Molecular ions in L1544. II. The ionization degree

Details Molecular ions in L1544. II. The ionization degree Molecular ions in L1544. II. The ionization degree

2001-09-03

arxiv.org/abs/astro-ph/0109023v1

Astrophys.J.565:344-358,2002

Astronomy and Astrophysics

Astrophysics

31 pages, 8 figures, to be published in ApJ

Scientific paper

10.1086/324302

The maps presented in Paper I are here used to infer the variation of the column densities of HCO+, DCO+, N2H+, and N2D+ as a function of distance from the dust peak. These results are interpreted with the aid of a crude chemical model which predicts the abundances of these species as a function of radius in a spherically symmetric model with radial density distribution inferred from the observations of dust emission at millimeter wavelengths and dust absorption in the infrared. Our main observational finding is that the N(N2D+)/N(N2H+) column density ratio is of order 0.2 towards the L1544 dust peak as compared to N(DCO+)/N(HCO+) = 0.04. We conclude that this result as well as the general finding that N2H+ and N2D+ correlate well with the dust is caused by CO being depleted to a much higher degree than molecular nitrogen in the high density core of L1544. Depletion also favors deuterium enhancement and thus N2D+, which traces the dense and highly CO-depleted core nucleus, is much more enhanced than DCO+. Our models do not uniquely define the chemistry in the high density depleted nucleus of L1544 but they do suggest that the ionization degree is a few times 10^{-9} and that the ambipolar diffusion time scale is locally similar to the free fall time. It seems likely that the lower limit which one obtains to ionization degree by summing all observable molecular ions is not a great underestimate of the true ionization degree. We predict that atomic oxygen is abundant in the dense core and, if so, H3O+ may be the main ion in the central highly depleted region of the core.

Affiliated with

Also associated with

No associations

Rating

Molecular ions in L1544. II. The ionization degree 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 Molecular ions in L1544. II. The ionization degree, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Molecular ions in L1544. II. The ionization degree will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-354454