Illuminating a tadpole’s metamorphosis III: quantifying past and present environmental impact

ABSTRACT We combine Multi-Unit Spectroscopic Explorer and Atacama Large Millimeter/sub-millimeter Array observations with theoretical models to evaluate how a tadpole-shaped globule located in the Carina Nebula has been influenced by its environment. This globule is now relatively small (radius ∼2500 au), hosts a protostellar jet+outflow (HH 900), and, with a blueshifted velocity of ∼10 km s−1, is travelling faster than it should be if its kinematics were set by the turbulent velocity dispersion of the precursor cloud. Its outer layers are currently still subject to heating, but comparing the internal and external pressures implies that the globule is in a post-collapse phase. Intriguingly the outflow is bent, implying that the Young Stellar Object (YSO) responsible for launching it is comoving with the globule, which requires that the star formed after the globule was up to speed since otherwise it would have been left behind. We conclude that the most likely scenario is one in which the cloud was much larger before being subject to radiatively driven implosion, which accelerated the globule to the high observed speeds under the photoevaporative rocket effect and triggered the formation of the star responsible for the outflow. The globule may now be in a quasi-steady state following collapse. Finally, the HH 900 YSO is likely ≳1 M⊙ and may be the only star forming in the globule. It may be that this process of triggered star formation has prevented the globule from fragmenting to form multiple stars (e.g. due to heating) and has produced a single higher mass star.

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Submillimeter Array Observations of Magnetic Fields in Star Forming Regions

Proceedings of the International Astronomical Union ◽

10.1017/s174392131100024x ◽

2010 ◽

Vol 6 (S270) ◽

pp. 103-106

Author(s):

R. Rao ◽

J.-M. Girart ◽

D. P. Marrone

Keyword(s):

Magnetic Field ◽

Star Formation ◽

Magnetic Fields ◽

Computational Models ◽

Dominant Role ◽

Theoretical Models ◽

Mass Star ◽

Star Forming ◽

Star Forming Regions ◽

Low Mass

AbstractThere have been a number of theoretical and computational models which state that magnetic fields play an important role in the process of star formation. Competing theories instead postulate that it is turbulence which is dominant and magnetic fields are weak. The recent installation of a polarimetry system at the Submillimeter Array (SMA) has enabled us to conduct observations that could potentially distinguish between the two theories. Some of the nearby low mass star forming regions show hour-glass shaped magnetic field structures that are consistent with theoretical models in which the magnetic field plays a dominant role. However, there are other similar regions where no significant polarization is detected. Future polarimetry observations made by the Submillimeter Array should be able to increase the sample of observed regions. These measurements will allow us to address observationally the important question of the role of magnetic fields and/or turbulence in the process of star formation.

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Chemistry in the Envelopes around Massive Young Stars

Highlights of Astronomy ◽

10.1017/s1539299600013095 ◽

2002 ◽

Vol 12 ◽

pp. 146-148

Author(s):

Ewine F. van Dishoeck ◽

Floris F.S. van der Tak

Keyword(s):

Young Star ◽

Young Stars ◽

High Mass ◽

Mass Star ◽

Star Forming ◽

Star Forming Regions ◽

Chemical Studies ◽

H Ii Region ◽

Infrared Wavelengths ◽

Collapse Phase

AbstractRecent chemical studies of high-mass star-forming regions at submillimeter and infrared wavelengths reveal large variations in the abundances depending on evolutionary state. Such variations can be explained by freezing out of molecules onto grains in the cold collapse phase, followed by evaporation and high-temperature chemical reactions when the young star heats the envelope. Thus, the chemical composition can be a powerful diagnostic tool. A detailed study of a set of infrared-bright massive young stars reveals systematic increases in the gas/solid ratios and abundances of evaporated molecules with temperature. This ‘global heating’ plausibly results from the gradual dispersion of the envelopes. We argue that these objects form the earliest phase of massive star formation, before the ‘hot core’ and ultracompact H II region phase.

