scholarly journals Parameter study for the burst mode of accretion in massive star formation

2020 ◽  
Vol 500 (4) ◽  
pp. 4448-4468
Author(s):  
D M-A Meyer ◽  
E I Vorobyov ◽  
V G Elbakyan ◽  
J Eislöffel ◽  
A M Sobolev ◽  
...  
Keyword(s):  
Star Formation ◽  
Gravitational Instability ◽  
Young Stellar Objects ◽  
High Mass ◽  
Formation Mechanisms ◽  
Parameter Study ◽  
Mass Star ◽  
Stellar Objects ◽  
Burst Mode ◽  
Protostellar Jets

ABSTRACT It is now a widely held view that, in their formation and early evolution, stars build up mass in bursts. The burst mode of star formation scenario proposes that the stars grow in mass via episodic accretion of fragments migrating from their gravitationally unstable circumstellar discs, and it naturally explains the existence of observed pre-main-sequence bursts from high-mass protostars. We present a parameter study of hydrodynamical models of massive young stellar objects (MYSOs) that explores the initial masses of the collapsing clouds (Mc = 60–$200\, \rm M_{\odot }$) and ratio of rotational-to-gravitational energies (β = 0.005–0.33). An increase in Mc and/or β produces protostellar accretion discs that are more prone to develop gravitational instability and to experience bursts. We find that all MYSOs have bursts even if their pre-stellar core is such that β ≤ 0.01. Within our assumptions, the lack of stable discs is therefore a major difference between low- and high-mass star formation mechanisms. All our disc masses and disc-to-star mass ratios Md/M⋆ > 1 scale as a power law with the stellar mass. Our results confirm that massive protostars accrete about $40\, -\, 60{{\ \rm per\ cent}}$ of their mass in the burst mode. The distribution of time periods between two consecutive bursts is bimodal: there is a short duration ($\sim 1\, -\, 10~\rm yr$) peak corresponding to the short, faintest bursts and a long-duration peak (at $\sim 10^{3}\, -\, 10^{4} \rm yr$) corresponding to the long, FU-Orionis-type bursts appearing in later disc evolution, i.e. around $30\, \rm kyr$ after disc formation. We discuss this bimodality in the context of the structure of massive protostellar jets as potential signatures of accretion burst history.

scholarly journals Formation of high-mass stars in an isolated environment in the Large Magellanic Cloud

2019 ◽  
Vol 71 (2) ◽  
Author(s):  
Ryohei Harada ◽  
Toshikazu Onishi ◽  
Kazuki Tokuda ◽  
Sarolta Zahorecz ◽  
Annie Hughes ◽  
...  
Keyword(s):  
Star Formation ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Young Stellar Objects ◽  
High Mass ◽  
Mass Star ◽  
Giant Molecular Clouds ◽  
Stellar Objects ◽  
Stellar Cluster ◽  
The Galaxy

Abstract The aim of this study is to characterize the distribution and basic properties of the natal gas associated with high-mass young stellar objects (YSOs) in isolated environments in the Large Magellanic Cloud. High-mass stars usually form in giant molecular clouds (GMCs) as part of a young stellar cluster, but some OB stars are observed far from GMCs. By examining the spatial coincidence between the high-mass YSOs and 12CO (J = 1–0) emission detected by NANTEN and Mopra observations, we selected ten high-mass YSOs that are located away from any of the NANTEN clouds but are detected by the Mopra pointed observations. The ALMA observations revealed that a compact molecular cloud whose mass is a few thousand solar masses or smaller is associated with the high-mass YSOs, which indicates that these compact clouds are the sites of high-mass star formation. The high density and high temperature throughout the clouds are explained by the severe photodissociation of CO due to the lower metallicity than in the Galaxy. The star formation efficiency ranges from several to as high as ∼40%, indicating efficient star formation in these environments. The enhanced turbulence may be a cause of the efficient star formation therein, as judged from the gas velocity information and the association with the lower density gas.

scholarly journals Massive young stellar objects in the N 66/NGC 346 region of the SMC

