Observational Tests of Multiple Star Formation Scenarios: Case Studies of VLA 1623-2417 and L1551 IRS 5

This paper examines whether observations of young multiple stellar systems are consistent with theoretical predictions regarding the prevalence of multiplicity in star-forming environments. We analyze two well-studied protostellar systems: VLA 1623-2417, a hierarchical multiple system in Rho Ophiuchi containing at least four components (A1, A2, B, and W), and L1551 IRS 5, a close binary (possibly triple) in Taurus. We assess which observational features align with proposed mechanisms while carefully distinguishing consistency from validation. Recent ALMA, VLA, and JWST data reveal complex circummultiple disk structures with spiral features and gaps indicating dynamical interactions, accretion streamers demonstrating material flow, and distributed outflow activity. However, these features are also predicted by standard turbulent fragmentation models without requiring systematic "advantages" for multiples over singles. We critically evaluate each proposed mechanism against observations and find that while multiplicity is clearly common in young stellar populations, current data cannot establish whether it is preferentially "optimal" versus simply a natural outcome of turbulent cloud fragmentation. The hierarchical nature of VLA 1623 highlights that theoretical frameworks must extend beyond simple binaries to address the full complexity of observed multiple systems. Keywords: star formation, multiple systems, protostars, binary stars, VLA 1623-2417, L1551 IRS 5, ALMA, VANDAM, FAUST, turbulent fragmentation, accretion, angular momentum Related identifiers: Uses data from: ALMA (ADS/JAO.ALMA) Uses data from: VANDAM Survey (VLA/ALMA Nascent Disk and Multiplicity) Uses data from: FAUST ALMA Large Program Uses data from: Karl G. Jansky Very Large Array (VLA) Uses data from: James Webb Space Telescope (JWST)