How to detect the signatures of self-gravitating circumstellar discs with the Atacama Large Millimeter/sub-millimeter Array

In this paper, we present simulated Atacama Large Millimeter/sub-millimeter Array (ALMA) observations of self-gravitating circumstellar discs with different properties in size, mass and inclination, located in four of the most extensively studied and surveyed star-forming regions. Starting from a smoothed particle hydrodynamics simulation and representative dust opacities, we have initially constructed maps of the expected emission at sub-mm wavelengths of a large sample of discs with different properties. We have then simulated realistic observations of discs as they may appear with ALMA using the Common Astronomy Software Application ALMA simulator. We find that, with a proper combination of antenna configuration and integration time, the spiral structure characteristic of self-gravitating discs is readily detectable by ALMA over a wide range of wavelengths at distances comparable to TW Hydrae (similar to 50 pc), Taurus-Auriga and Ophiucus (similar to 140 pc) star-forming regions. However, for discs located in Orion complex (similar to 400 pc) only the largest discs in our sample (outer radius of 100 au) show a spatially resolved structure while the smaller ones (outer radius of 25 au) are characterized by a spiral structure that is not conclusively detectable with ALMA.