2004ApJ...613.1023L

Query : 2004ApJ...613.1023L

2004ApJ...613.1023L - Astrophys. J., 613, 1023-1036 (2004/October-1)

On the enhanced interstellar scattering toward B1849+005.

LAZIO T.J.W.

Abstract (from CDS):

This paper reports new Very Large Array (VLA) and Very Long Baseline Array (VLBA) observations of the extragalactic source B1849+005 (Galactic coordinates ℓ=33°.44, b=+0°.21) at frequencies between 0.33 and 15 GHz and the reanalysis of archival VLA observations at 0.33, 1.5, and 4.9 GHz. The structure of this source is complex, confirming previous suggestions, but interstellar scattering dominates the structure of the central component at least to 15 GHz. An analysis of the phase structure functions of the interferometric visibilities shows the density fluctuations along this line of sight to be anisotropic (axial ratio = 1.3) with a frequency-independent position angle and having an inner scale of roughly a few hundred kilometers. The anisotropies occur on length scales of order 1015 cm (D/5 kpc), which within the context of certain magnetohydrodynamic turbulence theories indicates the length scale on which the kinetic and magnetic energy densities are comparable. A conservative upper limit on the velocity of the scattering material is 1800 km/s, based on the lack of changes in the shapes of the 0.33 GHz images. In the 0.33 GHz field of view, there are a number of other sources that might also be heavily scattered, which would suggest that there are large changes in the scattering strength on lines of sight separated by a degree or less. Both B1849+005 and PSR B1849+00 are highly scattered, and they are separated by only 13'. If the lines of sight are affected by the same ``clump'' of scattering material, it must be at least 2.3 kpc distant. However, a detailed attempt to account for the scattering observables toward these sources (angular broadening of the extragalactic source, pulse broadening of the pulsar, and upper limits on the angular broadening of the pulsar) does not produce a self-consistent set of parameters for a clump that can reproduce all three measured scattering observables. A clump of Hα emission, possibly associated with the H II region G33.418-0.004, lies between these two lines of sight, but it seems unable to account for all of the required excess scattering.

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Journal keyword(s): Galaxies: Individual: Alphanumeric: B1849+005 - ISM: Structure - Stars: Pulsars: Individual: Alphanumeric: B1849+00 - Radio Continuum: General - Scattering

Nomenclature: Table 5: [L2004b] JHHMMSS.sss+DDMMSS.ss N=47.

