The evolution of radio galaxies: their infancy

Pedro Augusto

Grupo de Astronomia, Universidade da Madeira, Caminho da Penteada, 9000-390 Funchal, Portugal

In order to understand the origin and evolution of radio galaxies, searches for the youngest such sources have been conducted. Compact-medium symmetric objects (CSO-MSOs) are thought to be the earliest stages of radio sources, with possible ages of <10^3 yrs for CSOs (<1 kpc in size) and 10^4--10^5 yrs for MSOs (1--15 kpc). From a literature selection in heterogeneous surveys, we have established a sample of 37 confirmed CSOs: the typical CSO resides on a z<0.5 galaxy, has a flat radio spectrum (α_thin< 0.5; S_ν propor. ν^-α), is <0.3 kpc in size, has an arm length ratio ≤2, and well-aligned (θ ≤ 20°) opposite lobes with a flux density ratio ≤10. With the objective of improving the statistics of large CSOs (0.3--1 kpc) and flat-spectrum MSOs (with only three cases known), we have built a sample of 157 flat-spectrum radio sources resolved with the VLA-A at 8.4 GHz. We here sum up the status of our study of this sample, which includes the confirmation of, at least, two new flat-spectrum MSOs (two other sources lack redshifts for their final classification as either flat-spectrum MSOs or large CSOs), virtually doubling the number of such sources known.

 

Class:	Proceedings
Links:	ADS
Reference:	Augusto P., 2007, At the Edge of the Universe: Latest Results from the Deepest Astronomical Surveys ASP Conference Series, Vol. 380, proceedings of the conference held 9-13 October, 2006 at Sintra, Portugal. Edited by José Afonso, Henry C. Ferguson, Bahram Mobasher, and Ray Norris., p.261
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