scholarly journals The Formation of Massive Stars

2010 ◽  
Vol 6 (S270) ◽  
pp. 57-64
Author(s):  
Ian A. Bonnell ◽  
Rowan J Smith
Keyword(s):  
Star Formation ◽  
Magnetic Fields ◽  
Massive Star ◽  
Massive Stars ◽  
Cluster Formation ◽  
High Mass ◽  
Prestellar Cores ◽  
Stellar Mergers ◽  
Massive Clusters ◽  
Viable Mechanism

AbstractThere has been considerable progress in our understanding of how massive stars form but still much confusion as to why they form. Recent work from several sources has shown that the formation of massive stars through disc accretion, possibly aided by gravitational and Rayleigh-Taylor instabilities is a viable mechanism. Stellar mergers, on the other hand, are unlikely to occur in any but the most massive clusters and hence should not be a primary avenue for massive star formation. In contrast to this success, we are still uncertain as to how the mass that forms a massive star is accumulated. there are two possible mechanisms including the collapse of massive prestellar cores and competitive accretion in clusters. At present, there are theoretical and observational question marks as to the existence of high-mass prestellar cores. theoretically, such objects should fragment before they can attain a relaxed, centrally condensed and high-mass state necessary to form massive stars. Numerical simulations including cluster formation, feedback and magnetic fields have not found such objects but instead point to the continued accretion in a cluster potential as the primary mechanism to form high-mass stars. Feedback and magnetic fields act to slow the star formation process and will reduce the efficiencies from a purely dynamical collapse but otherwise appear to not significantly alter the process.

scholarly journals Luminous Blue Variables, cool hypergiants and some impostors in the H-R diagram

2003 ◽  
Vol 212 ◽  
pp. 38-46
Author(s):  
Roberta M. Humphreys
Keyword(s):  
Magnetic Fields ◽  
Mass Loss ◽  
Surface Activity ◽  
Massive Star ◽  
Massive Stars ◽  
High Mass ◽  
Luminous Blue Variables ◽  
Star Evolution ◽  
High Mass Loss ◽  
Massive Star Evolution

Current observations of the S Dor/LBVs and candidates and the implications for their important role in massive star evolution are reviewed. Recent observations of the cool hypergiants are altering our ideas about their evolutionary state, their atmospheres and winds, and the possible mechanisms for their asymmetric high mass loss episodes which may involve surface activity and magnetic fields. Recent results for IRC+10420, ρ Cas and VY CMa are highlighted. S Dor/LBVs in eruption, and the cool hypergiants in their high mass loss phases with their optically thick winds are not what their apparent spectra and temperatures imply; they are then ‘impostors’ on the H-R diagram. The importance of the very most massive stars, like η Carinae and the ‘supernovae impostors’ are also discussed.

Twinkle little stars: Massive stars are quenched in strong magnetic fields

2018 ◽  
Vol 14 (A30) ◽  
pp. 118-118
Author(s):  
Fatemeh S. Tabatabaei ◽  
M. Almudena Prieto ◽  
Juan A. Fernández-Ontiveros
Keyword(s):  
Star Formation ◽  
Magnetic Fields ◽  
Molecular Clouds ◽  
Massive Star ◽  
Massive Stars ◽  
Radio Continuum ◽  
Small Scale ◽  
Massive Star Formation ◽  
Low Mass ◽  
Formation Efficiency

AbstractThe role of the magnetic fields in the formation and quenching of stars with different mass is unknown. We studied the energy balance and the star formation efficiency in a sample of molecular clouds in the central kpc region of NGC 1097, known to be highly magnetized. Combining the full polarization VLA/radio continuum observations with the HST/Hα, Paα and the SMA/CO lines observations, we separated the thermal and non-thermal synchrotron emission and compared the magnetic, turbulent, and thermal pressures. Most of the molecular clouds are magnetically supported against gravitational collapse needed to form cores of massive stars. The massive star formation efficiency of the clouds also drops with the magnetic field strength, while it is uncorrelated with turbulence (Tabatabaei et al. 2018). The inefficiency of the massive star formation and the low-mass stellar population in the center of NGC 1097 can be explained in the following steps: I) Magnetic fields supporting the molecular clouds prevent the collapse of gas to densities needed to form massive stars. II) These clouds can then be fragmented into smaller pieces due to e.g., stellar feedback, non-linear perturbations and instabilities leading to local, small-scale diffusion of the magnetic fields. III) Self-gravity overcomes and the smaller clouds seed the cores of the low-mass stars.

scholarly journals The ALMA Survey of 70 μm Dark High-mass Clumps in Early Stages (ASHES). IV. Star Formation Signatures in G023.477

