The origin of massive O-type field stars

Wit, W. J. de; Testi, L.; Palla, F.; Vanzi, L.; Zinnecker, H.

doi:10.1051/0004-6361:20040454

Cited by 109 publications

(146 citation statements)

References 58 publications

(65 reference statements)

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“…This conclusion leads us to challenge the received hypothesis that clusters are the fundamental building blocks of the stellar populations in galaxies (de Wit et al 2004(de Wit et al , 2005. In this view, clusters are given an independent existence from before the time that stars form.…”

Section: Discussionmentioning

confidence: 96%

The Scale‐Free Character of the Cluster Mass Function and the Universality of the Stellar Initial Mass Function

Selman

Melnick

2008

Astrophysical Journal

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Our recent determination of a Salpeter slope for the initial mass function (IMF) in the field of 30 Doradus appears to be in conflict with simple probabilistic counting arguments advanced in the past to support observational claims of a steeper IMF in the LMC field. In this paper we reexamine these arguments and show by explicit construction that, contrary to these claims, the field IMF is expected to be exactly the same as the stellar IMF of the clusters out of which the field was presumably formed. We show that the current data on the mass distribution of clusters themselves is in excellent agreement with our model, and is consistent with a single spectrum by the number of stars of the type n , with between À1.8 and À2.2 down to the smallest clusters, without any preferred mass scale for cluster formation. We also use the random sampling model to estimate the statistics of the maximal mass star in clusters, and confirm the discrepancy with observations found by Weidner & Kroupa. We argue that rather than signaling the violation of the random sampling model, these observations reflect the gravitationally unstable nature of systems with one very large mass star. We stress the importance of the random sampling model as a null hypothesis, whose violation would signal the presence of interesting physics.

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Section: Discussionmentioning

confidence: 96%

The Scale‐Free Character of the Cluster Mass Function and the Universality of the Stellar Initial Mass Function

Selman

Melnick

2008

Astrophysical Journal

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“…In the Milky Way, similar observations can reach fainter magnitudes and thus imply certainty of isolation (e.g. de Wit et al 2004). Characterization of the environment of very massive stars is a powerful tool not only to investigate their formation process, but also to understand how the IMF is sampled.…”

Section: Introductionmentioning

confidence: 98%

The little-studied cluster Berkeley 90 – III. Cluster parameters

Marco

Negueruela

2016

Mon. Not. R. Astron. Soc.

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The open cluster Berkeley 90 is the home to one of the most massive binary systems in the Galaxy, LS III +46 • 11, formed by two identical, very massive stars (O3.5 If* + O3.5 If*), and a second early-O system (LS III +46 • 12 with an O4.5 IV((f)) component at least). Stars with spectral types earlier than O4 are very scarce in the Milky Way, with no more than 20 examples. The formation of such massive stars is still an open question today, and thus the study of the environments where the most massive stars are found can shed some light on this topic. To this aim, we determine the properties and characterize the population of Berkeley 90 using optical, near-infrared and WISE photometry and optical spectroscopy. This is the first determination of these parameters with accuracy. We find a distance of 3.5 +0.5 −0.5 kpc and a maximum age of 3 Ma. The cluster mass is around 1 000 M (perhaps reaching 1 500 M if the surrounding population is added), and we do not detect candidate runaway stars in the area. There is a second population of young stars to the Southeast of the cluster that may have formed at the same time or slightly later, with some evidence for low-activity ongoing star formation.

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“…A comprehensive analysis of isolated field O-type stars (hereafter referred to as O-stars) in our Galaxy was conducted by de Wit et al (2004Wit et al ( , 2005 who found that 4 ± 2 percent of the O-stars in their sample (model derived value from observations) could not be traced back to clusters and hence, likely formed in isolation. Similarly, Lamb et al (2010) looked at the Small Magellanic Cloud (SMC) and found three O-stars that are in sparse-clusters.…”

Section: Introductionmentioning

confidence: 99%

“…In addition to the de Wit et al (2004Wit et al ( , 2005 findings, there have been several theoretical investigations of the likelihood of isolated, massive star formation. Firstly, Oey et al (2004) noted that the number of stars per cluster appears to follow a powerlaw like slope.…”

Section: Introductionmentioning

confidence: 99%

The VLT-FLAMES Tarantula Survey

Bressert

Bastian

Evans

et al. 2012

A&A

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Whether massive stars ( > ∼ 30 M ) can occasionally form in relative isolation (e.g. in clusters with M < 100 M ) or if they require a large cluster of lower-mass stars around them is a key test in the differentiation of star-formation theories as well as how the initial mass function of stars is sampled. Previous attempts to find O-type stars that formed in isolation were hindered by the possibility that such stars are merely runaways from clusters, i.e., their current isolation does not reflect their birth conditions. We introduce a new method to find O-type stars that are not affected by such a degeneracy. Using the VLT-FLAMES Tarantula Survey and additional high resolution imaging we have identified stars that satisfy the following constraints: 1) they are O-type stars that are not detected to be part of a binary system based on radial velocity (RV) time series analysis; 2) they are designated spectral type O7 or earlier; 3) their velocities are within 1σ of the mean of OB-type stars in the 30 Doradus region, i.e. they are not runaways along our line-of-sight; 4) the projected surface density of stars does not increase within 3 pc towards the O-star (no evidence for clusters); 5) their sight lines are associated with gaseous and/or dusty filaments in the interstellar medium (ISM); and 6) if a second candidate is found in the direction of the same filament with which the target is associated, both are required to have similar velocities. With these criteria, we have identified 15 stars in the 30 Doradus region, which are strong candidates for being high-mass stars that have formed in isolation. Additionally, we employed extensive Monte Carlo stellar cluster simulations to confirm that our results rule out the presence of clusters around the candidates. Eleven of these are classified as Vz stars, possibly associated with the zero-age main sequence. We include a newly discovered Wolf-Rayet star as a candidate, although it does not meet all of the above criteria.

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The origin of massive O-type field stars

Cited by 109 publications

References 58 publications

The Scale‐Free Character of the Cluster Mass Function and the Universality of the Stellar Initial Mass Function

The Scale‐Free Character of the Cluster Mass Function and the Universality of the Stellar Initial Mass Function

The little-studied cluster Berkeley 90 – III. Cluster parameters

The VLT-FLAMES Tarantula Survey

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