TMC-1C: An accreting starless core

S. Schnee, P. Caselli, A. Goodman, H. G. Arce, J. Ballesteros-Paredes, K. Kuchibhotla

Research output: Contribution to journalArticlepeer-review

34 Scopus citations


We have mapped the starless core TMC-1C in a variety of molecular lines with the IRAM 30 m telescope. High-density tracers show clear signs of self-absorption, and subsonic infall asymmetries are present in N 2H+(1-0) and DCO+(2-1) lines. The inward velocity profile in N2H+(1-0) is extended over a region about 7000 AU in radius around the dust continuum peak, which is the most extended "infalling" region observed in a starless core with this tracer. The kinetic temperature (∼12 K) measured from C17O and C18O suggests that their emission comes from a shell outside the colder interior traced by the millimeter continuum dust. The C 18O(2-1) excitation temperature drops from 12 to ≃ 10 K away from the center. This is consistent with a volume density drop of the gas traced by the C18O lines, from ≃4 × 104 cm -3 toward the dust peak to ≃6 × 103 cm -3 at a projected distance from the dust peak of 80″ (or 11,000 AU). The column density implied by the gas and dust show similar N 2H+ and CO depletion factors (fD ≤ 6). This can be explained with a simple scenario in which: (1) the TMC-1C core is embedded in a relatively dense environment [n(H2) ≃ 10 4 cm-3], where CO is mostly in the gas phase and the N2H+ abundance had time to reach equilibrium values; (2) the surrounding material (rich in CO and N2H+) is accreting onto the dense core nucleus; (3) TMC-1C is older than 3 × 105 yr, to account for the observed abundance of N2H + across the core (≃ 10-10 with respect to H 2); and (4) the core nucleus is either much younger (≃10 4 yr) or "undepleted" material from the surrounding envelope has fallen toward it in the past 10,000 yr.

Original languageEnglish (US)
Pages (from-to)1839-1857
Number of pages19
JournalAstrophysical Journal
Issue number2
StatePublished - Dec 20 2007
Externally publishedYes


  • Dust, extinction
  • Stars: formation
  • Submillimeter

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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