The ALMA Survey of Star Formation and Evolution in Massive Protoclusters with Blue Profiles (ASSEMBLE): Core Growth, Cluster Contraction, and Primordial Mass Segregation

Xu, Fengwei; Wang, Ke; Liu, Tie; Tang, Mengyao; Evans II, Neal J.; Palau, Aina; Morii, Kaho; He, Jinhua; Sanhueza, Patricio; Liu, Hong-Li; Stutz, Amelia; Zhang, Qizhou; Chen, Xi; Li, Pak Shing; Gómez, Gilberto C.; Vázquez-Semadeni, Enrique; Li, Shanghuo; Mai, Xiaofeng; Lu, Xing; Liu, Meizhu; Chen, Li; Li, Chuanshou; Shi, Hongqiong; Ren, Zhiyuan; Li, Di; Garay, Guido; Bronfman, Leonardo; Dewangan, Lokesh; Juvela, Mika; Lee, Chang Won; Zhang, S.; Yue, Nannan; Wang, Chao; Ge, Yifei; Jiao, Wenyu; Luo, Qiuyi; Zhou, J.-W.; Tatematsu, Ken’ichi; Chibueze, James O.; Su, Keyun; Sun, Shenglan; Ristorcelli, I.; Toth, L. Viktor

doi:10.3847/1538-4365/acfee5

Cited by 6 publications

(8 citation statements)

References 157 publications

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“…When star clusters are primordially mass-segregated (i.e., massive stars form preferentially in cluster central regions; see, e.g., Bonnell & Bate 2006;Myers et al 2014;Xu et al 2024), their inner regions undergo an early excess of stellar evolutionary mass losses (although, contrary to the case of a top-heavy IMF, the cluster as a whole does not). Because of their central location, such stellar evolutionary mass losses remove a greater fraction of the cluster binding energy than for nonprimordially segregated clusters.…”

Section: Primordial Mass Segregationmentioning

confidence: 99%

Cracking the Relation between Mass and 1P Star Fraction of Globular Clusters. I. Present-day Cluster Masses as a First Tool

Parmentier

2024

ApJ

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The phenomenon of multiple stellar populations is exacerbated in massive globular clusters, with the fraction of first-population (1P) stars a decreasing function of the cluster present-day mass. We decipher this relation in far greater detail than has been done so far. We assume (i) a fixed stellar mass threshold for the formation of second-population (2P) stars, (ii) a power-law scaling F 1 P ∝ m ecl − 1 between the mass m ecl of newly formed clusters and their 1P star fraction F 1P, and (iii) a constant F 1P over time. The F 1P(m ecl) relation is then evolved up to an age of 12 Gyr for tidal field strengths representative of the entire Galactic halo. The 12 Gyr old model tracks cover the present-day distribution of Galactic globular clusters in the (mass, F 1P) space extremely well. The distribution is curtailed on its top right side by the scarcity of clusters at large Galactocentric distances and on its bottom left side by the initial scarcity of very high-mass clusters and dynamical friction. Given their distinct dissolution rates, “inner” and “outer” model clusters are offset from each other, as observed. The locus of Magellanic Clouds clusters in the (mass, F 1P) space is as expected for intermediate-age clusters evolving in a gentle tidal field. Given the assumed constancy of F 1P, we conclude that 2P stars do not necessarily form centrally concentrated. We infer a minimum mass of 4 · 105 M ⊙ for multiple-population clusters at secular evolution onset. This high-mass threshold severely limits the number of 2P stars lost from evolving clusters, thereby fitting the low 2P star fraction of the Galactic halo field.

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Section: Primordial Mass Segregationmentioning

confidence: 99%

Cracking the Relation between Mass and 1P Star Fraction of Globular Clusters. I. Present-day Cluster Masses as a First Tool

Parmentier

2024

ApJ

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“…Gas feeding or gravitational collapse of clumps and subclumps would increase the mass dynamic range, as can be seen in Figure 7. Xu et al (2024) suggest that the gravitational concentration or gas accretion toward the center of mass would result in the appearance of mass segregation and in the increase of the -parameter.…”

Section: Early Fragmentation Picturementioning

confidence: 99%

The ALMA Survey of 70 μm Dark High-mass Clumps in Early Stages (ASHES). XI. Statistical Study of Early Fragmentation

