The earliest phases of high-mass star formation: the NGC 6334-NGC 6357 complex

Russeil, D.; Zavagno, A.; Motte, F.; Schneider, N.; Bontemps, Sylvain; Walsh, A. J.

doi:10.1051/0004-6361/200913632

Cited by 75 publications

(156 citation statements)

References 91 publications

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“…Integrating the estimated star formation rate in the Galactic disk (McKee & Williams 1997) within a volume of a 3 kpc radius suggests a star formation rate of ∼0.2 M /yr in the selected molecular cloud complexes. With such an estimate, and assuming a standard initial mass function (Kroupa 2001) and a lifetime of 1 × 10 5 yr (Motte et al 2007;Russeil et al 2010), the HOBYS survey should reveal about 250 high-mass protostars (from IR-quiet to IR-bright).…”

Section: Discussionmentioning

confidence: 99%

“…Given their high densities (∼10 5 cm −3 ) and cooler temperatures, they probably are gravitationally bound and represent the highmass analog of low-mass prestellar cores. These three objects are among the first massive prestellar cores, since virtually none have been detected in surveys of the Cygnus X and NGC 6334 complexes (Motte et al 2007;Russeil et al 2010).…”

Section: Discovery Of Intermediate-/high-mass Prestellar Coresmentioning

confidence: 99%

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Initial highlights of the HOBYS key program, theHerschelimaging survey of OB young stellar objects

Motte¹,

Zavagno²,

Bontemps³

et al. 2010

A&A

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We present the initial highlights of the HOBYS key program, which are based on Herschel images of the Rosette molecular complex and maps of the RCW120 H ii region. Using both SPIRE at 250/350/500 μm and PACS at 70/160 μm or 100/160 μm, the HOBYS survey provides an unbiased and complete census of intermediate-to high-mass young stellar objects, some of which are not detected by Spitzer. Key core properties, such as bolometric luminosity and mass (as derived from spectral energy distributions), are used to constrain their evolutionary stages. We identify a handful of high-mass prestellar cores and show that their lifetimes could be shorter in the Rosette molecular complex than in nearby low-mass star-forming regions. We also quantify the impact of expanding H ii regions on the star formation process acting in both Rosette and RCW 120.

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Section: Discussionmentioning

confidence: 99%

Section: Discovery Of Intermediate-/high-mass Prestellar Coresmentioning

confidence: 99%

Initial highlights of the HOBYS key program, theHerschelimaging survey of OB young stellar objects

Motte¹,

Zavagno²,

Bontemps³

et al. 2010

A&A

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192

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“…In Russeil et al (2010), we presented a census of highmass young stellar objects at various evolutionary stages: we identified 1 starless clump, 6 IR-quiet protostars, and 9 highluminosity IR protostars in NGC 6334-NGC 6357. Since the timescale of the high-mass young objects cannot be derived directly, a statistical method was used.…”

Section: The Ob Stars Censusmentioning

confidence: 99%

“…The extinction map and the morphology of the 1.2 mm cold dust emission seem to indicate that NGC 6334 and NGC 6357 are connected by a filamentary structure, suggesting that both regions belong to a single complex (Russeil et al 2010).…”

Section: Introductionmentioning

confidence: 98%

Statistical study of OB stars in NGC 6334 and NGC 6357

Russeil

Zavagno

Adami

et al. 2012

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Context. Star-forming complexes are large structures exhibiting massive star-formation at different stages of evolution, from dense cores to well-developed H ii regions. They are very interesting for the study of the formation and evolution of stars. NGC 6334 and NGC 6357 are two active and relatively nearby star-forming complexes. From the extinction map and the sub-mm cold dust emission, and because they have similar velocities, these regions are most likely connected. However, located in the direction of the Galactic center their radial velocity is not representative of their distance. An alternative is then to determine the distance of NGC 6334 and NGC 6357 from their stellar content. Aims. Our aim is to perform a census of O-B3 ionising stars in NGC 6334 and NGC 6357, to determine the extinction coefficient, and the distance of both regions. A census of O-B3 stars is an essential basis for estimating the statistical lifetime of the earliest massive star-forming phases. Methods. We performed a U, B, V, and R photometric survey of a large area covering NGC 6334 and NGC 6357 with the VIMOS (ESO-VLT) and the MOSAIC (CTIO) instruments. This allows us to have a complete census of O to B3 stars up to V = 22.6 mag. The OB stars are selected based on their U − B and B − V colors. The most robust extinction coefficient is determined from color−color plots before computing the distance of the OB stars. Results. We find a higher value than typical of the diffuse interstellar medium for R V of 3.53 ± 0.08 and 3.56 ± 0.15 for NGC 6357 and NGC 6334, respectively. Adopting these R V values, the distances of NGC 6357 and NGC 6334 are 1.9 ± 0.4 kpc and 1.7 ± 0.3 kpc. We conclude that, within the error bars, both regions are thus at the same distance of 1.75 kpc (weighted mean). We confirm that the value of R V is linked to the large dust grain content. In particular, we found that there are more very small grains in NGC 6357 than in NGC 6334, suggesting that NGC 6357 could be more evolved than NGC 6334. Placed in the Galactic context, the NGC 6334-NGC 6357 complex appears to be located at the inner edge of the Sagittarius-Carina arm. Our census of O to B3 stars leads to a count of ∼230, which allows us to determine the statistical lifetime of the earliest phases of the massive stars. The starless and the protostellar phases have a mean statistical lifetime of ∼1.5 × 10 4 yr and ∼2.2 × 10 5 yr, respectively.

