[\ion(C)(ii)] 158 and [\ion(O)(i)] 63 MU M ISO-Observations of L1457

Abstract

We report here the results of [C Ii] 158 and [O I] 63 mu m fine-structure line observations along two cuts across a molecular clump of L1457 (MBM 12) carried out with ISO-LWS. [C Ii] emission was detected at all positions observed. It can be assigned to the cooling of the diffuse atomic interstellar medium. We observed excess [C Ii] emission from the dense clumpy molecular component. It is likely to originate from molecular gas that is irradiated by an interstellar FUV-radiation field of order chi (1-2) chi_0 . Using PDR models for a spherical symmetry we find the molecular gas of L1457 consists of clumps with a density n_H ~ 10(5) cm(-3) . Their masses range between 10(-4) and 10(-3) M_⊙ consistent with the clump distribution derived from high resolution CO observations. [O I] 63 mu m emission was not detected toward L1457. Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, The Netherlands and the United Kingdom) and with the participation of ISAS and NASA.