All Figures

$\begin{figure} {\resizebox{7.5cm}{!}{\includegraphics[angle=270]{4770fi1a.eps}} } {\resizebox{7.5cm}{!}{\includegraphics[angle=270]{4770fi1b.eps}} } \end{figure}$ Figure 1: Mass distribution estimated from the integrated flux of continuum emission measured with a) interferometers (see Table 1) and b) single-dish telescopes (see Table 2), and computed using the best-fit opacity exponent $\beta = 0.85$ .
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In the text

$\begin{figure} {\resizebox{5.5cm}{!}{\includegraphics[angle=0]{4770fi2a.eps}}\hs... ...e}\resizebox{5.5cm}{!}{\includegraphics[angle=0]{4770fi2c.eps}} } \end{figure}$ Figure 2: Spectra toward the center of the IRAS 4A envelope obtained with the 30 m telescope or taken from the JCMT archive: a) CS and N₂H⁺ spectra, b) C³⁴S spectra along with CS(2-1) and N₂H⁺(1-0), c) HCO⁺, H¹³CO⁺, HC¹⁸O⁺, and DCO⁺ spectra along with N₂H⁺(1-0). The vertical dotted lines show the position of the blue peak, the red peak, and the dip of the CS(2-1) spectrum in a) and b), and the same for HCO⁺(3-2) in c). The temperature scale is in $T_{{\rm mb}}$ . The beamwidth ( HPBW) is given for each spectrum.
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In the text

$\begin{figure} {\resizebox{8.8cm}{!}{\includegraphics[angle=270]{4770fi3.eps}} } \end{figure}$ Figure 3: a) CS(2-1) intensity maps toward IRAS 4A integrated over [-4.10, 5.91] km s^-1 (thick contours), [6.06, 8.31] km s^-1 (grey scale), and [8.46, 15.50] km s^-1 (dashed contours). The contours go from 1.5 to 6 by 1.5 and from 1.5 to 3 by 1.5 K km s^-1, respectively. b) CS(5-4) intensity maps integrated over [-1.37, 5.91] km s^-1 (thick contours), [6.26, 8.11] km s^-1 (grey scale), and [8.46, 12.00] km s^-1 (dashed contours). The contours are 2 and 4, and 0.7 and 1.4 K km s^-1, respectively. The intensity scale is $T_{{\rm a}}^\star$ . The IRAM 30 m beam size is shown in each panel ( HPBW). The big/white and small/black crosses mark the positions of IRAS 4A and IRAS 4B, respectively.
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In the text

$\begin{figure} {\resizebox{8.8cm}{!}{\includegraphics[angle=270]{4770fi4.eps}} } \end{figure}$ Figure 4: Map of H¹³CO⁺(1-0) spectra taken toward IRAS 4A with the IRAM 30 m telescope. Each spectrum is divided into two components, filled in black for v < 7.30 km s^-1 and in grey for v > 7.30 km s^-1. The half-power beam width is 28 $\hbox {$^{\prime \prime }$ }$ .
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In the text

$\begin{figure} {\resizebox{8.8cm}{!}{\includegraphics[angle=270]{4770fi5.eps}} } \end{figure}$ Figure 5: Maps of N₂H⁺(101-012) intensity integrated over a) the blueshifted velocity range [5.95, 7.30] km s^-1 and b) the redshifted velocity range [7.30, 8.65] km s^-1, observed with the IRAM 30 m telescope ( HPBW 26 $\hbox {$^{\prime \prime }$ }$ , shown on the left). The first contour and contour step are 0.25 K km s^-1 on $T_{{\rm a}}^\star$ scale on both maps. The big cross marks the central position we used for IRAS 4A. The small crosses mark the positions of the VLA and BIMA continuum sources observed by Reipurth et al. (2002) and Looney et al. (2000). The dashed line separates the two components. It emphasizes the spatial shift between them and their shell-like structure.
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In the text

$\begin{figure} {\resizebox{8.8cm}{!}{\includegraphics[angle=270]{4770fi6.eps}} } \end{figure}$ Figure 6: a) Density, b) infall velocity, and c) mass infall rate profiles of the collapse model induced by compression described in Sect. 4.1 at times 0.8402, 0.8533, 0.8581, 0.8657, 0.8763, 0.8920, and $0.9249 \times 10^6$ yr, corresponding to renormalized times after the formation of the central protostar of approximately -7, 7, 11, 19, 30, 45, and $78 \times 10^3$ yr, respectively. The thick line corresponds to $1.9 \times 10^4$ yr and indicates the "best-fit'' model used in Sect. 4.3 and shown in Fig. 7. The dashed areas in (a) show the constraints deduced for IRAS 4A from the interferometric and single-dish continuum measurements (see Sect. 3.1).
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In the text

