Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS)

Abstract

Context . It remains a fundamental research question in astrochemistry to characterize the inventory of complex organic molecules formed during the early stages of star formation, which may affect the eventual chemical composition of protoplanetary disks and potentially planets. So far, only studies of individual sources or selected samples of molecular species have been conducted and the relative importance of environmental and evolutionary effects on the chemical composition remains unclear. Aims . The Atacama Large Millimeter/submillimeter Array (ALMA) provides the angular resolution and sensitivity to zoom in on the hot ( T > 100 K) gas surrounding embedded solar-type protostars and chart their molecular inventories with high accuracy. The ALMA Large Program Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS) aims to provide comprehensive inventories of the molecular content of a sample of protostellar sources to understand the chemical impact of their environments and evolutionary stages. Methods . COMPASS is an unbiased spectral survey of 11 line-rich Class 0 and I protostellar sources in the spectral range from 279.0 to 311.7 GHz at 0.15–0.5″ angular resolution with ALMA, corresponding to the inner ∼100 au (radius) around the targeted sources. Through this survey, unique chemical fingerprints of each source can be established. Results . This paper provides an overview of the COMPASS program and the adopted strategy in terms of observational setups and targeted sources. We also present a qualitative comparison of the spatial distributions of selected molecules and the relative strengths of the line fluxes of selected complex organics. Conclusions . The qualitative comparisons suggest that chemical differences between sources may be present, for example, between the abundances of groups of oxygen- and nitrogen-bearing species, but also that such variations occur at levels smaller than an order of magnitude. Quantitative comparisons of abundances at these levels require the large bandwidth of the survey, as well as a careful analysis of the excitation and strengths of the several thousands of lines detected toward each source in the survey, as will be explored in forthcoming papers.

The authors' abstract, as published at the source. Astronomy and Astrophysics, 2026 · DOI ↗