2015 Seminar List:
We discuss the evolution of dust and gas in star-forming regions via multi-wavelength observation from the IR to the mm.
First, we present observational evidences of dust grain growth and ice formation in Infrared Dark Clouds (IRDCs), that are considered as initial stages of massive star and star cluster formation, by analyzing photometric (Spitzer-IRAC, Spitzer-MIPS and Herschel-PACS) and spectroscopic (Spitzer-IRS) data of an IRDC, G028.37+00.07. Since massive star-forming regions are generally rare, far and deeply embedded in dense molecular clouds, it has been difficult to determine the dust extinction law in these regions in the mid- to far-infrared range. We use ¡±saturation-based extinction mapping" (Butler & Tan 2012, Lim & Tan 2014) applied to imaging and spectroscopic data to measure this extinction law, which is sensitive to growth of ~micron-sized dust grains and ice mantle formation.
We investigate the variation of the extinction law in different environments as parameterized by mass surface density and compare to theoretical models of dust evolution.
We find flatter opacity curves in higher mass surface density regions, which indicate grain growth via coagulation and find agreements of specific shapes of the extinction law that indicate ice mantle formation in the densest regions. We discuss implications of these results for studies of the probability distribution functions (PDFs) of star-forming clouds.
Second, we study a large population of star-forming clumps from the Census of High- and Medium-mass Protostars (CHaMP) survey that have been mapped in multiple molecular lines with the Mopra telescope. We consider different tracers of clump mass (HCO+, 13CO and sub-mm continuum) and examine trends in these properties as a function of the evolutionary stage of star cluster formation as parameterized by the bolometric luminosity to mass ratio of the clumps.