Summary Talk: What is Happening to Massive Stars in Galaxies?

Highlights of the IAU Symposium 116 are reviewed. Some of the general themes running through the meeting are identified. These include:i) the fruitful interaction between observation, laboratory work and theory. ii) the need for understanding and, if possible, correcting for the effects of incompleteness and bias in observing lists. iii) the importance of the Magellanic Clouds, as the nearest independently evolving stellar systems, in the study of massive star formation and evolution in galaxies.

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A survey of the most massive stars in the Magellanic Clouds

Proceedings of the International Astronomical Union ◽

10.1017/s1743921308028688 ◽

2008 ◽

Vol 4 (S256) ◽

pp. 343-348

Author(s):

Alceste Z. Bonanos

Keyword(s):

Star Formation ◽

Massive Star ◽

Massive Stars ◽

Magellanic Clouds ◽

Eclipsing Binaries ◽

Large Impact ◽

Massive Star Formation ◽

Fundamental Parameters ◽

Precise Data ◽

Formation And Evolution

AbstractDespite the large impact very massive stars (>30 M⊙) have in astrophysics, their fundamental parameters remain uncertain. I present results of a survey aiming to characterize the most massive stars in the Magellanic Clouds. The survey targets the brightest, blue, eclipsing binaries discovered by the OGLE microlensing survey, for which masses and radii are measured to 5%. Such precise data are rare and provide constraints for theories of massive star formation and evolution at low metallicities.

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Line-driven ablation of circumstellar discs – IV. The role of disc ablation in massive star formation and its contribution to the stellar upper mass limit

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/sty3394 ◽

2018 ◽

Vol 483 (4) ◽

pp. 4893-4900 ◽

Cited By ~ 3

Author(s):

Nathaniel Dylan Kee ◽

Rolf Kuiper

Keyword(s):

Star Formation ◽

Massive Star ◽

Loss Rate ◽

Massive Stars ◽

Mass Loss Rate ◽

Ablation Rate ◽

Massive Star Formation ◽

Future Studies ◽

Accretion Rates

Abstract Radiative feedback from luminous, massive stars during their formation is a key process in moderating accretion on to the stellar object. In the prior papers in this series, we showed that one form such feedback takes is UV line-driven disc ablation. Extending on this study, we now constrain the strength of this effect in the parameter range of star and disc properties appropriate to forming massive stars. Simulations show that ablation rate depends strongly on stellar parameters, but that this dependence can be parameterized as a nearly constant, fixed enhancement over the wind mass-loss rate, allowing us to predict the rate of disc ablation for massive (proto)stars as a function of stellar mass and metallicity. By comparing this to predicted accretion rates, we conclude that ablation is a strong feedback effect for very massive (proto)stars which should be considered in future studies of massive star formation.

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HII regions and star formation in the Magellanic Clouds

Symposium - International Astronomical Union ◽

10.1017/s0074180900200211 ◽

1991 ◽

Vol 148 ◽

pp. 139-144 ◽

Cited By ~ 2

Author(s):

Robert C. Kennicutt

Keyword(s):

Star Formation ◽

Interstellar Medium ◽

Massive Star ◽

Massive Stars ◽

Hii Regions ◽

Magellanic Clouds ◽

H Ii Regions ◽

Distant Galaxies ◽

Close Range ◽

Mass Functions

The H II regions in the Magellanic Clouds provide an opportunity to characterize the global star formation properties of a galaxy at close range. They also provide a unique laboratory for testing empirical tracers of the massive star formation rates and initial mass functions in more distant galaxies, and for studying the dynamical interactions between massive stars and the interstellar medium. This paper discusses several current studies in these areas.

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

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319003715 ◽

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.

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The multiplicity of massive stars: a 2016 view

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317003209 ◽

2016 ◽

Vol 12 (S329) ◽

pp. 110-117 ◽

Cited By ~ 5

Author(s):

Hugues Sana

Keyword(s):

Star Formation ◽

Formation Process ◽

Massive Star ◽

Main Sequence ◽

Initial Conditions ◽

Massive Stars ◽

Massive Star Formation ◽

Future Evolution

AbstractMassive stars like company. Here, we provide a brief overview of progresses made over the last 5 years by a number of medium and large surveys. These results provide new insights on the observed and intrinsic multiplicity properties of main sequence massive stars and on the initial conditions for their future evolution. They also bring new interesting constraints on the outcome of the massive star formation process.

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The VLT-FLAMES Tarantula Survey

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833433 ◽

2018 ◽

Vol 618 ◽

pp. A73 ◽

Cited By ~ 24

Author(s):

F. R. N. Schneider ◽

O. H. Ramírez-Agudelo ◽

F. Tramper ◽

J. M. Bestenlehner ◽

N. Castro ◽

...

