Detecting faint Debris Discs around M dwarfs

M dwarfs, as the most common stars in our galaxy, are commonly observed in exoplanetary surveys. A growing number of earth-like planets are detected around M dwarfs. Still, a mystery is why we do not find planetesimal belts around these stars. Planetesimal belts form after the protoplanetary disc disappears. The leftover planetesimals collide and create dusty discs, a.k.a. debris discs. Herschel showed that debris discs around M dwarfs are rare (5%) in contrast to Sun-like stars (20%) and A-type stars (30%). We analyzed a Herschel survey that observed 94 M dwarfs to find debris discs, where two new discs were detected. To test the reasons for this, we created a synthetic population of discs around these M stars based on different assumptions for their properties. We then tested if IRAM or ALMA would detect these discs around this M dwarf sample. Even though ALMA had better detection rates than IRAM, we showed that the possibility of finding new and fainter discs around low-mass stars is limited for these facilities. We have now tested our discs around the 94 M dwarfs for AtLAST. At the maximum detection rate (depending on the exact disc assumptions) for AtLAST, almost all our synthetic M dwarf debris discs were detected. The advantages of AtLAST are the high sensitivity, a lower resolution compared to ALMA, and no maximum recoverable scale (MRS) because it is a single-dish telescope. Discs around M dwarfs have a faint flux, and if they are split into several beams, most become undetectable for ALMA. For AtLAST, only a small number of discs is marginally resolved. Therefore, we calculate a ~50% higher detection rate than for ALMA. If we observed the 94 M dwarfs of the former DEBRIS Herschel survey with AtLAST, we could detect an order of magnitude more M dwarf debris discs.