Kinematic and thermal structure at the onset of high-mass star formation - ISOSS23053

AbstractWithin the ‘earliest phases of star formation’ (EPoS) Herschel project, we observed the NH3 inversion lines of 6 very young high-mass star-forming regions at high spatial resolution (3-5″) with the JVLA. While the Herschel data provide details about the dust continuum, the ammonia data reveal the kinematics and temperatures. Here we present the exciting star-forming clump ISOSS23053 that shows multiple velocity components. We observe a prominent velocity step within the clump, which could be a sign of colliding or converging flows that triggers star formation. Furthermore, we used the JVLA in the C-array configuration to study this source in more detail and we present the first results from the new data. They support the idea of converging flows, as we observe two components in the NH3(1,1) and (2,2) line, whereas the higher excited NH3(3,3) line shows one component that links the two lower excited lines.

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Survey of ortho-H2D+ in high-mass star-forming regions

Astronomy and Astrophysics ◽

10.1051/0004-6361/202039010 ◽

2020 ◽

Vol 644 ◽

pp. A34

Author(s):

G. Sabatini ◽

S. Bovino ◽

A. Giannetti ◽

F. Wyrowski ◽

M. A. Órdenes ◽

...

Keyword(s):

Star Formation ◽

Formation Process ◽

Strong Dependence ◽

Cosmic Ray ◽

High Mass ◽

Clear Correlation ◽

Mass Star ◽

Large Sample ◽

Star Forming ◽

Star Forming Regions

Context. Deuteration has been suggested to be a reliable chemical clock of star-forming regions due to its strong dependence on density and temperature changes during cloud contraction. In particular, the H3+ isotopologues (e.g. ortho-H2D+) seem to act as good proxies of the evolutionary stages of the star formation process. While this has been widely explored in low-mass star-forming regions, in the high-mass counterparts only a few studies have been pursued, and the reliability of deuteration as a chemical clock remains inconclusive. Aims. We present a large sample of o-H2D+ observations in high-mass star-forming regions and discuss possible empirical correlations with relevant physical quantities to assess its role as a chronometer of star-forming regions through different evolutionary stages. Methods. APEX observations of the ground-state transition of o-H2D+ were analysed in a large sample of high-mass clumps selected from the ATLASGAL survey at different evolutionary stages. Column densities and beam-averaged abundances of o-H2D+ with respect to H2, X(o-H2D+), were obtained by modelling the spectra under the assumption of local thermodynamic equilibrium. Results. We detect 16 sources in o-H2D+ and find clear correlations between X(o-H2D+) and the clump bolometric luminosity and the dust temperature, while only a mild correlation is found with the CO-depletion factor. In addition, we see a clear correlation with the luminosity-to-mass ratio, which is known to trace the evolution of the star formation process. This would indicate that the deuterated forms of H3+ are more abundant in the very early stages of the star formation process and that deuteration is influenced by the time evolution of the clumps. In this respect, our findings would suggest that the X(o-H2D+) abundance is mainly affected by the thermal changes rather than density changes in the gas. We have employed these findings together with observations of H13CO+, DCO+, and C17O to provide an estimate of the cosmic-ray ionisation rate in a sub-sample of eight clumps based on recent analytical work. Conclusions. Our study presents the largest sample of o-H2D+ in star-forming regions to date. The results confirm that the deuteration process is strongly affected by temperature and suggests that o-H2D+ can be considered a reliable chemical clock during the star formation processes, as proved by its strong temporal dependence.

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44 GHz Methanol Maser Surveys

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312006795 ◽

2012 ◽

Vol 8 (S287) ◽

pp. 133-140

Author(s):

S. E. Kurtz

Keyword(s):

Star Formation ◽

Formation Process ◽

Class Ii ◽

Class I ◽

High Mass ◽

Mass Star ◽

Star Forming ◽

Methanol Maser ◽

Star Forming Regions ◽

Methanol Masers

AbstractClass I 44 GHz methanol masers are not as well-known, as common, or as bright as their more famous Class II cousins at 6.7 and 12.2 GHz. Nevertheless, the 44 GHz masers are commonly found in high-mass star forming regions. At times they appear to trace dynamically important phenomena; at other times they show no obvious link to the star formation process. Here, we summarize the major observational efforts to date, including both dedicated surveys and collateral observations. The principal results are presented, some that were expected, and others that were unexpected.

