A survey of Low Luminosity Compact sources and its implication for evolution of radio-loud AGNs. I. Radio data

摘要

We present a new sample of Compact Steep Spectrum (CSS) sources with radioluminosity below 10^26 W/Hz at 1.4 GHz called the low luminosity compact (LLC)objects. The sources have been selected from FIRST survey and observed withMERLIN at L-band and C-band. The main criterion used for selection wasluminosity of the objects and approximately one third of the CSS sources fromthe new sample have a value of radio luminosity comparable to FRIs. About 80%of the sources have been resolved and about 30% of them have weak extendedemission and disturbed structures when compared with the observations of higherluminosity CSS sources. We studied correlation between radio power and linearsize, and redshift with a larger sample that included also published samples ofcompact objects and large scale FRIIs and FRIs. The low luminosity compactobjects occupy the space in radio power versus linear size diagram below themain evolutionary path of radio objects. We suggest that many of them might beshort-lived objects, and their radio emission may be disrupted several timesbefore becoming FRIIs. We conclude that there exists a large population ofshort-lived low luminosity compact objects unexplored so far and part of themcan be precursors of large scale FRIs.