The Formation of Very Massive Stars

Krumholz, Mark R.

doi:10.1007/978-3-319-09596-7_3

Cited by 49 publications

(36 citation statements)

References 161 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The existence of a physical m max -M ecl relation is thus taken to be established (Weidner et al 2014). Although the theory has been successful in describing the stellar contents of whole galaxies (e.g., Weidner et al 2013b), it has been debated if the relation exists (see Section 2.1 in Weidner et al 2013a for details) or if star formation is a purely stochastic process (e.g., Krumholz 2015). This is a fundamental issue for understanding galaxy-wide IMFs and how massive stars form, and we here thus stress that the data do not support the hypothesis that star formation is stochastic (see Section 7 of Kroupa 2015).…”

Section: The Binary Fraction Among the Ejected O Star Systemsmentioning

confidence: 99%

“…For example, Hsu et al (2012Hsu et al ( , 2013 presented that L1641, the low-density star-forming region (containing as many as »1600 stars) of the Orion A cloud, is deficient of massive (O and early B) stars compared to the canonical IMF with 3-4σ significance and that with a probability of only 3% the southern region of L1461 and the ONC can be drawn from the same population, supporting that the high-mass end of the IMF is dependent on environmental density. In Section 4.2 of Krumholz (2015) three references (Calzetti et al 2010;Fumagalli et al 2011;Andrews et al 2013) are cited as containing evidence against a physical m max -M ecl relation. Weidner et al (2014) critically discuss these works, showing Andrews et al (2013) data to be entirely consistent with the physical m max -M ecl relation.…”

Section: The Binary Fraction Among the Ejected O Star Systemsmentioning

confidence: 99%

See 1 more Smart Citation

Dependency of Dynamical Ejections of O Stars on the Masses of Very Young Star Clusters

Kroupa

Pflamm-Altenburg

2015

ApJ

109

149

View full text Add to dashboard Cite

Massive stars can be efficiently ejected from their birth star clusters through encounters with other massive stars. We study how the dynamical ejection fraction of O star systems varies with the masses of very young star clusters, M ecl , by means of direct N-body calculations. We include diverse initial conditions by varying the half-mass radius, initial mass segregation, initial binary fraction, and orbital parameters of the massive binaries. The results show robustly that the ejection fraction of O star systems exhibits a maximum at a cluster mass offor all models, even though the number of ejected systems increases with cluster mass. We show that lower mass clusters) are the dominant sources for populating the Galactic field with O stars by dynamical ejections, considering the mass function of embedded clusters. About 15% (up to ≈38%, depending on the cluster models) of O stars of which a significant fraction are binaries, and which would have formed in a ≈10 Myr epoch of star formation in a distribution of embedded clusters, will be dynamically ejected to the field. Individual clusters may eject 100% of their original O star content. A large fraction of such O stars have velocities up to only 10 km s −1 . Synthesising a young star cluster mass function, it follows, given the stellar-dynamical results presented here, that the observed fractions of field and runaway O stars, and the binary fractions among them, can be well understood theoretically if all O stars form in embedded clusters.

show abstract

Section: The Binary Fraction Among the Ejected O Star Systemsmentioning

confidence: 99%

Section: The Binary Fraction Among the Ejected O Star Systemsmentioning

confidence: 99%

Dependency of Dynamical Ejections of O Stars on the Masses of Very Young Star Clusters

Kroupa

Pflamm-Altenburg

2015

ApJ

109

149

View full text Add to dashboard Cite

show abstract

“…This points to the idea that the spin rates of the low-∆RV, wide and low-q spectroscopic binaries have seldom been modified since the stars were formed and thus reflect the outcome of the formation process. While the formation process of massive stars is heavily debated (e.g., Zinnecker & Yorke 2007;Tan et al 2014;Krumholz 2015), most theories agree on the need for disk-mediated accretion. In its simplest form, the collapse of the initial natal cloud and the gas-accretion phase concentrate by far more angular momentum in the central region than can be stored in a single star.…”

