2009A&A...503..747P


C.D.S. - SIMBAD4 rel 1.7 - 2020.08.15CEST22:29:19

2009A&A...503..747P - Astronomy and Astrophysics, volume 503, 747-754 (2009/9-1)

Radio spectral index images of the spiral galaxies NGC 0628, NGC 3627, and NGC 7331.

PALADINO R., MURGIA M. and ORRU E.

Abstract (from CDS):

To understand the cosmic-ray propagation mechanism in galaxies and its correlation with the sites of star formation, we compare the spatially resolved radio spectral index of three spiral galaxies with their IR distribution. We present new low-frequency radio continuum observations of the galaxies NGC 0628, NGC 3627, and NGC 7331, taken at 327MHz with the Very Large Array. We complemented our data set with sensitive archival observations at 1.4GHz and studied the variations in the radio spectral index within the disks of these spiral galaxies. We also compared the spectral index distribution and the IR distribution, using 70µm Spitzer observations. We find that in these galaxies the nonthermal spectral index is anticorrelated with the radio brightness. Bright regions, like the bar in NGC 3627 or the circumnuclear region in NGC 7331, are characterized by a flatter spectrum with respect to the underlying disk. Therefore, a systematic steepening of the spectral index with the increasing distance from the center of these galaxies is observed. Furthermore, by comparing the radio images with the 70µm images of the Spitzer satellite, we find that a similar anticorrelation exists between the radio spectral index and the infrared brightness, as expected from the local correlation between the radio continuum and the infrared emission. Our results support the idea that the electron diffusion must be efficient in regions of intense star formation. The observed anticorrelation between radio brightness and spectral index may imply that the cosmic ray density and the magnetic field strength are significantly higher in these regions than in their surroundings.

Abstract Copyright:

Journal keyword(s): radio continuum: galaxies - galaxies: spiral - galaxies: ISM - stars: formation

Simbad objects: 9

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Number of rows : 9

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 M 74 G 01 36 41.772 +15 47 00.46 10.52 10.00 9.46 9.16   ~ 1410 1
2 3C 48 QSO 01 37 41.2995845985 +33 09 35.079126038   16.62 16.20     ~ 2507 2
3 NAME Per B AGN 04 37 04.37510272 +29 40 13.8184969   21.7       ~ 473 2
4 ICRF J054236.1+495107 Sy1 05 42 36.13789843 +49 51 07.2337251   18.45 17.80 17.210   ~ 1270 1
5 NAME Leo Triplet IG 11 19 +13.2           ~ 102 1
6 M 66 GiP 11 20 15.026 +12 59 28.64 9.85 9.65 8.92     ~ 1163 4
7 M 51 GiP 13 29 52.698 +47 11 42.93   9.26 8.36 8.40   ~ 3799 4
8 3C 286 Sy1 13 31 08.2885060664 +30 30 32.960825108   17.51 17.25     ~ 3740 1
9 NGC 7331 LIN 22 37 04.102 +34 24 57.31 10.65 10.35 9.48     ~ 1113 2

    Equat.    Gal    SGal    Ecl

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2020.08.15-22:29:19

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