A CS Survey of Massive Stars Embedded in Molecular Clouds

Bronfman, L.; May, J.; Nyman, L. A.; Thaddeus, P.

doi:10.1007/978-94-011-3384-5_4

Cited by 178 publications

(306 citation statements)

References 9 publications

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“…The presence of an envelope around the IRAS sources is confirmed by their association with high-density gas, and the existence of hot gas by the detection of a hot core and water or methanol masers (e.g. Bronfman et al 1996;Plume et al 1997). In this way, studies by e.g., Molinari et al (2000) and Sridharan et al (2002) have identified massive young stellar objects harboring highluminosity infrared protostars (see also Mueller et al 2002;Faúndez et al 2004).…”

mentioning

confidence: 83%

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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mentioning

confidence: 83%

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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“…However, the search for Class II methanol and hydroxyl masers yielded negative results (van der Walt, Gaylard & MacLeod 1995; Edris, Fuller & Cohen 2007). Several molecules like CS, HCO + , NH3, N2H + , CH3CCH have also been observed towards this region (Bronfman, Nyman & May 1996;Alakoz et al 2002;Shirley et al 2013;Lu et al 2014).…”

Section: Introductionmentioning

confidence: 99%

Radio and infrared study of the star-forming region IRAS 20286+4105

Ramachandran

Das

Tej

et al. 2016

Mon. Not. R. Astron. Soc.

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A multi-wavelength investigation of the star forming complex IRAS 20286+4105, located in the Cygnus-X region, is presented here. Near-infrared K-band data is used to revisit the cluster / stellar group identified in previous studies. The radio continuum observations, at 610 and 1280 MHz show the presence of a HII region possibly powered by a star of spectral type B0 -B0.5. The cometary morphology of the ionized region is explained by invoking the bow-shock model where the likely association with a nearby supernova remnant is also explored. A compact radio knot with non-thermal spectral index is detected towards the centre of the cloud. Mid-infrared data from the Spitzer Legacy Survey of the Cygnus-X region show the presence of six Class I YSOs inside the cloud. Thermal dust emission in this complex is modelled using Herschel far-infrared data to generate dust temperature and column density maps. Herschel images also show the presence of two clumps in this region, the masses of which are estimated to be ∼ 175 M and 30 M . The mass-radius relation and the surface density of the clumps do not qualify them as massive star forming sites. An overall picture of a runaway star ionizing the cloud and a triggered population of intermediate-mass, Class I sources located toward the cloud centre emerges from this multiwavelength study. Variation in the dust emissivity spectral index is shown to exist in this region and is seen to have an inverse relation with the dust temperature.

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“…There are only one core and an extend structure showed in the N2H + emission, but several cores are identified in other molecular emission. From IR emission, we find that it is probable a starless source associated with an UCHII region in its southeast (Bronfman et al 1996). According to the discussion of section 4.1, it may be an infall candidate.…”

Section: The MM and Infrared Emission In The Irdcsmentioning

confidence: 75%

“…Bronfman et al (1996) suggested that IRDC G341.942-00.167 is associated with an UCHII region. We also detect strong 24 µm and 8 µm emission in this cloud.…”

Section: The MM and Infrared Emission In The Irdcsmentioning

confidence: 99%

A systemic study of 14 southern infrared dark clouds with N2H+, HNC, HCO+ and HCN lines

Liu

Wang

2013

Monthly Notices of the Royal Astronomical Society

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We have studied 14 southern infrared dark clouds (IRDCs) using the data taken from the Millimetre Astronomy Legacy Team 90 GHz (MALT90) survey and the GLIMPSE and MIPSGAL mid-infrared survey of the inner Galaxy. The physical and chemical characteristics of the 14 IRDCs are investigated using N 2 H + (1-0), HNC(1-0), HCO + (1-0), and HCN(1-0) molecular lines. We find that the 14 IRDCs are in different evolutionary stages from the "starless" to the sources with an UCHII region. Three IRDCs are detected to have the star forming activities. The integrated intensity ratios I HCO + /HCN , I N2H + /HCN , and I HNC/HCN are all about 1.5, which is different from the previous measurements, suggesting that the integrated intensity ratios may be affected by the cloud environments. The integrated intensities of HNC, HCO + and HCN show a tight correlation for the 14 IRDCs, implying a close link to the chemical evolution of these three species in the IRDCs. The derived excitation temperature for each IRDC is less than 25 K. We estimate the abundances of the four molecules from 10 −11 to 10 −9 , and the average abundance ratios N HNC /N HCN = 1.47 ± 0.50, N HNC /N HCO + = 1.74 ± 0.22, N HCN /N HCO + = 1.21 ± 0.41.

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A CS Survey of Massive Stars Embedded in Molecular Clouds

Cited by 178 publications

References 9 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

Radio and infrared study of the star-forming region IRAS 20286+4105

A systemic study of 14 southern infrared dark clouds with N2H+, HNC, HCO+ and HCN lines

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