Benchmarking the IRDC G351.77-0.53: Gaia DR3 Distance, Mass Distribution, and Star Formation Content

While intensively studied, it remains unclear how the star formation (SF) in infrared dark clouds (IRDCs) compares to that of nearby clouds. We study G351.77-0.53 (henceforth G351), a cluster-forming filamentary IRDC. We begin by characterizing its young stellar object (YSO) content. Based on the average parallax of likely members, we obtain a Gaia distance of similar to 2.0 +/- 0.14 kpc, resolving the literature distance ambiguity. Using our Herschel-derived N(H-2) map, we measure a total gas mass of 10 200 M-circle dot (within 11 pc(2)) and the average line-mass profile of the entire filament, which we model as lambda = 1660(w/pc)(0.62) M-circle dot pc(-1). At w < 0.63 pc, our lambda profile is higher and has a steeper power-law index than lambda profiles extracted in Orion A and most of its substructures. Based on the YSOs inside the filament area, we estimate the SF efficiency (SFE) and SF rate (SFR). We calculate a factor of 5 incompleteness correction for our YSO catalogue relative to Spitzer surveys of Orion A. The G351 SFE is similar to 1.8 times lower than that of Orion A and lower than the median value for local clouds. We measure SFR and gas masses to estimate the efficiency per free-fall time, epsilon(ff). We find that epsilon(ff) is similar to 1.1 dex below the previously proposed mean local relation, and similar to 4.7x below Orion A. These observations indicate that local SF-relations do not capture variations present in the Galaxy. We speculate that cloud youth and/or magnetic fields might account for the G351 inefficiency.