2021 ◽  
Vol 923 (2) ◽  
pp. 147
Author(s):  
Kaho Morii ◽  
Patricio Sanhueza ◽  
Fumitaka Nakamura ◽  
James M. Jackson ◽  
Shanghuo Li ◽  
...  
Keyword(s):  
Star Formation ◽  
Magnetic Fields ◽  
Line Emission ◽  
High Mass ◽  
Mass Star ◽  
Dark Cloud ◽  
Early Stages ◽  
Star Formation Activity ◽  
Prestellar Cores ◽  
The Masses

Abstract With a mass of ∼1000 M ⊙ and a surface density of ∼0.5 g cm−2, G023.477+0.114, also known as IRDC 18310-4, is an infrared dark cloud (IRDC) that has the potential to form high-mass stars and has been recognized as a promising prestellar clump candidate. To characterize the early stages of high-mass star formation, we have observed G023.477+0.114 as part of the Atacama Large Millimeter/submillimeter Array (ALMA) Survey of 70 μm Dark High-mass Clumps in Early Stages. We have conducted ∼1.″2 resolution observations with ALMA at 1.3 mm in dust continuum and molecular line emission. We have identified 11 cores, whose masses range from 1.1 to 19.0 M ⊙. Ignoring magnetic fields, the virial parameters of the cores are below unity, implying that the cores are gravitationally bound. However, when magnetic fields are included, the prestellar cores are close to virial equilibrium, while the protostellar cores remain sub-virialized. Star formation activity has already started in this clump. Four collimated outflows are detected in CO and SiO. H2CO and CH3OH emission coincide with the high-velocity components seen in the CO and SiO emission. The outflows are randomly oriented for the natal filament and the magnetic field. The position-velocity diagrams suggest that episodic mass ejection has already begun even in this very early phase of protostellar formation. The masses of the identified cores are comparable to the expected maximum stellar mass that this IRDC could form (8–19 M ⊙). We explore two possibilities on how IRDC G023.477+0.114 could eventually form high-mass stars in the context of theoretical scenarios.

scholarly journals On Heating, Ionization, and Star Formation in the Galactic Center Region

1989 ◽  
Vol 136 ◽  
pp. 171-177 ◽  
Author(s):  
Mark Morris
Keyword(s):  
Star Formation ◽  
Magnetic Fields ◽  
Massive Star ◽  
Direct Evidence ◽  
Galactic Center ◽  
Massive Stars ◽  
Interstellar Gas ◽  
Red Supergiants ◽  
Alternative Sources ◽  
Poloidal Magnetic Fields

The ionization of interstellar gas and the heating of dust near the galactic center are usually assumed to be dominated overall by the radiation emanating from young, massive stars. This paper questions that assumption by pointing to the paucity of direct evidence for current star formation and by considering alternative sources of ionization and luminosity. It is suggested that star formation can be inhibited by the strong, poloidal magnetic fields observed in the galactic center. The presence of some red supergiants (e.g., IRS7) can be understood if massive star formation occurs episodically.

Magnetic massive stars in star forming regions

2018 ◽  
Vol 14 (A30) ◽  
pp. 132-132
Author(s):  
Swetlana Hubrig ◽  
Markus Schöller ◽  
Silva P. Järvinen
Keyword(s):  
Magnetic Field ◽  
Star Formation ◽  
Magnetic Fields ◽  
Active Sites ◽  
Massive Stars ◽  
High Mass ◽  
Mass Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
Gas Cloud

AbstractOne idea for the origin of magnetic fields in massive stars suggests that the magnetic field is the fossil remnant of the Galactic ISM magnetic field, amplified during the collapse of the magnetised gas cloud. A search for the presence of magnetic fields in massive stars located in active sites of star formation led to the detection of rather strong magnetic fields in a few young stars. Future spectropolarimetric observations are urgently needed to obtain insights into the mechanisms that drive the generation of kG magnetic fields during high-mass star formation.

scholarly journals Formation of massive stars

2010 ◽  
Vol 6 (S270) ◽  
pp. 33-40
Author(s):  
Maria T. Beltrán
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Massive Stars ◽  
Point Of View ◽  
High Mass ◽  
Observational Research ◽  
Current Status ◽  
Dark Clouds ◽  
Star Formation Activity ◽  
Infrared Dark Clouds

AbstractThe formation of high-mass stars represents a challenge from both a theoretical and an observational point of view. Here, we present an overview of the current status of the observational research on this field, outlining the progress achieved in recent years on our knowledge of the initial phases of massive star formation. The fragmentation of cold, infrared-dark clouds, and the evidence for star formation activity on some of them will be discussed, together with the kinematics of the gas in hot molecular cores, which can give us insights on the mechanism leading to the birth of an OB star.