Section: The Nature Of the Low-velocity Peak And The Formation Of Masmentioning

confidence: 99%

The VLT-FLAMES Tarantula Survey

Ramírez-Agudelo

Sana

Mink

et al. 2015

A&A

View full text Add to dashboard Cite

Context. The initial distribution of spin rates of massive stars is a fingerprint of their elusive formation process. It also sets a key initial condition for stellar evolution and is thus an important ingredient in stellar population synthesis. So far, most studies have focused on single stars. Most O stars are, however, found in multiple systems. Aims. By establishing the spin-rate distribution of a sizeable sample of O-type spectroscopic binaries and by comparing the distributions of binary subpopulations with one another and with that of presumed-single stars in the same region, we aim to constrain the initial spin distribution of O stars in binaries, and to identify signatures of the physical mechanisms that affect the evolution of the spin rates of massive stars. Methods. We use ground-based optical spectroscopy obtained in the framework of the VLT-FLAMES Tarantula Survey (VFTS) to establish the projected equatorial rotational velocities ( e sin i) for components of 114 spectroscopic binaries in 30 Doradus. The e sin i values are derived from the full width at half maximum (FWHM) of a set of spectral lines, using a FWHM vs. e sin i calibration that we derive based on previous line analysis methods applied to single O-type stars in the VFTS sample. Results. The overall e sin i distribution of the primary stars resembles that of single O-type stars in the VFTS, featuring a lowvelocity peak (at e sin i < 200 km s −1 ) and a shoulder at intermediate velocities (200 < e sin i < 300 km s −1 ). The distributions of binaries and single stars, however, differ in two ways. First, the main peak at e sin i ∼ 100 km s −1 is broader and slightly shifted towards higher spin rates in the binary distribution than that of the presumed-single stars. This shift is mostly due to short-period binaries (P orb ∼ < 10 d). Second, the e sin i distribution of primaries lacks a significant population of stars spinning faster than 300 km s −1 , while such a population is clearly present in the single-star sample. The e sin i distribution of binaries with amplitudes of radial velocity variation in the range of 20 to 200 km s −1 (mostly binaries with P orb ∼ 10−1000 d and/or with q < 0.5) is similar to that of single O stars below e sin i ∼ < 170 km s −1 . Conclusions. Our results are compatible with the assumption that binary components formed with the same spin distribution as single stars, and that this distribution contains few or no fast-spinning stars. The higher average spin rate of stars in short-period binaries may either be explained by spin-up through tides in such tight binary systems, or by spin-down of a fraction of the presumed-single stars and long-period binaries through magnetic braking (or by a combination of both mechanisms). Most primaries and secondaries of SB2 systems with P orb ∼ < 10 d appear to have similar rotational velocities. This is in agreement with tidal locking in close binaries where the components have similar radii. The lack of very rapidly spinning stars among binary systems supports the ide...

show abstract

“…The details of this process are under investigation (see recent reviews by, e.g., Tan et al 2014;Krumholz 2015;Motte et al 2017) and an increasing number of studies have suggested that they form through dynamical processes initiated by cloud formation (e.g., Schneider et al 2010a;Csengeri et al 2011;Peretto et al 2013;Nguyen-Luong et al 2013).…”

Section: Introductionmentioning

confidence: 99%

The earliest phases of high-mass star formation, as seen in NGC 6334 by Herschel-HOBYS

Tigé

Motte

Russeil

et al. 2017

A&A

View full text Add to dashboard Cite

Aims. To constrain models of high-mass star formation, the Herschel-HOBYS key program aims at discovering massive dense cores (MDCs) able to host the high-mass analogs of low-mass prestellar cores, which have been searched for over the past decade. We here focus on NGC 6334, one of the best-studied HOBYS molecular cloud complexes. Methods. We used Herschel/PACS and SPIRE 70−500 µm images of the NGC 6334 complex complemented with (sub)millimeter and mid-infrared data. We built a complete procedure to extract ∼0.1 pc dense cores with the getsources software, which simultaneously measures their far-infrared to millimeter fluxes. We carefully estimated the temperatures and masses of these dense cores from their spectral energy distributions (SEDs). We also identified the densest pc-scale cloud structures of NGC 6334, one 2 pc × 1 pc ridge and two 0.8 pc × 0.8 pc hubs, with volume-averaged densities of ∼10 5 cm −3 . Results. A cross-correlation with high-mass star formation signposts suggests a mass threshold of 75 M for MDCs in NGC 6334. MDCs have temperatures of 9.5−40 K, masses of 75−1000 M , and densities of 1 × 10 5 −7 × 10 7 cm −3 . Their mid-infrared emission is used to separate 6 IR-bright and 10 IR-quiet protostellar MDCs while their 70 µm emission strength, with respect to fitted SEDs, helps identify 16 starless MDC candidates. The ability of the latter to host high-mass prestellar cores is investigated here and remains questionable. An increase in mass and density from the starless to the IR-quiet and IR-bright phases suggests that the protostars and MDCs simultaneously grow in mass. The statistical lifetimes of the high-mass prestellar and protostellar core phases, estimated to be 1−7 × 10 4 yr and at most 3 × 10 5 yr respectively, suggest a dynamical scenario of high-mass star formation. Conclusions. The present study provides good mass estimates for a statistically significant sample, covering the earliest phases of high-mass star formation. High-mass prestellar cores may not exist in NGC 6334, favoring a scenario presented here, which simultaneously forms clouds, ridges, MDCs, and high-mass protostars.

show abstract

The Formation of Very Massive Stars

Cited by 49 publications

References 161 publications

Dependency of Dynamical Ejections of O Stars on the Masses of Very Young Star Clusters

Dependency of Dynamical Ejections of O Stars on the Masses of Very Young Star Clusters

The VLT-FLAMES Tarantula Survey

The earliest phases of high-mass star formation, as seen in NGC 6334 by Herschel-HOBYS

Contact Info

Product

Resources

About