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High-mass Star Formation in the Regions IRAS 19217+1651 and 23151+5912

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312006904 ◽

2012 ◽

Vol 8 (S287) ◽

pp. 182-183

Author(s):

V. Migenes ◽

I. T. Rodríguez ◽

M. A. Trinidad

Keyword(s):

Water Vapor ◽

Star Formation ◽

Spatial Resolution ◽

High Sensitivity ◽

High Mass ◽

Continuum Emission ◽

Mass Star ◽

Star Forming ◽

Star Forming Regions

AbstractWe present and discuss VLA-EVLA high-sensitivity and spatial resolution observations of Water Vapor MASERs and continuum emission towards two sources that have been proposed in the literature to be high-mass star forming regions: IRAS 19217+1651 and 23151+5912. Our results indicate the presence of disks which can confirm that these regions are high-mass star forming regions.

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SEQUENTIAL STAR FORMATION IN RCW 34: A SPECTROSCOPIC CENSUS OF THE STELLAR CONTENT OF HIGH-MASS STAR-FORMING REGIONS

The Astrophysical Journal ◽

10.1088/0004-637x/713/2/883 ◽

2010 ◽

Vol 713 (2) ◽

pp. 883-899 ◽

Cited By ~ 33

Author(s):

A. Bik ◽

E. Puga ◽

L.B.F.M. Waters ◽

M. Horrobin ◽

Th. Henning ◽

...

Keyword(s):

Star Formation ◽

High Mass ◽

Mass Star ◽

Stellar Content ◽

Star Forming ◽

Star Forming Regions

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325 GHz Water Masers in Orion Source I

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312006916 ◽

2012 ◽

Vol 8 (S287) ◽

pp. 184-185

Author(s):

Florian Niederhofer ◽

Elizabeth Humphreys ◽

Ciriaco Goddi ◽

Lincoln J. Greenhill

Keyword(s):

Star Formation ◽

Massive Star ◽

High Mass ◽

Mass Star ◽

Compact Disk ◽

Volume Source ◽

Star Forming ◽

Star Forming Regions ◽

Water Masers ◽

Excitation Conditions

AbstractRadio Source I in the Orion BN/KL region provides the closest example of high mass star formation. It powers a rich ensemble of SiO and H2O masers, and is one of only three star-forming regions known to display SiO maser emission. Previous monitoring of different SiO masers with the VLBA and VLA has enabled the resolution of a compact disk and a protostellar wind at radii <100 AU from Source I, which collimates into a bipolar outflow at radii of 100-1000 AU (see contribution by Greenhill et al., this volume). Source I may provide the best case of disk-mediated accretion and outflow recollimation in massive star formation. Here, we report preliminary results of sub-arcsecond resolution 325 GHz H2O maser observations made with the SMA. We find that 325 GHz H2O masers trace a more collimated portion of the Source I outflow than masers at 22 GHz, but occur at similar radii suggesting similar excitation conditions. A velocity gradient perpendicular to the outflow axis, indicating rotation, supports magneto-centrifugal driving of the flow.

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FUGIN hot core survey. I. Survey method and initial results for l = 10°–20°

Publications of the Astronomical Society of Japan ◽

10.1093/pasj/psab021 ◽

2021 ◽

Author(s):

Kazuki Sato ◽

Tetsuo Hasegawa ◽

Tomofumi Umemoto ◽

Hiro Saito ◽

Nario Kuno ◽

...

Keyword(s):

