The Wolf–Rayet Content of the Galaxies of the Local Group and Beyond

Neugent, Kathryn F.; Massey, Philip

doi:10.3390/galaxies7030074

Cited by 29 publications

(22 citation statements)

References 129 publications

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“…In Geneva SSPs, however, these trends are evident to a lesser degree, likely as a result of the high massloss rates of the Geneva isochrones leading to the selection of a large number of late-type WC spectra. Nevertheless, the WR features (in both Geneva and Parsec SSPs) show an overall behaviour with stellar metallicity that qualitatively agrees with the spectroscopic observations of star-forming regions in nearby galaxies (Crowther 2007;Neugent & Massey 2019).…”

Section: The Improvements To the Spectral Featuressupporting

confidence: 86%

Stellar populations and physical properties of starbursts in the antennae galaxy from self-consistent modelling of MUSE spectra

Gunawardhana

Brinchmann

Weilbacher

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We have modelled the stellar and nebular continua and emission-line intensity ratios of massive stellar populations in the Antennae galaxy using high resolution and self-consistent libraries of model HII regions around central clusters of aging stars. The model libraries are constructed using the stellar population synthesis code, Starburst99, and photoionisation model, Cloudy. The Geneva and PARSEC stellar evolutionary models are plugged into Starburst99 to allow comparison between the two models. Using a spectrum-fitting methodology that allows the spectral features in the stellar and nebular continua (e.g. Wolf-Rayet features, Paschen jump), and emission-line diagnostics to constrain the models, we apply the libraries to the high-resolution MUSE spectra of the starbursting regions in the Antennae galaxy. Through this approach, we were able to model the continuum emission from Wolf-Rayet stars and extract stellar and gas metallicities, ages, electron temperatures and densities of starbursts by exploiting the full spectrum. From the application to the Antennae galaxy, we find that (1) the starbursts in the Antennae galaxy are characterised by stellar and gas metallicities of around solar, (2) the star-forming gas in starbursts in the Western loop of NGC 4038 appears to be more enriched, albeit slightly, than the rest of galaxy, (3) the youngest starbursts are found across the overlap region and over parts of the western-loop, though in comparison, the regions in the western-loop appear to be at a slightly later stage in star-formation than the overlap region, and (4) the results obtained from fitting the Geneva and Parsec models are largely consistent.

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Section: The Improvements To the Spectral Featuressupporting

confidence: 86%

Stellar populations and physical properties of starbursts in the antennae galaxy from self-consistent modelling of MUSE spectra

Gunawardhana

Brinchmann

Weilbacher

et al. 2020

Monthly Notices of the Royal Astronomical Society

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“…Thus, binary-stripped stars and cWR stars are always He stars, but the converse does not hold. The discovery of WR stars relies on image subtractions taken with narrow-band filters (see recent review by Neugent & Massey 2019). The filters are designed to focus on the most prominent emission features of WR stars.…”

Section: Definitionsmentioning

confidence: 99%

Why binary interaction does not necessarily dominate the formation of Wolf-Rayet stars at low metallicity

