Low-Mass Clumps in TMC-1: Scaling Laws in the Small-Scale Regime

Details Low-Mass Clumps in TMC-1: Scaling Laws in the Small-Scale Regime Low-Mass Clumps in TMC-1: Scaling Laws in the Small-Scale Regime

Apr 1998

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998apj...497..842p&link_type=abstract

Astrophysical Journal v.497, p.842

Astronomy and Astrophysics

Astronomy

50

Ism: Clouds, Ism: Individual Name: Taurus Molecular Cloud, Ism: Molecules, Stars: Formation, Radio Lines: Ism

Scientific paper

We present new observational data on the small-scale structure of the Taurus molecular cloud 1 (TMC-1) in the regime of 0.02-0.04 pc and 0.04-0.6 M&sun;. Our analysis is based on high-resolution, high-S/N, observations of an 8' x 8' area centered on the "cyanopolyyne peak" in the southeastern part of the TMC-1 ridge. The observations were made in the CCS 22 and 45 GHz transitions using NASA's Deep Space Network 70 m and 34 m telescopes at the Goldstone facility. The CCS emission in this region originates in three narrow components centered on LSR velocities of ~5.7, 5.9, and 6.1 km s-1. These components each represent a separate cylindrical feature elongated along the ridge. Among the three velocity components we identified a total of 45 clumps with a typical CCS column density of ~a few x 1013 cm-2, an H2 density of ~a few x 104 cm-3, and a mass in the range of 0.04-0.6 M&sun;. The statistical properties of these small-scale clumps are compared with those of the larger "NH3 cores" in cold clouds and "CS cores" in the hotter Orion region. The CCS clumps in TMC-1 are found to conform to Larson's scaling laws (relating observed line width to clump size) derived from the larger cores down to the small-scale regime (0.02 pc and 0.04 M&sun;). These clumps represent a regime in which microturbulence is small, amounting to ~10% of the thermal pressure inside a clump. Of the 45 clumps, only five appear to be gravitationally unstable to collapse. All unbound clumps have masses less than 0.2 M&sun;, while bound clumps have masses in the range 0.15-0.6 M&sun;. The 6.1 km s-1 velocity feature contains all the gravitationally unstable clumps and is the most likely site for future star formation.

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