EDP Sciences
Free Access
Issue
A&A
Volume 562, February 2014
Article Number A3
Number of page(s) 42
Section Interstellar and circumstellar matter
DOI https://doi.org/10.1051/0004-6361/201322596
Published online 29 January 2014

Online material

Appendix A: Kinematic distances and physical properties of the clumps

The kinematic distances of the clumps listed in Col. (4) of Table 1 are based on the Galactic rotation curve model by Reid et al. (2009). As the sources are associated with IRDCs, it is assumed that they lie at a near distance in which case there is more IR background radiation against which to see the source in absorption. The clump distances were adopted from Paper I with the following exception. In Paper I, for the first quadrant field G1.87 we had radial velocity data only towards a filamentary cloud near the field centre (see Figs. 1 and 5 in Paper I). As discussed in Paper I, the negative radial velocity of the cloud (~−41 km s-1) suggests that it lies at a far distance. The far distance solution (~10.6 kpc) was therefore adopted for all the clumps in the field. In the present paper, we used the MALT90 N2H+(1−0) radial velocity data to determine the G1.87 clump distances. As a high-density gas tracer, N2H+ is expected to be well-suited for this purpose. Moreover, N2H+(1−0) was detected towards all sources in the present study. The radial velocities of the clumps were typically found to be ~40−50 km s-1 (i.e. positive rather than negative), and the corresponding near kinematic distances were derived to be ~7 kpc as shown in Table 1. We note that the near-far kinematic distance ambiguity towards G13.22−SMM 29 (IRAS 18117-1738) was resolved by Sewilo et al. (2004). This source was placed at the far distance because H2CO absorption was seen between the source velocity and the velocity at the tangent point.

The clump effective radii listed in Table 1 correspond to the kinematic distances explained above. The rest of the physical properties of the clumps listed in Table 1 were revised from those presented in Paper I by making the following modifications. The masses and densities of the clumps were previously calculated by assuming that the dust-to-gas mass ratio is 1/100. However, this value refers to the canonical dust-to-hydrogen mass ratio, Mdust/MH (e.g. Draine 2011; Table 23.1 therein). Assuming that the clumps’ chemical composition is similar to the solar mixture, i.e. the mass fractions for hydrogen, helium, and heavier elements are X = 0.71, Y = 0.27, and Z = 0.02, respectively, the ratio of total mass (H+He+metals) to hydrogen mass is 1/X ≃ 1.41. The total dust-to-gas mass ratio is therefore Mdust/Mgas = Mdust/(1.41MH) = 1/141. For the assumed gas composition, the mean molecular weight per H2 molecule, needed in the calculation of the column and number densities, is μH2 ≃ 2.82 (Kauffmann et al. 2008; Appendix A.1 therein). As explained in Paper I, the dust temperature was assumed to be Tdust = 15 K for IR-dark clumps, and 20 K for clumps associated with Spitzer IR emission. For G2.11−SMM 5 and G13.22−SMM 29, which are associated with IRAS sources, the dust colour temperatures were derived to be 30 and 18.9 K, respectively (Paper I). For G13.22−SMM 32, which is associated with an H ii region, we adopted the value10Tdust = 30 K. Finally, the dust opacity per unit dust mass at 870 μm was taken to be κ870 = 1.38 cm2 g-1, the value interpolated from the widely used Ossenkopf & Henning (1994) model describing graphite-silicate dust grains that have coagulated and accreted thin ice mantles over a period of 105 yr at a gas density of 105 cm-3.

