2004/11/05 by Jonathan Swift, J. Swift, William J. Welch +3 · 2 citations
Chemistry · Earth and Planetary Sciences · Physics and Astronomy · #Angular momentum #Astronomy #Astrophysics #Astrophysics and Star Formation Studies #Atmospheric Ozone and Climate #Classical mechanics #Kinetic energy #Mean kinetic temperature #Molecular cloud #Physics #Protostar #Spectroscopy and Laser Applications #Star formation #Stars #Virial theorem #astro-ph
paper · pdf · doi:10.1086/427257
published as Astrophys.J. 620 (2005) 823-834 · 27 pages, 7 figures, ApJ accepted
arxiv created 2004/11/05 · openalex publication_date 2005/02/20 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Large-field surveys of NH 3 , C 2 S, 13 CO, and C 18 O in the L1551 dark cloud have revealed a prolate, pre-protostellar molecular core (L1551 MC) in a relatively quiescent region to the northwest of the well-known IRS 5 source. The kinetic temperature is measured to be 9 K, the total mass is ~2 M ☉ , and the average particle density is 10 4 -10 5 cm -3 . L1551 MC is 2 25 × 1 11 in projection, oriented at a position angle of 133°. The turbulent motions are on the order of the sound speed in the medium and contain 4% of the gravitational energy, E grav , of the core. The angular momentum vector is projected along the major axis of L1551 MC, corresponding to a rotational energy of 2.5 × 10 -3 i | E grav |. The thermal energy constitutes about a third of | E grav |, and the virial mass is approximately equal to the total mass. L1551 MC is gravitationally bound and in the absence of strong, ~160 μG magnetic fields will likely contract on a ~0.3 Myr timescale. The line profiles of many molecular species suggest that the cold quiescent interior is surrounded by a dynamic, perhaps infalling envelope that is embedded within the ambient molecular gas of L1551.