EDP Sciences
Open Access
Issue
A&A
Volume 582, October 2015
Article Number A118
Number of page(s) 24
Section Interstellar and circumstellar matter
DOI https://doi.org/10.1051/0004-6361/201424426
Published online 22 October 2015

Online material

Appendix A: OH absorption

Figure A.1 is a map that indicates the positions where the profiles in Fig. A.2 were produced using the 1667-MHz OH absorption data cube. Positions 14 are located in the OH-streamer head, 57 in the mid, and 810 in the tail part. Positions 1113 are in the +80  km s-1 cloud, and positions 1416 are in the northern part of the +20  km s-1 cloud. The OH parameters, obtained from a Gaussian analysis of these profiles, are presented in Table A.1.

Figure A.3 is a position-velocity diagram of the OH absorption at 1667 MHz of the inner region of the GC. It is a visualisation through the entire data cube seen face-on from the right ascension-velocity side. The angular resolution is , and the velocity resolution is 8.8  km s-1. The prominent features are labelled in the figure. We note the bridge between the EMR near side and the CND SW lobe.

thumbnail Fig. A.1

Locations of the OH absorption profiles, labelled by triangles. The magenta contours indicate the OH-streamer, the olive-coloured contours depict the +80 cloud, and the purple contours delineate parts of the +20  km s-1 cloud, at 50, 85, and 32  km s-1, respectively. The lowest contour level is at 3.5σ (90 mJy/beam), and the contour interval is 1σ spacing. Position numbers 110 belong to the OH-streamer, 1113 are in the +80  km s-1 cloud, and 1416 are inside the +20  km s-1 cloud.

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thumbnail Fig. A.2

1667-MHz OH absorption line profiles at the positions shown in Fig. A.1. The angular resolution is , and the velocity resolution is 8.8  km s-1.

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Table A.1

Parameters obtained from the Gaussian decomposition of the profiles at Positions 116 in Fig. A.1.

thumbnail Fig. A.3

Position-velocity diagram (RA, Vel) of OH absorption at 1667 MHz. This is a visualisation through the entire data cube as seen from the right ascension-velocity side. The 1665 MHz data overlap at velocities higher than about 160  km s-1, see Fig. 3 in Sandqvist (1973). The wedge scale indicates the OH absorption in Jy/beam. (“HNVG” stands for high negative velocity gas, “MB” the molecular belt.)

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Appendix B: 1667 MHz OH-absorption

thumbnail Fig. B.1

1667-MHz OH-absorption at 111 >VLSR> 67  km s-1. The lowest contour level is 50 mJy/beam (~2σ) and the contour spacing is also ~2σ. The wedge scale is in mJy/beam. The position of Sgr A* is marked with a plus sign.

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thumbnail Fig. B.2

1667-MHz OH-absorption at 59 >VLSR> 15  km s-1. The lowest contour level is 50 mJy/beam (~2σ), and the contour spacing is also ~2σ. The wedge scale is in mJy/beam. The position of Sgr A* is labelled with a plus sign.

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thumbnail Fig. B.3

1667-MHz OH-absorption at 6 >VLSR> −38.0  km s-1. The lowest contour level is 50 mJy/beam (~2σ), and the contour spacing is also ~2σ. The wedge scale is in mJy/beam. The position of Sgr A* is labelled with a plus sign.

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thumbnail Fig. B.4

1667-MHz OH-absorption at −47 >VLSR> −91  km s-1. The lowest contour level is 50 mJy/beam (~2σ), and the contour spacing is also ~2σ. The wedge scale is in mJy/beam. The position of Sgr A* is labelled with a plus sign.

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thumbnail Fig. B.5

1667-MHz OH-absorption at −99 >VLSR> −143  km s-1. The lowest contour level is 50 mJy/beam (~2σ), and the contour spacing is also ~2σ. The wedge scale is in mJy/beam. The position of Sgr A* is labelled with a plus sign.

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thumbnail Fig. B.6

1667-MHz OH-absorption at −152 >VLSR> −196  km s-1. The lowest contour level is 50 mJy/beam (~2σ), and the contour spacing is also ~2σ. The wedge scale is in mJy/beam. The position of Sgr A* is labelled with a plus sign.