2018 ◽  
Vol 615 ◽  
pp. A121 ◽  
Author(s):  
M. Rubio ◽  
R. H. Barbá ◽  
V. M. Kalari
Keyword(s):  
Star Formation ◽  
Magellanic Cloud ◽  
Young Stellar Objects ◽  
High Mass ◽  
Spectral Energy ◽  
Mass Star ◽  
Spectral Features ◽  
Small Magellanic Cloud ◽  
Energy Distributions ◽  
Stellar Objects

We present HK spectra of three sources located in the N 66 region of the Small Magellanic Cloud. The sources display prominent stellar Brγ and extended H2 emission, and exhibit infrared excesses at λ > 2 μm. Based on their spectral features, and photometric spectral energy distributions, we suggest that these sources are massive young stellar objects. The findings are interpreted as evidence of on-going high mass star formation in N 66.

scholarly journals Massive Star Formation Throughout the Galactic Disk

2009 ◽  
Vol 5 (H15) ◽  
pp. 798-798
Author(s):  
Stan Kurtz
Keyword(s):  
Star Formation ◽  
Galactic Plane ◽  
Galactic Disk ◽  
Young Stellar Objects ◽  
High Mass ◽  
Molecular Gas ◽  
Mass Star ◽  
Ionized Gas ◽  
Stellar Objects ◽  
Infrared Spectral

AbstractHigh-mass star formation is manifestly a phenomenon of the Galactic Plane. The process begins with pre-stellar cores, evolves to proto-stellar objects, and culminates in massive main-sequence stars. Because massive young stellar objects are deeply embedded, the radio, sub-mm, and far/mid-infrared spectral windows are the most revealing. Galactic plane surveys at these wavelengths trace hot and cold molecular gas, interstellar masers, warm dust, and ionized gas that are present during star formation.

scholarly journals A documentary of high-mass star formation: Probing the dynamical evolution of Orion Source I on 10–100 AU scales using SiO masers

2007 ◽  
Vol 3 (S242) ◽  
pp. 130-134 ◽  
Author(s):  
L. D. Matthews ◽  
C. Goddi ◽  
L. J. Greenhill ◽  
C. J. Chandler ◽  
M. J. Reid ◽  
...  
Keyword(s):  
Star Formation ◽  
Dynamical Evolution ◽  
Young Stellar Objects ◽  
High Mass ◽  
Mass Star ◽  
Stellar Objects ◽  
Very Large Array ◽  
Long Baseline ◽  
Comprehensive Picture ◽  
Very Long Baseline Array

AbstractA comprehensive picture of high-mass star formation has remained elusive, in part because examples of high-mass young stellar objects (YSOs) tend to be relatively distant, deeply embedded, and confused with other emission sources. These factors have impeded dynamical investigations within tens of AU of high-mass YSOs—scales that are critical for probing the interfaces where outflows from accretion disks are launched and collimated. Using observations of SiO masers obtained with the Very Large Array (VLA) and the Very Long Baseline Array (VLBA), the KaLYPSO project is overcoming these limitations by mapping the structure and dynamical/temporal evolution of the material 10-1000 AU from the nearest high-mass YSO: Radio Source I in the Orion BN/KL region. Our data include ~40 epochs of VLBA observations over a several-year period, allowing us to track the proper motions of individual SiO maser spots and to monitor changes in the physical conditions of the emitting material with time. Ultimately these data will provide 3-D maps of the outflow structure over approximately 30% of the outflow crossing time. Here we summarize recent results from the KaLYPSO project, including evidence that high-mass star formation occurs via disk-mediated accretion.

scholarly journals Rapid and efficient mass collection by a supersonic cloud–cloud collision as a major mechanism of high-mass star formation

2020 ◽  
Author(s):  
Yasuo Fukui ◽  
Tsuyoshi Inoue ◽  
Takahiro Hayakawa ◽  
Kazufumi Torii
Keyword(s):  
Magnetic Field ◽  
Star Formation ◽  
Gravitational Instability ◽  
Mass Function ◽  
Initial Mass Function ◽  
High Mass ◽  
Mass Star ◽  
Major Mechanism ◽  
Dense Cores ◽  
The Magnetic Field

