THE QUaD GALACTIC PLANE SURVEY. II. A COMPACT SOURCE
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Culverhouse, T.; Bock, J. J.; Bowden, M.; Brown, Michael L.; Cahill, G.; Castro, Paulo Francisco de; Church, S.; Friedman, Robert; Ganga, K.; Gear, Walter Kieran; Gupta, S.; Hinderks, J.; Kovac, J. M.; Lange, A. E.; Leitch, E. M.; Melhuish, S. J.; Memari, Y.; Murphy, John A.; Orlando, A.; Pryke, C.; Schwarz, R.; O'Sullivan, Créidhe M.; Piccirillo, L.; Rajguru, N.; Rusholme, B.; Taylor, Andy; Thompson, K. L.; Turner, A. H.; Wu, Emily; Zemcov, Michael

doi:10.1088/0067-0049/195/1/8

Cited by 25 publications

(23 citation statements)

References 48 publications

(84 reference statements)

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“…However, as it shows mid-infrared emission, it has been classified as an infrared bright source in König et al (2017). Based on radio observations, Culverhouse et al (2011) find a spectral index consistent with the criteria for UCHII regions from Wood & Churchwell (1989), suggesting that it hosts already formed highmass star(s). Nevertheless, consistently with its low L bol /M, we find a relatively high X(OD), suggesting that the bulk of the gas is chemically young and has not yet been strongly impacted by the star formation process.…”

Section: Decreasing Od Abundance Towards the More Evolved Sourcesmentioning

confidence: 74%

SOFIA/GREAT observations of OD and OH rotational lines towards high-mass star forming regions

Csengeri

Wyrowski

Menten

et al. 2022

A&A

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Context. Only recently, OD, the deuterated isotopolog of hydroxyl, OH, has become accessible in the interstellar medium; spectral lines from both species have been observed in the supra-Terahertz and far infrared regime. Studying variations of the OD/OH abundance amongst different types of sources can deliver key information on the formation of water, H2O. Aims. With observations of rotational lines of OD and OH towards 13 Galactic high-mass star forming regions, we aim to constrain the OD abundance and infer the deuterium fractionation of OH in their molecular envelopes. For the best studied source in our sample, G34.26+0.15, we were able to perform detailed radiative transfer modelling to investigate the OD abundance profile in its inner envelope. Methods. We used the Stratospheric Observatory for Infrared Astronomy (SOFIA) to observe the 2Π3∕2 J = 5∕2−3∕2 ground-state transition of OD at 1.3 THz (215 μm) and the rotationally excited OH line at 1.84 THz (163 μm). We also used published high-spectral-resolution SOFIA data of the OH ground-state transition at 2.51 THz (119.3 μm). Results. Absorption from the 2Π3∕2 OD J = 5∕2−3∕2 ground-state transition is prevalent in the dense clumps surrounding active sites of high-mass star formation. Our modelling suggests that part of the absorption arises from the denser inner parts, while the bulk of it as seen with SOFIA originates in the outer, cold layers of the envelope for which our constraints on the molecular abundance suggest a strong enhancement in deuterium fractionation. We find a weak negative correlation between the OD abundance and the bolometric luminosity to mass ratio, an evolutionary indicator, suggesting a slow decrease of OD abundance with time. A comparison with HDO shows a similarly high deuterium fractionation for the two species in the cold envelopes, which is of the order of 0.48% for the best studied source, G34.26+0.15. Conclusions. Our results are consistent with chemical models that favour rapid exchange reactions to form OD in the dense cold gas. Constraints on the OD/OH ratio in the inner envelope could further elucidate the water and oxygen chemistry near young high-mass stars.