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High-Mass Star and Massive Cluster Formation in the Milky Way

Annual Review of Astronomy and Astrophysics ◽

10.1146/annurev-astro-091916-055235 ◽

2018 ◽

Vol 56 (1) ◽

pp. 41-82 ◽

Cited By ~ 89

Author(s):

Frédérique Motte ◽

Sylvain Bontemps ◽

Fabien Louvet

Keyword(s):

Star Formation ◽

Milky Way ◽

Galactic Plane ◽

Cluster Formation ◽

Theoretical Models ◽

High Mass ◽

High Angular Resolution ◽

Mass Star ◽

Star Forming ◽

Massive Cluster

This review examines the state-of-the-art knowledge of high-mass star and massive cluster formation, gained from ambitious observational surveys, which acknowledges the multiscale characteristics of these processes. After a brief overview of theoretical models and main open issues, we present observational searches for the evolutionary phases of high-mass star formation, first among high-luminosity sources and more recently among young massive protostars and the elusive high-mass prestellar cores. We then introduce the most likely evolutionary scenario for high-mass star formation, which emphasizes the link of high-mass star formation to massive cloud and cluster formation. Finally, we introduce the first attempts to search for variations of the star-formation activity and cluster formation in molecular cloud complexes in the most extreme star-forming sites and across the Milky Way. The combination of Galactic plane surveys and high–angular resolution images with submillimeter facilities such as Atacama Large Millimeter Array (ALMA) are prerequisites to make significant progress in the forthcoming decade.

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A Search for High-Mass Stars Forming in Isolation using CORNISH and ATLASGAL

Publications of the Astronomical Society of Australia ◽

10.1017/pasa.2015.48 ◽

2015 ◽

Vol 32 ◽

Cited By ~ 1

Author(s):

Chenoa D. Tremblay ◽

Andrew J. Walsh ◽

Steven N. Longmore ◽

James S. Urquhart ◽

Carsten König

Keyword(s):

Galactic Plane ◽

Sample Selection ◽

Theoretical Models ◽

Radio Continuum ◽

High Mass ◽

Continuum Emission ◽

Mass Star ◽

Promising Candidate ◽

Star Forming ◽

Infrared Measurements

AbstractTheoretical models of high-mass star formation lie between two extreme scenarios. At one extreme, all the mass comes from an initially gravitationally bound core. At the other extreme, the majority of the mass comes from cluster scale gas, which lies far outside the initial core boundary. One way to unambiguously show high-mass stars can assemble their gas through the former route would be to find a high-mass star forming in isolation. Making use of recently available CORNISH and ATLASGAL Galactic plane survey data, we develop sample selection criteria to try and find such an object. From an initial list of approximately 200 sources, we identify the high-mass star-forming region G13.384 + 0.064 as the most promising candidate. The region contains a strong radio continuum source, that is powered by an early B-type star. The bolometric luminosity, derived from infrared measurements, is consistent with this. However, sub-millimetre continuum emission, measured in ATLASGAL, as well as dense gas tracers, such as HCO+(3–2) and N2H+(3–2) indicate that there is less than ~ 100 M⊙ of material surrounding this star. We conclude that this region is indeed a promising candidate for a high-mass star forming in isolation.

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GASTON: Galactic Star Formation with NIKA2. Evidence for the mass growth of star-forming clumps

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab200 ◽

2021 ◽

Author(s):

A J Rigby ◽

N Peretto ◽

R Adam ◽

P Ade ◽

M Anderson ◽

...

Keyword(s):

Star Formation ◽

Large Scale ◽

Galactic Plane ◽

High Sensitivity ◽

High Mass ◽

Evolutionary Stage ◽

Mass Star ◽

Mass Growth ◽

Star Forming ◽

Compact Source

Abstract Determining the mechanism by which high-mass stars are formed is essential for our understanding of the energy budget and chemical evolution of galaxies. By using the New IRAM KIDs Array 2 (NIKA2) camera on the Institut de Radio Astronomie Millimétrique (IRAM) 30-m telescope, we have conducted high-sensitivity and large-scale mapping of a fraction of the Galactic plane in order to search for signatures of the transition between the high- and low-mass star-forming modes. Here, we present the first results from the Galactic Star Formation with NIKA2 (GASTON) project, a Large Programme at the IRAM 30-m telescope which is mapping ≈2 deg2 of the inner Galactic plane (GP), centred on ℓ = 23${_{.}^{\circ}}$9, b = 0${_{.}^{\circ}}$05, as well as targets in Taurus and Ophiuchus in 1.15 and 2.00 mm continuum wavebands. In this paper we present the first of the GASTON GP data taken, and present initial science results. We conduct an extraction of structures from the 1.15 mm maps using a dendrogram analysis and, by comparison to the compact source catalogues from Herschel survey data, we identify a population of 321 previously-undetected clumps. Approximately 80 per cent of these new clumps are 70 μm-quiet, and may be considered as starless candidates. We find that this new population of clumps are less massive and cooler, on average, than clumps that have already been identified. Further, by classifying the full sample of clumps based upon their infrared-bright fraction – an indicator of evolutionary stage – we find evidence for clump mass growth, supporting models of clump-fed high-mass star formation.