Abstract A supersonic cloud–cloud collision produces a shock-compressed layer which leads to formation of high-mass stars via gravitational instability. We carried out a detailed analysis of the layer by using the numerical simulations of magneto-hydrodynamics which deal with colliding molecular flows at a relative velocity of 20 km s−1 (Inoue & Fukui 2013, ApJ, 774, L31). Maximum density in the layer increases from 1000 cm−3 to more than 105 cm−3 within 0.3 Myr by compression, and the turbulence and the magnetic field in the layer are amplified by a factor of ∼5, increasing the mass accretion rate by two orders of magnitude to more than 10−4 $ M_{\odot } $ yr−1. The layer becomes highly filamentary due to gas flows along the magnetic field lines, and dense cores are formed in the filaments. The massive dense cores have size and mass of 0.03–0.08 pc and 8–$ 50\, M_{\odot } $ and they are usually gravitationally unstable. The mass function of the dense cores is significantly top-heavy as compared with the universal initial mass function, indicating that the cloud–cloud collision preferentially triggers the formation of O and early B stars. We argue that the cloud–cloud collision is a versatile mechanism which creates a variety of stellar clusters from a single O star like RCW 120 and M 20 to tens of O stars of a super star cluster like RCW 38 and a mini-starburst W 43. The core mass function predicted by the present model is consistent with the massive dense cores obtained by recent ALMA observations in RCW 38 (Torii et al. 2021, PASJ, in press) and W 43 (Motte et al. 2018, Nature Astron., 2, 478). Considering the increasing evidence for collision-triggered high-mass star formation, we argue that cloud–cloud collision is a major mechanism of high-mass star formation.

scholarly journals 1D, 2D and 3D Collapse of Interstellar Clouds

1980 ◽  
Vol 58 ◽  
pp. 235-246
Author(s):  
W.M. Tscharnuter
Keyword(s):  
Star Formation ◽  
Gravitational Instability ◽  
Numerical Models ◽  
Young Stellar Objects ◽  
Stellar Objects ◽  
Interstellar Clouds ◽  
B Stars ◽  
Theoretical Investigations ◽  
2D And 3D

This review is concerned with recent theoretical investigations and numerical models of star formation with varions symmetries. Observations strongly support the fact that stars condense out of cool (≈10 K) and dense (103-104 atoms/cm3) interstellar clouds due to gravitational instability and collapse. Bright, young stellar objects (0- and B-stars are always found in the vicinity of coloud complexes.

scholarly journals Infalling Streamer-Disk-Outflow System in a Nearby High-mass Star Formation Region

2021 ◽  
Author(s):  
Xi Chen ◽  
Zhiyuan Ren ◽  
Da-Lei Li ◽  
Tie Liu ◽  
Ke Wang ◽  
...  
Keyword(s):  
Direct Detection ◽  
Theoretical Models ◽  
Young Stellar Objects ◽  
High Mass ◽  
Similar Process ◽  
Mass Star ◽  
Solar Mass ◽  
Low Mass Stars ◽  
Stellar Objects ◽  
Low Mass

Abstract Theoretical models and numerical simulations suggest that high mass star (with mass > 8 solar mass) can be formed either via monolithic collapse of a massive core or competitive accretion, but the dominant mechanism is currently unclear. Although recent high resolution observations with the Atacama Large Millimeter/submillimeter Array (ALMA) have detected physical and kinematic features, such as disks, outflows and filamentary structures surrounding the high mass young stellar objects (HMYSO), direct detection of the infalling gas towards the HMYSO is still the key to distinguish the different scenarios. Chemically fresh gas inflows have been detected towards low-mass stars being formed, which are consistent with the accretion-disk-outflow process. In this work we report the detection of a chemically fresh inflow which is feeding HMYSO growth in the nearby high mass star-forming region G352.63-1.07. High quality images of the dust and molecular lines from both ALMA and the Submillimeter Array (SMA) have consistently revealed a gravitationally-controlled gas inflow towards a rotating structure (disk or torus) around the HMYSO. The HMYSO is also observed to have an outflow, but it can be clearly separated from the inflow. These kinematic features provide observational evidence to support the conjecture that high-mass stars can be formed in a similar process to that observed in the low-mass counterparts. The chemically fresh infalling streamers could also be related with the disk configuration, fragmentation and accretion bursts that occur in both simulations and observations.

