2012MNRAS.427..664S


Query : 2012MNRAS.427..664S

2012MNRAS.427..664S - Mon. Not. R. Astron. Soc., 427, 664-678 (2012/November-3)

Modelling the Galactic distribution of free electrons.

SCHNITZELER D.H.F.M.

Abstract (from CDS):

An accurate picture of how free electrons are distributed throughout the Milky Way leads to more reliable distances for pulsars and more accurate maps of the magnetic field distribution in the Milky Way. In this paper we test eight models of the free electron distribution in the Milky Way that have been published previously, and we introduce four additional models that explore the parameter space of possible models further. These new models consist of a simple exponential thick-disc model, and updated versions of the models by Taylor & Cordes and Cordes & Lazio with more extended thick discs. The final model we introduce uses the observed Hα intensity as a proxy for the total electron column density, also known as the dispersion measure (DM). Since accurate maps of Hα intensity are now available, this final model can in theory outperform the other models. We use the latest available data sets of pulsars with accurate distances (through parallax measurements or association with globular clusters) to optimize the parameters in these models. In the process of fitting a new scale height for the thick disc in the model by Cordes & Lazio, we discuss why this thick disc cannot be replaced by the thick disc that Gaensler et al. advocated in a recent paper. In the second part of our paper we test how well the different models can predict the DMs of these pulsars at known distances. We base our test on the ratios between the modelled and observed DMs, rather than on absolute deviations, and we identify systematic deviations between the modelled and observed DMs for the different models. For almost all models the ratio between the predicted and the observed DM cannot be described very well by a Gaussian distribution. We therefore calculate the deviations N between the modelled and observed DMs instead, and compare the cumulative distributions of N for the different models. Almost all models perform well, in that they predict DMs within a factor of 1.5–2 of the observed DMs for about 75 per cent of the lines of sight. This is somewhat surprising since the models we tested range from very simple models that only contain a single exponential thick disc to very complex models like the model by Cordes & Lazio. We show that the model by Taylor & Cordes that we updated with a more extended thick disc consistently performs better than the other models we tested. Finally, we analyse which sightlines have DMs that prove difficult to predict by most models, which indicates the presence of local features in the interstellar medium between us and the pulsar.

Abstract Copyright: © 2012 CSIRO Monthly Notices of the Royal Astronomical Society © 2012 RAS

Journal keyword(s): pulsars: general - ISM: structure - Galaxy: general - Galaxy: structure

