Which molecule traces what: Chemical diagnostics of protostellar sources

The physical and chemical conditions in Class 0/I protostars are fundamental unlocking the protostellar accretion process its impact on planet formation. aim is to determine which components traced by different molecules at sub-arcsecond scales (100 - 400 au). We use a suite of Atacama Large Millimeter/submillimeter Array (ALMA) datasets Band 6 (1 mm), 5 (1.8 mm) 3 (3 spatial resolutions 0.5 3" for 16 sources. envelope well C$^{18}$O, DCO$^+$ N$_2$D$^+$, with freeze-out CO governing chemistry scales. Molecular outflows seen classical shock tracers like SiO SO, but ice-mantle products such as CH$_3$OH HNCO released also observed. molecular jet prominent not only SO occasionally H$_2$CO. cavity walls show UV-irradiation C$_2$H c-C$_3$H$_2$ CN. hot inner envelope, apart from showing emission complex organic (COMs), presents compact small H$_2$S, OCS H$^{13}$CN, most likely related ice sublimation high-temperature chemistry. Sub-arcsecond millimeter-wave observations allow identify those (simple) that best trace each system. COMs found both (high excitation lines) (lower-excitation comparable abundances. can coexist hydrocarbons same sources, they components. In near future, mid-IR JWST-MIRI will provide complementary information about hottest gas mantle content, unprecedented sensitivity ALMA