Narrow Na and K absorption lines toward T Tauri stars: Tracing the atomic envelope of molecular clouds

Ilaria Pascucci, S. Edwards, M. Heyer, E. Rigliaco, L. Hillenbrand, U. Gorti, D. Hollenbach, M. N. Simon

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

We present a detailed analysis of narrow Na i and K i absorption resonance lines toward nearly 40 T Tauri stars in Taurus with the goal of clarifying their origin. The Na i λ5889.95 line is detected toward all but one source, while the weaker K i λ7698.96 line is detected in about two-thirds of the sample. The similarity in their peak centroids and the significant positive correlation between their equivalent widths demonstrate that these transitions trace the same atomic gas. The absorption lines are present toward both disk and diskless young stellar objects, which excludes cold gas within the circumstellar disk as the absorbing material. A comparison of Na i and CO detections and peak centroids demonstrates that the atomic gas and molecular gas are not co-located, the atomic gas being more extended than the molecular gas. The width of the atomic lines corroborates this finding and points to atomic gas about an order of magnitude warmer than the molecular gas. The distribution of Na i radial velocities shows a clear spatial gradient along the length of the Taurus molecular cloud filaments. This suggests that absorption is associated with the Taurus molecular cloud. Assuming that the gradient is due to cloud rotation, the rotation of the atomic gas is consistent with differential galactic rotation, whereas the rotation of the molecular gas, although with the same rotation axis, is retrograde. Our analysis shows that narrow Na i and K i absorption resonance lines are useful tracers of the atomic envelope of molecular clouds. In line with recent findings from giant molecular clouds, our results demonstrate that the velocity fields of the atomic and molecular gas are misaligned. The angular momentum of a molecular cloud is not simply inherited from the rotating Galactic disk from which it formed but may be redistributed by cloud-cloud interactions.

Original languageEnglish (US)
Article number14
JournalAstrophysical Journal
Volume814
Issue number1
DOIs
StatePublished - Nov 20 2015

Fingerprint

T Tauri stars
monatomic gases
tracing
molecular clouds
molecular gases
envelopes
gas
resonance lines
centroids
galactic rotation
gradients
cold gas
radial velocity
tracers
filaments
angular momentum
velocity distribution
gases
tracer
interactions

Keywords

  • circumstellar matter
  • ISM: clouds
  • ISM: individual objects (Taurus)
  • ISM: kinematics and dynamics
  • stars: formation
  • stars: kinematics and dynamics

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Narrow Na and K absorption lines toward T Tauri stars : Tracing the atomic envelope of molecular clouds. / Pascucci, Ilaria; Edwards, S.; Heyer, M.; Rigliaco, E.; Hillenbrand, L.; Gorti, U.; Hollenbach, D.; Simon, M. N.

In: Astrophysical Journal, Vol. 814, No. 1, 14, 20.11.2015.

Research output: Contribution to journalArticle

Pascucci, I, Edwards, S, Heyer, M, Rigliaco, E, Hillenbrand, L, Gorti, U, Hollenbach, D & Simon, MN 2015, 'Narrow Na and K absorption lines toward T Tauri stars: Tracing the atomic envelope of molecular clouds', Astrophysical Journal, vol. 814, no. 1, 14. https://doi.org/10.1088/0004-637X/814/1/14
Pascucci, Ilaria ; Edwards, S. ; Heyer, M. ; Rigliaco, E. ; Hillenbrand, L. ; Gorti, U. ; Hollenbach, D. ; Simon, M. N. / Narrow Na and K absorption lines toward T Tauri stars : Tracing the atomic envelope of molecular clouds. In: Astrophysical Journal. 2015 ; Vol. 814, No. 1.
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