New detections of Galactic molecular absorption systems toward ALMA calibrator sources

作者：Ando Ryo^*; Kohno Kotaro; Tamura Yoichi; Izumi Takuma; Umehata Hideki; Nagai Hiroshi

来源：Publications of the Astronomical Society of Japan, 2016, 68(1): 6.

DOI：10.1093/pasj/psv110

• ISM: abundances
• ISM: molecules
• quasars: absorption lines
• radio lines: ISM

We report on Atacama Large Millimeter/submillimeter Array (ALMA) detections of molecular absorption lines in Bands 3, 6, and 7 toward four radio-loud quasars, which were observed as the bandpass and complex gain calibrators. The absorption systems, three of which are newly detected, are found to be Galactic origin. Moreover, HCO absorption lines toward two objects are detected, which almost doubles the number of HCO absorption samples in the Galactic diffuse medium. In addition, high HCO-to-(HCO+)-C-13 column density ratios are found, suggesting that the interstellar media (ISM) observed toward the two calibrators are in photodissociation regions, which observationally illustrates the chemistry of diffuse ISM driven by ultraviolet (UV) radiation. These results demonstrate that calibrators in the ALMA Archive are potential sources for the quest for new absorption systems and for detailed investigation of the nature of the ISM.

• 出版日期2016-2
• 单位中国科学院国家天文台