Simbad objects: 68

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Number of rows : 68
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 3C 48 QSO 01 37 41.2996631208 +33 09 35.080388820   16.62 16.20     ~ 2924 2
2 3C 286 Sy1 13 31 08.2883506368 +30 30 32.960091564   17.51 17.25     ~ 4558 2
3 NGC 6334B rG 17 20 21.810 -35 52 48.25           ~ 113 0
4 NAME Galactic Center reg 17 45 39.60213 -29 00 22.0000           ~ 16269 0
5 NAME Sgr A* X 17 45 40.03599 -29 00 28.1699           ~ 4970 3
6 QSO J1824+1044 Bla 18 24 02.85524975 +10 44 23.7739493   17.66 17.27 16.71   ~ 182 1
7 [L2004b] J183510.617+014552.86 Rad 18 35 10.617 +01 45 52.86           ~ 1 0
8 [L2004b] J183718.258-015026.68 Rad 18 37 18.258 -01 50 26.68           ~ 1 0
9 [L2004b] J184144.789-015252.35 Rad 18 41 44.789 -01 52 52.35           ~ 1 0
10 [L2004b] J184358.583+015327.68 Rad 18 43 58.583 +01 53 27.68           ~ 1 0
11 [L2004b] J184407.675+003317.10 Rad 18 44 07.675 +00 33 17.10           ~ 1 0
12 [L2004b] J184450.864+013715.89 Rad 18 44 50.864 +01 37 15.89           ~ 1 0
13 [L2004b] J184517.789+000742.94 Rad 18 45 17.789 +00 07 42.94           ~ 1 0
14 [L2004b] J184603.708+000339.24 Rad 18 46 03.708 +00 03 39.24           ~ 1 0
15 [L2004b] J184605.681+002538.53 Rad 18 46 05.681 +00 25 38.53           ~ 1 0
16 [L2004b] J184614.538-011940.83 Rad 18 46 14.538 -01 19 40.83           ~ 1 0
17 [L2004b] J184623.171+001828.74 Rad 18 46 23.171 +00 18 28.74           ~ 1 0
18 [L2004b] J184631.286+000908.35 Rad 18 46 31.286 +00 09 08.35           ~ 1 0
19 [L2004b] J184639.510+001623.36 Rad 18 46 39.510 +00 16 23.36           ~ 1 0
20 [L2004b] J184641.266+005514.98 Rad 18 46 41.266 +00 55 14.98           ~ 1 0
21 [L2004b] J184653.543+004102.80 Rad 18 46 53.543 +00 41 02.80           ~ 1 0
22 [L2004b] J184709.999+014155.15 Rad 18 47 09.999 +01 41 55.15           ~ 1 0
23 [L2004b] J184743.843+015433.63 Rad 18 47 43.843 +01 54 33.63           ~ 1 0
24 [L2004b] J184755.076+012219.10 Rad 18 47 55.076 +01 22 19.10           ~ 1 0
25 [L2004b] J184823.488-012358.55 Rad 18 48 23.488 -01 23 58.55           ~ 1 0
26 PSR B1845-01 Psr 18 48 23.59600 -01 23 58.4800           ~ 154 0
27 [L2004b] J184825.281+004636.09 Rad 18 48 25.281 +00 46 36.09           ~ 1 0
28 [L2004b] J184834.187+003618.25 Rad 18 48 34.187 +00 36 18.25           ~ 1 0
29 [L2004b] J184845.681+015255.68 Rad 18 48 45.681 +01 52 55.68           ~ 1 0
30 [L2004b] J184912.392+021132.05 Rad 18 49 12.392 +02 11 32.05           ~ 1 0
31 SNR G031.9+00.0 SNR 18 49 16.3 -00 55 01           ~ 368 2
32 [L2004b] J184933.461+015429.11 Rad 18 49 33.461 +01 54 29.11           ~ 1 0
33 [L2004b] J185010.398+002004.02 Rad 18 50 10.398 +00 20 04.02           ~ 1 0
34 [L2004b] J185020.140+004913.91 Rad 18 50 20.140 +00 49 13.91           ~ 1 0
35 [L2004b] J185040.088+035733.61 Rad 18 50 40.088 +03 57 33.61           ~ 1 0
36 [L2004b] J185112.962+002737.89 Rad 18 51 12.962 +00 27 37.89           ~ 1 0
37 GAL 033.50+00.20 HII 18 51 46.71 +00 35 32.3           ~ 24 0
38 QSO J1851+005 QSO 18 51 46.72295 +00 35 32.3649           ~ 138 1
39 [L2004b] J185152.819+004001.42 Rad 18 51 52.819 +00 40 01.42           ~ 1 0
40 [L2004b] J185212.978+022252.19 Rad 18 52 12.978 +02 22 52.19           ~ 1 0
41 [KB94] 21 HII 18 52 20.3 +00 25 50           ~ 6 0
42 [L2004b] J185227.364+003200.70 Rad 18 52 27.364 +00 32 00.70           ~ 1 0
43 PSR B1849+00 Psr 18 52 27.42 +00 32 02.0           ~ 76 0
44 SNR G033.6+00.1 SNR 18 52 29.000 +00 38 42.00           ~ 302 2
45 RAFGL 2271 SFR 18 53 18.54 +01 14 57.9           ~ 537 0
46 [L2004b] J185323.434+002137.42 Rad 18 53 23.434 +00 21 37.42           ~ 1 0
47 [L2004b] J185336.039+002714.06 Rad 18 53 36.039 +00 27 14.06           ~ 1 0
48 [L2004b] J185337.212+025456.68 Rad 18 53 37.212 +02 24 56.68           ~ 1 0
49 [L2004b] J185343.689+001956.05 Rad 18 53 43.689 +00 19 56.05           ~ 1 0
50 [L2004b] J185434.997+022751.16 Rad 18 54 34.997 +02 27 51.16           ~ 1 0
51 [L2004b] J185459.951+021539.94 Rad 18 54 59.951 +02 15 39.94           ~ 1 0
52 [L2004b] J185609.016+000204.43 Rad 18 56 09.016 +00 02 04.43           ~ 1 0
53 SNR G034.6-00.5 SNR 18 56 10.650 +01 13 21.30           ~ 1034 2
54 [L2004b] J185627.229+013557.48 Rad 18 56 27.229 +01 35 57.48           ~ 1 0
55 [L2004b] J185631.711+001727.47 Rad 18 56 31.711 +00 17 27.47           ~ 1 0
56 [L2004b] J185643.059+003250.93 Rad 18 56 43.059 +00 32 50.93           ~ 1 0
57 PSR B1854+00 Psr 18 57 00.80 +00 57 16.8           ~ 33 0
58 [L2004b] J185716.674+001121.39 Rad 18 57 16.674 +00 11 21.39           ~ 1 0
59 [L2004b] J185721.043+004528.03 Rad 18 57 21.043 +00 45 28.03           ~ 1 0
60 PSR B1855+02 Psr 18 57 43.65400 +02 12 41.0000           ~ 65 0
61 [L2004b] J185749.365+005117.91 Rad 18 57 49.365 +00 51 17.91           ~ 1 0
62 [L2004b] J185807.936+012549.86 Rad 18 58 07.936 +01 25 49.86           ~ 1 0
63 [L2004b] J185844.966+005559.52 Rad 18 58 44.966 +00 55 59.52           ~ 1 0
64 [L2004b] J185908.028+004148.99 Rad 18 59 08.028 +00 41 48.99           ~ 1 0
65 3C 394 Rad 18 59 23.363 +12 59 12.10           ~ 63 1
66 PKS J1941-1524 Sy1 19 41 14.9996710393 -15 24 31.311811663           ~ 83 1
67 NAME Cyg Complex reg 20 32 +45.0           ~ 667 0
68 V* V1521 Cyg HXB 20 32 25.78 +40 57 27.9           WN4/5-6/7 2035 2

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