EDP Sciences
Free Access
Issue
A&A
Volume 553, May 2013
Article Number A119
Number of page(s) 15
Section Galactic structure, stellar clusters and populations
DOI https://doi.org/10.1051/0004-6361/201220822
Published online 20 May 2013

Online material

Appendix A: Velocity components of the observed filaments

thumbnail Fig. A.1

Total velocity dispersion versus observed central column density. Similar plot to Fig. 6 for the filaments observed in IC 5146, Aquila and Polaris. The six C18O spectra showing two or three velocity components are flagged in yellow.

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The N2H+(1−0) and C18O(1−0)/(2–1) spectra observed toward the sample of filaments studied in this work are shown in Appendix A. The 23 filaments detected in N2H+(1−0) in Aquila, IC 5146, and Polaris all show a single velocity component (cf. Figs. A.2, A.4, A.6 and A.9). This is consistent with the view that the filaments are velocity coherent structures

(e.g., Hacar & Tafalla 2011). While most of the filaments detected in C18O show one velocity component, some of them show multiple (two or three) C18O velocity components (such as filaments 20, 22, 23, 25, 26 in Aquila and filament 4 in Polaris – see Figs. A.7, A.8 and A.11). Some of these multiple C18O velocity components may be due to line-of-sight mixing of emissions not necessarily tracing the selected filament, but background and/or foreground structures (especially in the case of the Aquila Rift which is a region close to the Galactic plane).

Assuming that interstellar filaments are velocity-coherent structures, the most likely velocity component associated with each filament was considered (selecting the velocity component with the velocity closest to that of neighboring filaments). Its properties were then used in the discussion of the results presented in this paper (see detailed explanations in the captions of the figures presenting the observed spectra).

In order to investigate how the uncertainty in selecting the relevant velocity component affects our results, the 6 filaments with spectra showing more than one C18O velocity component were flagged in the sample. Figure A.1 shows the total velocity dispersion as a function of central column density for the resulting subsample of 38 filaments, where the velocity dispersions of the filaments inferred from the C18O spectra (which show multiple velocity components) corresponding to filaments 20, 22, 23, 25, 26 in Aquila and 4 in Polaris are flagged in yellow. Our general conclusions on filament properties, such as total velocity dispersion, central column density, and mass per unit length remain unchanged whether or not we take the 6 flagged filaments into account.

thumbnail Fig. A.2

N2H+(1−0) spectra observed toward filaments 6, 12, 13 in IC 5146. The filament numbers are indicated at the upper right of each panel. The corresponding one velocity hyperfine structure Gaussian fits are highlighted in blue.

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thumbnail Fig. A.3

C18O(2–1) spectra observed toward 6 filaments in IC 5146. The filament numbers are indicated at the upper right of each panel. The corresponding single-component Gaussian fits are highlighted in blue.

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thumbnail Fig. A.4

N2H+(1−0) spectra observed toward 9 filaments in Aquila. The numbers indicated on the upper right hand side of the plots, correspond to the filaments marked on the column density map of Fig. A.5 and listed in Table 1. The corresponding single-component hyperfine structure Gaussian fits are highlighted in blue. Note that the y-axis scale is not the same for all spectra, but has been adjusted to match the peak temperatures which vary between  ~ 0.2 to  > 3 K.

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thumbnail Fig. A.5

Curvelet component of the column density map of the Aquila field around the Serpens South filaments taken from André et al. (2010). The curvelet component is obtained using a morphological component analysis algorithm (MCA, from Starck et al. 2003) which enhances the contrast of the filamentary structure against the more diffuse background of the cloud. The positions of the observed spectra are plotted in red squares and blue triangles for N2H+ and C18O, respectively. The numbers correspond to the filaments listed in Table 1 and are given at the upper right of the spectra in Fig. A.4 and some of the spectra of Fig. A.7.

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thumbnail Fig. A.6

Continuation of Fig. A.4 presenting the N2H+(1−0) spectra observed toward 9 filaments in Aquila.

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thumbnail Fig. A.7

C18O(1−0) spectra observed toward 6 filaments in Aquila. The corresponding Gaussian fits are highlighted in blue. Note that the scale of the y-axis has been adjusted to match the peak temperature of each spectrum. Note 1: filament 20 shows two components separated by 0.63 km s-1. The component at VLSR = 7.17 km s-1 have been chosen to be tracing the filament, since this component has a velocity component which is closer to the average velocity ( km s-1) of the filaments in Aquila which show one velocity component. Note 2: the spectrum observed at the position of filament 22 shows two velocity components, one centered at 6.5 km s-1 and the other at 7.7 km s-1. The strongest component has been selected for similar reasons to that explained for filament 20. Note 3: the spectrum observed at the position of filament 25 has two velocity components (at 5.0 km s-1 and 6.52 km s-1, respectively). The strongest component has been selected for similar reasons to that explained for filament 20. Note 4: the spectrum observed at the position of filament 26 shows three velocity components centered at 7.28 km s-1, 8.45 km s-1 and 9.17 km s-1, respectively. The component centered at 7.28 km s-1 has been selected because it is the component with the closest VLSR value to the mean of neighboring filaments in Aquila.

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thumbnail Fig. A.8

C18O(1−0) spectra observed toward filaments 23 and 24 in Aquila, located in the south west part of the region. The positions of the two filaments are shown on a blow up of the column density map (cf., Könyves et al. 2010)on the right hand side. Filament 24 shows a single velocity C18O(1−0) spectrum at VLSR = 6.87 km s-1, while C18O(1−0) spectrum observed toward filament 23 shows three velocity components at VLSR = 5.77 km s-1, 9.13 km s-1 and 10.3 km s-1. The relevant velocity component associated to filament 23 is most probably the component at VLSR = 5.77 km s-1 (the closest to the LSR velocity of the neighboring filament 24), while the other components are likely associated to clouds/filaments observed on the same line-of-sight.

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thumbnail Fig. A.9

N2H+(1−0) spectrum observed toward filament 1 in Polaris. The corresponding hyperfine structure Gaussian fit is highlighted in blue.

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thumbnail Fig. A.10

Curvelet component of the column density map of a subregion in the Polaris Cloud taken from André et al. (2010). The positions of the observed spectra are plotted in red squares and blue triangles for N2H+ and C18O, respectively. The numbers correspond to the filaments listed in Table 1.

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thumbnail Fig. A.11

C18O(1−0) spectra observed toward 6 filaments in Polaris. The corresponding Gaussian fits are highlighted in blue. Note 1: the spectrum observed toward filament 4 shows two velocity components. Both velocity components have similar linewidths (0.19 km s-1 and 0.14 km s-1, respectively), they are separated by  ~0.8 km s-1. They most probably belong to two filaments which are seen on the same line-of-sight (but a large map would be needed to study the kinematics of the field). The component observed at  −4.5 km s-1 has been taken to be representative of filament 4.

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© ESO, 2013

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