Abstract

  The earliest phases of the high-mass star-forming regions (HMSFRs) have many extremely complicated astrophysical processes, such as fragmentations, infall, and outflows. Kinematic studies are not enough to understand all the mysteries. Therefore, whether chemistry can be a powerful tool in probing the nature of these processes is the main question astrochemists and observers try to answer. I will present on how to address this question through a number of mm wavelength observations during my PhD studies (Sep. 2011-Feb. 2015). Using the interferometers (NOEMA and SMA), combined with the single dished telescopes (IRAM 30 m), we carried several line surveys and studied several well-known HMSFRs, covering the evolutionary stages from the high-mass starless cores to the high-mass hot cores. At 1 mm/3mm, continuums for these sources present resolved substructures at the high spatial resolution <1000 AU. Spectra from different substructures in the same source vary. Moreover, different species, especially the complex organic molecules, in each source are distinctive in spatial distribution and column density, for which possible reasons I will discuss include: (1) Intensive kinematic processes (e.g., shocks, outflows) locally in different substructures (e.g. in Orion-KL); (2) Hierarchical fragmentation and evolutionary sequence along the filament direction within small scale (<5000 AU, e.g., in NGC 7538 S); (3) Non-LTE and population inversion of certain excitations (e.g., in NGC 7538 IRS1); (4) Chemical and kinetic complexity from the large scale (>10000 AU) to small scale (<6000 AU) in the cold early albeit “active” phase of high mass star formation (e.g., 4 Herschel Infrared Dark Clouds G28.34S, IRDC 18530, IRDC 18306, and IRDC 18308). I will also introduce my current commitment to two large programs— “CORE” (fragmentation and disk formation during high-mass star formation) and “SOLIS” (seeds of life in space).