Free Access
Volume 563, March 2014
Article Number L2
Number of page(s) 10
Section Letters
Published online 25 February 2014

Online material

Table 1

List of emission lines detected at the peak of the dust continuum emission at 219 GHz towards IRAS2A.

Table 2

Properties of identified emission lines detected toward the continuum peak emission of IRAS2A around 219 GHz.

thumbnail Fig. 3

Emission and residual maps of the continuum emission and CH3OCHO line emission at 217 GHz. a) The left and right panels, respectively, show the PdBI continuum emission map and residuals map. The residuals map was obtained by removing the two secondary sources as point sources, then removing the best-fit power-law model visibilities from the data visibilities, and imaging the residuals table. Contours show the levels of 3σ, 5σ, and 8σ, and then 10σ to 100σ in 10σ steps. The cross shows the phase center of our observations, coinciding with the peak of the continuum emission at 1.4 mm. b) The left and right panels, respectively, show the CH3OCHO emission and residual maps. In the maps, the rms noise level is σ = 2.8 mJy/beam. Contours show the 3σ, 5σ, and 8σ, and then 10σ to 60σ in 10σ steps.

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thumbnail Fig. 4

Emission maps for most of the identified molecular emission lines in the spectrum of IRAS2A. While CO isotopologues and H2CO (upper set of panels) are tracing the large-scale envelope and outflow structures, complex molecules (rows 2 to 7) are tracing a compact but often spatially-resolved emission centered on the maximum of the continuum emission. Some molecular lines are blended, see Table 1 for further information. Contours show the 3σ, 5σ, and 8σ, and then 10σ to 100σ in 20σ steps.

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Appendix A: Line identification

We extracted the WideX spectrum at the continuum emission peak (αJ2000 = 03h28m55.575s, δJ2000 = 31°1437.05) shown in Fig. A.1. The line identification was performed with the XCLASS software3 under the assumption of local thermodynamic equilibrium. Our spectroscopic database contains all entries of the CDMS (Müller et al. 2005) and JPL (Pickett et al. 1998) catalogs, as well as a few private entries (for more details, see Belloche et al. 2013). The spectra were modeled species by species. For most species, an excitation temperature of 100 K was assumed for the LTE modeling, while for a few species the detection of several transitions with significantly different upper-level energies allowed us to leave the temperature as a free

parameter of our modeling (finding temperatures up to ~250 K for CH3OH and HNCO, for example). For each species, the spectra in all three frequency setups were modeled at once, using five parameters: source size, temperature, column density, line width, and velocity offset with respect to the systemic velocity of the source. The emission of all transitions was assumed to come from a source of size (average FWHM, see Sect. 3). The fit optimization was performed by eye. For a few species (SO, SiO, CO), it was necessary to include several velocity components to account for the shape of the detected lines. A total of 86 emission lines with peak signal-to-noise ratios higher than 3 were detected at the position of the continuum emission peak, in setup S2, among which 55 are identified, see Table 1.

thumbnail Fig. A.1

Continuum-subtracted WideX spectrum around 218.5 GHz (setup S2), at the position of the maximum of 1.4 mm continuum emission towards IRAS2A (shown in Fig.1a).

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© ESO, 2014

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