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Description
NGC 7129 FIRS 2 (hereafter FIRS 2) is an intermediate-mass (2 to 8M_{sun}_) protostar located at a distance of 1250pc. High spatial resolution observations are required to resolve the hot core at its center. We present a molecular survey from 218200MHz to 221800MHz carried out with the IRAM Plateau de Bure Interferometer. These observations were complemented with a long integration single-dish spectrum taken with the IRAM 30m telescope. We used a Local Thermodynamic Equilibrium (LTE) single temperature code to model the whole dataset. The interferometric spectrum is crowded with a total of ~300 lines from which a few dozens remain unidentified yet. The spectrum has been modeled with a total of 20 species and their isomers, isotopologues and deuterated compounds. Complex molecules like methyl formate (CH_3_OCHO), ethanol (CH_3_CH_2_OH),g lycolaldehyde (CH_2_OHCHO), acetone (CH_3_COCH_3_), dimethyl ether (CH_3_OCH_3_), ethyl cyanide (CH_3_CH_2_CN) and the aGg' conformer of ethylene glycol (aGg'-(CH_2_OH)_2_) are among the detected species. The detection of vibrationally excited lines of CH_3_CN, CH_3_OCHO, CH_3_OH, OCS, HC_3_N and CH_3_CHO proves the existence of gas and dust at high temperatures. In fact, the gas kinetic temperature estimated from the vibrational lines of CH_3_CN, ~405K, is similar to that measured in massive hot cores. Our data allow an extensive comparison of the chemistry in FIRS 2 and the Orion hot core. We find a quite similar chemistry in FIRS 2 and Orion. Most of the studied fractional molecular abundances agree within a factor of 5. Larger differences are only found for the deuterated compounds D_2_CO and CH_2_DOH and a few molecules (CH_3_CH_2_CN, SO_2_, HNCO and CH_3_CHO). Since the physical conditions are similar in both hot cores, only different initial conditions (warmer pre-collapse phase in the case of Orion) and/or different crossing time of the gas in the hot core can explain this behavior.
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