An ALMA search for substructure and fragmentation in starless cores in Orion B North

TL;DR

This study uses ALMA observations to detect and analyze starless and protostellar cores in Orion B North, comparing findings with simulations and other regions to understand core properties and star formation processes.

Contribution

First ALMA survey of starless cores in Orion B North, combining observations with simulations and virial analysis to compare core properties across regions.

Findings

34 continuum sources detected, 4 likely starless

Observed starless core count matches simulation predictions

Chamaeleon I cores are less gravitationally bound than Orion B North and Ophiuchus

Abstract

We present Atacama Large Millimeter/submillimeter Array (ALMA) Cycle 3 observations of 73 starless and protostellar cores in the Orion B North molecular cloud. We detect a total of 34 continuum sources at 106 GHz, and after comparisons with other data, 4 of these sources appear to be starless. Three of the four sources are located near groupings of protostellar sources, while one source is an isolated detection. We use synthetic observations of a simulation modeling a collapsing turbulent, magnetized core to compute the expected number of starless cores that should be detectable with our ALMA observations and find at least two (1.52) starless core should be detectable, consistent with our data. We run a simple virial analysis of the cores to put the Orion B North observations into context with similar previous ALMA surveys of cores in Chamaeleon I and Ophiuchus. We conclude that the Chamaeleon I starless core population is characteristically less bounded than the other two populations, along with external pressure contributions dominating the binding energy of the cores. These differences may explain why the Chamaeleon I cores do not follow turbulent model predictions, while the Ophiuchus and Orion B North cores are consistent with the model.