The Cygnus superbubble revisited

Uyanıker, B.; Fürst, E.; Reich, W.; Aschenbach, B.; Wielebinski, R.

doi:10.1051/0004-6361:20010387

Cited by 123 publications

(146 citation statements)

References 61 publications

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“…The Cygnus X molecular complex has already formed generations of high-mass stars, since it contains several OB associations (Uyaniker et al 2001) and numerous H ii regions (Wendker et al 1991). We here discuss its ability to form highmass stars in the near future by making a census of embedded H ii regions (Sect.…”

Section: The High Potential Of Cygnus X Dense Cores To Form Massive Smentioning

confidence: 99%

“…Table 5 gives our current estimates of the number of massive young stellar objects forming and stars already formed in Cygnus X. The number and age of OB stars in Cygnus X are taken to be those of the Cyg OB2 association (Knödlseder 2000;Hanson 2003), increasing uncertainties to take into account the other (smaller) OB associations which have different ages (Uyaniker et al 2001). The number of H ii regions is crudely given by the numbers of centimeter free-free sources observed in Cygnus X (Wendker et al 1991).…”

Section: Lifetime Of High-mass Protostarsmentioning

confidence: 99%

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The earliest phases of high-mass star formation: a 3 square degree millimeter continuum mapping of Cygnus X

Motte

Bontemps

Schilke

et al. 2007

A&A

327

722

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Aims. Our current knowledge of high-mass star formation is mainly based on follow-up studies of bright sources found by IRAS, and is thus biased against its earliest phases, inconspicuous at infrared wavelengths. We therefore started searching, in an unbiased way and in the closest high-mass star-forming complexes, for the high-mass analogs of low-mass pre-stellar cores and class 0 protostars. Methods. We have made an extensive 1.2 mm continuum mosaicing study of the Cygnus X molecular cloud complex using the MAMBO cameras at the IRAM 30 m telescope. The ∼ 3 • 2 imaged areas cover all the high-column density (A V ≥ 15 mag) clouds of this nearby (∼ 1.7 kpc) cloud complex actively forming OB stars. We then compared our millimeter maps with mid-infrared images, and have made SiO(2-1) follow-up observations of the best candidate progenitors of high-mass stars. Results. Our complete study of Cygnus X with ∼ 0.09 pc resolution provides, for the first time, an unbiased census of massive young stellar objects. We discover 129 massive dense cores (FWHM size ∼ 0.1 pc, M 1.2 mm = 4 − 950 M ⊙ , volume-averaged density ∼ 10 5 cm −3 ), among which ∼ 42 are probable precursors of high-mass stars. A large fraction of the Cygnus X dense cores (2/3 of the sample) remain undetected by the MSX satellite, regardless of the mass range considered. Among the most massive (> 40 M ⊙ ) cores, infrared-quiet objects are driving powerful outflows traced by SiO emission. Our study qualifies 17 cores as good candidates for hosting massive infrared-quiet protostars, while up to 25 cores potentially host high-luminosity infrared protostars. We fail to discover in the high-mass analogs of pre-stellar dense cores (∼ 0.1 pc, > 10 4 cm −3 ) in Cygnus X, but find several massive starless clumps (∼ 0.8 pc, 7 × 10 3 cm −3 ) that might be gravitationally bound. Conclusions. Since our sample is derived from a single molecular complex and covers every embedded phase of high-mass star formation, it gives the first statistical estimates of their lifetime. In contrast to what is found for low-mass class 0 and class I phases, the infrared-quiet protostellar phase of high-mass stars may last as long as their better-known high-luminosity infrared phase. The statistical lifetimes of high-mass protostars and pre-stellar cores (∼ 3 × 10 4 yr and < 10 3 yr) in Cygnus X are one and two order(s) of magnitude smaller, respectively, than what is found in nearby, low-mass star-forming regions. We therefore propose that high-mass pre-stellar and protostellar cores are in a highly dynamic state, as expected in a molecular cloud where turbulent processes dominate.

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Section: The High Potential Of Cygnus X Dense Cores To Form Massive Smentioning

confidence: 99%

Section: Lifetime Of High-mass Protostarsmentioning

confidence: 99%

The earliest phases of high-mass star formation: a 3 square degree millimeter continuum mapping of Cygnus X

Motte

Bontemps

Schilke

et al. 2007

A&A

327

722

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“…Hanson 2003). On the other hand, several studies locate DR15 at a lower distance, about 700-800 pc (Wendker et al 1991;Uyanıker et al 2001;Redman et al 2003).…”

