On the mass segregation of cores and stars

Alcock, Hayley L; Parker, R. J.

doi:10.1093/mnras/stz2646

Cited by 12 publications

(9 citation statements)

References 61 publications

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“…This is even more the case for the disk fragmentation process, which is expected to take over at scales smaller than ∼100 au. As a consequence, only a handful of studies investigated the effect of core multiplicity on the resulting IMF, and they were only based on stellar multiplicity prescriptions (Swift & Williams 2008;Hatchell & Fuller 2008;Alcock & Parker 2019;Clark & Whitworth 2021). The authors used a wide range of core mass distributions between subfragments, also called mass partitions, varying from equipartition to a strong imbalance.…”

Section: Introductionmentioning

confidence: 99%

Alma-Imf

Pouteau

Motte

Nony

et al. 2022

A&A

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Aims. The processes that determine the stellar initial mass function (IMF) and its origin are critical unsolved problems, with profound implications for many areas of astrophysics. The W43-MM2&MM3 mini-starburst ridge hosts a rich young protocluster, from which it is possible to test the current paradigm on the IMF origin. Methods. The ALMA-IMF Large Program observed the W43-MM2&MM3 ridge, whose 1.3 mm and 3 mm ALMA 12 m array continuum images reach a ~2500 au spatial resolution. We used both the best-sensitivity and the line-free ALMA-IMF images, reduced the noise with the multi-resolution segmentation technique MnGSeg, and derived the most complete and most robust core catalog possible. Using two different extraction software packages, getsf and GExt2D, we identified ~200 compact sources, whose ~100 common sources have, on average, fluxes consistent to within 30%. We filtered sources with non-negligible free-free contamination and corrected fluxes from line contamination, resulting in a W43-MM2&MM3 catalog of 205 getsf cores. With a median deconvolved FWHM size of 3400 au, core masses range from ~0.1 M⊙ to ~70 M⊙ and the getsf catalog is 90% complete down to 0.8 M⊙. Results. The high-mass end of the core mass function (CMF) of W43-MM2&MM3 is top-heavy compared to the canonical IMF. Fitting the cumulative CMF with a single power-law of the form N(> log M) ∝ Mα, we measured α = −0.95 ± 0.04, compared to the canonical α = −1.35 Salpeter IMF slope. The slope of the CMF is robust with respect to map processing, extraction software packages, and reasonable variations in the assumptions taken to estimate core masses. We explore several assumptions on how cores transfer their mass to stars (assuming a mass conversion efficiency) and subfragment (defining a core fragment mass function) to predict the IMF resulting from the W43-MM2&MM3 CMF. While core mass growth should flatten the high-mass end of the resulting IMF, core fragmentation could steepen it. Conclusions. In stark contrast to the commonly accepted paradigm, our result argues against the universality of the CMF shape. More robust functions of the star formation efficiency and core subfragmentation are required to better predict the resulting IMF, here suggested to remain top-heavy at the end of the star formation phase. If confirmed, the IMFs emerging from starburst events could inherit their top-heavy shape from their parental CMFs, challenging the IMF universality.

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Section: Introductionmentioning

confidence: 99%

Alma-Imf

Pouteau

Motte

Nony

et al. 2022

A&A

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“…Many works have focused on the spatial structure of young clusters. Whether there is (or not) spatial-mass segregation, whether such segregation is primordial or the result of a relaxation process, or what is the density structure of the stars, are just a few questions that have been addressed by a number of authors (e.g., Hillenbrand & Hartmann 1998;Goodwin & Whitworth 2004;Goodwin et al 2007;Allison et al 2009;Moeckel & Bonnell 2009;Bate 2012;Agertz et al 2013;Alcock & Parker 2019).…”

Section: Discussionmentioning

confidence: 99%

Gravity or turbulence V: Star forming regions undergoing violent relaxation

Bonilla-Barroso,

Ballesteros-Paredes,

Hernández

et al. 2022

Preprint

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Using numerical simulations of the formation and evolution of stellar clusters within molecular clouds, we show that the stars in clusters formed within collapsing molecular cloud clumps exhibit a constant velocity dispersion regardless of their mass, as expected in a violent relaxation processes. In contrast, clusters formed in turbulence-dominated environments exhibit an inverse mass segregated velocity dispersion, where massive stars exhibit larger velocity dispersions than low-mass cores, consistent with massive stars formed in massive clumps, which in turn, are formed through strong shocks. We furthermore use Gaia EDR3 to show that the stars in the Orion Nebula Cluster exhibit a constant velocity dispersion as a function of mass, suggesting that it has been formed by collapse within one free-fall time of its parental cloud, rather than in a turbulence-dominated environment during many free-fall times of a supported cloud. Additionally, we have addressed several of the criticisms of models of collapsing star forming regions: namely, the age spread of the ONC, the comparison of the ages of the stars to the free-fall time of the gas that formed it, the star formation efficiency, and the mass densities of clouds vs the mass densities of stellar clusters, showing that observational and numerical data are consistent with clusters forming in clouds undergoing a process of global, hierarchical and chaotic collapse, rather than been supported by turbulence.

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“…Mass segregation could occur at cluster formation. Hence, investigation of mass segregation in young clusters could give insights into the process of cluster formation (Sagar et al 1988;Fischer et al 1998;Raboud & Mermilliod 1998;Alcock & Parker 2019). Interactions between cluster stars can cause energy transfer from high-mass stars to low-mass stars.…”

Section: The Dynamical State Of Mass Segregationmentioning

confidence: 99%

An Investigation of Open Clusters Berkeley 68 and Stock 20 Using CCD UBV and Gaia DR3 Data

Yontan

2023

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We performed detailed photometric and astrometric analyses of the open star clusters Berkeley 68 and Stock 20. This was based on ground-based CCD UBV photometric data complemented by space-based Gaia Data Release 3 (DR3) photometry and astrometry. A total of 198 and 51 stars were identified as likely cluster members for Berkeley 68 and Stock 20, respectively. Two-color diagrams were used to derive the reddening and photometric metallicity for each cluster. The reddening for Berkeley 68 and Stock 20 is E(B − V) = 0.520 ± 0.032 mag and 0.400 ± 0.048 mag, respectively. Photometric metallicity [Fe/H] is −0.13 ± 0.08 dex for Berkeley 68 and −0.01 ± 0.06 dex for Stock 20. Keeping as constant reddening and metallicity, we determined the distance moduli and ages of the clusters through fitting isochrones to the UBV and Gaia-based color–magnitude diagrams. Photometric distances are d = 3003 ± 165 pc for Berkeley 68 and 2911 ± 216 pc for Stock 20. The cluster ages are 2.4 ± 0.2 Gyr and 50 ± 10 Myr for Berkeley 68 and Stock 20, respectively. Present-day mass function slopes were found to be Γ = 1.38 ± 0.71 and Γ = 1.53 ± 0.39 for Berkeley 68 and Stock 20, respectively. These values are compatible with the value of Salpeter. The relaxation times were estimated as 32.55 and 23.17 Myr for Berkeley 68 and Stock 20, respectively. These times are less than the estimated cluster ages, indicating that both clusters are dynamically relaxed. Orbit integration was carried out only for Berkeley 68 since radial velocity data were not available for Stock 20. Analysis indicated that Berkeley 68 was born outside the solar circle and belongs to the thin-disk component of the Milky Way.

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On the mass segregation of cores and stars

Cited by 12 publications

References 61 publications

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Gravity or turbulence V: Star forming regions undergoing violent relaxation

An Investigation of Open Clusters Berkeley 68 and Stock 20 Using CCD UBV and Gaia DR3 Data

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