$\begin{figure} {\resizebox{18cm}{!}{\includegraphics[angle=270]{4770fi7.eps}} } \end{figure}$ Figure 7: a) Density, b) kinetic temperature, c) CS molecular abundance, d) non-thermal line broadening (FWHM), and e) infall velocity profiles of the collapse model at time $1.9 \times 10^4$ yr used for the radiative transfer modeling of Fig. 8.
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In the text

$\begin{figure} {\resizebox{8.8cm}{!}{\includegraphics[angle=270]{4770fi8.eps}} } \end{figure}$ Figure 8: CS, C³⁴S, and N₂H⁺ spectra (histograms) in units of main-beam temperature observed toward IRAS 4A along the longitude axis (see references in Fig. 2). Synthetic spectra corresponding to the collapse model at time $1.9 \times 10^4$ yr described in Sect. 4.1 are superimposed (red/thick line). The dotted line indicates the envelope systemic velocity used for the computation of the radiative transfer (7.20 km s^-1 for CS and C³⁴S, and 7.24 km s^-1 for N₂H⁺).
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In the text

$\begin{figure} {\resizebox{8.5cm}{!}{\includegraphics[angle=0]{4770fi9.eps}} } \end{figure}$ Figure 9: CS, C³⁴S, and N₂H⁺ spectra in units of main-beam temperature observed toward the center of IRAS 4A (histograms). Each column shows a different model (thick line). Synthetic spectra corresponding to the collapse model at time $1.9 \times 10^4$ yr described in Sect. 4.1 are superimposed in the central column (in red). In the left and right columns, the synthetic spectra (in green and blue) were obtained with the same input model, except for the non-thermal broadening, which was in both cases uniform with $\Delta V_{{\rm NT}} =$ 0.4 and 1.1 km s^-1, respectively. The dotted line indicates the systemic velocity of the envelope that was used to compute the radiative transfer (see Fig. 8).
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In the text

$\begin{figure} {\resizebox{8cm}{!}{\includegraphics[angle=0]{4770fi10.eps}} } \par \end{figure}$ Figure 10: CS and C³⁴S spectra in units of main-beam temperature observed toward the center of IRAS 4A (histograms). Each column shows a different model (thick line). Synthetic spectra corresponding to the collapse model described in Sect. 4.1 at times -7, 7, 19, and $45 \times 10^3$ yr are superimposed from left to right (in light blue, blue, red, and green). For each model, the scaling of the abundance profile was adjusted to match the peak intensity of the C³⁴S(2-1) line. The dotted line indicates the systemic velocity of the envelope that was used to compute the radiative transfer (see Fig. 8).
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In the text

$\begin{figure} {\resizebox{7.5cm}{!}{\includegraphics[angle=270]{4770fi1a.eps}} } {\resizebox{7.5cm}{!}{\includegraphics[angle=270]{4770fi1b.eps}} } \end{figure}$	Figure 1: Mass distribution estimated from the integrated flux of continuum emission measured with a) interferometers (see Table 1) and b) single-dish telescopes (see Table 2), and computed using the best-fit opacity exponent $\beta = 0.85$ .
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$\begin{figure} {\resizebox{8.8cm}{!}{\includegraphics[angle=270]{4770fi4.eps}} } \end{figure}$	Figure 4: Map of H¹³CO⁺(1-0) spectra taken toward IRAS 4A with the IRAM 30 m telescope. Each spectrum is divided into two components, filled in black for v < 7.30 km s^-1 and in grey for v > 7.30 km s^-1. The half-power beam width is 28 $\hbox {$^{\prime \prime }$ }$ .
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$\begin{figure} {\resizebox{18cm}{!}{\includegraphics[angle=270]{4770fi7.eps}} } \end{figure}$	Figure 7: a) Density, b) kinetic temperature, c) CS molecular abundance, d) non-thermal line broadening (FWHM), and e) infall velocity profiles of the collapse model at time $1.9 \times 10^4$ yr used for the radiative transfer modeling of Fig. 8.
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