Star Formation ◽

Galactic Plane ◽

High Mass ◽

Survey Method ◽

H Ii Regions ◽

Mass Star ◽

Star Forming ◽

Bolometric Luminosity ◽

Star Forming Regions ◽

Starting Point

Abstract We have developed a method to make a spectral-line-based survey of hot cores, which represent an important stage of high-mass star formation, and applied the method to the data of the FUGIN (FOREST Unbiased Galactic plane Imaging survey with the Nobeyama 45 m telescope) survey. First, we select hot core candidates by searching the FUGIN data for the weak hot core tracer lines (HNCO and CH3CN) by stacking, and then we conduct follow-up pointed observations on these candidates in C34S, SO, OCS, HC3N, HNCO, CH3CN, and CH3OH J = 2–1 and J = 8–7 lines to confirm and characterize them. We applied this method to the l = 10°–20° portion of the FUGIN data and identified 22 “HotCores” (compact sources with more than two significant detections of the hot core tracer lines, i.e., SO, OCS, HC3N, HNCO, CH3CN, or CH3OH J = 8–7 lines) and 14 “DenseClumps” (sources with more than two significant detection of C34S, CH3OH J = 2–1, or the hot core tracer lines). The identified HotCores are found to be associated with signposts of high-mass star formation such as ATLASGAL clumps, WISE H ii regions, and Class II methanol masers. Many of the FUGIN HotCores are identified with the Herschel Hi-GAL clumps with a median mass of 6.8 × 102 M⊙ and a median bolometric luminosity of 7.4 × 103 L⊙. Five of the seven HotCores with stronger CH3CN lines exhibit elevated gas temperatures of 50–100 K. These observations suggest that FUGIN HotCores are closely related to the formation of stars with medium to high mass. For those associated with ATLASGAL clumps, their bolometric luminosity to clump mass ratios are consistent with the star formation stages centered at the hot core phase. The catalog of FUGIN HotCores provides a useful starting point for further statistical studies and detailed observations of high-mass star forming regions.

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Fragmentation and disk formation during high-mass star formation

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833021 ◽

2018 ◽

Vol 617 ◽

pp. A100 ◽

Cited By ~ 26

Author(s):

H. Beuther ◽

J. C. Mottram ◽

A. Ahmadi ◽

F. Bosco ◽

H. Linz ◽

...

Keyword(s):

Star Formation ◽

Spectral Line ◽

Angular Resolution ◽

Spatial Scales ◽

High Mass ◽

Continuum Emission ◽

Mass Star ◽

Star Forming ◽

Disk Formation ◽

Star Forming Regions

Context. High-mass stars form in clusters, but neither the early fragmentation processes nor the detailed physical processes leading to the most massive stars are well understood. Aims. We aim to understand the fragmentation, as well as the disk formation, outflow generation, and chemical processes during high-mass star formation on spatial scales of individual cores. Methods. Using the IRAM Northern Extended Millimeter Array (NOEMA) in combination with the 30 m telescope, we have observed in the IRAM large program CORE the 1.37 mm continuum and spectral line emission at high angular resolution (~0.4″) for a sample of 20 well-known high-mass star-forming regions with distances below 5.5 kpc and luminosities larger than 104 L⊙. Results. We present the overall survey scope, the selected sample, the observational setup, and the main goals of CORE. Scientifically, we concentrated on the mm continuum emission on scales on the order of 1000 AU. We detect strong mm continuum emission from all regions, mostly due to the emission from cold dust. The fragmentation properties of the sample are diverse. We see extremes where some regions are dominated by a single high-mass core whereas others fragment into as many as 20 cores. A minimum-spanning-tree analysis finds fragmentation at scales on the order of the thermal Jeans length or smaller suggesting that turbulent fragmentation is less important than thermal gravitational fragmentation. The diversity of highly fragmented vs. singular regions can be explained by varying initial density structures and/or different initial magnetic field strengths. Conclusions. A large sample of high-mass star-forming regions at high spatial resolution allows us to study the fragmentation properties of young cluster-forming regions. The smallest observed separations between cores are found around the angular resolution limit which indicates that further fragmentation likely takes place on even smaller spatial scales. The CORE project with its numerous spectral line detections will address a diverse set of important physical and chemical questions in the field of high-mass star formation.

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Low-Mass Versus High-Mass Star Formation

Symposium - International Astronomical Union ◽

10.1017/s0074180900061933 ◽

1997 ◽

Vol 182 ◽

pp. 537-549

Author(s):

T. W. Hartquist ◽

J. E. Dyson

Keyword(s):

Star Formation ◽

Young Stars ◽

High Mass ◽

Mass Star ◽

Low Mass Stars ◽

Star Forming ◽

Star Forming Regions ◽

Dense Cores ◽

Global Properties ◽

Low Mass

Structures like the clumps identified in the CO maps of the Rosette Molecular Cloud and the dense cores such as those in B5, a cluster of cores and young low-mass stars, are key to considerations of star formation. Whether star formation is a self-inducing process or one that causes itself to turn off depends greatly on whether the responses of the interclump and intercore media to young stars cause the collapse of clumps or cores to be faster than their ablation. We present a naive introduction to the lengthscales over which such responses are significant, mention ways in which the responses might induce collapse, review some of the little that is known of how flows of media around clumps and cores ablate them, and then return to the issue of the lengthscales over which such responses are significant by considering the global properties of mass-loaded flows in clumpy star forming regions.

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