2024MNRAS.528..577M

Large-scale observations of the Perseus Molecular Cloud (MC) with Nanshan 26-m telescope are presented using the 6 cm ortho-H₂CO (1₁₀-1₁₁) transition. As a probe of dense gas at low temperatures, the H₂CO absorption extends over the main parts of the Perseus MC. A comparison of the H₂CO absorption line with the ¹²CO and ¹³CO (J = 1-0) emissions shows that the H₂CO and CO are similarly distributed over the Perseus but that H₂CO correlates better with ¹³CO. Comparison with the Herschel-derived H₂ column density shows that both the ¹³CO and H₂CO column densities vary linearly with the H₂ column density. The main parameters of H₂CO absorption line data show a log-normal distribution, which suggests that the strong non-thermal line-broadening results from large-scale supersonic turbulence related to the star formation. Formaldehyde absorption serves well as a tracer of star formation activity and also the H₂CO-to-¹³CO and H₂CO-to-H₂ abundances systematically trace the star formation activity in the six subregions of Perseus MC. The H₂CO abundances anticorrelate with the number of prestellar and protostellar cores and the IRIS 12 μm flux in the six subregions and reveal the star formation history in the Perseus MC.