L1544: A Starless Dense Core with Extended Inward Motions

• DOI: 10.1086/306115
• Publication Date: 2002-07-26T18:50:42Z
• Authors: M. Tafalla; D. Mardones; P. C. Myers; P. Caselli; R. Bachiller; P. J. Benson
• Keywords: 13. Climate action; 0103 physical sciences; 01 natural sciences; 7. Clean energy

We present a multiline study of the dense core L1544 in Taurus molecular complex. Although does not harbor an embedded star, it presents several characteristics cores that have already undergone star formation, suggesting may be rather advanced its evolution toward becoming star-forming core. The spectral lines from interesting dichotomy, with thick gas tracers suffering very strong self absorption while CO and isotopes are being absorbed at all. presence absorptions allows us to both density structure kinematics detail. A simple analysis shows is almost isothermal due subthermal excitation outer layers. has decrease outward rapidly, detailed radiative transfer calculation simultaneously fits three two CS approximately follows r-1.5 power law. absorptions, addition, allow measure relative velocity between inner layers core, we find there global pattern inward motions (background foreground approaching each other). speed background changes position, use two-layer model deduce constant velocity, material systematic interpret as arising components. explore origin by comparing our observations models gravitational collapse. which infall starts center propagates (as inside-out collapse Shu) inconsistent large extension (that suggests age) lack extreme youth). Ambipolar diffusion seems also ruled out because amount (up 0.1 km s-1) fact ionized species move speeds similar those neutrals. Other seem problems fitting data, so if infalling, doing manner contemplated standard theories formation. Our illustrates how little still known about physical conditions precede formation studies starless urgently needed.