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

Ossenkopf, V.; Ormel, Chris W.; Simon, R.; Sun, K.; Stützki, J.

doi:10.1051/0004-6361/200810611

Cited by 4 publications

(6 citation statements)

References 28 publications

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“…In contrast to that, the largest ratio of atomic carbon to CO we find is ∼12% in IRDC 18454 whereas the ratio is lower in the other regions going down to values of ∼7% in the most quiescent region G11.11 ( §2). A similar value of 8% was also found in the lower-spatial-resolution [CI]/ 13 CO study of the G48.66 region by Ossenkopf et al (2011). Although our sample of four regions is too small to derive firm conclusions, we do see a trend of increasing atomic-to-molecular gas ratio from the earliest, most quiescent infrared dark and starless clouds to regions that are in a more evolved environments with radiation sources nearby, e.g.,the high-mass protostellar object IRAS 18223-1243 at the northern end of the IRDC 18223 or the W43 mini-starburst near IRDC 18454.…”

Section: Carbon Phasessupporting

confidence: 87%

“…The [CI] map exhibits even larger differences with more emission in east-west extension in the southern part of the map. These spatial substructures could not be identified by the previous lowerspatial-resolution [CI] observations by Ossenkopf et al (2011) but are consistent with the two peaks of emission seen there. The biggest difference arises in the ionized carbon [CII] map.…”

Section: G4866supporting

confidence: 70%

“…We selected four infrared dark clouds that exhibit a variety of environments. While G11.11 (also know as The Snake, e.g., Henning et al 2010;Kainulainen et al 2013) and G48.66 (e.g., Ossenkopf et al 2011;Pitann et al 2013) are rather isolated IRDCs (G48.66 shows slightly more star formation activity), IRDC 18223 is an infrared dark filament that has already formed a high-mass protostellar object with ∼ 10 4 L at one end (e.g., Beuther et al 2010). Finally, IRDC 18454 is also a starless dark cloud, however in the very close environment of the Galactic mini-starburst W43 .…”

Section: The Samplementioning

confidence: 99%

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Carbon in different phases ([CII], [CI], and CO) in infrared dark clouds: Cloud formation signatures and carbon gas fractions

Beuther

Ragan

Ossenkopf

et al. 2014

A&A

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Context. How molecular clouds form out of the atomic phase and what the relative fractions of carbon are in the ionized, atomic, and molecular phase are questions at the heart of cloud and star formation. Aims. We want to understand the kinematic processes of gas flows during the formation of molecular clouds. In addition to that, we aim at determining the abundance ratios of carbon in its various gas phases from the ionized to the molecular form. Methods. Using multiple observatories from Herschel and SOFIA to APEX and the IRAM 30 m telescope, we mapped the ionized and atomic carbon as well as carbon monoxide ([CII] at 1900 GHz, [CI] at 492 GHz, and C 18 O(2-1) at 220 GHz) at high spatial resolution (12 − 25 ) in four young massive infrared dark clouds (IRDCs).Results. The three carbon phases were successfully mapped in all four regions, only in one source does the [CII] line remain a nondetection. With these data, we dissect the spatial and kinematic structure of the four IRDCs and determine the abundances of gas phase carbon in its ionized, atomic, and most abundant molecular form (CO). Both the molecular and atomic phases trace the dense structures well, with [CI] also tracing material at lower column densities.[CII] exhibits diverse morphologies in our sample from compact to diffuse structures, probing the cloud environment. In at least two out of the four regions, we find kinematic signatures strongly indicating that the dense gas filaments have formed out of a dynamically active and turbulent atomic and molecular cloud, potentially from converging gas flows. The atomic carbon-to-CO gas mass ratios are low between 7% and 12% with the lowest values found toward the most quiescent region. In the three regions where [CII] is detected, its mass is always higher by a factor of a few than that of the atomic carbon. While the ionized carbon emission depends on the radiation field, we also find additional signatures that indicate that other processes, for example, energetic gas flows can contribute to the [CII] excitation as well.Conclusions. Combining high-resolution maps in the different carbon phases reveals the dynamic interplay of the various phases of the interstellar medium during cloud formation. Extending these studies to more evolved stages and combining the observations with molecular cloud formation simulations including the chemistry and radiative transfer will significantly improve our understanding of the general interstellar medium, cloud and star formation processes.

