Interferometric Observations of Cyanopolyynes toward the G28.28-0.36 High-Mass Star-Forming Region

Abstract

We have carried out interferometric observations of cyanopolyynes, HC${}_3$N, HC${}_5$N, and HC${}_7$N, in the 36 GHz band toward the G28.28$-$0.36 high-mass star-forming region using the Karl G. Jansky Very Large Array (VLA) Ka-band receiver. The spatial distributions of HC${}_3$N and HC${}_5$N are obtained. HC${}_5$N emission is coincident with a 450 $\mu$m dust continuum emission and this clump with a diameter of $\sim 0.2$ pc is located at the east position from the 6.7 GHz methanol maser by $\sim 0.15$ pc. HC${}_7$N is tentatively detected toward the clump. The HC${}_3$N : HC${}_5$N : HC${}_7$N column density ratios are estimated at 1.0 : $\sim 0.3$ : $\sim 0.2$ at an HC${}_7$N peak position. We discuss possible natures of the 450 $\mu$m continuum clump associated with the cyanopolyynes. The 450 $\mu$m continuum clump seems to contain deeply embedded low- or intermediate-mass protostellar cores, and the most possible formation mechanism of the cyanopolyynes is the warm carbon chain chemistry (WCCC) mechanism. In addition, HC${}_3$N and compact HC${}_5$N emission is detected at the edge of the 4.5 $\mu$m emission, which possibly implies that such emission is the shock origin.

12 pages, 7 figures, 4 tables, Accepted for publication in The Astrophysical Journal