High density structure of the L 1455 dark cloud

• Published in: Astronomy and astrophysics (Berlin) 1993-03, Vol.270 (1-2), p.432-443
• Main Authors: JUAN, J, BACHILLER, R, KÖMPE, C, MARTIN-PINTADO, J
• Format: Article
• Language: English
• Subjects: Astronomy; Earth, ocean, space; Exact sciences and technology; H ii regions. Emission and reflection nebulae; Interstellar medium (ism) and nebulae in milky way; Stellar systems. Galactic and extragalactic objects and systems. The universe
• ISSN: 0004-6361; 1432-0746

The dark cloud L 1455, in the local Perseus complex, has been mapped with moderate angular resolution (2 and 1 arcmin) in the 1 - 0 and 2 - 1 lines of CS and C(S-34) and with high angular resolution (40 arcsec beam) in the (1,1) and (2,2) lines of NH3. These observations provide, for the first time, a very detailed picture of the cloud structure over different scales. Two velocity components (at 4.8 and 5.5 km/s) are observed in this region of the sky. We have produced maps of the two clouds, and we find that the 4.8 km/s cloud is the one related to the star formation and outflow activity. The physical conditions of the dense gas have been derived from our multiline observations. The dense core, traced by the NH3 emission, is fragmented in several clumps with masses of 0.6 to 4 solar masses, kinetic temperatures of 12 K, and central densities of a few x 10,000/cu cm. These clumps are slightly heated toward the edges. In spite of the fact that the CS lines become excited at densities higher than those required by the NH3 lines, the CS is observed to be spatially more extended than the NH3 emission. We tentatively conclude that no ammonia molecules are present at the outer regions of the cloud, where CS is still well detected; this ammonia deficiency could be due to photodissociation effects.