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Constraining photoionization models with a reprojected optical diagnostic diagram

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3259 ◽

2020 ◽

Vol 499 (4) ◽

pp. 5749-5764 ◽

Cited By ~ 1

Author(s):

Xihan Ji ◽

Renbin Yan

Keyword(s):

Star Formation ◽

Active Galactic Nuclei ◽

Galactic Nuclei ◽

Theoretical Models ◽

Line Ratio ◽

Star Forming ◽

Optical Diagnostic ◽

Diagnostic Diagram ◽

Upper Limits ◽

Nitrogen Abundance

ABSTRACT Optical diagnostic diagrams are powerful tools to separate different ionizing sources in galaxies. However, the model-constraining power of the most widely used diagrams is very limited and challenging to visualize. In addition, there have always been classification inconsistencies between diagrams based on different line ratios, and ambiguities between regions purely ionized by active galactic nuclei (AGNs) and composite regions. We present a simple reprojection of the 3D line ratio space composed of [N ii]λ6583/H α, [S ii]λλ6716, 6731/H α, and [O iii]λ5007/H β, which reveals its model-constraining power and removes the ambiguity for the true composite objects. It highlights the discrepancy between many theoretical models and the data loci. With this reprojection, we can put strong constraints on the photoionization models and the secondary nitrogen abundance prescription. We find that a single nitrogen prescription cannot fit both the star-forming locus and AGN locus simultaneously, with the latter requiring higher N/O ratios. The true composite regions stand separately from both models. We can compute the fractional AGN contributions for the composite regions, and define demarcations with specific upper limits on contamination from AGN or star formation. When the discrepancy about nitrogen prescriptions gets resolved in the future, it would also be possible to make robust metallicity measurements for composite regions and AGNs.

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

Astronomy and Astrophysics ◽

10.1051/0004-6361/201118350 ◽

2012 ◽

Vol 538 ◽

pp. A140 ◽

Cited By ~ 16

Author(s):

P. D. Klaassen ◽

L. Testi ◽

H. Beuther

Keyword(s):

High Mass ◽

Mass Star ◽

Star Forming ◽

Star Forming Regions

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Nitrogen and hydrogen fractionation in high-mass star-forming cores from observations of HCN and HNC

Astronomy and Astrophysics ◽

10.1051/0004-6361/201730576 ◽

2018 ◽

Vol 609 ◽

pp. A129 ◽

Cited By ~ 12

Author(s):

L. Colzi ◽

F. Fontani ◽

P. Caselli ◽

C. Ceccarelli ◽

P. Hily-Blant ◽

...

Keyword(s):

Solar System ◽

Solar Nebula ◽

Rotational Transition ◽

High Mass ◽

Evolutionary Stage ◽

Mass Star ◽

Stellar Cluster ◽

Star Forming ◽

Star Forming Regions ◽

Dense Cores

The ratio between the two stable isotopes of nitrogen, 14N and 15N, is well measured in the terrestrial atmosphere (~272), and for the pre-solar nebula (~441, deduced from the solar wind). Interestingly, some pristine solar system materials show enrichments in 15N with respect to the pre-solar nebula value. However, it is not yet clear if and how these enrichments are linked to the past chemical history because we have only a limited number of measurements in dense star-forming regions. In this respect, dense cores, which are believed to be the precursors of clusters and also contain intermediate- and high-mass stars, are important targets because the solar system was probably born within a rich stellar cluster, and such clusters are formed in high-mass star-forming regions. The number of observations in such high-mass dense cores has remained limited so far. In this work, we show the results of IRAM-30 m observations of the J = 1−0 rotational transition of the molecules HCN and HNC and their 15N-bearing counterparts towards 27 intermediate- and high-mass dense cores that are divided almost equally into three evolutionary categories: high-mass starless cores, high-mass protostellar objects, and ultra-compact Hii regions. We have also observed the DNC(2–1) rotational transition in order to search for a relation between the isotopic ratios D/H and 14N/15N. We derive average 14N/15N ratios of 359 ± 16 in HCN and of 438 ± 21 in HNC, with a dispersion of about 150–200. We find no trend of the 14N/15N ratio with evolutionary stage. This result agrees with what has been found for N2H+ and its isotopologues in the same sources, although the 14N/15N ratios from N2H+ show a higher dispersion than in HCN/HNC, and on average, their uncertainties are larger as well. Moreover, we have found no correlation between D/H and 14N/15N in HNC. These findings indicate that (1) the chemical evolution does not seem to play a role in the fractionation of nitrogen, and that (2) the fractionation of hydrogen and nitrogen in these objects is not related.

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