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Appendix C: TL/TC at 1667 MHz

thumbnail Fig. C.1

TL/TC at 1667 MHz 111 >VLSR> 67  km s-1. The position of Sgr A* is shown with a plus sign.

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thumbnail Fig. C.2

TL/TC at 1667 MHz 59 >VLSR> 15  km s-1. The position of Sgr A* is shown with a plus sign, and the four compact H ii regions are marked by letters AD.

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thumbnail Fig. C.3

TL/TC at 1667 MHz 6 >VLSR> −38  km s-1. The position of Sgr A* is shown with a plus sign.

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thumbnail Fig. C.4

TL/TC at 1667 MHz −47 >VLSR> −91  km s-1. The position of Sgr A* is shown with a plus sign.

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thumbnail Fig. C.5

TL/TC at 1667 MHz −99 >VLSR> −143  km s-1. The position of Sgr A* is shown with a plus sign.

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thumbnail Fig. C.6

TL/TC at 1667 MHz −152 >VLSR> −196  km s-1. The position of Sgr A* is shown with a plus sign.

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Appendix D: 1665 MHz OH-absorption

thumbnail Fig. D.1

1665-MHz OH-absorption at 59 >VLSR> 15  km s-1. The lowest contour level is 50 mJy/beam (~2σ), and the contour spacing is also ~2σ. The wedge scale is in mJy/beam. The position of Sgr A* is labelled with a plus sign.

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Appendix E: TL/TC at 1665 MHz

thumbnail Fig. E.1

TL/TC at 1665 MHz at 59 >VLSR> 15  km s-1. The position of Sgr A* is labelled with a plus sign, and the four compact H ii regions are labelled by letters AD.

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Appendix F: HO in the OH-streamer/+80 km s-1 cloud/CND SW shock region

To further investigate the proposed shock region towards the SW part of the CND, we have used the Odin satellite to observe the water isotope, HO, which is tracer of shock (or strong UV) regions (Karlsson et al. 2013). The observations were performed towards the position (RA, Dec) of (J2000.0) during April 2013 and April 2014. The total ON-source integration time of the combined data was 62.5 h. An HO profile was also obtained towards the same position in February 2013, with a total ON-source integration time of 9.4 h. Odin’s HPBW at the H2O frequencies is 2.́1. The profiles are shown in Fig. F.1, together with C18O J = 1−0 and 21 profiles obtained with SEST. We refer to Karlsson et al. (2013) for a detailed description of Odin and SEST observations and analysis of the Sgr A complex region. Here we simply present our new results and their interpretation.

The HO profile shows a remarkably wide absorption component at positive velocities, in addition to the well-known EMR and 3-kpc Arm features near −130 and −50  km s-1, respectively. This positive-velocity region covers the velocity range of the interacting components discussed in the main part of the paper, viz. the OH-Streamer, the +80  km s-1 cloud and the +20  km s-1 cloud/SS. We obtain a total column density of the order of N(HO) ~2.2 × 1014 cm-2, which corresponds to N(HO) ~5.5 × 1016, assuming a HO/HO abundance ratio of 250 in the inner Galactic centre (Wilson & Rood 1994). From our two C18O lines we obtain, in the same region and velocity interval, a molecular hydrogen column density of N(H2) ≈ 4.0 × 1022 cm-2, assuming a C18O/H2 abundance ratio of 2 × 10-7 (Goldsmith 1999). These values result in an abundance ratio [o-H2O/H2] = X(o-H2O) ~1.4 × 10-6. Such a high abundance ratio of H2O is

comparable to what is found in, for example, the low-velocity outflow region of Orion (Persson et al. 2007), where it has been interpreted as desorption of water ice from dust grains due to shock effects.

thumbnail Fig. F.1

HO (black line), HO (lower magenta line), C18O J = 1−0 (middle magenta line), and C18O J = 2−1 (upper magenta line) profiles towards the SW position in the CND, coinciding with the position of interaction between the OH Streamer, the +80  km s-1 cloud and the SS/+20  km s-1 cloud. The HO antenna temperature scale has been multiplied by a factor of 10. The HO antenna temperature scale has been lowered by 0.7 K for clarity. The intensity scales of the two C18O profiles are in units of brightness temperature, the J = 2−1 profile having been raised by 0.1 K for clarity. The channel resolution is 3  km s-1 for all the profiles.

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© ESO, 2015

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