Abstract

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 ∼ 2.0 ± 0.14 kpc, resolving the literature distance ambiguity. Using our Herschel-derived N(H2) map, we measure a total gas mass of 10 200 M (within 11 pc2) and the average line-mass profile of the entire filament, which we model as λ = 1660(w/pc)0.62 M pc−1. At w < 0.63 pc, our λ profile is higher and has a steeper power-law index than λ 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 ∼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, ff. We find that ff is ∼1.1 dex below the previously proposed mean local relation, and ∼ 4.7× 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.