Morii,

Sanhueza,

Zhang

et al. 2024

ApJ

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Fragmentation during the early stages of high-mass star formation is crucial for understanding the formation of high-mass clusters. We investigated fragmentation within 39 high-mass star-forming clumps as part of the Atacama Large Millimeter/submillimeter Array Survey of 70 μm Dark High-mass Clumps in Early Stages (ASHES) survey. Considering projection effects, we have estimated core separations for 839 cores identified from the continuum emission and found mean values between 0.08 and 0.32 pc within each clump. We find compatibility of the observed core separations and masses with the thermal Jeans length and mass, respectively. We also present subclump structures revealed by the 7 m array continuum emission. Comparison of the Jeans parameters using clump and subclump densities with the separation and masses of gravitationally bound cores suggests that they can be explained by clump fragmentation, implying the simultaneous formation of subclumps and cores within rather than a step-by-step hierarchical fragmentation. The number of cores in each clump positively correlates with the clump surface density and the number expected from the thermal Jeans fragmentation. We also find that the higher the fraction of protostellar cores, the larger the dynamic range of the core mass, implying that the cores are growing in mass as the clump evolves. The ASHES sample exhibits various fragmentation patterns: aligned, scattered, clustered, and subclustered. Using the Q -parameter, which can help distinguish between centrally condensed and subclustered spatial core distributions, we finally find that in the early evolutionary stages of high-mass star formation, cores tend to follow a subclustered distribution.

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“…Core-scale (0.1 pc and n > 10 5 cm −3 ) infall motions have been statistically studied (Wu & Evans 2003;Wu et al 2007;Contreras et al 2018;Xu et al 2023a) and filamentary accretion flows are resolved in high-resolution observations (Peretto et al 2013;Liu et al 2016;Lu et al 2018;Yuan et al 2018;Chen et al 2019;Sanhueza et al 2021;Redaelli et al 2022;Xu et al 2023b;Yang et al 2023). Hence, the identified ACA sources are likely to continue to accumulate mass throughout their evolution, achieving further growth of the core mass and enhancement of the surface density (Liu et al 2023a;Xu et al 2024b). Using H 13 CO + (1-0), Zhou et al (2022) identified 68 hub-filament systems with clear velocity gradients in the ATOMS survey.…”

Section: Massive Star-forming Regions With Supersonic Turbulencementioning

confidence: 99%

“…Furthermore, using ALMA with a resolution of approximately 0.02 pc, Xu et al (2024b) identified a sublinear correlation between the mass of the clump and the mass of its most massive core, in a sample of 11 massive protoclusters that show clump-scale infall motion. For comparison, no such correlation was found in a sample of 39 massive early-stage clumps from Morii et al (2023).…”

Section: Introductionmentioning

confidence: 99%

The ALMA-QUARKS Survey. II. The ACA 1.3 mm Continuum Source Catalog and the Assembly of Dense Gas in Massive Star-Forming Clumps

Xu 许,

Wang,

Liu

et al. 2024

Res. Astron. Astrophys.

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Leveraging the high resolution, sensitivity, and wide frequency coverage of the Atacama Large Millimeter/submillimeter Array (ALMA), the QUARKS survey, standing for "Querying Underlying mechanisms of massive star formation with ALMA-Resolved gas Kinematics and Structures", is observing 139 massive gas clumps at ALMA Band 6 (λ∼1.3 mm). This paper introduces the Atacama Compact Array (ACA) 7-m data of the QUARKS survey, describing the ACA observations and data reduction. Combining multi-wavelength data, we provide the first edition of QUARKS atlas, offering insights into the multiscale and multiphase interstellar medium (ISM) in high-mass star formation. The ACA 1.3 mm catalog includes 207 continuum sources that are called ACA sources. Their gas kinetic temperatures are estimated using three formaldehyde transitions with a non-LTE radiation transfer model, and the mass and density are derived from a dust emission model. The ACA sources are massive (16-84 percentile values of 6-160M⊙), gravity-dominated (M~R1.1) fragments within the massive clumps, with supersonic turbulence (Mach Number>1) and embedded star-forming protoclusters. We find a linear correlation between the masses of the fragments and the massive clumps, with a ratio of 6% between the two. When considering the fragments as representative of dense gas, the ratio indicates a dense gas fraction (DGF) of 6%, although with a wide scatter ranging from 1% to 10%. If we consider the QUARKS massive clumps to be what is observed at various scales, then the size-independent DGF indicates a self-similar fragmentation or collapsing mode in protocluster formation. With the ACA data over four orders of magnitude of luminosity-to-mass ratio (L/M), we find that the DGF increases significantly with L/M which indicates clump evolutionary stage. We observed a limited fragmentation at subclump scale, which can be explained by dynamic global collapse process.

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The ALMA Survey of Star Formation and Evolution in Massive Protoclusters with Blue Profiles (ASSEMBLE): Core Growth, Cluster Contraction, and Primordial Mass Segregation

Cited by 6 publications

References 157 publications

Cracking the Relation between Mass and 1P Star Fraction of Globular Clusters. I. Present-day Cluster Masses as a First Tool

Cracking the Relation between Mass and 1P Star Fraction of Globular Clusters. I. Present-day Cluster Masses as a First Tool

The ALMA Survey of 70 μm Dark High-mass Clumps in Early Stages (ASHES). XI. Statistical Study of Early Fragmentation

The ALMA-QUARKS Survey. II. The ACA 1.3 mm Continuum Source Catalog and the Assembly of Dense Gas in Massive Star-Forming Clumps

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