Physical processes in the ISM

Initiating Clustered Star Formation: the Hierarchical Structure of Dense Molecular Clumps

21 Oct 2013, 09:00

9h

MPE

Poster Poster Session: Collapse of molecular clouds and the IMF (Poster 19-20)

Speaker

Ke Wang (ESO)

Description

We present high-resolution Submillimeter Array (SMA) 1.3 and 0.88 mm broad band observations, and Jansky Very Large Array (JVLA) observations in NH3 (J,K) = (1,1) up to (5,5), as well as H2O and CH3OH maser lines toward the two most massive and dense molecular clumps (>~10^3 Msun within <1pc) in the filamentary IR-dark cloud (IRDC) G11.11-0.12, also known as the "Snake" nebula. The sensitive high-resolution images reveal hierarchical fragmentation from the ~1 pc clump scale down to ~0.01 pc condensation scale. At each fragmenting scale, the mass of the fragments is orders of magnitude larger than the thermal Jeans mass. This is common to all the four clumps that we have studied in three IRDCs, suggesting that turbulence plays a dominant role in the initial stages of clustered star formation. Masers, shock heated NH3 gas, and outflows indicate intense ongoing star formation in some cores while no such signatures are found in others. Furthermore, chemical differentiation between the cores reflects a sequential growth of these star formation seeds. The mass function of the resolved condensations is consistent with a power law with an index of alpha = 2.0+/-0.2 and a turnover at 2.7 Msun. Our combined SMA+JVLA observations of several IRDC clumps have presented so far the deepest view of the early stages prior to the hot core phase, revealing snapshots of physical and chemical properties at various stages along an apparent evolutionary sequence.