Shenar

Gilkis

Vink

et al. 2020

A&A

102

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Context. Classical Wolf-Rayet (WR) stars are massive, hydrogen depleted, post main-sequence stars that exhibit emission-line dominated spectra. For a given metallicity Z, stars exceeding a certain initial mass M WR single (Z) can reach the WR phase through intrinsic mass-loss or eruptions (single-star channel). In principle, stars of lower masses can reach the WR phase via stripping through binary interactions (binary channel). Because winds become weaker at low Z, it is commonly assumed that the binary channel dominates the formation of WR stars in environments with low metallicity such as the Small and Large Magellanic Clouds (SMC, LMC). However, the reported WR binary fractions of 30 − 40% in the SMC (Z = 0.002) and LMC (Z = 0.006) are comparable to that of the Galaxy (Z = 0.014), and no evidence for the dominance of the binary channel at low Z could be identified observationally. Here, we explain this apparent contradiction by considering the minimum initial mass M WR spec (Z) needed for the stripped product to appear as a WR star. Aims. By constraining M WR spec (Z) and M WR single (Z), we estimate the importance of binaries in forming WR stars as a function of Z. Methods. We calibrate M WR spec (Z) using the lowest-luminosity WR stars in the Magellanic Clouds and the Galaxy. A range of M WR single values are explored using various evolution codes. We estimate the additional contribution of the binary channel by considering the interval [M WR spec (Z), M WR single (Z)], which characterizes the initial-mass range in which the binary channel can form additional WR stars. Results. The WR-phenomenon ceases below luminosities of log L≈4. 9, 5.25, and 5.6 [L ] in the Galaxy, the LMC, and the SMC, respectively, which translates to minimum He-star masses of 7.5, 11, 17 M and minimum initial masses of M WR spec = 18, 23, 37 M . Stripped stars with lower initial masses in the respective galaxies would tend to not appear as WR stars. The minimum mass necessary for self-stripping, M WR single (Z), is strongly model dependent, but lies in the range 20 − 30, 30 − 60, and 40 M for the Galaxy, LMC, and SMC, respectively. We find that that the additional contribution of the binary channel is a non-trivial and model-dependent function of Z that cannot be conclusively claimed to be monotonically increasing with decreasing Z. Conclusions. The WR spectral appearance arises from the presence of strong winds. Therefore, both M WR spec and M WR single increase with decreasing metallicity. Considering this, we show that one should not a-priori expect that binary interactions become increasingly important in forming WR stars at low Z, or that the WR binary fraction grows with decreasing Z.

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“…Still a popular subject, Neugent and Massey [370] provide an update for our Local Group. Following Webster's pioneering work, Gaia has enabled distances to over 1000 planetary nebulae González-Santamaría et al [371].…”

Section: Discussionmentioning

confidence: 99%

History of Astronomy in Australia: Big-Impact Astronomy from World War II until the Lunar Landing (1945–1969)

Graham

Kenyon

Bull³

et al. 2021

Galaxies

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Radio astronomy commenced in earnest after World War II, with Australia keenly engaged through the Council for Scientific and Industrial Research. At this juncture, Australia’s Commonwealth Solar Observatory expanded its portfolio from primarily studying solar phenomena to conducting stellar and extragalactic research. Subsequently, in the 1950s and 1960s, astronomy gradually became taught and researched in Australian universities. However, most scientific publications from this era of growth and discovery have no country of affiliation in their header information, making it hard to find the Australian astronomy articles from this period. In 2014, we used the then-new Astrophysics Data System (ADS) tool Bumblebee to overcome this challenge and track down the Australian-led astronomy papers published during the quarter of a century after World War II, from 1945 until the lunar landing in 1969. This required knowledge of the research centres and facilities operating at the time, which are briefly summarised herein. Based on citation counts—an objective, universally-used measure of scientific impact—we report on the Australian astronomy articles which had the biggest impact. We have identified the top-ten most-cited papers, and thus also their area of research, from five consecutive time-intervals across that blossoming quarter-century of astronomy. Moreover, we have invested a substantial amount of time researching and providing a small tribute to each of the 62 scientists involved, including several trail-blazing women. Furthermore, we provide an extensive list of references and point out many interesting historical connections and anecdotes.

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The Wolf–Rayet Content of the Galaxies of the Local Group and Beyond

Cited by 29 publications

References 129 publications

Stellar populations and physical properties of starbursts in the antennae galaxy from self-consistent modelling of MUSE spectra

Stellar populations and physical properties of starbursts in the antennae galaxy from self-consistent modelling of MUSE spectra

Why binary interaction does not necessarily dominate the formation of Wolf-Rayet stars at low metallicity

History of Astronomy in Australia: Big-Impact Astronomy from World War II until the Lunar Landing (1945–1969)

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