An Atacama Large Millimeter/submillimeter Array Survey of Chemistry in Disks around M4–M5 Stars

M-stars are the most common hosts of planetary systems in Galaxy. Protoplanetary disks around thus offer a prime opportunity to study chemistry planet-forming environments. We present an ALMA survey molecular line emission toward sample five protoplanetary M4-M5 stars (FP Tau, J0432+1827, J1100-7619, J1545-3417, and Sz 69). These observations can resolve chemical structures down tens AU. Molecular lines $^{12}$CO, $^{13}$CO, C$^{18}$O, C$_2$H, HCN detected all disks. Lines H$_2$CO DCN 2/5 1/5 disks, respectively. For with resolved HCN, emission, we observe substructures similar those previously found solar-type (e.g., rings, holes, plateaus). C$_2$H excitation conditions estimated interior pebble disk edge for bright J1100-7619 consistent previous measurements stars. The correlation between fluxes extends our sample, but typical C$_2$H/HCN ratio is higher sample. This latter finding reminiscent hydrocarbon enhancements by observational infrared surveys innermost ($<$10AU) regions M-star which intriguing since disk-averaged heavily influenced flux levels outermost disk, exterior edge. Overall, observable at 10-100AU appears hydrocarbons may be more abundant cooler