A millimeter survey of ultra-compact HII-regions and associated molecular clouds

Churchwell, E.; Sievers, A.; Thum, C.

doi:10.1051/0004-6361/200912241

Cited by 27 publications

(36 citation statements)

References 31 publications

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“…To have an idea of how large the overestimate of the line widths could be, we checked the value toward source #242 (associated with the G29-UC region and G29-HMC core), which has been extensively observed in different molecular tracers. The line width estimated with 13 CO is 6.2 km s −1 and is similar to the values of ∼5.5 km s −1 estimated in CS (5-4) and (7-6), and HCO + (3-2) with the JCMT and the IRAM 30-m telescopes (Olmi et al 1999;Churchwell et al 2010). M virial depends on the density profile, and for a power-law density distribution of the type ρ ∝ r −p , the virial mass should be multiplied by a factor 3(5 − 2p)/5(3 − p), which is ≤1 for p < 3.…”

Section: Evolutionary Phase Of the Sourcessupporting

confidence: 83%

A Hi-GAL study of the high-mass star-forming region G29.96–0.02

Beltrán

Olmi

Cesaroni

et al. 2013

A&A

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Context. G29.96−0.02 is a high-mass star-forming cloud observed at 70, 160, 250, 350, and 500 μm as part of the Herschel survey of the Galactic plane (Hi-GAL) during the science demonstration phase. Aims. We wish to conduct a far-infrared study of the sources associated with this star-forming region by estimating their physical properties and evolutionary stage, and investigating the clump mass function, the star formation efficiency and rate in the cloud. Methods. We have identified the Hi-GAL sources associated with the cloud, searched for possible counterparts at centimeter and infrared wavelengths, fitted their spectral energy distribution and estimated their physical parameters. Results. A total of 198 sources have been detected in all 5 Hi-GAL bands, 117 of which are associated with 24 μm emission and 87 of which are not associated with 24 μm emission. We called the former sources 24 μm-bright and the latter ones 24 μm-dark. The color of the 24 μm-dark sources is smaller than that of the 24 μm-bright ones. The 24 μm-dark sources have lower L bol and L bol /M env than the 24 μm-bright ones for similar M env , which suggests that they are in an earlier evolutionary phase. The G29-SFR cloud is associated with 10 NVSS sources and with extended centimeter continuum emission well correlated with the 70 μm emission. Most of the NVSS sources appear to be early B or late O-type stars. The most massive and luminous Hi-GAL sources in the cloud are located close to the G29-UC region, which suggests that there is a privileged area for massive star formation toward the center of the G29-SFR cloud. Almost all the Hi-GAL sources have masses well above the Jeans mass but only 5% have masses above the virial mass, which indicates that most of the sources are stable against gravitational collapse. The sources with M env > M virial and that should be undergoing collapse and forming stars are preferentially located at < ∼ 4 of the G29-UC region, which is the most luminous source in the cloud. The overall SFE of the G29-SFR cloud ranges from 0.7 to 5%, and the SFR ranges from 0.001 to 0.008 M yr −1 , consistent with the values estimated for Galactic Hii regions. The mass spectrum of the sources with masses above 300 M , well above the completeness limit, can be well-fitted with a power law of slope α = 2.15 ± 0.30, consistent with the values obtained for the whole l = 30 • , associated with high-mass star formation, and l = 59 • , associated with low-to intermediate-mass star formation, Hi-GAL SDP fields.