Multiple Feedback in Low-Metallicity Massive Star Formation

2018 ◽  
Vol 14 (S344) ◽  
pp. 190-194
Author(s):  
Kei E. I. Tanaka ◽  
Jonathan C. Tan ◽  
Yichen Zhang ◽  
Takashi Hosokawa
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Massive Stars ◽  
Lower Surface ◽  
Mass Star ◽  
Massive Star Formation ◽  
Cluster Galaxy ◽  
Prestellar Cores ◽  
Low Metallicity ◽  
The Impact

AbstractWe theoretically investigate the impact of feedback and its metallicity dependence in massive star formation from prestellar cores at all metallicity range. We include the feedback by MHD disk winds, radiation pressure, and photoevaporation solving the evolution of protostars and accretion flows self-consistently. Interestingly, we find that the feedback does not set the upper mass limit of stellar birth mass at any metallicity. At the solar metallicity, the MHD disk wind is the dominant feedback to set the star formation efficiencies (SFEs) from the prestellar cores similar to low-mass star formation. The SFE is found to be lower at lower surface density environment. The photoevaporation becomes significant at the low metallicity of Z < 10−2 Z⊙. Considering this efficient photoevaporation, we conclude that the IMF slope is steeper, i.e., massive stars are rarer at the extremely metal-poor environment of 10−5 − 10−3Z⊙. Our study raises a question on the common assumption of the universal IMF with a truncated at 100M⊙. Since the total feedback strength in the cluster/galaxy scale is sensitive to the number fraction of massive stars, the re-evaluations of IMF at various environments are necessary.

scholarly journals The coupled effects of protostellar outflows, radiation feedback, magnetic fields and turbulence on the formation of massive stars and Orion-like clusters

2012 ◽  
Vol 10 (H16) ◽  
pp. 580-582
Author(s):  
Richard I. Klein
Keyword(s):  
Magnetic Fields ◽  
Molecular Clouds ◽  
Massive Stars ◽  
Critical Role ◽  
High Mass ◽  
Feedback Effects ◽  
Pressure Feedback ◽  
Protostellar Outflows ◽  
Effects Of Feedback ◽  
Massive Clusters

AbstractFeedback processes from massive stars plays a critical role in their formation, destroy the molecular clouds in which they are born and shape the evolution of galaxies. In this talk I will discuss our recent 3D AMR simulations that are the first to include the coupled feedback effects of protostellar outflows combined with protostellar heating and radiation pressure feedback and magnetic fields, in a single computation and their effects on the infalling dusty gas in the surrounding environs of the accreting core envelope. These simulations will address the detailed effects of feedback on the formation of high mass stars and massive clusters with implications for the IMF.

scholarly journals Hot molecular cores, sites of high mass star formation

1999 ◽  
Vol 193 ◽  
pp. 559-567
Author(s):  
Susana Lizano ◽  
Mayra Osorio
Keyword(s):  
Star Formation ◽  
Density Distribution ◽  
Flux Density ◽  
Massive Star ◽  
Massive Stars ◽  
High Mass ◽  
Mass Star ◽  
Accretion Rates ◽  
Flux Density Distribution

We model the flux-density distribution of hot molecular cores as in-falling envelopes of gas and dust onto a central massive star. The envelopes are heated by both the stellar luminosity and the accretion luminosity. We find that, in order to reproduce the observed fluxes, these objects require high mass accretion rates Ṁ ≃ 10−4−3 M⊙yr−1 infalling onto central late B-type stars. We discuss the implications of this intense accretion phase on the formation of massive stars.

scholarly journals Comparison of Low-Mass and High-Mass Star Formation

2015 ◽  
Vol 11 (S315) ◽  
pp. 154-162 ◽  
Author(s):  
Jonathan C. Tan
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Initial Conditions ◽  
Cluster Formation ◽  
Theoretical Models ◽  
High Mass ◽  
Mass Star ◽  
Massive Star Formation ◽  
Low Mass ◽  
Core Accretion

AbstractI review theoretical models of star formation and how they apply across the stellar mass spectrum. Several distinct theories are under active study for massive star formation, especiallyTurbulent Core Accretion,Competitive AccretionandProtostellar Mergers, leading to distinct observational predictions. These include the types of initial conditions, the structure of infall envelopes, disks and outflows, and the relation of massive star formation to star cluster formation. Even for Core Accretion models, there are several major uncertainties related to the timescale of collapse, the relative importance of different processes for preventing fragmentation in massive cores, and the nature of disks and outflows. I end by discussing some recent observational results that are helping to improve our understanding of these processes.

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