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Context. Understanding the formation of substructures in protoplanetary disks is vital for gaining insights into dust growth and the process of planet formation. Studying these substructures in highly embedded Class 0 objects using the Atacama Large Millimeter-submillimeter Array (ALMA), however, poses significant challenges. Nonetheless, it is imperative to do so to unravel the mechanisms and timing behind the formation of these substructures. Aims. In this study, we present high-resolution ALMA data at Bands 6 and 4 of the NGC 1333 IRAS4A Class 0 protobinary system. This system consists of two components, A1 and A2, which are separated by 1.8″ and located in the Perseus molecular cloud at a distance of ~293 pc. Methods. To gain a comprehensive understanding of the dust properties and formation of substructures in the early stages, we conducted a multiwavelength analysis of IRAS4A1. Additionally, we sought to address whether the lack of observed substructures in very young disks could be attributed to factors such as high degrees of disk flaring and large scale heights. To explore this phenomenon, we employed radiative transfer models using RADMC-3D. We employed different approaches and compared the model outcomes with our observational data. This comparison allowed us to gain insights into the challenges in detecting substructures in nascent disks and shed light on the potential influence of the dust scale height on observations of protoplanetary disks. Results. The continuum data revealed the presence of two disks-envelopes around A1 and A2, along with structure connecting the two sources. Furthermore, spectral index measurements indicate lower optical depth within the A2 disk compared to the A1 disk. Our multiwavelength analysis of A1 discovered characteristics such as high dust surface density, substantial dust mass within the disk, and elevated dust temperatures. These findings suggest the presence of large dust grains compared to the ones in the interstellar medium (ISM), greater than 100 microns in size within the region. By employing RADMC-3D, we confirmed that increasing the scale height creates the appearance of an asymmetry in protoplanetary disks. Our findings indicate that a scale height of at least 0.3 (H/R) is necessary to produce this observed asymmetry. Furthermore, while there’s no direct detection of any substructure, our models indicate that some substructure, such as a small gap, must be present. However, reproducing the intensity profile along the major and minor axes necessitates considering other processes that may be occurring within the IRAS4A1 disk. Conclusions. The result implies that disk substructures may be masked or obscured by a large scale height in combination with a high degree of flaring in Class 0 disks. 

The stellar initial mass function (IMF) is critical to our understanding of star formation and the effects of young stars on their environment. On large scales, it enables us to use tracers such as UV or Hα emission to estimate the star formation rate of a system and interpret unresolved star clusters across the Universe. So far, there is little firm evidence of large-scale variations of the IMF, which is thus generally considered “universal”. Stars form from cores, and it is now possible to estimate core masses and compare the core mass function (CMF) with the IMF, which it presumably produces. The goal of the ALMA-IMF large programme is to measure the core mass function at high linear resolution (2700 au) in 15 typical Milky Way protoclusters spanning a mass range of 2.5 × 10³to 32.7 × 10³M_⊙. In this work, we used two different core extraction algorithms to extract ≈680 gravitationally bound cores from these 15 protoclusters. We adopted a per core temperature using the temperature estimate from the point-process mapping Bayesian method (PPMAP). A power-law fit to the CMF of the sub-sample of cores above the 1.64M_⊙completeness limit (330 cores) through the maximum likelihood estimate technique yields a slope of 1.97 ± 0.06, which is significantly flatter than the 2.35 Salpeter slope. Assuming a self-similar mapping between the CMF and the IMF, this result implies that these 15 high-mass protoclusters will generate atypical IMFs. This sample currently is the largest sample that was produced and analysed self-consistently, derived at matched physical resolution, with per core temperature estimates, and cores as massive as 150M_⊙. We provide both the raw source extraction catalogues and the catalogues listing the source size, temperature, mass, spectral indices, and so on in the 15 protoclusters. 

Context.The star formation process leads to an increased chemical complexity in the interstellar medium. Sites associated with high-mass star and cluster formation exhibit a so-called hot core phase, characterized by high temperatures and column densities of complex organic molecules. Aims.We aim to systematically search for and identify a sample of hot cores toward the 15 Galactic protoclusters of the ALMA-IMF Large Program and investigate their statistical properties. Methods.We built a comprehensive census of hot core candidates toward the ALMA-IMF protoclusters based on the detection of two CH₃OCHO emission lines at 216.1 GHz. We used the source extraction algorithm GExt2D to identify peaks of methyl formate (CH₃OCHO) emission, a complex species commonly observed toward sites of star formation. We performed a cross-matching with the catalog of thermal dust continuum sources from the ALMA-IMF 1.3 mm continuum data to infer their physical properties. Results.We built a catalog of 76 hot core candidates with masses ranging from ~0.2M_⊙to ~80M_⊙, of which 56 are new detections. A large majority of these objects, identified from methyl formate emission, are compact and rather circular, with deconvolved full width at half maximum (FWHM) sizes of ~2300 au on average. The central sources of two target fields show more extended, but still rather circular, methyl formate emission with deconvolved FWHM sizes of ~6700 au and 13 400 au. About 30% of our sample of methyl formate sources have core masses above 8M_⊙and range in size from ~1000 au to 13 400 au, which is in line with measurements of archetypical hot cores. The origin of the CH₃OCHO emission toward the lower-mass cores may be explained as a mixture of contributions from shocks or may correspond to objects in a more evolved state (i.e., beyond the hot core stage). We find that the fraction of hot core candidates increases with the core mass, suggesting that the brightest dust cores are all in the hot core phase. Conclusions.Our results suggest that most of these compact methyl formate sources are readily explained by simple symmetric models, while collective effects from radiative heating and shocks from compact protoclusters are needed to explain the observed extended CH₃OCHO emission. The large fraction of hot core candidates toward the most massive cores suggests that they rapidly enter the hot core phase and that feedback effects from the forming protostar(s) impact their environment on short timescales. 

Abstract We present a catalog of 315 protostellar outflow candidates detected in SiOJ= 5 − 4 in the ALMA-IMF Large Program, observed with ∼2000 au spatial resolution, 0.339 km s⁻¹velocity resolution, and 2–12 mJy beam⁻¹(0.18–0.8 K) sensitivity. We find median outflow masses, momenta, and kinetic energies of ∼0.3M_⊙, 4M_⊙km s⁻¹, and 10⁴⁵erg, respectively. Median outflow lifetimes are 6000 yr, yielding median mass, momentum, and energy rates of $\dot{M}$= 10^−4.4M_⊙yr⁻¹, $\dot{P}$= 10^−3.2M_⊙km s⁻¹yr⁻¹, and $\dot{E}$= 1L_⊙. We analyze these outflow properties in the aggregate in each field. We find correlations between field-aggregated SiO outflow properties and total mass in cores (∼3σ–5σ), and no correlations above 3σwith clump mass, clump luminosity, or clump luminosity-to-mass ratio. We perform a linear regression analysis and find that the correlation between field-aggregated outflow mass and total clump mass—which has been previously described in the literature—may actually be mediated by the relationship between outflow mass and total mass in cores. We also find that the most massive SiO outflow in each field is typically responsible for only 15%–30% of the total outflow mass (60% upper limit). Our data agree well with the established mechanical force−bolometric luminosity relationship in the literature, and our data extend this relationship up toL≥ 10⁶L_⊙and $\dot{P}$≥ 1M_⊙km s⁻¹yr⁻¹. Our lack of correlation with clumpL/Mis inconsistent with models of protocluster formation in which all protostars start forming at the same time.