Appendix B: Maps of spectral-line emission

The integrated intensity maps of the detected spectral lines are presented in Figs. B.1B.14. In each panel, the line emission is shown as contours overlaid on the Spitzer 8 μm image.

thumbnail Fig. B.1

Contour maps of integrated intensity of the MALT90 lines detected towards G1.87−SMM 1. In each panel, the contours are overlaid on the arcsinh-scaled Spitzer 8 μm image (cf. Fig. 1). The contour levels start at 3σ for H13CO+, SiO, HN13C, C2H, CH3CN, and 13CS. For HNCO(40, 4 − 30, 3), HCN, HCO+, HNC, HC3N, and N2H+, the contours start at 26σ, 23σ, 20σ, 30σ, 6σ, and 15σ, respectively. In all cases, the contours go in steps of 3σ. The average 1σ value in TMB units is ~ 0.69 K km s-1. The red plus sign marks the LABOCA 870 μm peak position of the clump. A scale bar indicating the 1 pc projected length is indicated. The line emission is extended in many cases, and the HCN, HCO+, and HNC emissions are well correlated with each other. The N2H+ emission also shows some resemblance to these species. The spatial distributions of HNCO and HC3N appear to be similar to each other, while weak CH3CN emission traces reasonably well the 8 μm absorption feature.

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thumbnail Fig. B.2

Similar to Fig. B.1 but towards G1.87−SMM 8, 10, 15. The contour levels start at 3σ for SiO, HN13C, C2H, and HC3N. For HNCO(40, 4 − 30, 3), HCN, HCO+, HNC, and N2H+, the contours start at 9σ, 16σ, 15σ, 12σ, and 5σ, respectively. In all cases, the contours go in steps of 3σ. The average 1σ value in TMB units is ~ 0.70 K km s-1. The LABOCA 870 μm peak positions of the clumps are marked by red plus signs. A scale bar indicating the 1 pc projected length is indicated. The spatial distributions of the HCN, HCO+, and HNC emissions appear to be quite similar. Those of HNCO and N2H+ show some similarities also.

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thumbnail Fig. B.3

Similar to Fig. B.1 but towards G1.87−SMM 12, 14, 16. The contour levels start at 3σ for H13CO+, HN13C, C2H, HC3N, and CH3CN. For SiO, HNCO(40, 4 − 30, 3), HCN, HCO+, HNC, and N2H+, the contours start at 5σ, 15σ, 19σ, 10σ, 15σ, and 6σ, respectively. In all cases, the contours go in steps of 3σ. The average 1σ value in TMB units is ~ 0.63 K km s-1. The LABOCA 870 μm peak positions of the clumps are marked by red plus signs. A scale bar indicating the 1 pc projected length is indicated. The emissions of HNCO, HCN, HCO+, HNC, HC3N, and N2H+ are extended in a similar fashion, but the HNCO emission is clearly the strongest.

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thumbnail Fig. B.4

Similar to Fig. B.1 but towards G1.87−SMM 14, 16, 17, 21, 24. The contour levels start at 3σ for SiO, HN13C, C2H, and HC3N. For HNCO(40, 4 − 30, 3), HCN, HCO+, HNC, and N2H+, the contours start at 8σ, 8σ, 5σ, 5σ, and 5σ, respectively. In all cases, the contours go in steps of 3σ. The average 1σ value in TMB units is ~ 0.78 K km s-1. The LABOCA 870 μm peak positions of the clumps are marked by red plus signs. The 870 μm peak of SMM 17 (west of SMM 21) lies just outside the MALT90 map (cf. Fig. 1, middle left panel). A scale bar indicating the 1 pc projected length is indicated. The HCN and HNC emissions show some morphological similarities.

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thumbnail Fig. B.5

Similar to Fig. B.1 but towards G1.87−SMM 20, 23, 30. The contour levels start at 3σ for HN13C, C2H, and CH3CN, and 5σ for SiO, HNCO(40, 4 − 30, 3), HCN, HCO+, HNC, HC3N, and N2H+. In all cases, the contours go in steps of 3σ. The average 1σ value in TMB units is ~ 0.63 K km s-1. The LABOCA 870 μm peak positions of the clumps are marked by red plus signs. A scale bar indicating the 1 pc projected length is indicated. Good correlations are seen between the peak emissions of SiO, HNCO, HC3N, CH3CN, and N2H+. The HNC emission also shows its maxima in-between the submm peaks.

