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

Klaassen, Pamela; Testi, L.; Beuther, H.

doi:10.1051/0004-6361/201118350

Cited by 29 publications

(42 citation statements)

References 52 publications

(104 reference statements)

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“…C.1. The observed detection rate is similar to that of Klaassen et al (2012) despite the lower sensitivity, and is somewhat lower than reported by Leurini et al (2014), who had, on the other hand, a factor of ∼ 2 higher sensitivity for the same transition. These studies focused on more evolved, mostly infrared-bright clumps, many of them hosting UC-H II regions.…”

Section: Sio (8-7) Emission Towards Infrared-quiet Massive Clumpssupporting

confidence: 77%

The ATLASGAL survey: The sample of young massive cluster progenitors

Csengeri

Bontemps

Wyrowski

et al. 2017

A&A

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Context. The progenitors of high-mass stars and clusters are still challenging to recognise. Only unbiased surveys, sensitive to compact regions of high dust column density, can unambiguously reveal such a small population of particularly massive and cold clumps. Aims. Here we use the ATLASGAL survey to identify a sample of candidate progenitors of massive clusters in the inner Galaxy. Methods. We characterise a flux limited sample of compact sources selected from the ATLASGAL survey. Sensitive mid-infrared data at 21−24 µm from the WISE and MIPSGAL surveys were explored to search for embedded objects, and complementary spectroscopic data were used to investigate their stability and their star formation activity. Results. We identify an unbiased sample of infrared-quiet massive clumps in the Galaxy that potentially represent the earliest stages of massive cluster formation. An important fraction of this sample consists of sources that have not been studied in detail before. We first find that clumps hosting more evolved embedded objects and infrared-quiet clumps exhibit similar physical properties in terms of mass and size, suggesting that the sources are not only capable of forming high-mass stars, but likely also follow a single evolutionary track leading to the formation of massive clusters. The majority of the clumps are likely not in virial-equilibrium, suggesting collapse on the clump scale. Conclusions. We identify the precursors of the most massive clusters in the Galaxy within our completeness limit, and argue that these objects are undergoing large-scale collapse. This is in line with the low number of infrared-quiet massive clumps and earlier findings that star formation, in particular for high-mass objects is a fast, dynamic process. We propose a scenario in which massive clumps start to fragment and collapse before their final mass is accumulated indicating that strong self-gravity and global collapse is needed to build up rich clusters and the most massive stars.

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Section: Sio (8-7) Emission Towards Infrared-quiet Massive Clumpssupporting

confidence: 77%

The ATLASGAL survey: The sample of young massive cluster progenitors

Csengeri

Bontemps

Wyrowski

et al. 2017

A&A

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“…Although infall with high accretion rates has been reported towards these types of sources (e.g. Klaassen et al 2012), the detection of the broad outflow component suggests that there is accretion ongoing not only from the envelope, but also onto the (proto)stars leading to jets. Considering that most of our clumps eventually form not only a single star, but a protocluster, these jets may originate from younger protostars nearby UC-H II regions, which have been frequently observed with high angular resolution data (e.g.…”

Section: Sio As a Tracer Of Protostellar Activity And Shocksmentioning

confidence: 99%

“…Spectral surveys have so far targeted a few selected sources in mostly distinct evolutionary stages, such as UC-H II regions, high-mass protostellar objects (HMPOs; e.g. Klaassen et al 2012), and infrared dark clouds (IRDCs; e.g. Beuther & Sridharan 2007;Vasyunina et al 2011).…”

Section: Introductionmentioning

confidence: 99%

ATLASGAL-selected massive clumps in the inner Galaxy

Csengeri

Leurini

Wyrowski

et al. 2016

A&A

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Context. The processes leading to the birth of high-mass stars are poorly understood. The key first step to reveal their formation processes is characterising the clumps and cores from which they form. Aims. We define a representative sample of massive clumps in different evolutionary stages selected from the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL), from which we aim to establish a census of molecular tracers of their evolution. As a first step, we study the shock tracer, SiO, mainly associated with shocks from jets probing accretion processes. In low-mass young stellar objects (YSOs), outflow and jet activity decreases with time during the star formation processes. Recently, a similar scenario was suggested for massive clumps based on SiO observations. Here we analyse observations of the SiO (2−1) and (5−4) lines in a statistically significant sample to constrain the change of SiO abundance and the excitation conditions as a function of evolutionary stage of massive star-forming clumps. Methods. We performed an unbiased spectral line survey covering the 3-mm atmospheric window between 84−117 GHz with the IRAM 30 m telescope of a sample of 430 sources of the ATLASGAL survey, covering various evolutionary stages of massive clumps. A smaller sample of 128 clumps has been observed in the SiO (5−4) transition with the APEX telescope to complement the (2−1) line and probe the excitation conditions of the emitting gas. We derived detection rates to assess the star formation activity of the sample, and we estimated the column density and abundance using both an LTE approximation and non-LTE calculations for a smaller subsample, where both transitions have been observed. Results. We characterise the physical properties of the selected sources, which greatly supersedes the largest samples studied so far, and show that they are representative of different evolutionary stages. We report a high detection rate of >75% of the SiO (2−1) line and a >90% detection rate from the dedicated follow-ups in the (5−4) transition. Up to 25% of the infrared-quiet clumps exhibit high-velocity line wings, suggesting that molecular tracers are more efficient tools to determine the level of star formation activity than infrared colour criteria. We also find infrared-quiet clumps that exhibit only a low-velocity component (FWHM ∼ 5−6 km s −1 ) SiO emission in the (2−1) line. In the current picture, where this is attributed to low-velocity shocks from cloud-cloud collisions, this can be used to pinpoint the youngest, thus, likely prestellar massive structures. Using the optically thin isotopologue ( 29 SiO), we estimate that the (2−1) line is optically thin towards most of the sample. Furthermore, based on the line ratio of the (5−4) to the (2−1) line, our study reveals a trend of changing excitation conditions that lead to brighter emission in the (5−4) line towards more evolved sources. Our models show that a proper treatment of non-LTE effects and beam dilution is necessary to constrain trends in the SiO column den...

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

Cited by 29 publications

References 52 publications

The ATLASGAL survey: The sample of young massive cluster progenitors

The ATLASGAL survey: The sample of young massive cluster progenitors

ATLASGAL-selected massive clumps in the inner Galaxy

Tightening the belt: Constraining the mass and evolution in SDC335

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