scholarly journals Massive Star Formation: Observational Constraints

1997 ◽  
Vol 182 ◽  
pp. 525-536
Author(s):  
Ed Churchwell
Keyword(s):  
Star Formation ◽  
Accretion Disks ◽  
Massive Star ◽  
Young Stellar Objects ◽  
Mass Star ◽  
Structure And Properties ◽  
Low Mass Stars ◽  
Stellar Objects ◽  
The Past ◽  
Low Mass

Observations during the past several years strongly imply that virtually every star, independent of final mass, goes through a phase of rapid outflow simultaneously with rapid accretion during formation. The structure and properties of outflows and accretion disks associated with low-mass star formation has received intensive observational attention during the past several years (see the reviews and references in Lada 1985; Edwards, Ray, and Mundt 1993; Fukui et al. 1993; and this symposium). Young stellar objects (YSOs) with Lbol < 103 L⊘ will be referred to as “low-mass” stars in this review. The range of physical properties of CO outflows associated with YSOs of all masses are enormous, see Fukui et al. (1993). I will focus attention in this review on what we know about massive YSOs and their environments.

scholarly journals MULTIDIMENSIONAL CHEMICAL MODELING OF YOUNG STELLAR OBJECTS. II. IRRADIATED OUTFLOW WALLS IN A HIGH-MASS STAR-FORMING REGION

2009 ◽  
Vol 700 (1) ◽  
pp. 872-886 ◽  
Author(s):  
S. Bruderer ◽  
A.O. Benz ◽  
S. D. Doty ◽  
E. F. van Dishoeck ◽  
T. L. Bourke
Keyword(s):  
Young Stellar Objects ◽  
High Mass ◽  
Mass Star ◽  
Stellar Objects ◽  
Chemical Modeling ◽  
Star Forming

Magnetic field structures in star-forming regions revealed by imaging polarimetry at multi-wavelengths

2018 ◽  
Vol 14 (A30) ◽  
pp. 102-102
Author(s):  
Jungmi Kwon
Keyword(s):  
Magnetic Fields ◽  
Near Infrared ◽  
Infrared Imaging ◽  
Young Stellar Objects ◽  
High Mass ◽  
Mass Star ◽  
Stellar Objects ◽  
Star Forming ◽  
Star Forming Regions ◽  
Imaging Polarimetry

AbstractMagnetic fields are ubiquitous in various scales of astronomical objects, and they are considered as playing significant roles from star to galaxy formations. However, the role of the magnetic fields in star forming regions is less well understood because conventional optical polarimetry is hampered by heavy extinction by dust. We have been conducting extensive near-infrared polarization survey of various star-forming regions from low- and intermediate-mass to high-mass star-forming regions, using IRSF/SIRPOL in South Africa. Not only linear but also circular polarizations have been measured for more than a dozen of regions. Both linear and circular polarimetric observations at near-infrared wavelengths are useful tools to study the magnetic fields in star forming regions, although infrared circular polarimetry has been less explored so far. In this presentation, we summarize our results of the near-infrared polarization survey of star forming regions and its comparison with recent submillimeter polarimetry results. Such multi-wavelength approaches can be extended to the polarimetry using ALMA, SPICA in future, and others. We also present our recent results of the first near-infrared imaging polarimetry of young stellar objects in the Circinus molecular cloud, which has been less studied but a very intriguing cluster containing numerous signs of active low-mass star formation.

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