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thumbnail Fig. B.6

Similar to Fig. B.1 but towards G1.87−SMM 27, 28, 31. The contour levels start at 3σ for SiO, HN13C, C2H, CH3CN, and 13CS. For, HNCO(40, 4 − 30, 3), HNC, HCN, HCO+, HC3N, and N2H+, the contours start at 9σ, 7σ, 7σ, 4σ, 4σ, and 5σ, respectively. In all cases, the contours go in steps of 3σ. The average 1σ value in TMB units is ~ 0.63 K km s-1. The LABOCA 870 μm peak positions are marked by red plus signs. A scale bar indicating the 1 pc projected length is indicated. The SiO and HC3N emission morphologies resemble each other. HNC and N2H+ also share some common features (e.g. peak close to SMM 28).

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thumbnail Fig. B.7

Similar to Fig. B.1 but towards G1.87−SMM 38. The contour levels start at 3σ for H13CO+, SiO, HN13C, C2H, HNCO(40, 4 − 30, 3), HC3N, and N2H+. For HNC, the contours start at 5σ. In all cases, the contours go in steps of 3σ. The average 1σ value in TMB units is ~ 0.77 K km s-1. The clump’s LABOCA 870 μm peak position is marked by a red plus sign. A scale bar indicating the 1 pc projected length is indicated. We note that the SiO, HNC, HC3N, and N2H+ emissions peak towards the submm maximum. HNC and N2H+ show otherwise comparable spatial distributions.

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thumbnail Fig. B.8

Similar to Fig. B.1 but towards G2.11−SMM 5. In each panel, the contour levels start at 3σ, and go in steps of 3σ. The average 1σ value in TMB units is ~ 0.68 K km s-1. The clump’s LABOCA 870 μm peak position is marked by a red plus sign. A scale bar indicating the 1 pc projected length is indicated. The HCN, HCO+, HNC, and N2H+ show similar clump-like morphologies. The first two species also show an extension to the west of the emission peak.

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thumbnail Fig. B.9

Similar to Fig. B.1 but towards the filamentary IRDC G11.36. The contour levels start at 3σ in all cases except for N2H+, where they start at 5σ. In all cases, the contours go in steps of 3σ. The average 1σ value in TMB units is ~ 0.74 K km s-1. The LABOCA 870 μm peak positions of the clumps are marked by red plus signs. A scale bar indicating the 1 pc projected length is indicated. The HCN and HCO+ appear to concentrate towards SMM 5, while HNC, and particularly N2H+, trace the filamentary 8 μm absorption feature.

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thumbnail Fig. B.10

Similar to Fig. B.1 but towards G13.22−SMM 4, 5 around the N10/11 IR-bubble pair. The contour levels start at 3σ for H13CO+, SiO, HN13C, C2H, and HC3N, while for HCN, HCO+, HNC, and N2H+ they start at 5σ. In all cases, the contours go in steps of 3σ. The average 1σ value in TMB units is ~ 0.79 K km s-1. The LABOCA 870 μm peak positions of the clumps are marked by red plus signs. A scale bar indicating the 1 pc projected length is indicated. We note the extended morphological similarities between HCN, HCO+, HNC, and N2H+. C2H shows a ridge-like emission along the northwest-southeast direction. The emission of all the species peaks towards SMM 5.

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thumbnail Fig. B.11

Similar to Fig. B.1 but towards G13.22−SMM 6, 7, 10, 11 around the N10/11 bubble. The contour levels start at 3σ for H13CO+, HN13C, and C2H, while for HCN, HCO+, HNC, and N2H+ they start at 6σ, 6σ, 5σ, and 6σ, respectively. In all cases, the contours go in steps of 3σ. The average 1σ value in TMB units is ~ 0.70 K km s-1. The LABOCA 870 μm peak positions of the clumps are marked by red plus signs. The 870 μm peak of SMM 10 lies just outside the MALT90 map boundary. A scale bar indicating the 1 pc projected length is indicated. Emission from C2H, HCN, HCO+, HNC, and N2H+ are similarly spatially extended, peaking towards SMM 7.

