Transverse motions in CSOs?

TL;DR

This study uses VLBA observations of three CSOs to detect transverse hotspot motions, suggesting jet precession that may inhibit source growth and indicate an older GPS/CSO population.

Contribution

First detection of transverse hotspot motions in CSOs, proposing jet precession as a key factor affecting their evolution.

Findings

Transverse hotspot motions observed in all three CSOs.

Jet precession likely causes the observed transverse motions.

Potentially identifies an older population of GPS/CSOs.

Abstract

The measurement of proper motions in CSOs is a powerful tool to determine the dynamical evolution of the newly born extragalactic radio sources. We observed 3 CSOs with the VLBA in 2004 and in 2006 to monitor changes in their structure and measure the separation velocity of the hot spots. It is important to increase the size of the samples of CSOs with measured expansion velocity to test the existance of frustrated objects, and put stringent constraints on the current models. We found for all the three objects observed a transverse motion of the hotspots, and we suggest as the more likey explanation a precession in the jet axis. This behaviour likely inhibits or at least slows down the radio source growth because the head of the hotspot continuously hits new regions of the ISM. Therefore these radio sources may represent an old population of GPS/CSOs.