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Section: Carbon Phasessupporting

confidence: 87%

Section: G4866supporting

confidence: 70%

Section: The Samplementioning

confidence: 99%

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Carbon in different phases ([CII], [CI], and CO) in infrared dark clouds: Cloud formation signatures and carbon gas fractions

Beuther

Ragan

Ossenkopf

et al. 2014

A&A

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“…The majority of these objects belong to "Stage I", referring to the classification scheme of Robitaille et al (2006), and have low to intermediate masses. From a comparison of [CI] and 13 CO data, Ossenkopf et al (2011) inferred the presence of a young photodissociation region (PDR) ionized by the YSOs inside of G48.…”

mentioning

confidence: 99%

G048.66–0.29: Physical State of an Isolated Site of Massive Star Formation

Pitann

Linz

Ragan

et al. 2013

ApJ

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We present continuum observations of the infrared dark cloud (IRDC) G48.660.22 (G48) obtained with Herschel, Spitzer, and APEX, in addition to several molecular line observations. The Herschel maps are used to derive temperature and column density maps of G48 using a model based on a modified blackbody. We find that G48 has a relatively simple structure and is relatively isolated; thus this IRDC provides an excellent target to study the collapse and fragmentation of a filamentary structure in the absence of complicating factors such as strong external feedback. The derived temperature structure of G48 is clearly non-isothermal from cloud to core scale. The column density peaks are spatially coincident with the lowest temperatures (∼ 17.5 K) in G48. A total cloud mass of ∼ 390M is derived from the column density maps. By comparing the luminosity-to-mass ratio of 13 point sources detected in the Herschel /PACS bands to evolutionary models, we find that two cores are likely to evolve into high-mass stars (M ≥ 8 M ). The derived mean projected separation of point sources is smaller than in other IRDCs but in good agreement with theoretical predications for cylindrical collapse. We detect several molecular species such as CO, HCO + , HCN, HNC and N 2 H + . CO is depleted by a factor of ∼ 3.5 compared to the expected interstellar abundance, from which we conclude that CO freezes out in the central region. Furthermore, the molecular clumps, associated with the sub-millimeter peaks in G48, appear to be gravitationally unbound or just pressure confined. The analysis of critical line masses in G48 show that the entire filament is collapsing, overcoming any internal support.

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“…Previous atomic carbon fine structure line studies typically covered only comparably small areas not extending far into the more diffuse cloud envelope structures (e.g., Keene 1995;Schilke et al 1995;Ossenkopf et al 2011). In an attempt to study the early evolutionary stages of high-mass star formation, we investigated four IRDCs in ionized, atomic, and molecular carbon (Beuther et al 2014).…”

Section: Introductionmentioning

confidence: 99%

Dynamical cloud formation traced by atomic and molecular gas

Beuther

Wang

Soler

et al. 2020

A&A

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Context. Atomic and molecular cloud formation is a dynamical process. However, kinematic signatures of these processes are still observationally poorly constrained. Aims. We identify and characterize the cloud formation signatures in atomic and molecular gas. Methods. Targeting the cloud-scale environment of the prototypical infrared dark cloud G28.3, we employed spectral line imaging observations of the two atomic lines HI and [CI] as well as molecular lines observations in 13CO in the 1–0 and 3–2 transitions. The analysis comprises investigations of the kinematic properties of the different tracers, estimates of the mass flow rates, velocity structure functions, a histogram of oriented gradients (HOG) study, and comparisons to simulations. Results. The central infrared dark cloud (IRDC) is embedded in a more diffuse envelope of cold neutral medium traced by HI self-absorption and molecular gas. The spectral line data as well as the HOG and structure function analysis indicate a possible kinematic decoupling of the HI from the other gas compounds. Spectral analysis and position–velocity diagrams reveal two velocity components that converge at the position of the IRDC. Estimated mass flow rates appear rather constant from the cloud edge toward the center. The velocity structure function analysis is consistent with gas flows being dominated by the formation of hierarchical structures. Conclusions. The observations and analysis are consistent with a picture where the IRDC G28.3 is formed at the center of two converging gas flows. While the approximately constant mass flow rates are consistent with a self-similar, gravitationally driven collapse of the cloud, external compression (e.g., via spiral arm shocks or supernova explosions) cannot be excluded yet. Future investigations should aim at differentiating the origin of such converging gas flows.

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

Cited by 4 publications

References 28 publications

Carbon in different phases ([CII], [CI], and CO) in infrared dark clouds: Cloud formation signatures and carbon gas fractions

Carbon in different phases ([CII], [CI], and CO) in infrared dark clouds: Cloud formation signatures and carbon gas fractions

G048.66–0.29: Physical State of an Isolated Site of Massive Star Formation

Dynamical cloud formation traced by atomic and molecular gas

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