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thumbnail Fig. B.12

Similar to Fig. B.1 but towards G13.22−SMM 23, 27. The contour levels start at 3σ for H13CO+, SiO, HN13C, C2H, HNCO(40, 4 − 30, 3), HCN, and HC3N, while for HCO+, HNC, and N2H+ they start at 5σ, 4σ, and 5σ, respectively. In all cases, the contours go in steps of 3σ. The average 1σ value in TMB units is ~ 0.69 K km s-1. The LABOCA 870 μm peak positions of the clumps are marked by red plus signs. A scale bar indicating the 1 pc projected length is indicated. HCN, HCO+, HNC, and N2H+ show similar spatial distributions and their emission peaks are well correlated. Although weaker, H13CO+ and HC3N also peak near SMM 27.

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thumbnail Fig. B.13

Similar to Fig. B.1 but towards G13.22−SMM 29. The contour levels start at 3σ for H13CO+, SiO, and C2H, at 4σ for HCN and HNC, and at 5σ for HCO+ and N2H+. In all cases, the contours go in steps of 3σ. The average 1σ value in TMB units is ~ 0.66 K km s-1. The LABOCA 870 μm peak position of the clump is marked by a red plus signs. A scale bar indicating the 1 pc projected length is indicated. The HCO+ and HNC emissions show similar distributions, with HCN sharing some spatial features. The strong N2H+ emission peaks towards the HNC maximum.

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thumbnail Fig. B.14

Similar to Fig. B.1 but towards G13.22−SMM 32. The contour levels start at 3σ for H13CO+, SiO, C2H, HNCO(40, 4 − 30, 3), HCN, HC3N, and CH3CN, while for HCO+, HNC, and N2H+ they start at 4σ, 5σ, and 4σ, respectively. In all cases, the contours go in steps of 3σ. The average 1σ value in TMB units is ~ 0.57 K km s-1. The LABOCA 870 μm peak position of the clump is marked by a red plus sign. A scale bar indicating the 1 pc projected length is indicated. The spatial distributions of HCN, HCO+, HNC, and N2H+ are quite similar, but the different peak positions of HCO+ and N2H+ should be noted (as expected from their chemistry). C2H and HC3N also show weaker emission towards SMM 32, with some morphological similarities to the strongly emitting species.

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Appendix C: Spectra

The Hanning-smoothed spectra of the detected spectral lines are presented in Figs. C.1C.33. In each panel, the fit to the line is superimposed as a green line.

thumbnail Fig. C.1

Hanning-smoothed spectra towards G1.87−SMM 1. The single-Gaussian and hf structure fits are shown with green lines. The vertical red line plotted on double-peaked profiles indicates the radial velocity of the optically thin HC3N line. The velocity range is wider in the C2H and HCO+ (line emission peak) spectra than in the other panels to show all the detected lines (the additional velocity component is included for the latter).

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thumbnail Fig. C.2

Same as Fig. C.1 but towards G1.87−SMM 8.

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thumbnail Fig. C.3

Same as Fig. C.1 but towards G1.87−SMM 10.

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thumbnail Fig. C.4

Same as Fig. C.1 but towards G1.87−SMM 12. We note that the velocity range for the SiO and C2H spectra is wider for illustrative purposes. The vertical red line marks the radial velocity of the optically thin HC3N line.

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thumbnail Fig. C.5

Same as Fig. C.1 but towards G1.87−SMM 14. We note that the velocity range for the SiO and C2H spectra is wider for illustrative purposes. The vertical red line marks the radial velocity of the optically thin HC3N line.

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thumbnail Fig. C.6

Same as Fig. C.1 but towards G1.87−SMM 15. The vertical red line indicates the radial velocity of the optically thin HNCO line.

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thumbnail Fig. C.7

Same as Fig. C.1 but towards G1.87−SMM 16. In some of the spectra, the velocity range shown is wider for illustrative purposes. The vertical red line mark the velocity of the HNCO line.

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thumbnail Fig. C.8

Same as Fig. C.1 but towards G1.87−SMM 20.

