Detection of HCOOCH3 toward a low-mass protostar, NGC 1333 IRAS 4B

The rotational spectral lines of methylformate (HCOOCH3) have been detected toward a low-mass protostar, NGC 1333 IRAS 4B, with the Nobeyama 45 m radio telescope. The column density is derived to be (7-37) x 10 11 cm(-2), assuming a source size of 1 and the range of the excitation temperature to be from 50 K to 200 K. The column density is almost comparable to those found in other low-mass star-forming regions, NGC 1333 IRAS 4A and IRAS 16293-2422. The line width of HCOOCH3 is (1.0-1.2)kms(-1),which is narrower than that of the high-excitation line of CH3OH (8(-4)-9(-3)). Since NGC 1333 IRAS 4B is likely to be a Very Young protostar, HCOOCH3 appears even in the early stage of protostellar evolution. The spectral lines of HCOOCH3 could be Used as a novel tracer for detecting all onset of star formation.