Stellar populations in STARFORGE II: Comparison with observations

TL;DR

This study uses STARFORGE simulations to analyze stellar group formation, comparing synthetic observations with real data, and assesses the impact of observational biases on measuring group properties and dynamics.

Contribution

It introduces a comprehensive analysis of star-forming regions using realistic simulations and synthetic observations, highlighting biases affecting group property measurements and the limitations of kinematic traceback methods.

Findings

Observational biases can cause up to 100% uncertainty in group measurements.

Massive stars are often missing from surveys, affecting group mass estimates.

Kinematic traceback accuracy is limited, especially under observational biases.

Abstract

Recent studies suggest that most star-forming regions in our Galaxy form stellar associations rather than bound clusters. We analyse models from the STARFORGE simulation suite, a set of magneto-hydrodynamical simulations that include all key stellar feedback and radiative processes following star formation through cloud dispersal. We create synthetic observations by introducing observational biases such as random spurious measurements, unresolved binaries, and photometric sensitivity. These biases affect the measurement of the group mass, size, and velocity dispersion, introducing uncertainties of up to 100%, with accuracy improving as the number of system members increases. Furthermore, models favouring the formation of groups around massive stars were the most affected by observational biases, as massive stars contribute a larger fraction of the group mass and are often missing from astrometric surveys like Gaia. We compare the simulations to the Cepheus Far North (CFN) region, and show that CFN groups may have formed in a low-density environment similar to those modelled in STARFORGE but with massive stars not located preferentially in groups. We also question the effectiveness of the kinematic traceback method, showing that it is accurate within 20% only for certain associations with actual virial parameters above 2. However, observational biases can artificially raise the virial parameter by up to a factor ten, making it difficult to evaluate the reliability of the traceback age. Additionally, since stars continue to form during the dispersal of the parent cloud, we find no relation between the stellar-dynamical age difference and the length of the embedded phase.