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thumbnail Fig. C.9

Same as Fig. C.1 but towards G1.87−SMM 21. The vertical red line indicates the radial velocity of the HNCO line.

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thumbnail Fig. C.10

Same as Fig. C.1 but towards G1.87−SMM 23. We note that the velocity range for the HCN and HCO+ spectra is wider for illustrative purposes. The vertical red line indicates the radial velocity of the optically thin HC3N line.

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thumbnail Fig. C.11

Same as Fig. C.1 but towards G1.87−SMM 24. The vertical red line indicates the radial velocity of the HNCO line.

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thumbnail Fig. C.12

Same as Fig. C.1 but towards G1.87−SMM 27. The velocity range shown is wider for the C2H and HCO+ spectra. The vertical red line indicates the radial velocity of the optically thin HNCO line.

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thumbnail Fig. C.13

Same as Fig. C.1 but towards G1.87−SMM 28. The velocity range shown is wider for the C2H spectrum. The vertical red line indicates the radial velocity of the optically thin HNCO line.

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thumbnail Fig. C.14

Same as Fig. C.1 but towards G1.87−SMM 30. The vertical red line indicates the radial velocity of the optically thin HC3N line.

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thumbnail Fig. C.15

Same as Fig. C.1 but towards G1.87−SMM 31. The velocity range is wider for the HCN spectrum. The vertical red line indicates the radial velocity of the optically thin HNCO line.

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thumbnail Fig. C.16

Same as Fig. C.1 but towards G1.87−SMM 38.

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thumbnail Fig. C.17

Same as Fig. C.1 but towards G2.11−SMM 5. A wider velocity range for the HCO+ spectrum is shown because of the additional velocity component.

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thumbnail Fig. C.18

Same as Fig. C.1 but towards G11.36−SMM 1.

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thumbnail Fig. C.19

Same as Fig. C.1 but towards G11.36−SMM 2.

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thumbnail Fig. C.20

Same as Fig. C.1 but towards G11.36−SMM 3.

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thumbnail Fig. C.21

Same as Fig. C.1 but towards G11.36−SMM 4.

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thumbnail Fig. C.22

Same as Fig. C.1 but towards G11.36−SMM 5.

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thumbnail Fig. C.23

Same as Fig. C.1 but towards G11.36−SMM 6.

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thumbnail Fig. C.24

Same as Fig. C.1 but towards G11.36−SMM 7.

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thumbnail Fig. C.25

Same as Fig. C.1 but towards G13.22−SMM 4. There is an additional velocity component in the HCO+ spectrum.

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thumbnail Fig. C.26

Same as Fig. C.1 but towards G13.22−SMM 5. The velocity range is wider for the two C2H spectra.

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thumbnail Fig. C.27

Same as Fig. C.1 but towards G13.22−SMM 6.

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thumbnail Fig. C.28

Same as Fig. C.1 but towards G13.22−SMM 7. The C2H spectrum has a wider velocity range. Two velocity components are seen in the HCO+ and HNC spectra.

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thumbnail Fig. C.29

Same as Fig. C.1 but towards G13.22−SMM 11. Two velocity components are seen in the HCO+ and HNC spectra.

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thumbnail Fig. C.30

Same as Fig. C.1 but towards G13.22−SMM 23. Three velocity components are seen in the HCO+ spectrum, while two are visible in the HNC spectrum.

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thumbnail Fig. C.31

Same as Fig. C.1 but towards G13.22−SMM 27. The velocity range in the C2H spectrum is wider.

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thumbnail Fig. C.32

Same as Fig. C.1 but towards G13.22−SMM 29. The velocity range in the C2H spectrum is wider. Four velocity components are seen in the HCO+ spectrum, three in the HNC spectrum towards the LABOCA peak, and two in the HNC spectrum towards the line emission peak.

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thumbnail Fig. C.33

Same as Fig. C.1 but towards G13.22−SMM 32. The velocity range for the C2H spectra is wider. Two velocity components are detected in the HCO+ and HNC spectra towards the line emission peaks.

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© ESO, 2014

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