Keyword(s):

Star Formation ◽

Massive Star ◽

Massive Stars ◽

High Redshift ◽

Large Magellanic Cloud ◽

Giant Molecular Clouds ◽

Stellar Content ◽

Massive Star Formation ◽

Hii Region ◽

Mass Distributions

The 30 Doradus (30 Dor) nebula in the Large Magellanic Cloud (LMC) is the brightest HII region in the Local Group and a prototype starburst similar to those found in high redshift galaxies. It is thus a stepping stone to understand the complex formation processes of stars in starburst regions across the Universe. Here, we have studied the formation history of massive stars in 30 Dor using masses and ages derived for 452 mainly OB stars from the spectroscopic VLT-FLAMES Tarantula Survey (VFTS). We find that stars of all ages and masses are scattered throughout 30 Dor. This is remarkable because it implies that massive stars either moved large distances or formed independently over the whole field of view in relative isolation. We find that both channels contribute to the 30 Dor massive star population. Massive star formation rapidly accelerated about 8 Myr ago, first forming stars in the field before giving birth to the stellar populations in NGC 2060 and NGC 2070. The R136 star cluster in NGC 2070 formed last and, since then, about 1 Myr ago, star formation seems to be diminished with some continuing in the surroundings of R136. Massive stars within a projected distance of 8 pc of R136 are not coeval but show an age range of up to 6 Myr. Our mass distributions are well populated up to 200 M⊙. The inferred IMF is shallower than a Salpeter-like IMF and appears to be the same across 30 Dor. By comparing our sample of stars to stellar models in the Hertzsprung–Russell diagram, we find evidence for missing physics in the models above log L/L⊙ = 6 that is likely connected to enhanced wind mass loss for stars approaching the Eddington limit. Our work highlights the key information about the formation, evolution and final fates of massive stars encapsulated in the stellar content of 30 Dor, and sets a new benchmark for theories of massive star formation in giant molecular clouds.

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Massive Star Formation in the Sparsest Environments

Proceedings of the International Astronomical Union ◽

10.1017/s174392131600822x ◽

2015 ◽

Vol 11 (S315) ◽

Author(s):

Sally Oey ◽

Joel B. Lamb

Keyword(s):

Star Formation ◽

Massive Star ◽

Massive Stars ◽

Hii Regions ◽

Magellanic Cloud ◽

Small Magellanic Cloud ◽

Massive Star Formation ◽

Ob Stars ◽

Runaway Stars

AbstractThere is growing evidence that massive stars sometimes form in extremely sparse environments. The RIOTS4 survey presents a variety of evidence supporting this scenario, including a sample of 14 OB stars in the Small Magellanic Cloud (SMC) that appear to have formed in situ as field stars. This is based on the presence of dense, symmetric HII regions hosting apparent non-runaway stars. We also present a spatially complete IMF of SMC field OB stars for masses > 7 M⊙, showing that the slope is much steeper than the Salpeter value. The binary fraction among field OB stars is also the same as in clusters, based on a RIOTS4 subsample. These results suggest a relative, but incomplete, suppression of massive star formation in the sparsest regimes.

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Fast cloud–cloud collisions in a strongly barred galaxy: suppression of massive star formation

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa840 ◽

2020 ◽

Vol 494 (2) ◽

pp. 2131-2146 ◽

Cited By ~ 1

Author(s):

Yusuke Fujimoto ◽

Fumiya Maeda ◽

Asao Habe ◽

Kouji Ohta

Keyword(s):

Star Formation ◽

Massive Star ◽

Massive Stars ◽

Extreme Environment ◽

Bound State ◽

Observational Evidence ◽

Giant Molecular Clouds ◽

Massive Star Formation ◽

Barred Galaxies ◽

Cloud Properties

ABSTRACT Recent galaxy observations show that star formation activity changes depending on galactic environments. In order to understand the diversity of galactic-scale star formation, it is crucial to understand the formation and evolution of giant molecular clouds in an extreme environment. We focus on observational evidence that bars in strongly barred galaxies lack massive stars even though quantities of molecular gas are sufficient to form stars. In this paper, we present a hydrodynamical simulation of a strongly barred galaxy, using a stellar potential which is taken from observational results of NGC 1300, and we compare cloud properties between different galactic environments: bar, bar-end, and spiral arms. We find that the mean of cloud’s virial parameter is αvir ∼ 1 and that there is no environmental dependence, indicating that the gravitationally bound state of a cloud is not behind the observational evidence of the lack of massive stars in strong bars. Instead, we focus on cloud–cloud collisions, which have been proposed as a triggering mechanism for massive star formation. We find that the collision speed in the bar is faster than those in the other regions. We examine the collision frequency using clouds’ kinematics and conclude that the fast collisions in the bar could originate from random-like motion of clouds due to elliptical gas orbits shifted by the bar potential. These results suggest that the observed regions of lack of active star formation in the strong bar originate from the fast cloud–cloud collisions, which are inefficient in forming massive stars, due to the galactic-scale violent gas motion.

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The Massive Star Population at the Center of the Milky Way

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314007315 ◽

2014 ◽

Vol 9 (S307) ◽

pp. 426-430

Author(s):

Francisco Najarro ◽

Diego de la Fuente ◽

Tom R. Geballe ◽

Don F. Figer ◽

D. John Hillier

Keyword(s):

Star Formation ◽

Infrared Spectra ◽

Massive Star ◽

Milky Way ◽

Galactic Center ◽

Massive Stars ◽

Harsh Environment ◽

Massive Star Formation ◽

Tidal Interactions ◽

Stellar Properties

AbstractRecent detection of a large number of apparently isolated massive stars within the inner 80 pc of the Galactic Center has raised fundamental questions regarding massive star formation in a such a dense and harsh environment. Are these isolated stars the results of tidal interactions between clusters, are they escapees from a disrupted cluster, or do they represent a new mode of massive star formation in isolation? Noting that most of the isolated massive stars have spectral analogs in the Quintuplet Cluster, we have undertaken a combined analysis of the infrared spectra of both selected Quintuplet stars and the isolated objects using Gemini North spectroscopy. We present preliminary results, aiming at α-elements vs iron abundances, stellar properties, ages and radial velocities which will differentiate the top-heavy and star-formation scenarios.

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