Detection of Hco + 2 toward the Low-mass Protostar Iras 04368+2557 in L1527

The millimeter-wave rotational emission lines (404 − 303 and 505 − 404) of protonated carbon dioxide, HCO2 (HOCO ), has been detected toward the low-mass class 0 protostar IRAS 04368+2557 in L1527 with the IRAM 30 m telescope. This is the first detection of HCO2 except for the Galactic Center clouds. The column density of HCO2 averaged over the beam size (29 ) is determined to be 7.6 × 10 cm, assuming the rotational temperature of 12.3 K. The fractional abundance of gaseous CO2 relative to H2 is estimated from the column density of HCO2 with an aid of a simplified chemical model. If the HCO2 emission only comes from the evaporation region of CO2 near the protostar (T>∼50 K), the fractional abundance of CO2 is estimated to be higher than 6.6 × 10. This is comparable to the elemental abundance of carbon in interstellar clouds, and hence, the direct evaporation of CO2 from dust grain is unrealistic as a source of gaseous CO2 in L1527. A narrow line width of HCO2 also supports this. On the other hand, the fractional abundance of CO2 is estimated to be 2.9 × 10, if the source size is comparable to the beam size. These results indicate that gaseous CO2 is abundant even in the low-mass star-forming region. Possible production mechanisms of gaseous CO2 are discussed. Subject headings: ISM: molecules, ISM: individual(L1527)