A Molecular Line Survey of IRDC Star Forming Clumps with the Nobeyama 45M Telescope

Details A Molecular Line Survey of IRDC Star Forming Clumps with the Nobeyama 45M Telescope A Molecular Line Survey of IRDC Star Forming Clumps with the Nobeyama 45M Telescope

May 2011

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011iaus..280p.236l&link_type=abstract

The Molecular Universe, Posters from the proceedings of the 280th Symposium of the International Astronomical Union held in Tole

Astronomy and Astrophysics

Astronomy

Scientific paper

What constitutes the initial condition for massive star formation is hardly known. Such objects are probably difficult to find due to the dramatically shorter evolutionary timescale and the lack of proper tracers. Infrared dark clouds (IRDCs) are objects seen in absorption against the bright diffuse Galactic mid-infrared background and their cold dense nature with substantial masses strongly suggests IRDCs are sites for massive star and/or cluster formation. To achieve a more complete and unbiased census of the physical and chemical properties of IRDCs, we have undertaken a pilot molecular line survey of the star/cluster forming clumps MM1, MM4, and MM9 in IRDC G28.34+0.06 at the 3mm atmospheric window utilizing the Nobeyama Radio Observatory 45M Telescope. The survey has achieved at the moment a frequency coverage from 86 GHz to 98 GHz at a rms noise level of around 20 mK. Additional coverage over selected lines/frequencies at 40 GHz and 300 GHz bands were also obtained with the NRO 45M and ASTE, respectively. Dramatically different spectral signatures are found among these clumps, signifying their different physical and chemical properties likely related to the evolutionary stages. For example, hot core lines are clearly found in MM1, where around 30 number of species have been detected. MM4 perhaps also harbors hot core(s) as indicated by the detection of, for example, CH_3CN, CH_3OH and CH_3CHO, although the gas temperature derived from CH_3CN J=5-4 lines are noticeably cooler (<30 K) than that in MM1 (<50 K). With no hot core signature, MM9 has the highest values in [CCS]/[N2H+], marking its cold and early stage.

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