# A multifrequency study of giant radio sources III. Dynamical age vs. spectral age of the lobes of selected sources - Astrophysics > Cosmology and Nongalactic Astrophysics

A multifrequency study of giant radio sources III. Dynamical age vs. spectral age of the lobes of selected sources - Astrophysics > Cosmology and Nongalactic Astrophysics - Download this document for free, or read online. Document in PDF available to download.

Abstract: The dynamical ages of the opposite lobes of selected giant radio sources areestimated using the DYNAGE algorithm of Machalski et al., and compared withtheir spectral ages estimated and studied by Jamrozy et al. in Paper II. Asexpected, the DYNAGE fits give slightly different dynamical ages and othermodel-s parameters for the opposite lobes modelled independently each other,e.g. the age ratios are found between ~1.1 to ~1.4. Demanding similar values ofthe jet power and the radio core density for the same source, we look for aself-consistent solution for the opposite lobes, which results in differentdensity profiles along them found by the fit. We also show that a departurefrom the equipartition conditions assumed in the model, justified by X-rayobservations of the lobes of some nearby radio galaxies, and a relevantvariation of the magnetic-field strengths may provide an equalisation of thelobes- ages. A comparison of the dynamical and spectral ages shows that a ratioof the dynamical age to the spectral age of the lobes of investigated giantradio galaxies is between ~1 and ~5, i.e. is similar to that found for smallerradio galaxies e.g. Parma et al. 1999. Supplementing possible causes for thiseffect already discussed in the literature, like uncertainty of assumedparameters of the model, an influence of a possible departure from the energyequipartition assumption, etc. Arguments are given to suggest that DYNAGE canbetter take account of radiative effects at lower frequencies than thespectral-ageing analysis.The DYNAGE algorithm is especially effective forsources at high redshifts, for which an intrinsic spectral curvature is shiftedto low frequencies.

Author: ** J. Machalski 1, M. Jamrozy 1, D.J. Saikia 2 1 Jagiellonian Univ., 2 NCRA, TIFR**

Source: https://arxiv.org/