The lack of large compact symmetric objects

Pedro Augusto

Centro de Astronomia e Astrofisica da Universidade de Lisboa, Observatorio Astronomico, Tapada da Ajuda, 1349-018 Lisboa, Portugal
Universidade da Madeira, Dep. Matematica e Engenharias, Caminho da Penteada, 9000-390 Funchal, Portugal

In recent years, `baby' (< 10<sup>3</sup> yr) and `young' (10³-10⁵ yr) radio galaxies have been found and classified, although their numbers are still small (tens). Also, they have many different names, depending on the type of survey and scientific context in which they were found: compact steep spectrum sources (CSS), giga-Hertz peaked spectrum sources (GPS) and compact-medium symmetric objects (C-MSO). The latter have the radio galaxy structure more obvious and correspond to the `babies' (CSOs; < 1 kpc) and `young' (MSOs; 1-15 kpc) radio galaxies. The log-size distribution of CSOs shows a sharp drop at 0.3 kpc. This trend continues through flat-spectrum MSOs (over the full 1-15 kpc size range). In order to find out if this lack of large CSOs and flat-spectrum MSOs is due to poor sampling (lack of surveys that probe efficiently the 0.3-15 kpc size range) and/or has physical meaning (e.g. if the lobes of CSOs expand as they grow and age, they might become CSSs, `disappearing' from the flat-spectrum MSO statistics), we have built a sample of 157 flat-spectrum radio sources with structure on ˜0.3-15 kpc scales. We are using new, archived and published data to produce and inspect hundreds of multi-frequency multi-instrument maps and models. We have already found 13 new secure CSO/MSOs. We expect to uncover ˜30-40 new CSOs and MSOs, most on the 0.3-15 kpc size range, when our project is complete.

Class:	Proceeding
Links:	ADS
Reference:	Augusto, P., 2009, Astronomische Nachrichten, 330, p.190-192
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