A Parsec-scale Bipolar H 2 Outflow in the Massive Star-forming Infrared Dark Cloud Core MSXDC G053.11+00.05 MM1* †

Abstract

We present a parsec-scale molecular hydrogen (H 2 1–0 S(1) at 2.12 μ m) outflow discovered from the UKIRT Widefield Infrared Survey for H 2 . The outflow is located in the infrared dark cloud core MSXDC G053.11+00.05 MM1 at 1.7 kpc and is likely associated with two young stellar objects (YSOs) at the center. Although the overall morphology of the outflow is bipolar along the NE–SW direction with a brighter lobe to the southwest, the detailed structure consists of several flows and knots. With a total length of ∼1 pc, the outflow luminosity is fairly high with , implying a massive outflow-driving YSO if the entire outflow is driven by a single source. The two putative driving sources that are located at the outflow center show photometric variability of ≳1 mag in H - and K -bands. Together with their early evolutionary stage from spectral energy distribution (SED) fitting, this indicates that both are capable of ejecting outflows and may be eruptive variable YSOs. The YSO masses inferred from SED fitting are ∼10  M ⊙ and ∼5  M ⊙ , which suggests the association of the outflow with massive YSOs. The geometrical morphology of the outflow is well-explained by the lower-mass YSO by assuming a single-source origin; however, without kinematic information, the contribution from the higher mass YSO cannot be ruled out. Considering star formation process by fragmentation of a high-mass core into several lower-mass stars, we also suggest the possible presence of another, yet-undetected driving source that is deeply embedded in the core.