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“…In contrast, a first attempt to obtain an unbiased sample using a complete dust continuum imaging at the scale of the molecular complex Cygnus X (Motte et al 2007) was able to derive some more systematic results on the existence of a cold phase (IR-quiet massive dense cores and Class 0-like massive protostars) for high-mass star formation (Bontemps et al 2010;Csengeri et al 2011). Another survey of the molecular complex NGC 6334/NGC 6357 was conducted by Russeil et al (2010), who identified IR-quiet massive dense cores and estimated highmass protostellar lifetimes. The IR-quiet massive dense cores are suggested to host massive class 0 protostars as seen by the Herschel Space Telescope (Nguyen Luong et al 2011a).…”

Section: Introductionmentioning

confidence: 99%

Ammonia from cold high-mass clumps discovered in the inner Galactic disk by the ATLASGAL survey

Wienen

Wyrowski

Schüller

et al. 2012

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Context. The APEX Telescope Large Area Survey: the GALaxy (ATLASGAL) is an unbiased continuum survey of the inner Galactic disk at 870 μm. It covers ±60 • in Galactic longitude and aims to find all massive clumps at various stages of high-mass star formation in the inner Galaxy, particularly the earliest evolutionary phases. Aims. We aim to determine properties such as the gas kinetic temperature and dynamics of new massive cold clumps found by ATLASGAL. Most importantly, we derived their kinematical distances from the measured line velocities. Methods. We observed the ammonia (J, K) = (1, 1) to (3, 3) inversion transitions toward 862 clumps of a flux-limited sample of submm clumps detected by ATLASGAL and extracted 13 CO (1−0) spectra from the Galactic Ring Survey (GRS). We determined distances for a subsample located at the tangential points (71 sources) and for 277 clumps whose near/far distance ambiguity is resolved. Results. Most ATLASGAL clumps are cold with rotational temperatures from 10−30 K with a median of 17 K. They have a wide range of NH 3 linewidths (1−7 km s −1 ) with 1.9 km s −1 as median, which by far exceeds the thermal linewidth, as well as a broad distribution of high column densities from 10 14 to 10 16 cm −2 (median of 2 × 10 15 cm −2 ) with an NH 3 abundance in the range of 5 to 30 × 10 −8 . ATLASGAL sources are massive, > ∼ 100 M , and a fraction of clumps with a broad linewidth is in virial equilibrium. We found an enhancement of clumps at Galactocentric radii of 4.5 and 6 kpc. The comparison of the NH 3 lines as high-density probes with the GRS 13 CO emission as low-density envelope tracer yields broader linewidths for 13 CO than for NH 3 . The small differences in derived clump velocities between NH 3 (representing dense core material) and 13 CO (representing more diffuse molecular cloud gas) suggests that the cores are essentially at rest relative to the surrounding giant molecular cloud. Conclusions. The high detection rate (87%) confirms ammonia as an excellent probe of the molecular content of the massive, cold clumps revealed by ATLASGAL. A clear trend of increasing rotational temperatures and linewidths with evolutionary stage is seen for source samples ranging from 24 μm dark clumps to clumps with embedded HII regions. The survey provides the largest ammonia sample of high-mass star forming clumps and thus presents an important repository for the characterization of statistical properties of the clumps and the selection of subsamples for detailed, high-resolution follow-up studies.

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The earliest phases of high-mass star formation: the NGC 6334-NGC 6357 complex

Cited by 75 publications

References 91 publications

Initial highlights of the HOBYS key program, theHerschelimaging survey of OB young stellar objects

Initial highlights of the HOBYS key program, theHerschelimaging survey of OB young stellar objects

Statistical study of OB stars in NGC 6334 and NGC 6357

Ammonia from cold high-mass clumps discovered in the inner Galactic disk by the ATLASGAL survey

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