STUDY OF STRUCTURE AND SMALL-SCALE FRAGMENTATION IN TMC-1

Large-scale (CO)-O-18 maps show that the Taurus molecular cloud 1 (TMC -1) has numerous cores located along a ridge which extends about 12' b y at least 35'. The cores traced by (CO)-O-18 are about a few arcminut es (0.1-0.2 pc) in extent, typically contain about 0.5-3 M., and are p robably gravitationally bound. We present a detailed study of the smal l-scale fragmentary structure of one of these cores, called core D, wi thin TMC-1 using very high spectral and spatial resolution maps of CCS and CS. The CCS lines are excellent tracers for investigating the den sity, temperature, and velocity structure in dense cores. The high spe ctral resolution, 0.008 km s(-1), data consist mainly of single-dish, Nyquist-sampled maps of CCS at 22 GHz with 45 '' spatial resolution ta ken with NASA's 70 m DSN antenna at Goldstone. The high spatial resolu tion spectral line maps were made with the Very Large Array (9 '' reso lution) at 22 GHz and with the OVRO millimeter array in CCS and CS at 93 GHz and 98 GHz, respectively, with 6 '' resolution. These maps are supplemented with single-dish observations of CCS and (CCS)-S-34 spect ra at 33 GHz using a NASA 34 m DSN antenna, CCS 93 GHz, (CS)-S-34 (2-1 ), and (CO)-O-18 (1-0) single-dish observations made with the AT&T Bel l Laboratories 7 m antenna. Our high spectral and spatial CCS and CS m aps show that core D is highly fragmented. The single-dish CCS observa tions map out several clumps which range in size from similar to 45 '' to 90 '' (0.03-0.06 pc). These clumps have very narrow intrinsic line widths, 0.11-0.25 km s(-1), slightly larger than the thermal line wid th for CCS at 10 K, and masses about 0.03-0.2 M.. Interferometer obser vations of some of these clumps show that they have considerable addit ional internal structure, consisting of several condensations ranging in size from similar to 10 ''-30 '' (0.007-0.021 pc), also with narrow line widths. The mass of these smallest fragments is of order 0.01 M. . These small-scale structures traced by CCS appear to be gravitationa lly unbound by a large factor. Most of these objects have masses that fall below those of the putative proto-brown dwarfs (less than or simi lar to 0.1 M.). The presence of many small gravitationally unbound clu mps suggests that fragmentation mechanisms other than a purely Jeans g ravitational instability may be important for the dynamics of these co ld dense cores.