A 205 μm [N II] MAP OF THE CARINA NEBULA

Oberst, Thomas E.; Parshley, Stephen C.; Nikola, Thomas; Stacey, G. J.; Lohr, Ashley; Lane, Alan M.; Stark, A. A.; Kamenetzky, J.

doi:10.1088/0004-637x/739/2/100

Cited by 59 publications

(102 citation statements)

References 71 publications

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“…The electron densities derived from the [N ii] emission, n(e) ∼ 5 to 25 cm −3 , are two to three orders of magnitude higher than that in the disk's warm ionized medium (WIM), but consistent with those found from analysis of [N ii] emission in the Carina nebula, a luminous H ii region with numerous O stars (Oberst et al 2011). This paper is organized as follows.…”

Section: Introductionsupporting

confidence: 77%

“…The densities we derive are much larger than those characteristic of the disk's WIM, but are consistent with those derived for very bright nebula with numerous luminous O-type stars. For example, Oberst et al (2011) studied the Carina nebula, which has a very large UV flux, using emission from the [N ii] 205 μm and 122 μm lines along with an excitation model 6 , and find values of n(e) ranging from a few to over 100 cm −3 . In the discussion below we will use the results from our analysis of [N ii] and [C ii] emission to characterize some of the possible energy sources that can maintain such a hot dense ionized plasma.…”

Section: Discussionmentioning

confidence: 99%

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Ionized gas at the edge of the central molecular zone

Langer

Goldsmith

Pineda

et al. 2015

A&A

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Context. The edge of the central molecular zone (CMZ) is the location where massive dense molecular clouds with large internal velocity dispersions transition to the surrounding more quiescent and lower CO emissivity region of the Galaxy. Little is known about the ionized gas surrounding the molecular clouds and in the transition region. Aims. We determine the properties of the ionized gas at the edge of the CMZ near Sgr E using observations of N + and C + .Methods. We observed a small portion of the edge of the CMZ near Sgr E with spectrally resolved [C ii] 158 μm and [N ii] 205 μm fine structure lines at six positions with the GREAT instrument on SOFIA and in [C ii] using Herschel HIFI on-the-fly strip maps. We use the [N ii] spectra along with a radiative transfer model to calculate the electron density of the gas and the [C ii] maps to illuminate the morphology of the ionized gas and model the column density of CO-dark H 2 .Results. We detect two [C ii] and [N ii] velocity components, one along the line of sight to a CO molecular cloud at −207 km s −1 associated with Sgr E and the other at −174 km s −1 outside the edge of another CO cloud. From the [N ii] emission we find that the average electron density is in the range of ∼5 to 21 cm −3 for these features. This electron density is much higher than that of the disk's warm ionized medium, but is consistent with densities determined for bright diffuse H ii nebula. The column density of the CO-dark H 2 layer in the −207 km s −1 cloud is ∼1−2× 10 21 cm −2 in agreement with theoretical models. The CMZ extends further out in Galactic radius by ∼7 to 14 pc in ionized gas than it does in molecular gas traced by CO. Conclusions. The edge of the CMZ likely contains dense hot ionized gas surrounding the neutral molecular material. The high fractional abundance of N + and high electron density require an intense EUV field with a photon flux of order 10 6 to 10 7 photons cm −2 s −1 , and/or efficient proton charge exchange with nitrogen, at temperatures of order 10 4 K, and/or a large flux of X-rays. Sgr E is a region of massive star formation as indicated by the presence of numerous compact H ii regions. The massive stars are potential sources of the EUV radiation that ionizes and heat the gas. In addition, X-ray sources and the diffuse X-ray emission in the CMZ are candidates for ionizing nitrogen.

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Section: Introductionsupporting

confidence: 77%

Section: Discussionmentioning

confidence: 99%

Ionized gas at the edge of the central molecular zone

Langer

Goldsmith

Pineda

et al. 2015

A&A

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“…10. For our sources and NGC 2023, the properties of the dense phases fall very near either of the relationships discussed, the dense component of M17 however falls well above even the matter bounded trend given by Oberst et al (2011) by several orders of magnitude, this may be due to the dense clumps being independently gravitationally bound or transient objects -that would therefore have much higher densities than would be expected for pure pressure equilibrium between the clumps and their surroundings. Overall it seems that the simpler sources with a dominant exciting star (e.g., IRAS 23133+6050, S 106, NGC 2023, S 125, S 140) agree well with the trends, while the much more complex sources (e.g., W49A, M17, W3) have much more variance.…”

Section: Referencesmentioning

confidence: 47%

“…10). Conversely, Oberst et al (2011) suggest that their best fit line represents systems which are density bounded as opposed to the ionization bounded RNe, and hence they found a different relationship. We have also included the H ii region PDR sources from Table 9 while the RNe sources in Table 9 form part of the Young Owl et al (2002) by at least an order of magnitude than predicted by either relationship.…”

Section: Referencesmentioning

confidence: 92%

“…Dashed and solid black lines: theoretical prediction for the relationship between radiation field and density for a pressure bound H ii region and the best fit to the Young Owl et al (2002) data. Green dot-dashed line: best fit to the Carina nebula data of Oberst et al (2011). For a selection of sources we have also included the points representing the dense PDR component (denoted "dc") as opposed to the default values representing the interclump medium (denoted "ic").…”

Section: Referencesmentioning

confidence: 99%

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HerschelPACS and SPIRE spectroscopy of the photodissociation regions associated with S 106 and IRAS 23133+6050

Stock

Wolfire

Peeters

et al. 2015

A&A

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Context. Photodissociation regions (PDRs) contain a large portion of all of the interstellar matter in galaxies. Classical examples include the boundaries between ionized regions and molecular clouds in regions of massive star-formation, marking the point where all of the photons that are energetic enough to ionize hydrogen have been absorbed. Aims. To determine the physical properties of the PDRs associated with the star-forming regions IRAS 23133+6050 and S 106 and present them in the context of other Galactic PDRs associated with massive star-forming regions. Methods. We employ Herschel PACS and SPIRE spectroscopic observations to construct a full 55-650 μm spectrum of each object from which we measure the PDR cooling lines, other fine-structure lines, CO lines, and the total far-infrared flux. These measurements (and combinations thereof) are then compared to standard PDR models. Subsequently, detailed numerical PDR models are compared to these predictions, yielding additional insight into the dominant thermal processes in the PDRs and their structures. Results. We find that the PDRs of each object are very similar and can be characterized by a two-phase PDR model with a very dense, highly UV irradiated phase (n ∼ 10 6 cm −3 , G 0 ∼ 10 5 ) interspersed within a lower density, weaker radiation field phase (n ∼ 10 4 cm −3 , G 0 ∼ 10 4 ). We employed two different numerical models to investigate the data. We first used RADEX models to fit the peak of the 12 CO ladder, which in conjunction with the properties derived, yielded a temperature of around 300 K. Subsequent numerical modeling with a full PDR model revealed that the dense phase has a filling factor of around 0.6 in both objects. The shape of the 12 CO ladder was consistent with these components, with heating dominated by grain photoelectric heating. An extra excitation component for the hightest-J lines (J > 20) is required for S 106.

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