Infrared dark cloud

About: Infrared dark cloud is a research topic. Over the lifetime, 232 publications have been published within this topic receiving 13800 citations.

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~\micron) 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 likely associated with two young stellar objects (YSOs) at the center. The overall morphology of the outflow is bipolar along the NE-SW direction with a brighter lobe to the southwest, but the detailed structure consists of several flows and knots. With the total length of $\sim$1 pc, the outflow luminosity is fairly high with $L_{\rm H_{2}} > 6~L_{\sun}$, implying a massive outflow-driving YSO if the entire outflow is driven by a single source. The two putative driving sources, located at the outflow center, show photometric variability of $\gtrsim$1 mag in {\it H}- and {\it K}-bands. This, with their early evolutionary stage from spectral energy distribution (SED) fitting, indicates that both are capable of ejecting outflows and may be eruptive variable YSOs. The YSO masses inferred from SED fitting are $\sim$10~$M_{\sun}$ and $\sim$5~$M_{\sun}$, suggesting 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, but 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 deeply embedded in the core.

A multi-transition molecular line study of infrared dark cloud G331.71+00.59

Abstract: Using archive data from the Millimeter Astronomy Legacy Team Survey at 90 GHz (MALT90), carried out using the Mopra 22-m telescope, we made the first multi-transition molecular line study of infrared dark cloud (IRDC) MSXDC G331.71+00.59. Two molecular cores were found embedded in this IRDC. Each of these cores is associated with a known extended green object (EGO), indicating places of massive star formation. The HCO + (1–0) and HNC(1–0) transitions show prominent blue or red asymmetric structures, suggesting outflow and inflow activities of young stellar objects (YSOs). Other detected molecular lines include H 13 CO + (1–0), C 2 H(1–0), HC 3 N(10–9), HNCO(4 0,4 –3 0,3 ) and SiO (2–1), which are typical of hot cores and outflows. We regard the two EGOs as evolving from the IRDC to hot cores. Using public GLIMPS data, we investigate the spectral energy distribution of EGO G331.71+0.60. Our results support this EGO being a massive YSO driving the outflow. G331.71+0.58 may be at an earlier evolutionary stage.

A Luminous Blue Variable Star Interacting with a Nearby Infrared Dark Cloud

Abstract: G79.29+0.46 is a nebula created by a Luminous Blue Variable (LBV) star candidate characterized by two almost circular concentric shells. In order to investigate whether the shells are interacting with the infrared dark cloud (IRDC) G79.3+0.3 located at the southwestern border of the inner shell, we conducted Jansky Very Large Array observations of NH3(1,1), (2,2) and c-C3H2, and combined them with previous Effelsberg data. The overall NH3 emission consists of one main clump, named G79A, elongated following the shape of the IRDC, plus two fainter and smaller cores to the north, which spatially match the inner infrared shell. We analysed the NH3 spectra at each position with detected emission and inferred linewidth, rotational temperature, column density and abundance maps, and find that: i) the linewidth of NH3(1,1) in the northern cores is 0.5 km/s, slightly larger than in their surroundings; ii) the NH3 abundance is enhanced by almost one order of magnitude towards the northwestern side of G79A; iii) there is one `hot slab' at the interface between the inner infrared shell and the NH3 peak of G79A; iv) the western and southern edges of G79A present chemical differentiation, with c-C3H2 tracing more external layers than NH3, similar to what is found in PDRs. Overall, the kinematics and physical conditions of G79A are consistent with both shock-induced and UV radiation-induced chemistry driven by the LBV star. Therefore, the IRDC is not likely associated with the star-forming region DR15, but located farther away, near G79.29+0.46 at 1.4 kpc.