2019A&A...632A..12S


C.D.S. - SIMBAD4 rel 1.7 - 2020.10.31CET17:03:01

2019A&A...632A..12S - Astronomy and Astrophysics, volume 632A, 12-12 (2019/12-0)

CHANG-ES. XVI. An in-depth view of the cosmic-ray transport in the edge-on spiral galaxies NGC 891 and NGC 4565.

SCHMIDT P., KRAUSE M., HEESEN V., BASU A., BECK R., WIEGERT T., IRWIN J.A., HEALD G., RAND R.J., LI J.-T. and MURPHY E.J.

Abstract (from CDS):


Context. Cosmic-ray electrons (CREs) originating from the star-forming discs of spiral galaxies frequently form extended radio haloes that are best observable in edge-on galaxies, where their properties can be directly investigated as a function of vertical height above the disc.
Aims. For the present study, we selected two nearby edge-on galaxies from the Continuum Halos in Nearby Galaxies - an EVLA Survey (CHANG-ES), NGC 891 and 4565, which differ largely in their detectable halo extent and their star-formation rates (SFRs). Our aim is to figure out how such differences are related to the (advective and/or diffusive) CRE transport in the disc and in the halo.
Methods. We use wide-band 1.5 and 6GHz Very Large Array (VLA) observations obtained in the B, C, and D configurations, and combine the 6GHz images with Effelsberg observations to correct for missing short spacings. After subtraction of the thermal emission, we investigate the spatially resolved synchrotron spectral index distribution in terms of CRE spectral ageing. We further compute total magnetic field strengths assuming equipartition between the cosmic-ray (CR) energy density and the magnetic field, and measure synchrotron scale heights at both frequencies. Based on the fitted vertical profiles of the synchrotron intensity and on the spectral index profile between 1.5 and 6GHz, we create purely advective and purely diffusive CRE transport models by numerically solving the 1D diffusion-loss equation. In particular, we investigate for the first time the radial dependence of synchrotron and magnetic field scale heights, advection speeds, and diffusion coefficients, whereas previous studies of these two galaxies only determined global values of these quantities.
Results. We find that the overall spectral index distribution of NGC 891 is mostly consistent with continuous CRE injection. In NGC 4565, many of the local synchrotron spectra (even in the disc) feature a break between 1.5 and 6GHz and are thus more in line with discrete-epoch CRE injection (Jaffe-Perola (JP) or Kardashev-Pacholczyk (KP) models). This implies that CRE injection time-scales are lower than the synchrotron cooling time-scales. The synchrotron scale height of NGC 891 increases with radius, indicating that synchrotron losses are significant. NGC 891 is probably dominated by advective CRE transport at a velocity of ≥150km/s. In contrast, NGC 4565 is diffusion-dominated up to z=1kpc or higher, with a diffusion coefficient of ≥2x1028cm2/s.

Abstract Copyright: © P. Schmidt et al. 2019

Journal keyword(s): galaxies: spiral - galaxies: halos - galaxies: magnetic fields - galaxies: individual: NGC 891 - galaxies: individual: NGC 4565 - radio continuum: galaxies

VizieR on-line data: <Available at CDS (J/A+A/632/A12): list.dat fits/*>

Simbad objects: 12

goto Full paper

goto View the reference in ADS

Number of rows : 12

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 NGC 253 SyG 00 47 33.134 -25 17 19.68   8.03   6.94 8.1 ~ 2957 2
2 3C 48 QSO 01 37 41.2995845985 +33 09 35.079126038   16.62 16.20     ~ 2526 2
3 SN 1986J SN* 02 22 31.33 +42 19 56.4   18.4 18.4     SNII 306 1
4 NGC 891 H2G 02 22 32.907 +42 20 53.95 11.08 10.81 9.93 7.86   ~ 1536 2
5 7C 022737.60+401937.00 QSO 02 30 45.7106234427 +40 32 53.063097215     19.00 18.51   ~ 65 1
6 QSO B0248+430 QSO 02 51 34.53674204 +43 15 15.8291997     18.0 13.72   ~ 192 1
7 3C 82 QSO 03 14 44.2 +43 14 04     21.0     ~ 44 2
8 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 15001 1
9 7C 1219+2830 BLL 12 21 31.6902446544 +28 13 58.500383827   16.81 16.11 14.24   ~ 782 1
10 NGC 4565 LIN 12 36 20.804 +25 59 14.61   13.61 12.43     ~ 876 0
11 3C 286 Sy1 13 31 08.2885060664 +30 30 32.960825108   17.51 17.25     ~ 3777 1
12 UGC 10288 G 16 14 24.804 -00 12 27.14   13.5   13.4 12.9 ~ 102 0

    Equat.    Gal    SGal    Ecl

To bookmark this query, right click on this link: simbad:objects in 2019A&A...632A..12S and select 'bookmark this link' or equivalent in the popup menu


2020.10.31-17:03:01

© Université de Strasbourg/CNRS

    • Contact