| Résumé | 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. |
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