2018MNRAS.479.1465D

Query : 2018MNRAS.479.1465D

2018MNRAS.479.1465D - Mon. Not. R. Astron. Soc., 479, 1465-1490 (2018/September-2)

Calibrating the HISA temperature: Measuring the temperature of the Riegel-Crutcher cloud.

DENES H., McCLURE-GRIFFITHS N.M., DICKEY J.M., DAWSON J.R. and MURRAY C.E.

Abstract (from CDS):

H I self-absorption (HISA) clouds are clumps of cold neutral hydrogen (H I) visible in front of warm background gas, which makes them ideal places to study the properties of the cold atomic component of the interstellar medium. The Riegel-Crutcher (R-C) cloud is the most striking HISA feature in the Galaxy. It is one of the closest HISA clouds to us and is located in the direction of the Galactic Centre, which provides a bright background. High-resolution interferometric measurements have revealed the filamentary structure of this cloud; however, it is difficult to accurately determine the temperature and the density of the gas without optical depth measurements. In this paper, we present new H I absorption observations with the Australia Telescope Compact Array against 46 continuum sources behind the R-C cloud to directly measure the optical depth of the cloud. We decompose the complex H I absorption spectra into Gaussian components using an automated machine learning algorithm. We find 300 Gaussian components, from which 67 are associated with the R-C cloud (0 < vLSR < 10 km s–1, full width at half maximum < 10 km s–1). Combining the new H I absorption data with H I emission data from previous surveys, we calculate the spin temperature and find it to be between 20 and 80 K. Our measurements uncover a temperature gradient across the cloud with spin temperatures decreasing towards positive Galactic latitudes. We also find three new OH absorption lines associated with the cloud, which support the presence of molecular gas.

Abstract Copyright: © 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society

Journal keyword(s): Galaxy: evolution - (Galaxy): local interstellar matter - radio lines: ISM

Simbad objects: 51

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Number of rows : 51
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2026 		#notes
1 NAME Perseus Cloud SFR 03 35.0 +31 13           ~ 1553 0
2 PMN J1728-2845 Rad 17 28 28.974 -28 46 10.91           ~ 5 1
3 PMN J1728-2712 Rad 17 28 35.904 -27 12 35.53           ~ 4 1
4 PMN J1729-2657 Rad 17 29 08.216327 -26 57 50.74426           ~ 15 1
5 PMN J1729-2345 Rad 17 29 20.49 -23 45 35.0           ~ 4 1
6 PMN J1731-2457 Rad 17 31 07.200 -24 57 02.39           ~ 4 1
7 PMN J1731-2640 Rad 17 31 32.943 -26 40 14.15           ~ 4 1
8 PMN J1732-2855 Rad 17 32 03.884 -28 55 20.08           ~ 4 1
9 PMN J1732-2426 Rad 17 32 05.752 -24 26 52.04           ~ 5 1
10 PMN J1732-2235 Rad 17 32 52.863 -22 35 11.07           ~ 3 1
11 PMN J1735-2510 Rad 17 35 24.934 -25 10 35.87           ~ 4 1
12 NVSS J173620-283552 Rad 17 36 21.0 -28 35 52           ~ 2 1
13 NVSS J173713-224734 Rad 17 37 13.467 -22 47 31.37           ~ 3 1
14 PMN J1737-2604 Rad 17 37 18.410 -26 04 26.92           ~ 4 1
15 PMN J1737-2229 Rad 17 37 22.655 -22 30 00.48           ~ 5 1
16 PMN J1737-2547 Rad 17 37 53.21 -25 46 42.2           ~ 4 1
17 PMN J1738-2624 Rad 17 38 06.00 -26 24 44.7           ~ 4 1
18 PMN J1738-2044 Rad 17 38 11.6586825216 -20 44 10.308503364           ~ 3 1
19 PMN J1738-2219 Rad 17 38 50.714 -22 19 16.61           ~ 4 1
20 PMN J1739-2054 Rad 17 39 38.958 -20 55 04.92           ~ 3 1
21 PMN J1740-2841 Rad 17 40 07.8 -28 42 03           ~ 3 1
22 PMN J1742-2713 Rad 17 42 01.914 -27 13 17.50           ~ 5 1
23 PMN J1742-2037 Rad 17 42 24.710 -20 37 27.87           ~ 5 1
24 NVSS J174317-305819 Rad 17 43 17.8 -30 58 17           ~ 8 1
25 PMN J1743-1828 Rad 17 43 43.197 -18 28 38.83           ~ 4 1
26 NVSS J174351-261059 Rad 17 43 51.196 -26 10 58.57           ~ 3 1
27 QSO J1744-3116 Bla 17 44 23.57824 -31 16 36.2943           ~ 168 1
28 NVSS J174513-315104 Rad 17 45 13.22 -31 51 04.8           ~ 1 0
29 NAME Galactic Center reg 17 45 39.60213 -29 00 22.0000           ~ 16269 0
30 PMN J1746-1930 Rad 17 46 18.11 -19 30 07.3           ~ 4 1
31 PMN J1746-1826 Rad 17 46 37.746 -18 26 28.74           ~ 3 1
32 NVSS J174709-295802 Rad 17 47 09.38 -29 58 02.7           ~ 1 0
33 NVSS J174713-192135 Rad 17 47 13.80 -19 21 35.8           ~ 4 0
34 NVSS J174716-191954 Rad 17 47 16.09 -19 19 54.9           ~ 2 0
35 NVSS J174748-312315 Rad 17 47 48.228 -31 23 18.25           ~ 6 1
36 PMN J1748-3243 Rad 17 48 31.552 -32 41 01.86           ~ 4 1
37 PMN J1748-2252 Rad 17 48 32.599 -22 52 11.79           ~ 4 1
38 PMN J1749-2000 Rad 17 49 15.02 -20 00 33.7           ~ 4 1
39 PMN J1749-2109 Rad 17 49 31.786 -21 08 47.46           ~ 6 1
40 PMN J1751-2353 Rad 17 51 04.04 -23 52 15.2           ~ 3 0
41 NVSS J175114-323538 Rad 17 51 14.308 -32 35 42.25           ~ 5 1
42 PMN J1751-2524 Rad 17 51 51.26253123 -25 24 00.0635706           ~ 91 1
43 PMN J1752-2405 Rad 17 51 57.004 -24 04 24.57           ~ 4 1
44 PMN J1752-2104 Rad 17 52 18.46 -21 05 08.6           ~ 4 1
45 PMN J1752-2230 Rad 17 52 33.230 -22 30 12.32           ~ 8 1
46 NVSS J175427-235235 Rad 17 54 27.387 -23 52 34.51           ~ 5 1
47 PMN J1755-2232 Rad 17 55 26.284538 -22 32 10.61562           ~ 38 1
48 NVSS J175548-233322 Rad 17 55 48.625 -23 33 20.93           ~ 5 1
49 PMN J1757-2239 Rad 17 57 27.795 -22 38 59.82           ~ 7 1
50 ICRF J193925.0-634245 Sy2 19 39 25.0245304992 -63 42 45.640373400   18.87 18.37 17.64   ~ 1332 2
51 NAME Local Bubble ISM ~ ~           ~ 1059 0

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