Identification of a turnover in the initial mass function of a young stellar cluster down to 0.5 M$_{J}$

A successful theory of star formation should predict the number of objects as a function of their mass produced through star-forming events.

Previous studies in star-forming regions and the solar neighborhood identify a mass function increasing from the hydrogen-burning limit down to about 10 M$_{J}$.

Theory predicts a limit to the fragmentation process, providing a natural turnover in the mass function down to the opacity limit of turbulent fragmentation thought to be 2-10 M$_{J}$.

Programs to date have not been sensitive enough to probe the hypothesized opacity limit of fragmentation.

Here we present the first identification of a turnover in the initial mass function below 12 M$_{J}$ within NGC 2024, a young star-forming region.

With JWST/NIRCam deep exposures across 0.7-5 {\mu}m, we identified several free floating objects down to ~ 3 M$_{J}$ with sensitivity to 0.5 M$_{J}$.

We present evidence for a double power law model increasing from about 60 M$_{J}$ to roughly 12 M$_{J}$, consistent with previous studies, followed by a decrease down to 0.5 M$_{J}$.

Our results support the predictions of star and brown dwarf formation theory, identifying the theoretical turnover in the mass function and suggest the fundamental limit of turbulent fragmentation near 3 M$_{J}$.

;Comment: 16 pages, 4 figures, submitted 6 September 2024