Protostellar outflows and envelopes in our survey, which include 21 sources at different evolutionary stages. ¹²CO J = 2−1 integrated intensity maps trace the blueshifted (blue) and redshifted (red) molecular outflow lobes. C¹⁸O J = 2−1 integrated intensity maps, shown in green, trace the dense circumstellar envelope. The upper, middle, and bottom rows show Class 0, Class I, and flat-spectrum protostars, respectively, and are arranged in order of increasing T _bol (which we use as a proxy for age) from left to right. Source names are shown above each map. Each map has a diameter of about 50.″4, which is set by the 40% primary beam power response (compared to the center of the map). The coordinates of the center of the panels are given in Table 1.