust ratio. The bulk of dust is within a ´ 5 7 central region. An additional compact feature is detected at 390 μm. We obtain L IR = 2.96×10 6  L , a 25% decline from an average of mid-IR photometric levels observed in 1971-1977. This indicates a reduction in circumstellar extinction in conjunction with an increase in visual brightness, allowing 25%-40% of optical and UV radiation to escape from the central source. We also present an analysis of 12 CO and 13 CO J=5-4 through 9-8 lines, showing that the abundances are consistent with expectations for CNO-processed material. The [ 12 C II] line is detected in absorption, which we suspect originates in foreground material at very low excitation temperatures.

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Section: The Carbon Isotope Ratio and The Question Of C + In The Homusupporting

confidence: 76%

η Carinae's Dusty Homunculus Nebula from Near-infrared to Submillimeter Wavelengths: Mass, Composition, and Evidence for Fading Opacity

Morris

Gull

Hillier

et al. 2017

ApJ

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“…Since the [C II] 158 μm/[N II] 122 μm ratio largely depends on the electron density, 16−91% of the observed [C II] intensity comes from the ionized gas for the range of n e = 16−977 cm −3 . The contribution of the ionized gas to the [C II] 158 μm emission has been investigated in some star-forming regions: 27% or 20 ± 10% in the Carina nebula (Oberst et al 2006;Mizutani et al 2004), 20−70% in S171 (Okada et al 2003), and 30−80% in the σ Sco region (Okada et al 2006). Model calculations indicate that it is at least 10% and up to 50−60% according to Abel (2006), and ∼10% for Kaufman et al (2006).…”

Section: Resultsmentioning

confidence: 99%

Properties of active galactic star-forming regions probed by imaging spectroscopy with the Fourier transform spectrometer (FTS) onboard AKARI

Okada

Kawada

Murakami

et al. 2010

A&A

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Aims. We investigate the structure of the interstellar medium (ISM) and identify the location of possible embedded excitation sources from far-infrared (FIR) line and mid-infrared continuum emission maps. Methods. We carried out imaging spectroscopic observations of four giant Galactic star-forming regions with the Fourier transform spectrometer (FTS) onboard AKARI. We obtained [O III] 88 μm and [C II] 158 μm line intensity maps of all the regions: G3.270-0.101, G333.6-0.2, NGC 3603, and M 17. Results. For G3.270-0.101, we obtained high-spatial-resolution [O III] 88 μm line-emission maps and a FIR continuum map for the first time, which imply that [O III] 88 μm emission identifies the excitation sources more clearly than the radio continuum emission. In G333.6-0.2, we found a local [O III] 88 μm emission peak, which is indicative of an excitation source. This is supported by the 18 μm continuum emission, which is considered to trace the hot dust distribution. For all regions, the [C II] 158 μm emission is distributed widely as suggested by previous observations of star-forming regions. Conclusions. We conclude that [O III] 88 μm emission traces the excitation sources more accurately than the radio continuum emission, especially where there is a high density and/or column density gradient. The FIR spectroscopy provides a promising means of understanding the nature of star-forming regions.

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“…Although great strides have been made in understanding heating and cooling in nearby galaxies with the best techniques and spatial resolution available (Brauher et al 2008;Rubin et al 2009), the use of global values can make it difficult to ensure that emission averaged together arises from similar physical environments. Contursi et al (2002) noted that the integrated far-IR emission measured in global studies appears to be dictated by relatively few active regions that dominate the signal within the beam, whereas Mizutani et al (2004) showed that overlapping photodissociation regions (PDRs) within an aperture lead to discrepant far-IR diagnostics. It has also been shown that the observed [C ii] line deficit is increased if emission that does not originate from the dense gas around massive stars (e.g., non-PDR emission) is present (Luhman et al 2003).…”

Section: Heating the Ismmentioning

confidence: 99%

Resolving the Far-Ir Line Deficit: Photoelectric Heating and Far-Ir Line Cooling in NGC 1097 and NGC 4559

Croxall

Smith

Wolfire

et al. 2012

ApJ

108

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The physical state of interstellar gas and dust is dependent on the processes which heat and cool this medium. To probe heating and cooling of the interstellar medium over a large range of infrared surface brightness, on sub-kiloparsec scales, we employ line maps of [C ii] /PAH drops rapidly to 4%. We derived representative values of the local ultraviolet radiation density, G 0 , and the gas density, n H , by comparing our observations to models of photodissociation regions. The ratio G 0 /n H , derived from fine-structure lines, is found to correlate with the mean dust-weighted starlight intensity, U , derived from models of the IR spectral energy distribution. Emission from regions that exhibit a line deficit is characterized by an intense radiation field, indicating that small grains are susceptible to ionization effects. We note that there is a shift in the 7.7/11.3 μm PAH ratio in regions that exhibit a deficit in ([C ii] + [O i])/PAH, suggesting that small grains are ionized in these environments.

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Origin of diffuse C II 158 micron and Si II 35 micron emission in the Carina nebula

Abstract: 122 µm is about 8 and Si of about 50% of the solar abundance relative to N should be present in the gas phase. The present results suggest that efficient dust destruction takes place and a large fraction of Si returns to the gas in the Carina star-forming region.

Cited by 30 publications

References 81 publications

η Carinae's Dusty Homunculus Nebula from Near-infrared to Submillimeter Wavelengths: Mass, Composition, and Evidence for Fading Opacity

η Carinae's Dusty Homunculus Nebula from Near-infrared to Submillimeter Wavelengths: Mass, Composition, and Evidence for Fading Opacity

Properties of active galactic star-forming regions probed by imaging spectroscopy with the Fourier transform spectrometer (FTS) onboard AKARI

Resolving the Far-Ir Line Deficit: Photoelectric Heating and Far-Ir Line Cooling in NGC 1097 and NGC 4559

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