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Section: Evolutionary Phase Of the Sourcessupporting

confidence: 83%

A Hi-GAL study of the high-mass star-forming region G29.96–0.02

Beltrán

Olmi

Cesaroni

et al. 2013

A&A

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“…Fuller et al 2005;Churchwell et al 2010;Klaassen et al 2012;Rygl et al 2013;Duarte-Cabral et al 2013) have been calculated for massive star precursors (e.g. HMPOs, HCH), a greater value than that associated with their lower mass counterparts (Ṁ * ∼ c 3 s G 5 × 10 −6 M yr −1 ;Shu 1977;McKee & Tan 2003).…”

Section: The Evolutionary Status Of the Ionising Sources In Sdc335mentioning

confidence: 99%

Tightening the belt: Constraining the mass and evolution in SDC335

Avison

Peretto

Fuller

et al. 2015

A&A

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Aims. Recent ALMA observations identified one of the most massive star-forming cores yet observed in the Milky Way: SDC335-MM1, within the infrared dark cloud SDC335.579-0.292. Along with an accompanying core MM2, SDC335 appears to be in the early stages of its star formation process. We aim to constrain the properties of the stars forming within these two massive millimetre sources. Methods. Observations of SDC335 at 6, 8, 23 and 25 GHz were made with the Australia Telescope Compact Array. We report the results of these continuum measurements, which combined with archival data, allow us to build and analyse the spectral energy distributions (SEDs) of the compact sources in SDC335. Results. Three hyper-compact H regions within SDC335 are identified, two of which are within the MM1 core. For each HCH region, we fit a free-free emission curve to the data, providing the derivation of the sources' emission measure, ionising photon flux, and electron density. Using these physical properties we assign each HCH region a zero-age main sequence (ZAMS) spectral type, finding two protostars with characteristics of spectral type B1.5 and one with a lower limit of B1-B1.5. Ancillary data from infrared to mm wavelength are used to construct free-free component subtracted SEDs for the mm-cores, which allows us to calculate the bolometric luminosities and revise the previous gas mass estimates. Conclusions. The measured luminosities for the two mm-cores are lower than expected from accreting sources displaying characteristics of the ZAMS spectral type assigned to them. The protostars are still actively accreting, suggesting that a mechanism is limiting the accretion luminosity. We present the case for two different mechanisms capable of causing lower than expected accretion luminosity. Finally, using the ZAMS mass values as lower limit constraints, a final stellar population for SDC335 was synthesised finding SDC335 is likely to be in the process of forming a stellar cluster comparable to the Trapezium cluster and NGC 6334 I(N).

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“…The study of Churchwell et al (2010) observed a number of HII regions in HCO + (J = 3−2, 2−1). Nine of their sources overlap with our study.…”

Section: Detecting Infallsignatures With Hco +mentioning

confidence: 99%

Looking for outflow and infall signatures in high-mass star-forming regions

Klaassen

Testi

Beuther

2012

A&A

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Context. Many physical parameters change with time in star-forming regions. Here we attempt to correlate changes in the infall and outflow motions in high-mass star-forming regions with evolutionary stage using JCMT observations. Aims. From a sample of 45 high-mass star-forming regions in three phases of evolution, we investigate the presence of established infall and outflow tracers to determine whether there are any trends attributable to the age of the source. Methods. We obtained JCMT observations of HCO + /H 13 CO + J = 4−3 to trace large-scale infall, and SiO J = 8−7 to trace recent outflow activity. We compared the infall and outflow detections to the evolutionary stage of the host source (high-mass protostellar objects, hypercompact HII regions, and ultracompact HII regions). Results. We find a surprising lack of SiO detections in the middle stage (hypercompact HII regions), which may be an observational bias. When SiO is detected, we find that the integrated intensity of the line increases with evolutionary stage. The integrated intensity of SiO varies with the full width at half maximum of the H 13 CO + . All of the sources with infall signatures onto ultracompact HII regions have corresponding outflow signatures as well.

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A millimeter survey of ultra-compact HII-regions and associated molecular clouds

Cited by 27 publications

References 31 publications

A Hi-GAL study of the high-mass star-forming region G29.96–0.02

A Hi-GAL study of the high-mass star-forming region G29.96–0.02

Tightening the belt: Constraining the mass and evolution in SDC335

Looking for outflow and infall signatures in high-mass star-forming regions

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