Section: Critical Revision Of the Distancesmentioning

confidence: 99%

Ammonia observations in the LBV nebula G79.29+0.46

Rizzo

Palau

Jiménez-Esteban

et al. 2014

A&A

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Context. The surroundings of luminous blue variable (LBV) stars are excellent laboratories to study the effects of their high UV radiation, powerful winds, and strong ejection events onto the surrounding gas and dust. Aims. We aim at determining the physical parameters of the dense gas near G79.29+0.46, an LBV-candidate located at the centre of two concentric infrared rings, which may interact with the infrared dark cloud (IRDC) G79.3+0.3. Methods. The Effelsberg 100 m telescope was used to observe the NH 3 (1, 1) and (2, 2) emission in a field of view of 7 × 7 including the infrared rings and a part of the IRDC. In addition, we observed particular positions in the NH 3 (3,3) transition toward the strongest region of the IRDC, which is also closest to the ring nebula. Results. We report here the first coherent ring-like structure of dense NH 3 gas associated with an evolved massive star. It is well traced in both ammonia lines, surrounding an already known infrared ring nebula; its column density is two orders of magnitude lower than the IRDC. The NH 3 emission in the IRDC is characterized by a low and uniform rotational temperature (T rot ∼10 K) and moderately high opacities in the (1, 1) line. The rest of the observed field is spotted by warm or hot zones (T rot >30 K) and characterized by optically thin emission of the (1, 1) line. The NH 3 abundances are about 10 −8 in the IRDC, and 10 −10 -10 −9 elsewhere. The warm temperatures and low abundances of NH 3 in the ring suggest that the gas is being heated and photo-dissociated by the intense UV field of the LBV star. An outstanding region is found to the south-west (SW) of the LBV star within the IRDC. The NH 3 (3, 3) emission at the centre of the SW region reveals two velocity components tracing gas at temperatures >30 K. Of particular interest is the northern edge of the SW region, which coincides with the border of the ring nebula and a region of strong 6 cm continuum emission; here, the opacity of the (1, 1) line and the NH 3 abundance do not decrease as expected in a typical clump of an isolated cold dark cloud. This strongly suggests some kind of interaction between the ring nebula (powered by the LBV star) and the IRDC. We finally discuss the possibility of NH 3 evaporation from the dust grain mantles due to the already known presence of low-velocity shocks in the area. Conclusions. The detection of the NH 3 associated with this LBV ring nebula, as well as the special characteristics of the northern border of the SW region, confirm that the surroundings of G79.29+0.46 constitute an exemplary scenario, which merits to be studied in detail by other molecular tracers and higher angular resolutions.

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“…See Schneider et al (2006) or Reipurth & Schneider (2008) for a review on Cygnus X. The region also contains several OB clusters (Cyg OB1-4, 6, and 8) including the richest known OB cluster of the Galaxy, Cyg OB2 (Knödlseder 2000, Uyaniker et al 2001). Their energy injection from stellar winds and radiation could be a driving source for turbulence.…”

Section: Cygnus Xmentioning

confidence: 99%

The link between molecular cloud structure and turbulence

Schneider

Bontemps

Simon

et al. 2011

A&A

121

139

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Aims. We aim to better understand how the spatial structure of molecular clouds is governed by turbulence. For that, we study the large-scale spatial distribution of low-density molecular gas and search for characteristic length scales. Methods. We employ a 35 square degrees 13 CO 1→0 molecular line survey of Cygnus X and visual extinction (A V ) maps of 17 Galactic clouds to analyze the spatial structure with the Δ-variance method. This sample contains a large variety of different molecular cloud types with different star-forming activity.Results. The Δ-variance spectra obtained from the A V maps show differences between low-mass star-forming (SF) clouds and massive giant molecular clouds (GMC) in terms of shape of the spectrum and its power-law exponent β. Low-mass SF clouds have a double-peak structure with characteristic size scales around 1 pc (though with a large scatter around this value) and 4 pc. The GMCs show no characteristic scale in the A V -maps, which can partly be ascribed to a distance effect owing to a larger line-of-sight (LOS) confusion. The Δ-variance for Cygnus, determined from the 13 CO survey, shows characteristic scales at 4 pc and 40 pc, either reflecting the filament structure and large-scale turbulence forcing or -for the 4 pc scale -the scale below which the 13 CO 1→0 line becomes optically thick. Though there are different processes that can introduce characteristic scales, such as geometry, decaying turbulence, the transition scale from supersonic to subsonic turbulence (the sonic scale), line-of-sight effects and energy injection caused by expanding supernova shells, outflows, HII-regions, and although the relative contribution of these effects strongly varies from cloud to cloud, it is remarkable that the resulting turbulent structure of molecular clouds shows similar characteristics.

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The Cygnus superbubble revisited

Cited by 123 publications

References 61 publications

The earliest phases of high-mass star formation: a 3 square degree millimeter continuum mapping of Cygnus X

The earliest phases of high-mass star formation: a 3 square degree millimeter continuum mapping of Cygnus X

Ammonia observations in the LBV nebula G79.29+0.46

The link between molecular cloud structure and turbulence

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