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Section: Decreasing Od Abundance Towards the More Evolved Sourcesmentioning

confidence: 74%

SOFIA/GREAT observations of OD and OH rotational lines towards high-mass star forming regions

Csengeri

Wyrowski

Menten

et al. 2022

A&A

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“…Thus the 2 mm emission effectively sets an upper limit on the free-free at longer wavelengths which is sufficiently low to alleviate the concern that free-free emission may contribute to the flatness of the NTF radio spectrum (Yusef-Zadeh 2003). Dominance by nonthermal synchrotron emission at 2 mm is also supported by the finding that the Radio Arc filaments are one of the few polarized regions in low resolution 2 and 3 mm observations of the Galactic Center (Culverhouse et al 2011). Furthermore, since our measurements are made using local background subtraction along the filament, any diffuse free-free emission should not contribute to measured brightness unless the emitting gas is also highly confined to the same flux tube.…”

Section: Emission From the Radio Arc Ntfmentioning

confidence: 83%

2 mm GISMO Observations of the Galactic Center. II. A Nonthermal Filament in the Radio Arc and Compact Sources*

Staguhn

Arendt²,

Dwek³

et al. 2019

ApJ

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We have used the Goddard IRAM 2-Millimeter Observer (GISMO) with the 30 m IRAM telescope to carry out a 2 mm survey of the Galaxy's central molecular zone (CMZ). These observations detect thermal emission from cold ISM dust, thermal free-free emission from ionized gas, and nonthermal synchrotron emission from relatively flat-spectrum sources. Archival data sets spanning 3.6 µm to 90 cm are used to distinguish different emission mechanisms. After the thermal emission of dust is modeled and subtracted, the remaining 2 mm emission is dominated by free-free emission, with the exception of the brightest nonthermal filament (NTF) that runs though the middle of the bundle of filaments known as the Radio Arc. This is the shortest wavelength at which any NTF has been detected. The GISMO observations clearly trace this NTF over a length of ∼ 0.2 • , with a mean 2 mm spectral index which is steeper than at longer wavelengths. The 2 mm to 6 cm (or 20 cm) spectral index steepens from α ≈ −0.2 to −0.7 as a function distance from the Sickle H II region, suggesting that this region is directly related to the NTF. A number of unresolved (at 21 ′′ ) 2 mm sources are found nearby. One appears to be thermal dust emission from a molecular cloud that is associated with an enigmatic radio point source whose connection to the Radio Arc is still debated. The morphology and colors at shorter IR wavelengths indicate other 2 mm unresolved sources are likely to be compact H II regions. Junellie.Gonzalez-Quiles@nasa.gov * Based on observations carried out with the IRAM 30 m Telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain).

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“…Zhang et al 2019), it is actively forming stars and embedding a SN remnant (Duncan et al 1996) and several HII regions (e.g. Haverkorn et al 2006;Culverhouse et al 2011). As SNe feedback appears to be the main mechanism responsible for filament dissipation (see simulations by Smith et al 2020), this structure might be transient in nature.…”

Section: Discussionmentioning

confidence: 99%

OGHReS: Large-scale filaments in the outer Galaxy

Colombo

König

Urquhart

et al. 2021

A&A

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Filaments are a ubiquitous morphological feature of the molecular interstellar medium and are identified as sites of star formation. In recent years, more than 100 large-scale filaments (with a length > 10 pc) have been observed in the inner Milky Way. As they appear linked to Galactic dynamics, studying those structures represents an opportunity to link kiloparsec-scale phenomena to the physics of star formation, which operates on much smaller scales. In this Letter, we use newly acquired Outer Galaxy High Resolution Survey (OGHReS) 12CO(2-1) data to demonstrate that a significant number of large-scale filaments are present in the outer Galaxy as well. The 37 filaments identified appear tightly associated with inter-arm regions. In addition, their masses and linear masses are, on average, one order of magnitude lower than similar-sized molecular filaments located in the inner Galaxy, showing that Milky Way dynamics is able to create very elongated features in spite of the lower gas supply in the Galactic outskirts.

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THE QUaD GALACTIC PLANE SURVEY. II. A COMPACT SOURCE CATALOG

Cited by 25 publications

References 48 publications

SOFIA/GREAT observations of OD and OH rotational lines towards high-mass star forming regions

SOFIA/GREAT observations of OD and OH rotational lines towards high-mass star forming regions

2 mm GISMO Observations of the Galactic Center. II. A Nonthermal Filament in the Radio Arc and Compact Sources*

OGHReS: Large-scale filaments in the outer Galaxy

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