Fragmentation and disk formation during high-mass star formation: The IRAM NOEMA (Northern Extended Millimeter Array) large program CORE

TL;DR

This study uses high-resolution millimeter observations to analyze fragmentation, disk formation, and chemical processes in high-mass star-forming regions, revealing diverse fragmentation patterns and suggesting thermal gravitational fragmentation dominates over turbulence.

Contribution

The paper provides the first high-resolution survey of 20 high-mass star-forming regions, highlighting the diversity in fragmentation and the dominance of thermal gravitational processes.

Findings

Fragmentation varies from single cores to multiple cores within regions.

Thermal Jeans length scales are consistent with observed core separations.

Further fragmentation likely occurs below current resolution limits.

Abstract

Aims: We aim to understand the fragmentation as well as the disk formation, outflow generation and chemical processes during high-mass star formation on spatial scales of individual cores. Methods: Using the IRAM Northern Extended Millimeter Array (NOEMA) in combination with the 30m telescope, we have observed in the IRAM large program CORE the 1.37mm continuum and spectral line emission at high angular resolution (~0.4'') for a sample of 20 well-known high-mass star-forming regions with distances below 5.5kpc and luminosities larger than 10^4Lsun. Results: We present the overall survey scope, the selected sample, the observational setup and the main goals of CORE. Scientifically, we concentrate on the mm continuum emission on scales on the order of 1000AU. We detect strong mm continuum emission from all regions, mostly due to the emission from cold dust. The fragmentation properties of the sample are diverse. We see extremes where some regions are dominated by a single high-mass core whereas others fragment into as many as 20 cores. A minimum-spanning-tree analysis finds fragmentation at scales on the order of the thermal Jeans length or smaller suggesting that turbulent fragmentation is less important than thermal gravitational fragmentation. The diversity of highly fragmented versus singular regions can be explained by varying initial density structures and/or different initial magnetic field strengths. Conclusions: The smallest observed separations between cores are found around the angular resolution limit which indicates that further fragmentation likely takes place on even smaller spatial scales. The CORE project with its numerous spectral line detections will address a diverse set of important physical and chemical questions in the field of high-mass star formation.