The CI/CO/ ratio in the molecular cloud G 34.3 + 0.2

Little, L. T.; Gibb, A. G.; Heaton, B. D.; Ellison, Brian N.; Claude, S.

doi:10.1093/mnras/271.3.649

Cited by 19 publications

(18 citation statements)

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“…All numbers are summarised in Table 1. We find C i/CO abundance ratios between 0.07 and 0.13. The C i/CO abundance ratio previously measured in star-forming regions covers the range between about 0.03 and 3 2 (Mookerjea et al 2006;Little et al 1994;Sun et al 2008). The values found for G48.65-0.29 are found at the lower end of this range and this is consistent with the picture of atomic carbon being produced by star-formation processes in which more quiescent clouds, without internal UV fields, show lower C i/CO ratios than more evolved, active star-forming sites.…”

Section: Discussionmentioning

confidence: 88%

Spectroscopic [C i] mapping of the infrared dark cloud G48.65-0.29

Ossenkopf

Ormel

Simon

et al. 2010

A&A

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Aims. We report the first spectroscopic mapping of an atomic carbon line in an infrared dark cloud (IRDC). By observing the spatial distribution of the [C i] emission in an IRDC, comparing it with the 13 CO emission and the known distribution of internal heating sources, we can quantify the role of internal and external UV irradiation in the production of atomic carbon.Methods. We used the 2 × 4 pixel SMART receiver of the KOSMA observatory on Gornergrat to map the [C i] 3 P 1 − 3 P 0 line in the IRDC G48.65-0.29 and compared the resulting spectra with data from the BU-FCRAO 13 CO 1-0 Galactic Ring Survey.Results. The [C i]/ 13 CO effective beam temperature ratio falls at about 0.3 with local deviations by less than a factor two. All velocity components seen in 13 CO are also detected in [C i]. We find, however, significant differences in the morphology of the brightest regions seen in the two tracers. While 13 CO basically follows the column density distribution derived from the near-infrared (NIR) extinction and the submm continuum, the [C i] emission peaks at the locations of the two known NIR point sources. We find C i/CO abundance ratios between 0.07 and 0.13 matching the lower end of the range previously measured in star-forming regions. Conclusions. Evaluating the relative importance of the irradiation by embedded sources and by the Galactic interstellar UV field, we find that in G48.65-0.29 most [C i] emission can be attributed to externally illuminated surfaces. Embedded sources have a significant impact on the overall abundance distribution of atomic carbon as soon as they are found in an evolved state with noticeable NIR flux.

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Section: Discussionmentioning

confidence: 88%

Spectroscopic [C i] mapping of the infrared dark cloud G48.65-0.29

Ossenkopf

Ormel

Simon

et al. 2010

A&A

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“…For all sources, except G34.26+0.15, the virial masses coincide with the masses derived from 13 CO column densities within a factor of two. The comparison of the intensities of the 13 CO and C 18 O lines in G34.26+0.15, presented in Little et al (1994), leads to the conclusion that the 13 CO lines are not optically thin. Hence, the derived 13 CO column density and mass of this source are underestimated.…”

Section: Source Parameters Derived From the Mapsmentioning

confidence: 92%

Parameters of warm molecular clouds from methyl acetylene observations

et al. 2002

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Abstract. The results of a survey of 63 galactic star-forming regions in the 6K − 5K and 5K − 4K methyl acetylene lines at 102 and 85 GHz, respectively, are presented. Fourty-three sources were detected at 102 GHz, and twentyfive at 85 GHz. Emission was detected towards molecular clouds with kinetic temperatures 20-60 K (so-called "warm clouds"). The CH3CCH abundances in these clouds appeared to be about several units × 10 −9 . Five mapped sources were analyzed using the maximum entropy method. The sizes of the mapped clouds fall within the range between 0.1 and 1.7 pc, virial masses -between 90 -6200 M , and densities -between 6 × 10 4 and 6 × 10 5 cm −3 . The CH3CCH sources spatially coincide with the CO and CS sources. Chemical evolution simulations showed that the typical methyl acetylene abundance in the observed clouds corresponds to an age of ≈ 6 × 10 4 years.

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“…Bergin et al, 2004;Glover & Mac Low, 2007b). The assumption of one-dimensional symmetry, although computationally convenient, is less easy to justify, as the resulting models are unable to explain some notable features of real molecular clouds such as the widespread distribution of atomic carbon (Frerking et al, 1989;Little et al, 1994;Schilke et al, 1995). Accounting for clumping within the cloud greatly alleviates this issue (see e.g.…”

Section: Formation Of Molecular Cloudsmentioning

confidence: 99%

Physical Processes in the Interstellar Medium

Klessen

Glover

2015

Saas-Fee Advanced Course

170

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Interstellar space is filled with a dilute mixture of charged particles, atoms, molecules and dust grains, called the interstellar medium (ISM). Understanding its physical properties and dynamical behavior is of pivotal importance to many areas of astronomy and astrophysics. Galaxy formation and evolution, the formation of stars, cosmic nucleosynthesis, the origin of large complex, prebiotic molecules and the abundance, structure and growth of dust grains which constitute the fundamental building blocks of planets, all these processes are intimately coupled to the physics of the interstellar medium. However, despite its importance, its structure and evolution is still not fully understood. Observations reveal that the interstellar medium is highly turbulent, consists of different chemical phases, and is characterized by complex structure on all resolvable spatial and temporal scales. Our current numerical and theoretical models describe it as a strongly coupled system that is far from equilibrium and where the different components are intricately linked together by complex feedback loops. Describing the interstellar medium is truly a multi-scale and multi-physics problem. In these lecture notes we introduce the microphysics necessary to better understand the interstellar medium. We review the relations between large-scale and small-scale dynamics, we consider turbulence as one of the key drivers of galactic evolution, and we review the physical processes that lead to the formation of dense molecular clouds and that govern stellar birth in their interior.

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The CI/CO/ ratio in the molecular cloud G 34.3 + 0.2

Cited by 19 publications

References 0 publications

Spectroscopic [C i] mapping of the infrared dark cloud G48.65-0.29

Spectroscopic [C i] mapping of the infrared dark cloud G48.65-0.29

Parameters of warm molecular clouds from methyl acetylene observations

Physical Processes in the Interstellar Medium

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