Study of Complex Nitrogen and Oxygen-bearing Molecules toward the High-mass Protostar IRAS 18089–1732

Abstract

The observation of oxygen (O)- and nitrogen (N)-bearing molecules gives an idea about the complex prebiotic chemistry in the interstellar medium (ISM). Recent millimeter and submillimeter wavelength observations have shown the presence of complex O- and N-bearing molecules in the star-formation regions. So, the investigation of those molecules is crucial to understanding the chemical complexity in the star-forming regions. In this article, we present the identification of the rotational emission lines of N-bearing molecules ethyl cyanide (C2H5CN), cyanoacetylene (HC3N), and O-bearing molecules methyl formate (CH3OCHO) towards high-mass protostar IRAS 18089–1732 using the Atacama Compact Array (ACA). We also detected the emission lines of both N- and O-bearing molecule formamide (NH2CHO) in the envelope of IRAS 18089–1732. We have detected the v = 0 and 1 states rotational emission lines of CH3OCHO. We also detected the two vibrationally excited states of HC3N (v7 = 1 and v7 = 2). The estimated fractional abundances of C2H5CN, HC3N (v7 = 1), HC3N (v7 = 2), and NH2CHO towards the IRAS 18089–1732 are (1.40±0.5)×10^{−10}, (7.5±0.7)×10^{−11}, (3.1±0.4)×10^{−11}, and (6.25±0.82)×10^{−11}. Similarly, the estimated fractional abundances of CH3OCHO (v = 0) and CH 3 OCHO (v = 1) are (1.90±0.9)×10^{−9} and (8.90±0.8)×10^{−10}, respectively. We also created the integrated emission maps of the detected molecules, and the observed molecules may have originated from the extended envelope of the protostar. We show that C2H5CN and HC3N are most probably formed via the subsequential hydrogenation of the CH2CHCN and the reaction between C2H2 and CN on the grain surface of IRAS 18089–1732. We found that NH2CHO is probably produced due to the reaction between NH2 and H2CO in the gas phase. Similarly, CH3OCHO is possibly created via the reaction between radical CH3O and radical HCO on the grain surface of IRAS 18089–1732.