A C$^{18}$O study of the origin of the power-law nature in the IMF

TL;DR

This study maps C$^{18}$O cores in Orion A, revealing a core mass function with a power-law shape similar to the stellar IMF, suggesting the IMF's form is set at relatively low densities.

Contribution

It provides observational evidence linking the core mass function at low densities to the stellar IMF, highlighting the origin of the IMF's power-law nature.

Findings

C$^{18}$O cores are gravitationally bound.

Core mass function follows a power-law with index -2.3.

IMF-like distribution established at density ~10^3 cm$^{-3}$.

Abstract

We have performed C$^{18}$O ($J$=1--0) mapping observations of a $20'\times20'$ area of the OMC-1 region in the Orion A cloud. We identified 65 C$^{18}$O cores, which have mean radius, velocity width in FWHM, and LTE mass of 0.18$\pm$0.03 pc, 0.40$\pm$0.15 km s$^{-1}$, and 7.2$\pm$4.5 $M_\odot$, respectively. All the cores are most likely to be gravitationally bound by considering the uncertainty in the C$^{18}$O abundance. We derived a C$^{18}$O core mass function, which shows a power-law-like behavior above 5 $M_\odot$. The best-fit power-law index of $-2.3\pm0.3$ is consistent with those of the dense core mass functions and the stellar initial mass function (IMF) previously derived in the OMC-1 region. This agreement strongly suggests that the power-law form of the IMF has been already determined at the density of $\sim10^{3}$ cm$^{-3}$, traced by the C$^{18}$O ($J$=1--0) line.