CO molecular clumps and YSOs in NGC 602 region

We reveal the recent evolutionary past of the cluster through analysis of high-resolution (~0.4pc) Atacama Large Millimeter/submillimeter Array observations of molecular gas in the associated HII region N90. We identify 110 molecular clumps (R<0.8pc) traced by CO emission, and study the relationship between the clumps and associated young stellar objects (YSOs) and pre-main-sequence (PMS) stars.

The clumps have high virial parameters (typical {alpha}_vir_=4-11) and may retain signatures of a collision in the last <~8Myr between HI components of the adjacent supergiant shell SMC-SGS 1. We obtain a CO-bright-to-H2 gas conversion factor of X_CO,B_=(3.4+/-0.2)x10^20^cm^-2^ (K.km/s)^-1^, and correct observed clump properties for CO-dark H_2_ gas to derive a total molecular gas mass in N90 of 16600+/-2400M_{sun}_. We derive a recent (<~1Myr) star formation rate of 130+/-30M_{sun}_/Myr with an efficiency of 8%+/-3% assessed through comparing total YSO mass to total molecular gas mass.