Simbad objects: 74

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Number of rows : 74
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
#notes
1 NGC 104 GlC 00 24 05.359 -72 04 53.20   5.78 4.09     ~ 3748 0
2 PSR B0031-07 Psr 00 34 08.9100 -07 21 56.000           ~ 302 0
3 PSR B0136+57 Psr 01 39 19.744 +58 14 31.73     13.41     ~ 145 0
4 NAME Magellanic Clouds GrG 03 00 -71.0           ~ 6412 1
5 PSR B0329+54 Psr 03 32 59.3370698592 +54 34 45.028206408           ~ 609 1
6 PSR B0355+54 Psr 03 58 53.7165 +54 13 13.727           ~ 416 1
7 PSR J0437-47 Psr 04 37 15.7994581776 -47 15 08.544351636           DC 836 0
8 PSR B0450+55 Psr 04 54 07.709 +55 43 41.51           ~ 156 0
9 NGC 1851 GlC 05 14 06.76 -40 02 47.6           ~ 1341 0
10 PSR J0538+2813 Psr 05 38 25.06 +28 17 11.0           ~ 183 2
11 PSR B0628-28 Psr 06 30 49.3710 -28 34 42.200           ~ 278 0
12 NAME Geminga Psr 06 33 54.153 +17 46 12.91           ~ 1154 0
13 PSR B0656+14 Psr 06 59 48.1960 +14 14 19.400   24.85 24.90     ~ 814 1
14 PSR J0720-3125 Psr 07 20 24.9620 -31 25 50.083           ~ 9 0
15 PSR J0737-3039 Psr 07 37 51.248 -30 39 40.83           ~ 394 1
16 NAME GUM Nebula ISM 07 43 -42.1           ~ 407 1
17 PSR B0809+74 Psr 08 14 59.500 +74 29 05.70           ~ 387 0
18 PSR B0818-13 Psr 08 20 26.4020 -13 50 56.400           ~ 195 0
19 PSR B0823+26 Psr 08 26 51.438 +26 37 22.83           ~ 487 1
20 NAME Vela XYZ Rad 08 34.0 -45 50           ~ 1178 2
21 NAME Vela Pulsar Psr 08 35 20.65525 -45 10 35.1545     15.10     ~ 2219 1
22 PSR B0919+06 Psr 09 22 14.1600 +06 38 28.800           ~ 269 0
23 PSR B0950+08 Psr 09 53 09.2970 +07 55 36.400           ~ 725 2
24 PSR J1012+5307 Psr 10 12 33.4345449600 +53 07 02.548542576     19.5     DA 341 1
25 PSR J1022+10 Psr 10 22 58.011 +10 01 52.85           ~ 200 2
26 PSR B1133+16 Psr 11 36 03.0720 +15 51 15.500           ~ 639 0
27 PSR B1237+25 Psr 12 39 40.386 +24 53 49.87           ~ 441 0
28 M 53 GlC 13 12 55.25 +18 10 05.4   8.95 7.79     ~ 780 0
29 M 3 GlC 13 42 11.62 +28 22 38.2     6.39     ~ 2384 0
30 PSR B1451-68 Psr 14 56 00.0175876848 -68 43 40.034742348           ~ 178 0
31 PSR B1508+55 Psr 15 09 25.674 +55 31 32.90           ~ 281 1
32 M 5 GlC 15 18 33.22 +02 04 51.7   7.34 5.95     ~ 1887 0
33 PSR B1534+11 Psr 15 37 09.9603 +11 55 55.554           ~ 411 1
34 PSR B1541+09 Psr 15 43 38.815 +09 29 16.50           ~ 187 0
35 NGC 5986 GlC 15 46 03.00 -37 47 11.1     6.92     ~ 341 0
36 PSR B1556-44 Psr 15 59 41.5290 -44 38 45.740           ~ 123 0
37 M 4 GlC 16 23 35.22 -26 31 32.7           ~ 1771 0
38 M 13 GlC 16 41 41.634 +36 27 40.75     5.8     ~ 2115 0
39 PSR J1643-1224 Psr 16 43 38.15583 -12 24 58.7200           ~ 184 1
40 M 62 GlC 17 01 12.60 -30 06 44.5   8.55 7.39     ~ 569 0
41 PSR J1713+0447 Psr 17 13 49.53053 +07 47 37.5264           ~ 414 1
42 NGC 6342 GlC 17 21 10.14 -19 35 14.7   11.25 10.01     ~ 268 0
43 PSR J1738+0333 Psr 17 38 53.96317 +03 33 10.8390           ~ 135 1
44 NGC 6397 GlC 17 40 42.09 -53 40 27.6     5.17     ~ 1892 1
45 PSR J1744-1134 Psr 17 44 29.4172 -11 34 54.710           ~ 236 1
46 Cl Terzan 5 Cl* 17 48 05.00 -24 46 48.0           ~ 774 1
47 NGC 6440 GlC 17 48 52.67 -20 21 34.5   12.01 10.10     ~ 512 1
48 NGC 6441 GlC 17 50 13.06 -37 03 05.2   9.26 8.00     ~ 835 0
49 NGC 6517 GlC 18 01 50.376 -08 57 34.39   11.08       ~ 163 0
50 NGC 6522 GlC 18 03 34.08 -30 02 02.3   10.68 9.48     ~ 498 1
51 NGC 6539 GlC 18 04 49.74 -07 35 09.1           ~ 210 0
52 NGC 6544 GlC 18 07 20.58 -24 59 50.4   11.36 9.90     ~ 271 0
53 NGC 6624 GlC 18 23 40.51 -30 21 39.7           ~ 833 1
54 M 28 GlC 18 24 32.89 -24 52 11.4           ~ 726 0
55 M 22 GlC 18 36 23.94 -23 54 17.1   7.16 6.17     ~ 1304 0
56 RX J1856.6-3754 Psr 18 56 35.11 -37 54 30.5     25.7     ~ 413 0
57 PSR B1855+09 Psr 18 57 36.39161 +09 43 17.2322           DA 499 1
58 NGC 6749 GlC 19 05 15.36 +01 54 00.0     12.4     ~ 144 0
59 PSR J1909-3744 Psr 19 09 47.42820 -37 44 14.7740           ~ 242 2
60 NGC 6752 GlC 19 10 52.11 -59 59 04.4   6.96 6.28     ~ 1910 0
61 NGC 6760 GlC 19 11 12.06 +01 01 49.7   11.37 9.78     ~ 221 0
62 PSR B1929+10 Psr 19 32 14.0570 +10 59 33.380           ~ 725 0
63 M 71 GlC 19 53 46.49 +18 46 45.1   7.91 6.1     ~ 1078 0
64 PSR B2016+28 Psr 20 18 03.8999255016 +28 39 54.940329468           ~ 340 0
65 PSR B2021+51 Psr 20 22 49.8730 +51 54 50.233           ~ 255 1
66 PSR B2045-16 Psr 20 48 35.7700 -16 16 47.000           ~ 301 0
67 PSR B2053+36 Psr 20 55 31.3552 +36 30 21.489           ~ 91 0
68 PSR J2124-3358 Psr 21 24 43.8464 -33 58 44.961           ~ 268 1
69 M 15 GlC 21 29 58.33 +12 10 01.2   3       ~ 3037 0
70 M 30 GlC 21 40 22.12 -23 10 47.5     7.10     ~ 987 0
71 PSR J2144-3939 Psr 21 44 12.0500 -39 33 59.000           ~ 112 0
72 PSR B2145-07.8 Psr 21 45 50.45590 -07 50 18.5900           ~ 251 0
73 PSR B2154+40 Psr 21 57 01.840 +40 17 45.89           ~ 139 0
74 PSR B2310+42 Psr 23 13 08.5976 +42 53 12.987           ~ 128 0

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2022.09.28-02:31:19

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