Search for OB stars running away from young star clusters

Gvaramadze, V. V.; Kniazev, A. Y.; Kroupa, Pavel; Oh, Seungkyung

doi:10.1051/0004-6361/201117746

Cited by 62 publications

(84 citation statements)

References 91 publications

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“…They exhibit a bow-shock morphology at 70 μm (see Fig. A.5) which is similar to the bowshock features listed by Gvaramadze et al (2011), suggesting that they could be run-away stars coming from NGC 6334.…”

Section: Discussionsupporting

confidence: 71%

NGC 6334 and NGC 6357: Hαkinematics and the nature of the H II regions

Russeil

Tigé

Adami

et al. 2016

A&A

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Aims. NGC 6334 and NGC 6357 are amongst the most active, optically visible Galactic star-forming complexes. They are composed of several H ii regions that have a significant impact on their surrounding. The aim of this paper is to present a kinematic study of the optical H ii regions that belong to NGC 6334 and NGC 6357.Methods. We use Fabry-Perot interferometer observations of the Hα line, which cover NGC 6334 and NGC 6357. These observations allow us to analyse the Hα line profiles to probe the kinematics of the ionised gas of both regions. We complement the Hα observations with multi-wavelength data to specify the nature of the H ii regions. Results. We determine the dynamical nature of the optical H ii regions that belongs to NGC 6334 and NGC 6357. In NGC 6334, GUM 61 is an expanding wind shell-like H ii region, GUM 64b exhibits a champagne flow, GM1-24 is the Hα counterpart of two larger regions and H ii 351.2+0.5 is, in fact, composed of two H ii regions. In NGC 6357, H ii 353.08+0.28 and H ii 353.09+0.63 are probably stellar wind-shaped bubble H ii regions, while H ii 353.42+0.45 is a classical photo-ionised H ii region. We suggest that, at large scale, star-formation seems to be triggered where large/old H ii regions intersect. Inversely, stellar formation seems to have already started in the NGC 6334 north-east filament, irrespective of any evident external H ii region impact. While NGC 6357 shows more complicated kinematics, NGC 6334 is characterised by a more active stellar formation.

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Section: Discussionsupporting

confidence: 71%

NGC 6334 and NGC 6357: Hαkinematics and the nature of the H II regions

Russeil

Tigé

Adami

et al. 2016

A&A

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“…We retrieved the post-basic data calibrated MIPS 24 µm image of κ Cas (with units of MJy sr −1 ) from the NASA/IPAC infrared science archive 1 . In this image (presented for the first time in Gvaramadze et al 2011b) the astrosphere of κ Cas appears (see Fig. 1) as a clear arcuate structure with numerous cirrus-like filaments beyond it, some of which are apparently attached to the main (brightest) arc.…”

Section: Observational Datamentioning

confidence: 82%

“…Gvaramadze et al 2011a, b). Although the origin of this structure is not well understood, it seems likely that the regular interstellar magnetic field might play an important role in its formation (Gvaramadze et al 2011b).…”

Section: Introductionmentioning

confidence: 99%

An astrosphere around the blue supergiant κ Cas: possible explanation of its filamentary structure

Katushkina

Alexashov

Gvaramadze

et al. 2017

Monthly Notices of the Royal Astronomical Society

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High-resolution mid-infrared observations carried out by the Spitzer Space Telescope allowed one to resolve the fine structure of many astrospheres. In particular, they showed that the astrosphere around the B0.7 Ia star κ Cas (HD 2905) has a clear-cut arc structure with numerous cirrus-like filaments beyond it. Previously, we suggested a physical mechanism for the formation of such filamentary structures. Namely, we showed theoretically that they might represent the non-monotonic spatial distribution of the interstellar dust in astrospheres (viewed as filaments) caused by interaction of the dust grains with the interstellar magnetic field disturbed in the astrosphere due to colliding of the stellar and interstellar winds. In this paper, we invoke this mechanism to explain the structure of the astrosphere around κ Cas. We performed 3D magnetohydrodynamic modelling of the astrosphere for realistic parameters of the stellar wind and space velocity. The dust dynamics and the density distribution in the astrosphere were calculated in the framework of a kinetic model. It is found that the model results with the classical MRN size distribution of dust in the interstellar medium do not match the observations, and that the observed filamentary structure of the astrosphere can be reproduced only if the dust is composed mainly of big (µm-sized) grains. Comparison of the model results with observations allowed us to estimate parameters (number density and magnetic field strength) of the surrounding interstellar medium.

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“…For young H ii regions, O stars are likely ejected via dynamical encounters, which are enhanced by their high binary fraction (e.g., Leonard & Duncan 1990;Kroupa 2004); direct signatures of O-star escape can be seen in imaging of bow shocks (Gvaramadze et al 2011). Although the loss of ionizing stars from H ii regions could contribute to the discrepancy between SFR 24 and SFR SC , it cannot account for the full magnitude of the discrepancy.…”

Section: Runaway Massive Starsmentioning

confidence: 99%

Toward a Unification of Star Formation Rate Determinations in the Milky Way and Other Galaxies

Chomiuk

Povich

2011

The Astronomical Journal

326

287

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The star formation rate (SFR) of the Milky Way remains poorly known, with often-quoted values ranging from 1 to 10 M yr −1 . This situation persists despite the potential for the Milky Way to serve as the ultimate SFR calibrator for external galaxies. We show that various estimates for the Galactic SFR are consistent with one another once they have been normalized to the same initial mass function (IMF) and massive star models, converging to 1.9 ± 0.4 M yr −1 . However, standard SFR diagnostics are vulnerable to systematics founded in the use of indirect observational tracers sensitive only to high-mass stars. We find that absolute SFRs measured using resolved low/intermediate-mass stellar populations in Galactic H ii regions are systematically higher by factors of ∼2-3 compared with calibrations for SFRs measured from mid-IR and radio emission. We discuss some potential explanations for this discrepancy and conclude that it could be allayed if (1) the power-law slope of the IMF for intermediate-mass (1.5 M < m < 5M ) stars were steeper than the Salpeter slope or (2) a correction factor was applied to the extragalactic 24 μm SFR calibrations to account for the duration of star formation in individual mid-IR-bright H ii regions relative to the lifetimes of O stars. Finally, we present some approaches for testing whether a Galactic SFR of ∼2 M yr −1 is consistent with what we would measure if we could view the Milky Way as external observers. Using luminous radio supernova remnants and X-ray point sources, we find that the Milky Way deviates from expectations at the 1σ -3σ level, hinting that perhaps the Galactic SFR is overestimated or extragalactic SFRs need to be revised upward.

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Search for OB stars running away from young star clusters

Cited by 62 publications

References 91 publications

NGC 6334 and NGC 6357: Hαkinematics and the nature of the H II regions

NGC 6334 and NGC 6357: Hαkinematics and the nature of the H II regions

An astrosphere around the blue supergiant κ Cas: possible explanation of its filamentary structure

Toward a Unification of Star Formation Rate Determinations in the Milky Way and Other Galaxies

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