Alma-Imf

Abstract

Context. Among the most central open questions regarding the initial mass function (IMF) of stars is the impact of environment on the shape of the core mass function (CMF) and thus potentially on the IMF. Aims. The ALMA-IMF Large Program aims to investigate the variations in the core distributions (CMF and mass segregation) with cloud characteristics, such as the density and kinematic of the gas, as diagnostic observables of the formation process and evolution of clouds. The present study focuses on the W43-MM2&MM3 mini-starburst, whose CMF has recently been found to be top-heavy with respect to the Salpeter slope of the canonical IMF. Methods. W43-MM2&MM3 is a useful test case for environmental studies because it harbors a rich cluster that contains a statistically significant number of cores (specifically, 205 cores), which was previously characterized in Paper III. We applied a multi-scale decomposition technique to the ALMA 1.3 mm and 3 mm continuum images of W43-MM2&MM3 to define six subregions, each 0.5–1 pc in size. For each subregion we characterized the probability distribution function of the high column density gas, η-PDF, using the 1.3 mm images. Using the core catalog, we investigate correlations between the CMF and cloud and core properties, such as the η-PDF and the core mass segregation. Results. We classify the W43-MM2&MM3 subregions into different stages of evolution, from quiescent to burst to post-burst, based on the surface number density of cores, number of outflows, and ultra-compact HII presence. The high-mass end (>1 M⊙) of the subregion CMFs varies from close to the Salpeter slope (quiescent) to top-heavy (burst and post-burst). Moreover, the second tail of the η-PDF varies from steep (quiescent) to flat (burst and post-burst), as observed for high-mass star-forming clouds. We find that subregions with flat second η-PDF tails display top-heavy CMFs. Conclusions. In dynamical environments such as W43-MM2&MM3, the high-mass end of the CMF appears to be rooted in the cloud structure, which is at high column density and surrounds cores. This connection stems from the fact that cores and their immediate surroundings are both determined and shaped by the cloud formation process, the current evolutionary state of the cloud, and, more broadly, the star formation history. The CMF may evolve from Salpeter to top-heavy throughout the star formation process from the quiescent to the burst phase. This scenario raises the question of if the CMF might revert again to Salpeter as the cloud approaches the end of its star formation stage, a hypothesis that remains to be tested.

The ALMA-QUARKS Survey. I. Survey Description and Data Reduction

“…The core density of Sgr B2(M) is then derived to be ∼100 pc −2 . This value is much higher than the value (19 pc −2 ) of the mini-starburst ridges of W43 (Pouteau et al 2022(Pouteau et al , 2023, implying stronger mini-starburst activities in Sgr B2(M) compared with the W43 mini-starburst region, an analog of a forming super star cluster (Bally et al 2010).…”

“…These results may imply that the evolutionary tracks of the two regions may be regulated by some shared parameters of the environments, although the varying dust temperatures provide challenges for precisely deriving the core masses. On the other hand, the similarity of the CMFs between Sgr B2(M) and other highmass star-forming regions (with α < 1; e.g., Cheng et al 2018;Lu et al 2020;Pouteau et al 2023) implies that the QUARKS is sensitive enough to find out most of the high-mass cores in Sgr B2(M). The core density of Sgr B2(M) is then derived to be ∼100 pc −2 .…”

“…How stellar feedback from outflows, H II regions and stellar winds from formed OB protostars influences the formation of new generation of stars and reshapes gas distribution in clouds is highly debated (e.g., Krumholz et al 2014;Peters et al 2017;Schneider et al 2020;Zhang et al 2023b;Herrington et al 2023;Pouteau et al 2023). The ATOMS survey studied the impact of UC H II regions (S. Zhang et al 2023, in preparation) on their surrounding molecular gas, but detailed investigation was limited by sensitivity, and resolution.…”

ALMA-IMF. VIII. Combination of Interferometric Continuum Images with Single-dish Surveys and Structural Analysis of Six Protoclusters

“…dust where Σ dust is the dust surface density in grams per square centimeter and κ ν is the dust opacity. We set κ 1.3mm = 1 cm 2 g −1 (Ossenkopf & Henning 1994), as used in previous ALMA-IMF studies (e.g., Pouteau et al 2023;Nony et al 2023). We use T dust maps at 10″ resolution determined by applying Note.…”

“…Regarding the W43 protoclusters (MM1, MM2, and MM3), it has been proposed that they are in a mini-starburst stage. This proposal is based on their copious formation of cores from low to high masses, as seen in a variety of metrics such as their CFE, estimates of their SFE, and measurements of the slope of their CMF (Louvet et al 2014;Motte et al 2018b;Pouteau et al 2023). However, these protoclusters are significantly younger than W51-IRS2, W51-E, or G012.80.…”