Chemical diversity of dense cores in Orion B: The role of the environment

Pre-stellar cores are the sites of the earliest stages of star formation. Dust continuum observations are often used to identify and characterise their properties yet only a small fraction of them have been observed and studied in terms of their composition and dynamical status. Pre-stellar cores are often analysed as being analogous to template objects such as L1544 in Taurus, which could create an observational bias if this template were not representative of all possible pre-stellar cores. We explore the chemical diversity of pre-stellar cores and protostellar cores residing in the Orion B giant molecular cloud selected on their dust continuum emission to provide an unbiased view of their line emission properties and how they vary as function of the core parameters and environment. We made use of the large-scale maps of Orion B in 25 molecular lines, from which we extracted information for a sample of 1001 cores selected using positions extracted from dust continuum observations. The main properties of the core sample were derived using principal component analysis (PCA) and additional maps of physical parameters: the column density, Herschel far-ultraviolet (FUV) radiation field, G_0, and mean volume gas density, n. Additional high-spectral-resolution observations of served to evaluate the dynamical status of cores. The average line width of the cores is larger than what is typically expected for pre-stellar cores of closer star-forming regions, which suggests that cores in Orion B are subjected to stronger turbulence affecting their stability. The first factor of the PCA analysis explaining the variation in the detected line intensities is the core column density of molecular gas. The second factor explains how the core chemical composition is strictly linked to their environment, which can be traced by the ratio of the external FUV radiation field over the core volume density, Cold and shielded cores exhibit strong emission of and deuterated species, whereas cores exposed to radiation are devoid of typical core tracers, but exhibit emission of ̋COp, and HCN. The third factor explaining the core chemical diversity is the mean density along the core line of sight, which is also associated with freeze-out and fractionation signatures. Pre-stellar cores selected based on their dust emission exhibit a wide range of line emission patterns, which can be related to their intrinsic properties (column density, and mean volume density, n) and environment (presence or lack of FUV). The key parameter that distinguishes cores of different emission patterns is