Free Access
Volume 542, June 2012
Article Number A8
Number of page(s) 28
Section Interstellar and circumstellar matter
Published online 25 May 2012

Online material

Appendix A: H2O supplementary material

Table A.1 provides an overview of the specific observing mode used for each object, including (when applicable) the reference position used. Reference positions were primarily chosen from SWAS observations showing these regions to be emission free, and regions were in general checked against ground-based CO 1 − 0 observations.

thumbnail Fig. A.1

Emission ratio of H2O 110–101/CO 3–2 as a function of absolute velocity. All spectra have been centred at 0 km s-1. The top panel shows the ratio for all line wings where both H2O and CO emission exceeds 4σ. Line wings from Class 0 sources are shown in red, wings from Class I sources in blue. The average value is shown in black. The bottom panel shows the average value with the standard deviation shown in grey. The average values for the Class 0 and Class I sources in red and blue, respectively. The average ratios are taken in 1 km s-1 bins.

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Table A.1

Reference positions chosen for each source and obs ids.

Table A.2 provides the decomposition of each profile into Gaussians. Only saturated absorption features are not listed here.

Table A.2

Gaussian decomposition of the H2O line profiles.

Appendix B: CO supplementary material

The CO 3–2 data are presented here. This includes the spectra overplotted on the H2O spectra (Figs. B.1 and B.2). Magnifications to highlight the CO emission in the line wings are shown in Fig. B.3 where the spectra are shown on the same absolute scale as the H2O data in Figs. 1 and 2. The integrated intensities are provided in Table B.1.

Table B.1

Observed integrated CO 3–2 intensity in a 40′′ beam from the JCMT and APEX, and CO outflow force, FCO.

thumbnail Fig. B.1

Continuum-subtracted H2O 110–101 spectra of the observed Class 0 sources as presented in Fig. 1 with CO 3–2 spectra scaled and overplotted in blue. The CO 3–2 scaling factor is written in blue for each spectrum.

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thumbnail Fig. B.2

Same as Fig. B.1 but for Class I sources.

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thumbnail Fig. B.3

CO 3–2 data for each source as obtained with the JCMT or APEX. The velocity and intensity scales are the same as in Figs. 1 and 2.

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Appendix C: DUSTY modelling

All envelopes are modelled using the 1D spherically symmetric dust radiative transfer code DUSTY (Ivezić & Elitzur 1997). The procedure for modelling the envelopes is the same as outlined previously in Schöier et al. (2002) and Jørgensen et al. (2002), this work being an extension and update of the latter. In this setup, the density profile is assumed to be a power-law

with n ∝ r − p and the inner boundary, rin, of the envelope is set to be where the dust temperature is equal to 250 K. Three parameters are varied: the slope of the density profile, p, the size of the envelope, Y = rout/rin, and the dust optical depth at 100 μm, τ100. The dust opacity is taken from Ossenkopf & Henning (1994), Table 1, Col. 5, the so-called OH5, corresponding to dust grains with thin ice mantles. The radial extent and slope of emission as observed at 450 and 850 μm is modelled first, whereby p is determined. Secondly the spectral energy distribution (SED) is fitted with the remaining free parameters, Y and τ100. The envelope mass is directly related to τ100 and is best constrained by the SCUBA 850 μm flux.

The emission profiles were obtained from the SCUBA Legacy Archive (Di Francesco et al. 2008) or from LABOCA (e.g., for the case of HH46-IRS; van Kempen et al. 2009a). For sources with no available sub-mm continuum maps the emission was assumed to fall off with a slope of 1.5, and the derived envelope mass is therefore more uncertain due to poor sampling of the SED at long wavelengths (BHR71 and Ced110-IRS4, and HH46-IRS at 450 μm). Fixing the slope is most relevant for southern sources, for which little or no continuum data at 450 and 850 μm exist. The SEDs were assembled from the literature and consist of data points between 60 and 1300 μm. The long wavelength SED points (λ > 200 μm) are obtained from SCUBA/LABOCA, Bolocam and SEST. The short-wavelength points now include the Spitzer-MIPS points not available previously (Evans et al. 2009) and new Herschel-PACS data (Karska et al., in prep.; Green et al., in prep.). Model images were convolved to the appropriate observing beam for comparison. To ensure that the mass of the envelope corresponds to that measured from the sub-mm fluxes (e.g., Shirley et al. 2000), the 850 and 450 μm fluxes were given high weight in the fit.

The best-fit parameters along with the model results are listed in Table C.1. An overview of the fitted data and results are shown in Figs. C.1 − C.3. Sources which have previously been analysed by Jørgensen et al. (2002) were re-analysed, and in general there is good agreement between the two sets of results. The uncertainty on p and τ100 is of the order of 0.2–0.3, while it is somewhat higher for Y, of the order of  ~500.

The envelope mass is measured either at the Tdust = 10 K radius or at the n = 104 cm-3 radius, depending on which is smaller. The envelope masses range from 0.04 M (Elias 29) to  ~16 M (Ser SMM1). These masses are in good agreement with masses derived from the sub-mm flux alone, e.g., through scaling of the 850 μm flux assuming a constant dust temperature (Shirley et al. 2000). The mass estimates presented here fall well within the range of masses derived for these sources using other methods (Bontemps et al. 1996; Hogerheijde et al. 1997, 1998; Chen et al. 2008; Enoch et al. 2009; Jørgensen et al. 2009).

In this context it is important to note, that the modelling of the inner envelope is not realistic. Specifically, embedded disks are not taken into account and the model is expected to fail on scales smaller than a few 100 AU. In the Class I phase, disks can contribute significantly to the sub-mm fluxes (e.g., Jørgensen et al. 2007; Lommen et al. 2008), and their contribution has not been subtracted here. Therefore, the inferred envelope masses are upper limits, particularly for the Class I sources. The effect of an embedded disk is to add a point-source contribution to the flux at the center of the system and thus artificially increase the power-law density slope of the envelope. If the point source is subtracted, the p-value would decrease as well as the overall envelope mass. Thus, the values of p and Menv presented here for Class I sources are overestimates.

Table C.1

Best-fit DUSTY parameters and predictions.

thumbnail Fig. C.1

SEDs for each source (diamonds). The full line shows the best-fit SED.

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thumbnail Fig. C.2

850 μm radial profile for each source (diamonds). The dashed line shows the beam profile, and the full line shows the best-fit radial profile.

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thumbnail Fig. C.3

450 μm radial profile for each source (diamonds). The dashed line shows the beam profile, and the full line shows the best-fit radial profile.

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© ESO, 2012

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