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| Paper: |
The Evolution of Radio Galaxies: Their Infancy |
| Volume: |
380, At the Edge of the Universe: Latest Results from the Deepest Astronomical Surveys |
| Page: |
261 |
| Authors: |
Augusto, P. |
| Abstract: |
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 < 103 yrs for CSOs (< 1 kpc in size) and 104– 105 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 (αthin < 0.5; Sv ∝ v−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. |
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