A Survey for Infall Motions toward Starless Cores. II. $CS (2-1)$ and $N_2H^+ (1-0)$ Mapping Observations

Details A Survey for Infall Motions toward Starless Cores. II. $CS (2-1)$ and $N_2H^+ (1-0)$ Mapping Observations A Survey for Infall Motions toward Starless Cores. II. $CS (2-1)$ and $N_2H^+ (1-0)$ Mapping Observations

2001-05-30

arxiv.org/abs/astro-ph/0105515v1

Astrophys.J.Suppl. 136 (2001) 703-734

Astronomy and Astrophysics

Astrophysics

Two tex files for manuscript and tables, and 38 figures. To appear in ApJS

Scientific paper

10.1086/322534

We present the results of an extensive mapping survey of 53 `starless' cores in the optically thick line of CS 2-1 and the optically thin lines of N2H+ 1-0 and C18O 1-0. The purpose of this survey was to search for signatures of extended inward motions. This study finds 10 `strong' and 9 `probable' infall candidates, based on $\delta V_{CS}$ analysis and on the spectral shapes of CS lines. From our analysis of the blue-skewed CS spectra and the $\delta V_{CS}$ parameter, we find typical infall radii of 0.06-0.14 pc. Also, using a simple two layer radiative transfer model to fit the profiles, we derive one-dimensional infall speeds, half of whose values lie in the range of 0.05-0.09 km s$^{-1}$. These values are similar to those found in L1544 by Tafalla et al., and this result confirms that infall speeds in starless cores are generally faster than expected from ambipolar diffusion in a strongly sub-critical core. In addition, the observed infall regions are too extended to be consistent with the `inside-out' collapse model applied to a very low-mass star. In the largest cores, the spatial extent of the CS spectra with infall asymmetry is larger than the extent of the $\rm N_2H^+$ core by a factor of 2-3. All these results suggest that extended inward motions are a common feature in starless cores, and that they could represent a necessary stage in the condensation of a star-forming dense core.

Affiliated with

Also associated with

No associations

Rating

A Survey for Infall Motions toward Starless Cores. II. $CS (2-1)$ and $N_2H^+ (1-0)$ Mapping Observations does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with A Survey for Infall Motions toward Starless Cores. II. $CS (2-1)$ and $N_2H^+ (1-0)$ Mapping Observations, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and A Survey for Infall Motions toward Starless Cores. II. $CS (2-1)$ and $N_2H^+ (1-0)$ Mapping Observations will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-554950