... resolution

The central density obtained with the continuum data reduces to $\sim$ $6\times10^5$  $\hbox{{\rm cm}}^{-3}$ when averaged within 26 $^{\prime \prime }$.

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...1989)

The use of the relation found in L1544 by Caselli et al. (2002b) shifts the theoretical curves up by a factor of $\sim$1.3 in deuterium fractionation.

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...(

When D₂H⁺ is included in the model, Eq. (4) becomes:

$$\begin{eqnarray*}R_{\rm deut} & \simeq \frac{1/3 \left[\hbox{${\rm H}_{2}{\rm ... ...$ }\right]/\left[\hbox{${\rm H}_{3}^{+}$ }\right]\right)^2}\cdot \end{eqnarray*}$$

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... center

The linewidth toward the center and the observed $\Delta v$-b trend can also be matched assuming a central infall speed 1.5 times larger than the one calculated by CB in their model t₃ and no extra broadening (e.g. turbulence) needs to be invoked. However, this is not consistent with the CB model at time t₃ and we do not further discuss this possibility. On the other hand, recent ${\rm H}_{2}{\rm D}^{+}$ observations toward L1544 (Caselli et al. 2003) also imply larger central infall speed than predicted by CB-t₃ (van der Tak et al. 2003).

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